Text preview for : No_0301EFG.pdf part of Hitachi VTFX VTMX900ECT
VTMX900EUK
VTMX905EUK
VTMX905EVPS
VTMX910EUK
VTMX902EL
VTMX930EVPS
VTMX932EL
VTFX2000ELN
VTFX940EVPS
VTFX940EUKN
VTFX940ENA
VTFX942ELN
VTFX940ELN
VTFX952ELN
Back to : No_0301EFG.part1.rar | Home
No. 0301
VTMX900ECT VTMX900EUK VTMX905EUK VTMX905EVPS VTMX910EUK VTMX902EL VTMX930EVPS VTMX932EL VTFX2000ELN VTFX940EVPS VTFX940EUKN VTFX940ENA VTFX942ELN VTFX940ELN VTFX952ELN
Data contained within this Service manual is subject to alteration for improvement. Les données fournies dans le présent manuel d'entretien peuvent faire 'lobjet de modifications en vue de perfectionner le produit. Die in diesem Warungshandbuch t enthaltenen Spezifikationen können sich zwecks Verbesserungenändern.
SERVICE MANUAL MANUEL D'ENTRETIEN WARTUNGSHANDBUCH CAUTION:
Before servicing this chassis, it is important that the service technician read the "Safety Precautions and "Product Safety Notices in this service manual. " "
ATTENTION:
Avant d'effectuer l'entretien du châassis, le technicien doit lire les «Précautions de s écurité» et les «Notices de sécurité du produit» présentés dans le présent manuel.
VORSICHT:
Vor Öffnen des Gehäuses hat der Service-Ingenieur die ,,Sicherheitshinweise " und ,,Hinweise zur Produktsicherheit in diesem Wartungshandbuch zu lesen "
.
June 2000
1-6
Safety instructions
GB
Avertissements
F
Safety regulations demand that the set be restored to its original condition and that components identical with the original types be used. Safety components are marked by the symbol
Les normes de sécurité exigent qu'aprés réparation I'appareil soit remis dans son état d'origine et que soient utilisées les piéces de rechange identiques ŕ celles spécifiées. Les composants de sécurité sont marqués
!
!
All ICs and many other semi-conductors are susceptible to electrostatic discharges (ESD). Careless handling during repair may reduce life drastically. When repairing, make sure that you are conneted with the same potential as the mass of the set via a wrist wrap with resistance. Keep components and tools on the same potential. A set to be repaired should always be connected to the mains via a suitable isolating transformer. Never replace any modules or any other parts while the set is switched on. Use plastic instead of metal alignment tools. This in order to prelude short-circuit or to prevent a specific circuit from being rendered unstable.
Remarks
The direct voltages and oscillograms ought to be measured relative to the set mass. EXCEPTION At the power supply, the DC voltages and the oscillograms at the primary side are measured to LIVE GND. The direct voltages and oscillograms mentioned in the diagrams ought to be measured with a colour bar signal and the picture carrier at 503.25 MHz (C25). The oscillograms and direct voltages have been measured in RECORD or PLAY mode. The semiconductors, which are mentioned in the circuit diagram and in the parts lists, are fully exchangeable per position with the semiconductors in the set, irrespective of the type designation of these semiconductors.
Tout les IC et beaucoup d'autres semi-conducteurs sont sensibles aux décharger statiques (ESD). Leur longévité pourrait étre considérablement écourté par le fait qu'aucune précaution n'est prise ŕ leur manipulation. Lors de réparations s'assurer de bien étre relié au méme potential que la masse de l'appareil et enfiler le bracelet serti d'une résistance de sécurité. Veiller ŕ ce que les composants ainsi que les outils que I'on utilise soient également ŕ ce potentiel. Toujours alimenter un appareil ŕ réparer ŕ travers un transfo d'isolement. Ne jamais remplacer les modules ni d'autres composants quand I'appareil est sous tension. Pour l'ajustage, utiliser des outils en plastique au lieu d'instruments métalliques. Ceci afin d'éviter les court-circuits et exclure I'instabilité dans certains circuits.
Observations
La mésure des tensions continues et des oscillogrammes doit se faire par rapport ŕ la terre de l'appareil. EXCEPTION Sur l'unité d'alimentation la tension continue et l'oscillogramme sont mesurés sur le côte primaire en Live GND. La mésure des tensions continues et des oscillogrammes figurant sur le schéma doit se faire dans un signal de barre couleur porteuse image sur 503.25 MHz (C25). Les oscillogrammes et tension sont mésurées en mode RECORD ou PLAY. Les semi-conducteurs indiqués dans le schéma de principe et ŕ la liste des compostants, sont interchangeables par repčre sur ce chassis avec les semi-conducteurs de l'appareil quelle que soit la désignation de type donnée sur ces semiconducteurs.
Sicherheitshinweise
D
Die Sicherheitsvorschriften erfordern es, daß sich das Gerät nach der Reparatur in seinem originalen Zustand befindet und daß die zur Reparatur benutzten Ersatzteile mit den Originalersatzteilen identisch sind. Sicherheits-Bauteile sind mit der Markierung ! versehen Alle IC's und Halbleiter sind empfindlich gegen elektrostatische Entladungen (ESD). Unvorschriftmässige Behandlung von Halbleitern im Reparaturfall kann zur Zerstörung dieser Bauteile oder zu einer drastischen Reduzierung der Lebensdauer führen. Sorgen Sie dafür, daß Sie sich im Reparaturfall über ein Armband mit Widerstand auf dem gleichen Potential, wie die Masse des Gerätes befinden. Alle Bauteile, Werkzeuge und Hilfsmittel sind auf das gleiche Potential zu legen. Ein zu reparierendes Gerät ist immer über einen Trenntransformator an die Netzspannung anzuschließen. Bei eingeschaltetem Gerät dürfen keine Module oder sonstige Einzelteile ausgetauscht werden. Zum Abgleich sind ausschließlich Kunststoffwerkzeuge zu benutzen (keine Metallwerkzeuge verwenden). Dadurch wird vermieden, daß ein Kurzschluß entstehen kann oder eine Schaltung instabil wird.
Veiligheidsinstructies
NL
Veiligheidsbepalingen vereisen, dat het apparaat in zijn oorspronkelijke toestand wordt teruggebracht en dat onderdelen, indentiek aan de oorspronkelijke, worden toegepast. De veiligheidsonderdelen zijn aangeduid met het symbool
!
Alle IC's en vele andere halfgeleiders zijn gevoelig voor elektrostatische ontladingen (ESD). Onzorgvuldig behandelen tijdens reparatie kan de levensduur drastisch doen verminderen. Zorg ervoor, dat U tijdens reparatie via een polsband met weerstand verbonden bent met hetzelfde potentiaal als de massa van het apparaat. Houd componenten en hulpmiddelen ook op ditzelfde potentiaal. Sluit een apparaat dat gerepareerd wordt altijd via een scheidingstransformator aan op de netspanning. Verwissel nooit modules of andere onderdelen terwijl het apparaat is ingeschakeld. Gebruik voor het afregelen plastic i.p.v metalen gereedschap. Dit om mogelijke kortsluiting te voorkomen of een bepaalde schakeling instabiel te maken.
Anmerkungen
Die Gleichspannung und Oszillogramme sind gegen Gerätemasse zu messen. AUSNAHME Beim Netzteil sind die Gleichspannungen und Oszillogramme auf der Primärseite gegen Live GND gemessen. Die Gleichspannungen und Oszillogramme angeführt in den Schaltbildern sollen unter folgenden Bedingungen gemessen werden: Farbbalkensignal, Bildträger auf 503.25 MHz (C25) Die Oszillogramme und Gleichspannungen sind in RECORD oder PLAY gemessen. Die in den Stücklisten aufgeführten Bauteile sind positionsweise voll auswechselbar gegen die Bauteile in dem Gerät, ungeachtet der etwaigen Typenbezeichungen.
Opmerkingen
De gelijksspanningen en oscillogrammen dienen gemeten te worden ten opzichte van de apparaat aarde. De gelijksspanningen en oscillogrammen vermeld in de schema's dienen gemeten te worden met een kleurbalkensignaal beelddraaggolf op 503.25 MHz (C25). De oscillogrammen en gelijksspanningen zijn in RECORD of PLAY mode gemeten. De halfgeleiders, die in het pricipeschema en in de stuklijsten, zijn vermeld, zijn per positie volledig uitwisselbaar met de halfgeleiders in het apparaat, ongeacht de typeaanduiding op deze halfgeleiders.
1-7
Avvertimenti
I
Le prescrizioni di sicurezza richiedono che l'apparecchio sia ricondotto alle condizioni originali e che siano usati ricambi originali. Componenti di sicurezza sono marcati con
!
Tutti gli IC e semiconduttori sono sensibili a scariche elettrostatiche (ESD). Noncuranze durante la riparazione di semiconduttori possono danneggiarli o condurre ad una riduzione drastica della durata. Durante la riparazione assicurarsi di essere collegati allo stesso potenziale attraverso un bracciale di protezione contro scariche elettrostatiche. Inoltre tenere anche tutti i componenti e gli attrezzi a questo potenziale. Apparecchi da riparare bisogna collegarli sempre via un trasformatore isolante (separatore) alla tensione normale. Non scambiare moduli o altri componenti quando l'apparecchio č in funzione. Per l'accordo usare soltanto attrezzi di plastica (non usare attrezzi metallici). Cosí si evitano cortocircuiti e collegamenti instabili.
Osservazioni
Misurare le tensioni continue e gli oscillogrammi riferiendosi alla massa dell'apparecchio. ECCEZIONE Le tensioni continue e gli oscillogrammi dall'alimentatore sono misurati sulla parte primaria contro GND-Live. Le tensioni continue e gli oscillogrammi indicati negli schemi di collegamento devono essere misurati secondo le condizioni seguenti: segnale barre colore, portante dell'immagine su: 503.25 MHz (C25). Gli oscillogrammi e le tensioni continue sono misurati in RECORD o PLAYBACK. I componenti indicati nelle liste sono intercambiabili con quelli nell'apparecchio nonostante l'eventuale denominazione di modelli.
Avisos
E
Las instrucciones de seguridad exigen que después de la reparación el aparato se encuentre en el estado original y que las piezas de repuesto, utilizadas para la reparación, sean idénticas a las originales. Los componentes de seguridad estan marcados con
!
Todos los IC y semiconductores son sensibles a descargas electrostáticas (ESD). Un tratamiento no conforme a las instrucciones de semiconductores en caso de reparación, podría llevar a la destrucción de estos componentes, o a una reducción drástica de la duración. Tenga cuidado de que, en caso de reparación, estar al mismo potencial que la masa del aparato, por una pulsera con resistencia. Ponga todos los componentes, herramientas y recursos al mismo potencial. Para reparar un aparato hay que conectarlo siempre a la alimentación a traves de un transformador de aislamiento. Cuando un aparato está en marcha no pueden ser cambiados módulos u otras piezas de repuesto. Para los ajustes hay que utilizar exclusivamente herramientas de plástico (nunca herramientas metálicas). Así se evitaran cortocircuitos y circuitos inestables.
Notas
Hay que medir las tensiones continuas y los oscilogramas contra la masa del aparato. UITZONDERING: Bij het netgedeelte zijn de gelijkspanningen en oscillogrammen aan de primaire kant tegen Live GND gemeten. Las tensiones continuas y los oscilogramas mencionados en los esquemas tienen que ser medidos de manera siguiente: seńal barra de color portadora de imagen en 503.25MHz (C25) Los oscilogramas y las tensiones continuas son medidas en ,,RECORD" y ,,PLAYBACK" Los componentes mencionados en las listas se los puede cambiar por los componentes en el aparato, a pesar de eventuales designaciones de tipos.
1-8
Modifications
Description of the system used for publishing modification data and supplements to the service manual.
All modification data and supplements to the Service Manual are published by means of Service Information bulletins. Each Service information has a number, for example :
Tape deck
12345678 009271 AT-P2/0
00151 10WD51
Production code Factory indication Production date Tape deck type Factory code number Serial number
VR 00 - 01 GB
Language Sequence number Year Video cassette recorder
Note : The production code and the serial number on the tape deck need not correspond to the production code and the serial number on the type plate.
A Service Information bulletin concists of a front sheet, as the case may be followed by supplementary and/or replacement sheets. Replacement sheets serve to replace existing sheets in the Service Manual. These sheets are identified by an additional letter after the page number, for example 5-1a. Page 5-1a then takes the place of page 5-1. Supplementary sheets are inserted between the existing sheets in the Service Manual. These sheets can be identified by an additional figure following the page number, for example 5-1-1. Sheet 5-1-1 should be inserted after page 5-1.
Printed panels
The stickers are generally located on the track side of the module. Example :
AVR 01102 12345 KW 015 WD 01 123456
Serial number
Description of the system by means of which modifications are indicated in the recorder.
All important parts of the recorder, such as tape deck, p.c. boards and modules, are provided with a sticker. These stickers specify a number of product data. The meaning of this data will now be explained for the most important sections.
Production code Production week Printed board name Factory code
Remarks : The production code number will not always be mentioned.
The complete recorder
The type plate is located at the back of the recorder, below an example of such a type plate is given. Type plate :
SHOWVIEW IS A TRADEMARK APPLIED FOR BY GEMSTAR DEVELOPMENT CORP. SHOWVIEW SYSTEM IS MANUFACTURED UNDER LICENSE FROM GEMSTAR DEVELOPMENT CORP.
In case of an important modification, the last figure of the factory code number (point number) is increased by one. E.g. 6635.1 becomes 6635.2.
MADE IN EUROPE
220-240 V ~
50Hz
S AA AAA BBB CCC DDD EEE FFF GGG
MODEL NO: VR110/02 PROD.NO: VN 37 0015 123456
Service Option codes (A-G) Evolution code Type number
Serial number Production date Production center (VN), Production code
Note : - In the case of an important modification to the recorder the production code on the type plate is increased by one. E.g. 37 becomes 38. - In the case of an important modification to the service documentation the evolution code on the type plate is increased by one. E.g. AA becomes AB.
GB
1-9
GB D F
TECHNICAL DATA
TECHNISCHE DATEN
CARACTERISTIQUES
Mains voltage .................................. Netzspannung ...................................... Tension secteur ............................. 220 - 240 V, +/- 10% Mains frequency ............................. Netzfrequenz ....................................... Fréquence ...................................... 45 - 65 Hz Power consumption: ...................... Leistungsaufnahme: .............................. Puissance absorbée: ..................... mono 12.5 W during operation HiFi 16 W during operation without Low Power Standby ...... Standby ................................................ mode veille normal ........................ mono 4 W during standby HiFi 4.4 W during standby with Low Power Standby ........... Standby mit geringem Verbrauch ........ mode veille faible consommation .. < 4 W standby Ambient temperature ...................... Raumtemperatur .................................. Température ambiante .................. +10°C to +35°C Relative humidity ............................ Relative Luftfeuchtigkeit ...................... Humidité relative ............................ 20 - 80 % Dimensions ..................................... Abmessungen ...................................... Encombrement .............................. 380 x 260 x 94 mm Weight ............................................. Gewicht ................................................ Poids .............................................. 3,7 kg Fast forward/rewind time (turbo) ... Vor-/Rückspulzeit (turbo) ..................... Temps (re-)bobinage (turbo) ......... typ. 100s (E180 cass.) Position of use ................................ Betriebslage ......................................... Position d'emploi ........................... horizontally, max. 15° Video resolution .............................. Video-Auflösung .................................. Puissance absorbée ...................... 240 lines Audio ............................................... Audio .................................................... Audio SP: Linear Audio ................. 80Hz - 10kHz (+/-6 dB) Audio LP: Linear Audio .................. 80Hz - 5kHz (+/-6 dB) Stereo FM Audio ............................ 20Hz - 20kHz (+/-3dB)
NL E I
TECHNISCHE GEGEVENS
DATOS TECNICOS
DATI TECNICI
Netspanning .................................... Tensión de red ..................................... Tensione di alimentazione ............. 220 - 240 V Netfrequentie .................................. Frecuencia de red ................................ Frequenza di rete .......................... 45 - 65 Hz Opgenomen vermogen: .................. Consumo de potencia: ......................... Potenza assorbita: ......................... mono 12.5 W during operation HiFi 16 W during operation zonder Low Power Standby ...... sin standby de bajo consumo .............. in attesa non a basso consumo .... mono 4 W during standby HiFi 4.4 W during standby met Low Power Standby ........... con standby de bajo consumo ............. in attesa a basso consumo ............ < 4 W standby Omgevingstemperatuur .................. Temperatura ambiente ........................ Temperatura ambiente .................. +10°C to +35°C Relatieve vochtigheid ..................... Humedad relativa ................................ Umiditá relativa .............................. 20 - 80 % Afmetingen ...................................... Dimensiones ........................................ Dimensioni ..................................... 380 x 260 x 94 mm Gewicht ........................................... Peso ..................................................... Peso ............................................... 3,7 kg Vooruit/terugspoeltijd (turbo) .......... tiempo de (re-)bobinado (turbo) .......... Tempo di (ri-)avvolgimento (turbo) typ. 100s (E180 cass.) Gebruikspositie ............................... Posición de uso ................................... Posizione di funzionamento .......... horizontally, max. 15° Opplossend vermogen ................... Resolución video ................................. Risoluzione video .......................... 240 lines Audio ............................................... Audio .................................................... Audio SP: Linear Audio ................. 80Hz - 10kHz (+/-6 dB) Audio LP: Linear Audio .................. 80Hz - 5kHz (+/-6 dB) Stereo FM Audio ............................ 20Hz - 20kHz (+/-3dB)
Euroconnector (AV1) SCART plug 1
Connection to TV, monitor, projection TV ... Pin 1 Pin 2 Pin 3 Pin 6 Pin 7 Pin 8 ARO (audio right out) ARI (audio right in) ALO (audio left out) ALI (audio left in) Blue (out) **) Switching output: 500 mVrms +/- 3 dB 0,2 Vrms to 2Vrms 500 mVrms +/- 3 dB 0,2 Vrms to 2 Vrms Rout 1 kOhm Rin 10 kOhm Rout 1 kOhm Rin 10 kOhm
Cinch Audio/Video input on front panel (OPTION)
Audio: AINFR (audio right in) red 0.2 Vrms to 2 Vrms AINFL (audio left in) white 0.2 Vrms to 2 Vrms Input impedance 47 kOhm Video: VFR yellow Input impedance typ. 500 mVrms typ. 500 mVrms
(with R load = 10kOhm, C load < 2nF) low: 2V high: 9.5 V rise time: 5 ms
1 Vpp + 3 / -3 dB 75 Ohm
Pin 11 Green (out) **) Pin 15 Red (out) **) Pin 16 Blanking (out) **)
Cinch Audio Out Rear (OPTION)
AOUT1R (audio right out) red AOUT1L (audio left out) white 500 mVrms +/- 3 dB Rout1 kOhm 500 mVrms +/- 3 dB Rout1 kOhm
loop through enabled during standby, view-mode Rout 75 Ohm Pin 19 CVBS II (video out) 1 Vpp +1/-2dB Pin 20 CVBS I (video in) 1 Vpp +3/-3dB Rin 75 Ohm **) passive loop through from AV2
This outputs are in parallel with the corresponding outputs on Euroconnector 1.
Euroconnector (AV2) SCART plug 2
Connection to decoder, SAT tuner, video disc, 2nd VCR .... Pin 1 Pin 2 Pin 3 Pin 6 Pin 7 Pin 8 ARO (audio right out) ARI (audio right in) ALO (audio left out) ALI (audio left in) Blue (in) *) Switching input only 500 mVrms +/- 3 dB 0,2 Vrms to 2 Vrms 500 mVrms +/- 3 dB 0,2 Vrms to 2 Vrms low: 2 V (low) high: 4.5 V (high) Rout 1 kOhm Rin 10 kOhm Rout 1 kOhm Rin 10 kOhm Rin 10 kOhm Rin 10 kOhm
TUMOD
Modulator: Frequency range loop through 45 MHz - 860 MHz Gain: ANT IN - TV OUT 2 dB + 3 / -2 dB ANT IN - TUN OUT 2 dB + 3 / -2 dB Switch for RF input attenuation NO Frequency range out (tuned by IIC bus) Ch 21 - Ch55 Tuner: Frequency range
Pin 11 Green (in) *) Pin 15 Red (in) *) Pin 16 Blanking (in) *)
43 MHz - 860 MHz for UK 450 MHz - 860MHz < 100 dBµV > 60 dBµV
loop through enabled during standby, view-mode Pin 19 CVBS II (video out) 1 Vpp +1/- 2dB Rout 75 Ohm Pin 20 CVBS I (video in) 1 Vpp +3/-3 dB Rin 75 Ohm *) passive loop through to Euroconnector AV1
Input voltage max. min.
2-1
TOOLS FOR ERROR DIAGNOSIS
Replacement procedure components (chip) for leadless
3. Installation of leadless components
a. Presolder the contact points on the circuit board. Presolder
The following procedures are recommended for replacing leadless components used in this unit. Soldering iron
1. Preparation for replacement
a. Soldering iron Use a pencil-type soldering iron that uses less than 30W. Fig. 2-2 b. Using tweezers press down the part and solder both electrodes as shown below. Tweezers
b. Solder Use Eutectic solder (Tin 63%, Lead 37%) c. Soldering time Maximum 4 seconds.
Note: a. Leadless components must not be re-used after removal. b. Excessive mechanical stress and rubbing of the component electrode must be avoided.
Soldering iron solder Fig. 2-3 Note: Do not glue the replacement component to the circuit board.
2. Removing the leadless components
Grasp the leadless component body with tweezers and alternately apply heat to both electrodes. When the solder on both electrodes has melted, remove leadless component with a twisting motion. Note: a. Do not attempt to lift the component off the board until the component is completely disconnected from the board with a twisting motion. b. Be careful not to break the copper foil on the printed circuit board. Tweezers
How to remove/install the FLAT PACK IC
1. How to remove the Flat Pack IC
· Using a hot air Flat Pack IC unsoldering equipment
Chip
EXAMPLE Soldering iron Fig. 2-4 Fig. 2-1
GB
2-2
a. Prepare the hot air Flat Pack IC unsoldering equipment. Then apply hot air to Flat Pack lC for 5 - 8 seconds. b. Remove the Flat Pack lC with tweezers while applying the hot air. CAUTION: To avoid damage, do not apply the hot air to the chip parts around the Flat Pack lC for long periods. C.B.A. Hot air Flat Pack IC unsoldering equipment Soldering iron Masking tape Tweezers Fig. 2-7 Sharp pin b. Lift up each lead of the Flat Pack IC individually, using a sharp pin or non-solder wire (iron wire), while heating the pins using a fine tip soldering iron or a hot air blower.
· Using iron wire
FLAT PACK IC Fig. 2-5 a. Use unsoldering braid to remove the solder from all pins of the Flat Pack IC. Apply solder flux to all pins of the Flat Pack IC, to allow easy removal. b. Affix the wire to workbench or solid mounting point (see Fig. 2-8)
Put masking tape around the Flat Pack lC to protect adjacent parts. 2. The Flat Pack IC is fixed to the P.C.B. with glue; therefore take care not to break or damage any foil under the lC or on each pin when removing it. c. Pull up the wire as the solder melts in order to lift the IC lead from the P.C.B. contact pad, while heating the pins using a fine-tip soldering iron or hot air blower.
· Using a soldering iron
a. Use unsoldering braid to remove the solder from all pins of the Flat Pack IC. Apply solder flux to all pins of the Flat Pack IC, to allow easy removal.
Hot air blower ...
Solid mounting point
Iron wire
FLAT PACK IC
Unsoldering braid
Pull up gently to remove
... or soldering iron
Fig. 2-8 Note: When using a soldering iron care must be taken to ensure that the Flat Pack lC is not held by glue or the P.C.B. may be damaged if force is used. If the IC is glued, heat the IC with hot air to loosen the glue.
Soldering iron
Fig. 2-6
GB
2-3 2. How to install the FLAT PACK IC
a. Use unsoldering braid to remove the solder from the foil of each pin of the Flat Pack lC on the P.C.B. in order to install the replacement Flat Pack IC more easily. b. The "·" mark on the Flat Pack IC indicates pin 1. Make sure this mark matches the 1 on the P.C.B. when positioning for installation. Then pre-solder the four corners of the Flat Pack IC. (see Fig. 2-9). EXAMPLE
Voltage measurements
Color bar signal in SP REC and PB modes. Note: Voltage indications for the REC. and PB mode on the schematic diagrams are shown below:
REC. and PLAY mode (Identical voltages for both modes). PLAY mode Pin 1 on FLAT PACK IC is marked by a "·". REC. mode
Fig. 2-11 Fig. 2-9
Presolder Soldering iron
How to read wave forms
1 2 3
Connecting point Amplitude Time base Operating mode of the VCR
C.B.A. FLAT PACK IC Fig. 2-10 c. Solder all pins of the Flat Pack IC. Make sure that none of the pins have solder bridges between pins on the Flat Pack IC.
4
4
Note
All integrated circuits and many other semiconductor devices are electrostatically sensitive and therefore require the special handling techniques described in the "SAFETY INSTRUCTIONS" section of this manual.
2
1
Fig. 2-12
3
Voltage indication of Zener diodes
The Zener voltage of Zener diodes is indicated as such on schematic diagrams: Example: BZX79C20............Zener voltage: 20 Volts
GB
2-4
How to identify connectors on schematic diagrams
Each connector is labeled with a connector number and a pin number indicating to what component it is connected; in other words, its counterpart. Use the Connecting Wiring Diagram to find the connections between associated connectors. Example: The connections between C.B.A.s are shown below:
Test point information
With this model, test pin or components leads are used as contact points for adjustment and checking. In case of other test points with no test pin or components leads, use the foil solder pad to connect the measuring equipment.
Removal or installation of flat cables
a. Removal
Pull out the flat cable, holding it securely to avoid damaging individual wires (see fig. 2-14).
Connector no. and Pin no. on PCB
PCB to which this connector is connected
Flat cable
PULL
Connector Pin 1 Board
1
Connector no. to which the left connector is connected
Fig. 2-14
b. Installation
1. Adjust the position of the flat cable so that the lines on the flat cable align with the pins X of the trap connector (see fig. 2-14). Align individual wires with its individual trap connector hole. Then insert the flat cable wire into the trap connector. CAUTION: After installation, inspect the connection to insure that individual wires are not bent or touching other wires.
Fig. 2-13 2.
GB
2-5
Dismantling instructions
General guidelines for dismantling housing components, electronic parts and the drive mechanism
Always disconnect from mains before dismantling or assembly. Due to the supply voltages (hot circuit) on the primary side of the switched-mode power supply, an isolating transformer is required for the operation of the device. The drive or the drive/motherboard unit must not be pulled out by the cross struts! Components placed below the tape deck has to be inserted exactly.
Fig. 1 S A A
A
A
ä
ä
The use of a regulating isolating transformer is recommended for detecting faults around the power supply. All screws of the video recorder can be removed or tightened with a 10* torx screwdriver .
1. Housing cover (Fig. 1)
- Remove the four screws (A). - Push catch (S) inwards, lifting lid at the same time to move out of groove. - Slide housing cover back by approx. 1 cm. - Push centre of housing cover sides on underside approx. 1 cm outwards and lift up the housing cover. Assembly Assemble in reverse order.
S
S
S S
ä
ä ä
ä
2. Base plate (Fig. 2)
ä
The base plate may not be removed from the frame!
3. Front panel (Fig. 2)
Preparation Dismantle the housing lid as described in section 1. - Position the device with the base plate facing upwards. - Undo the six catches (S) one after the other, starting from the left or the right. - Remove the front panel by pulling it forwards. - For devices with shuttle print or socket print, disconnect the cabling to the motherboard. Assembly Assemble in reverse order (device in operational position). Important - The lift flap lever should be connected to the lift flap guide. - Check that all catches are engaged.
Fig. 2
S
* ...available from dealers
GB
ä
S
2-6
4. Dismantling of the motherboard/drive combination (Fig. 3) (Fig. 4)
Preparation Remove the housing cover as described in section 1. Remove the front panel as described in section 3.
M/K
K1
C
K2
C
K3
ä
ä
ä
ä
-
-
Move device into operational position (Fig. 3). Undo the two screws (B) of the stay and pull it up to remove it. Push back the lift by 5 cm after releasing both lift stops. Undo and remove the four fastening screws (C) of the drive. Detach the Cinch socket cable (K) and ground cable (M) from the socket print (if present). Remove the cables (K1; K2; K3) from the guides on the rear of the frame. Pull the Cinch socket holder with the socket and print up and out of the frame (if present). Position the device with the base plate facing up. Undo the 8 catches (S) from the rear right to the rear front and then from the rear left to the front left. After the weight of the motherboard/drive unit has released it from the frame, the catch (S) at the mains socket has to be released for a second time. The frame can be removed by lifting it off. Turn the motherboard/drive unit and move it into the service position (Fig. 5), if necessary. The device is operational in this position "Eject" must NOT be used !!!
ä
ä
C
B
ä
C
Lift protection
Caution: Adjustments can not be made in the service position. "Eject" must NOT be used !!! Assembly - Position the frame with the top open onto a level surface. - Hold the drive on the side at the lift and insert the motherboard/ drive unit into the frame, pushing it down lightly. Observe that the power supply and Scart sockets are positioned in openings. - Check that all 8 catches (S) are engaged. - Secure the drive with the four holding screws (C). - Move the lift into the "Eject" position. - Push the stay onto the frame with the chamfered side facing to the rear and secure with both screws (B). - Insert the Cinch socket into the opening and ensure that it engages. - Connect the Cinch socket and the ground cable (K ; M) (if present). - Insert the cables (K1; K2; K3) into the supports provided in the frame.
Fig. 3
S
S
ä
Fig. 4
- Replace the front panel and the housing cover.
ä
ä
ä
ä
GB
ä
B
ä
ä
ä
2-7
5. Dismantling the drive (Fig. 3)(Fig. 5)(Fig. 6)
Preparation Remove the housing cover as described in section 1. Remove the front panel as described in section 3. Undo the two screws (B) of the stay and pull it up to remove it. Push back lift by 5 cm after releasing both lift stops. Undo and remove the four fastening screws (C) of the drive. Undo and remove the ground screw (D) at the rear. (For this purpose, insert the screwdriver through the hole in the back panel). Remove the cables from the drive. Bend back the guard of the scanner cable. Remove the scanner cable from the socket. Return the lift into the "Eject" position. Slightly lift the left rear side of the drive to undo the connector to the capstan motor. Press both catches (S) together with fine pliers and lift the drive around the snapholders. The drive may be separated from the motherboard. Fig. 6 Assembly Assemble in reverse order. Important Observe that the cables (K1; K2; K3) are positioned in the supports on the rear of the frame and that the ground screw (D) is screwed in! C D C
ä
ä
-
C S
D
Fig. 5 Service position
ä
C
-
S
ä
GB
2-8
Circuit descriptions
1. Switched-mode power supply PS (PS Part) ................................................................................................................................................ 9 1.1 Technical data: ................................................................................................................................................................................................ 9 1.2 Functional principle: ....................................................................................................................................................................................... 9 1.3 Supply voltage part ......................................................................................................................................................................................... 9 1.4 Start-up with Mains-on: .................................................................................................................................................................................. 9 1.5 Normal mode: ................................................................................................................................................................................................. 9 1.6 Overload, power limitation, burst mode: ...................................................................................................................................................... 10 1.7 Standby mode: ............................................................................................................................................................................................. 10 2. Operating unit DC (DC part) ........................................................................................................................................................................ 10 2.1 Evaluation of the keyboard matrix ................................................................................................................................................................ 10 2.2 IR receiver and signal evaluation ................................................................................................................................................................. 10 2.3 Activation and function of the VFD display .................................................................................................................................................. 10 3. Central Control AIO (AIO part) .................................................................................................................................................................... 11 3.1 Analogue interface to the µC: ....................................................................................................................................................................... 11 3.2 Tape end - LED control : ............................................................................................................................................................................... 11 3.3 CMT detection (video detection with CSYNC) ............................................................................................................................................. 11 3.4 EE-PROM ..................................................................................................................................................................................................... 11 3.5 Easy link (P50) ............................................................................................................................................................................................. 11 3.6 Shuttle: ......................................................................................................................................................................................................... 11 3.7 Satmouse ...................................................................................................................................................................................................... 11 4. Deck electronics DE (DE part) .................................................................................................................................................................... 11 4.1 CTL stage ..................................................................................................................................................................................................... 11 4.2 Power on reset (POR) generator ................................................................................................................................................................. 12 4.3 The sensor interface : ................................................................................................................................................................................... 12 4.4 Interface to the head drum motor driver part ............................................................................................................................................... 12 4.5 Interface to the loading motor driver part: .................................................................................................................................................... 12 4.6 Interface to the capstan motor ..................................................................................................................................................................... 12 5. Front end FV (FV part) ................................................................................................................................................................................. 13 5.1 The front end comprises the following parts : .............................................................................................................................................. 13 5.2 The front end has been designed to receive the following systems: ........................................................................................................... 13 5.3 Tuner modulator (TUMOD) ........................................................................................................................................................................... 13 5.4 IF selection ................................................................................................................................................................................................... 13 5.5 IF demodulator ............................................................................................................................................................................................. 13 5.6 Audio demodulator ....................................................................................................................................................................................... 13 6. Video signal processing VS (VS part) ........................................................................................................................................................ 13 6.1 Switchover functions in the signal electronics IC LA71595M [7004]: .......................................................................................................... 13 6.2 Recording : ................................................................................................................................................................................................... 14 6.2.1 Luminance ................................................................................................................................................................................................. 14 6.2.2 Chrominance PAL ...................................................................................................................................................................................... 14 6.2.3 MESECAM ................................................................................................................................................................................................ 14 6.2.4 SECAM L ................................................................................................................................................................................................... 14 6.2.5 FM signal ................................................................................................................................................................................................... 14 6.3. Playback: ..................................................................................................................................................................................................... 15 6.3.1 FM signal ................................................................................................................................................................................................... 15 6.3.2 Luminance ................................................................................................................................................................................................. 15 6.3.3 Chroma PAL .............................................................................................................................................................................................. 15 6.3.4 Chroma MESECAM ................................................................................................................................................................................... 15 6.3.5 Chroma SECAM L ..................................................................................................................................................................................... 15 6.3.6 NTSC ......................................................................................................................................................................................................... 15 6.3.7 PAL M,N ..................................................................................................................................................................................................... 15 6.4 General ......................................................................................................................................................................................................... 15 7. Audio linear (AL part) ................................................................................................................................................................................... 16 7.1 Audio I/O for the 1-scart version ................................................................................................................................................................... 16 7.2 Audio I/O for the 2-scart version ................................................................................................................................................................... 16 7.3 Audio linear recording ................................................................................................................................................................................... 16 7.4 Audio linear playback .................................................................................................................................................................................... 16 7.5 Audio linear muting ....................................................................................................................................................................................... 16 8. Audio HiFi - for stereo units (AF part) ........................................................................................................................................................ 16 8.1 General ......................................................................................................................................................................................................... 16 8.2 Audio I/O ....................................................................................................................................................................................................... 16 8.3 Audio HiFi recording ..................................................................................................................................................................................... 16 8.4 Audio HiFi playback ...................................................................................................................................................................................... 16 8.5 Interface to the audio linear .......................................................................................................................................................................... 16 9. IN/OUT (IO part) ............................................................................................................................................................................................ 17 9.1 Video: ............................................................................................................................................................................................................ 17 9.1.1 Audio for the 2-scart version: .................................................................................................................................................................... 17 9.2 Decoder mode: (REC or STOP) ................................................................................................................................................................... 17 9.2.1 Program position with decoder (front end) ................................................................................................................................................ 17 9.2.2 External input with decoder ....................................................................................................................................................................... 17 10. Follow Me (FOME part) .............................................................................................................................................................................. 17 11. VPS/PDC, on-screen display (VPO part) .................................................................................................................................................. 17 11.1 VPS/PDC .................................................................................................................................................................................................... 17 11.2 OSD-PART .................................................................................................................................................................................................. 17
GB
2-9
1. Switched-mode power supply PS (PS Part)
1.1 Technical data:
Mains voltage: 195-264 Vrms Maximum output: 15W / 40W (continuous / maximum output) Operating frequency: 40 kHz Efficiency: approx. 75 % at maximum output Six different direct voltages are supplied on the power supply outputs.
1.4 Start-up with Mains-on:
Following connection to the mains, the capacitor [2310] is loaded via the start-up resistor [3318] and a current source between pin 8 and pin 6 on the IC [7303]. Once the voltage on [2310] and therefore the supply voltage Vcc on the IC [7303] has reached approx. 13V, the IC starts up and issues pulses to its output on pin 5. These pulses are used to control the gate on the power transistor [7302] (see Fig.2). The frequency has a fixed setting in the IC (approx. 40 kHz). The current input on the IC is approx. 5 mA in normal mode. If Vcc drops to below approx. 10V (e.g. with power limitation) or if Vcc exceeds around 15V (interruption of the control loop), the output on the IC [7303, pin 5] is blocked. All output voltages on the power supply, and therefore also Vcc, decrease. Once Vcc has dropped to below approx. 6.5V, a new start-up cycle begins. (See also "Overload, Power Limitation, Burst Mode" section)
1.2 Functional principle:
This power supply functions in a similar way to a blocking oscillator. In the supply voltage part [1300 to 2318], the mains voltage is rectified and buffered in the capacitor [2318]. From this direct voltage [2318] energy is transferred into the transformer [5301, pins 1-3] during the conductive phase of the switching transistor [7302] and is stored there as magnetic energy. This energy is passed to the secondary outputs on the power supply in the in the blocking phase of the switching transistor [7302]. With the switchon time of the switching transistor [7302], the energy transferred in every cycle is regulated in such a way that the output voltages remain constant regardless of changes in the load or input voltages. The power transistor is activated using the integrated switch [7303] Fig.1.
1.5 Normal mode:
With the power supply in normal mode, the periodic sequences in the circuit are divided primarily into the conductive and blocking phase of the switching transistor [7302]. During the conductive phase of the switching transistor [7302], current flows from the rectified mains voltage to the capacitor [2318] through the primary coil on the transformer [5301, pins 1-3], the transistor [7302] and resistors [3314, 3331] to earth (see Fig.1). The positive voltage on pin 1 of the transformer [5301] can be assumed to be constant for a switching cycle. The current in the primary coil on the transformer [5301] increases linearly in the pattern of U=L*di/dt. A magnetic field representing a certain volume of the primary current is formed inside the transformer. In this phase, the voltages on the secondary coils are polarised in such a way that the diodes [6300, 6301, 6306, 6308 and 6309] block. From the controller on [7301], a current is supplied to the CTRL input on the IC [pin 3, 7303] via optocoupler [7300]. Once the switch-on time for the switching transistor [7302] has been reached, which corresponds to the current supplied on the CTRL input, the switching transistor is switched off. Once the switching transistor has been switched off, the blocking phase begins. No more energy will be transferred into the transformer. The inductivity of the transformer will still attempt to maintain the current which has flowed through it (U=L*di/dt) at a constant level. As the primary current circuit is interrupted by the shut-off switching transistor [7302], the current will flow through the secondary coils.
1.3 Supply voltage part
The supply voltage part extends from the mains socket [1300] to the capacitor [2318]. Using the diodes [6310, 6311, 6312 and 6313] the a.c. supply voltage is rectified and buffered using the capacitor [2318]. The line reactor [5305] and capacitor [2316] create a filter to keep interference arising in the power supply away from the mains. Components [1302], [3326] and [3323] protect the power supply against short-term overvoltages in the mains, e.g. caused by indirect effects from lightning.
MC44608
VI
8
C demag
+
1
DEMAG current mirror current and voltage references 65mV/45mV
3318
start - up management
200 µA
current mirror
VCC 6
quick OVP UVL01
6307
5301
&
latched off phase start up phase
OVP - out
t
7300
200 µA 1 0 &
switching phase
start - up phase
output
2310
Vcc management
7302
buffer
stand - by stand - by management thermal shutdown
5
200 µA
ISENSE
&
PWM latch 0 latch OFF phase stand by regulation block & 1
2
leading edge blanking
CTRL
NC 7
Fig. 1
6305
3
3314
GND
4
6304
1
0
PWM comp
&
DRIVER
+
GB
2-10
The polarity of the voltages on the transformer is reversed, which means that the diodes [6300, 6301, 6306, 6308 and 6309] become conductive and current flows into the capacitors [2301, 2305, 2309, 2311 and 2312] and the load. This current is also ramp-shaped (di/ dt negative, therefore decreasing). The control adjustment for the switched-mode power supply is made by changing the conductive phase of the switching transistor (see Fig.2), so that either more or less energy is transferred from the rectified mains voltage to [2318] in the transformer. The control information is provided by the control element [7301]. This element compares the 5V output voltage via the voltage dividers [3300, 3306, 3336] with an internal 2.5V reference voltage. The output voltage from [7301] passes via an optocoupler [7300] (for the metallic isolation of the primary and secondary parts) as the current value to pin 3 on the IC [7303]. The switch-on time for the switching transistor [7302] is inversely proportional to the value of this current.
2. Operating unit DC (DC part)
The microcontroller TMP93CT76F [7899-A] is a 16 bit microcontroller fitted with 128Kb ROM and 2.5Kb RAM. It is the core element of the operating unit, fulfilling the following tasks with the respective functional groups: · · · · · · Integrated VFD driver Timer Evaluation of the keyboard matrix Decoding the remote control commands from the infra-red receiver pos. 6170 Activation of the display Back-up mode
1.6 Overload, power limitation, burst mode:
With an increasing load on one or more power supply outputs, the switch-on time for the power transistor [7302] also increases, and thus also the peak value of the delta-shaped current through this power transistor. The equivalent voltage circuit for this current profile is passed from resistors [3314] and [3331] via [3312] and [3347] to pin 2 on the IC [7305]. If the voltage on pin 2 reaches 1V in one switching cycle, the conductive phase of the switching transistor is ended immediately. This check is made in each individual switching cycle. This process ensures that no more than approx. 48W can be taken out of the mains ( = power limitation ). If the power supply reaches the power limit, the output voltages and the supply voltage Vcc on pin 6 of the IC [7303] will be reduced following further loading. If Vcc is less than approx. 10V at any point during this process, the output on the IC [7303, pin 5] is blocked. All output voltages and Vcc are reduced. Once Vcc has dropped to below approx. 6.5V, a new start-up cycle begins. If the overload status or short-circuit remains, the power limitation will be activated immediately and the voltages will continue to be reduced, followed by another start-up attempt ( Burst Mode ). The amount of power taken up from the mains in burst mode is low.
In normal operation, the µP is operated in dual-clock mode, i.e. both quartzes [1170, 1171] oscillate. The time is derived from the slow quartz [1170] (32.768 kHz), and the fast quartz [1171] (16MHz) is used to generate the system clock frequency. In case of a mains failure (back-up mode) the µP is not reset, but instead the mains failure is registered by the IPOR interrupt 3 [7899-B] (pin 67) and the µP is moved into "Sleep mode" (low power consumption). The 16MHz quartz is turned off and the 32kHz quartz is then used as the clock and system clock frequency. The operating voltage for the AIO is buffered by a back-up cell [pos. 2174, 2172]. A diode [6171] prevents this gold capacity from discharging.
2.1 Evaluation of the keyboard matrix
There are 12 different keys. Each key function is assigned a fixed voltage value. This value is decoded using an analogue/digital (A/ D) port (7899-B, pin 56). Each mechanical key position on the printed board can adopt any key function via a coding resistor. Pressing keys simultaneously may lead to undesired functions! Schematic:
STOP/EJECT
1.7 Standby mode:
In the `Standby` operating mode on the device, the 'STBY` control line is used to shut off the output voltages 14AL, 5VA and 5VD on the power supply to minimise the amount of power taken up from the mains. The supply to the display heating can also be switched off using the `I1WSTBY` control line. The power supply itself will continue to function continuously in the `Standby` operating mode with a switching frequency of 40kHz.
DC-KEY [7899-B, pin56]
10K
100K
MONITOR
470E
47K
27K
5K6
3K9
8K2
2K2
1K2
18K
12K
EJECT
STOP
STBY
PLAY
WIND
REW
STILL
2.2 IR receiver and signal evaluation
The IR receiver [6170] includes a selective, controlled amplifier in addition to a photo-diode. The photo-diode changes the received transmission (approx. 940nm) in electrical pulses, which are then amplified and demodulated. On the output of the IR receiver [7220] a level lift 0V/5V pulse sequence, which corresponds to the envelope curve of the received IR remote control command, can be measured. This pulse sequence is input into the controller for further signal evaluation via input IRR [7899-B, pin 46].
U3 = U GS
t ID I Dmax point of reversal
2.3 Activation and function of the VFD display
In principle, the VFD display [7170] is a tube triode in which the heating filaments in the tube serve as cathodes (F+,F-). The 7 grids (G1 - G7) are activated via PC2 - PC7, PD0 on the controller, and the 16 anodes (P1 - P16) are controlled via ports PE0 - PE7, PF0 PF7, PC0, PC1 on the controller, each with a positive potential compared to the cathode. The grids and anodes (digits and symbols to be displayed) are activated in the time-multiplex procedure, voltage lift 5V/-18V. A dimmer function is generated using pulse-width modulation of the grid control signals. At maximum display brightness, the pulse width for each grid is 2.16 ms. It can be reduced, controlled using software, which reduces the visual brightness of the VFD display accordingly. A digit or symbol is only illuminated if the corresponding anode and the surrounding grid are switched simultaneously to 5V for a certain time within a scanning period. The electrons emitted from the cathode are accelerated by the positively charged grid and hit the luminous layer of the anode which is also positively charged.
t
UDS
t
Fig.2
GB
UP
DOWN
REC
0E
2-11
During the remainder of the scanning period, the corresponding grid and parts of the anode are at -18V, due to the internal pulldown resistors in the controller. This potential is still lower than the average cathode potential of approx. -15V, prevents the acceleration of electrons, thus causing the relevant grid and anode segments to go dark. The heating direct voltage of the display (U = 3.5V) is supplied from the power supply via lines HELO or HEHI to pins F+ and F- to the VFD display. Resistors [3070] and [3071] restrict F- to approx. 15V.
3.3 CMT detection (video detection with CSYNC)
This has been extended due to identification problems with weak transmission signals and video signals not conforming to the STANDARD (common channel interference). The CSYNC line is supplied to the µP [7899-B] on pin 50. A hardware integration [7807,7808,7809] of the video pulse compensates the interference generated by the common channels and weak signals.
3.4 EE-PROM
The EE-PROM [7818] is a non-volatile memory which can be erased and written to electrically. (Data remains even if the operating voltage fails). Data specific to the device such as the X distance, head changeover position, preset stations, optional bytes etc. is stored in the EE-PROM [7818]. The data is accessed by the µP via the I˛C bus.
3. Central Control AIO (AIO part)
The microcontroller (µC) TMP93CT76F [7899-B] includes the following functions: · PWM outputs · A/D converters · Composite sync input · Special servo inputs for VCR functions · I˛C-BUS interface · Shuttle evaluation
3.5 Easy link (P50)
For the communication between the TV set, video recorder and the peripheral devices, a bi-directional single-wire bus is used, which runs via pin 10 to scart socket 1. The output signal is generated on pin 84 of the µC [7899-B], pin 68 is the signal input.
3.6 Shuttle:
The shuttle is connected to the motherboard on plug pos.1982. It is a binary coded rotary switch with a rotation angle of +/- 70 degrees and 16 switch positions. These are input and evaluated via four lines (shuttle b1 shuttle b4) to the input ports P24 P27 [7899B pins 2-5].
3.7 Satmouse
For activating a sat-receiver via an external infrared electronic transmission unit (Satmouse) a bi-directional data line, a shortcircuit proof +5V and earth are provided via a 3-pin 3.5mm jack [1941]. The +5V is limited to approx. 140 mA using a current limiting switch [7812 and peripherals].
4. Deck electronics DE (DE part)
The deck interface IC MP63100FP [7463] contains the following functional groups: · · · · · · CTL stage (tape synchronisation) Sensor interface Power on reset Head drum motor driver Loading motor driver Capstan motor control
4.1 CTL stage 3.1 Analogue interface to the µC:
The following analogue levels are supplied to the µC's internal analogue/digital (A/D) converter: · · · · · · · TAE/TAS TRIV TRIA AGC AFC 8SC1/2 Key-in Tape End / Tape Start Detection Tracking Information Video Tracking Information Audio Automatic Gain Control Automatic Frequency Control Pin 8 Scart1 or Scart2 switching voltage Keypad evaluation The IC M63100FP [7463] contains a read/write stage for the CTL track with the option of overwriting an existing CTL track without any interference. The playback stage is fitted with a "digital" fivestage AGC. This logic circuit identifies the size of the output signal supplied by the CTL head, and then selects the best amplification ratio in the playback stage using comparators. The CTL head voltage can therefore vary greatly, if Vmax / Vmin is great. The slowest tape speed is in LP mode. The fastest speed is adjusted during rewind. To ensure that the duty cycle in the tape sync is always reproduced correctly in the conditions mentioned above (important for detecting VISS marks), the amplifier must not be overdriven. The five-stage AGC alone cannot cover the large dynamic range of the input voltage. The amplifier is therefore also equipped with a low pass characteristic (fg = 3kHz typ.; internal).
3.2 Tape end - LED control :
The LED current is switched using transistor [7804]. The ON time is approx. 1 msec and the OFF time approx. 12 msec during playback and 1msec to 5.5msec during the winding functions. The LED current is typically 150 mA. In order to prevent interference from the relatively high pulsed current `spreading' through the entire unit, the LED is fed from the 14VM1, and filtered by 2 resistors [3800, 3805] with 10R each and a 220µF electrolytic capacitor [2803].
GB
2-12
In parallel with the CTL head is the RC cell comprising capacitor [2479] and resistor [3471]. The capacitor [2479], together with the CTL head inductivity, causes a resonance step-up at around 10 kHz and the resistor [3471] suppresses this step-up. This creates an aperiodic transient response in the resonance. Beyond the resonance frequency, there is an adjustment in terms of a steep fall in the frequency transmission characteristic. This effectively suppresses high-frequency pick-ups. The CTL head signal amplitude in standard play is around 1mVp (typ.) which means that the amplification for the playback amplifier must be correspondingly high. To avoid offset problems, a 100 µF electrolytic capacitor [2490] is fitted in the negative feedback branch for DC decoupling. The polarity of the playback amplifier can be changed using the Video Index Search System (VISS) voltage. This is the only way in which the µP can write a VISS mark on the tape without spikes. The Write/Read (W/R) signal is used to switch over between record and playback: W = "H", R = "L".
4.4 Interface to the head drum motor driver part
The head drum control voltage (speed and phase control information) is output via a µP-output (7899-B pin 35; PWM 14-bit). This pulse-wide modulated signal is fed to the motor driver IC M63100FP [7463 pin 11] and integrated with the capacitor [2469]. This IC already has a completely integrated `start-up' circuit fitted. For the commutation, the head drum motor driver uses the e.m.f. on the non-current carrying motor coil (transformer principle). The motor speed is also discharged from there at the same time. The phase of the head disc is discharged from a position coil. The speed and phase are multiplexed into one signal [7463 pin 6] and output, which means that the falling edge of the signal is available with a positive edge for the speed (FG/450Hz) and at 25Hz for the position pulse (PG). The motor driver M63100FP [7463] is connected to the head drum motor on the motherboard using plug [1948]. · · DRUM is the speed-phase control signal. The resolution is 14 bit. PG/FG is the combined POS/tachometer signal from the M63100FP [7463].
4.2 Power on reset (POR) generator
The POR generator contained in the M63100FP [7463] requires only one external capacitor [2477], which specifies the length of the POR pulse. For 33 nF, tPOR is approx. 30ms. The response threshold of the reset circuit is between 4.5 and 4.8 V. Supply fluctuations which are shorter than tPOR/100 area and which do not fall below 4.0 V, do not trigger the POR. The µP is reset using the inverted POR.
4.5 Interface to the loading motor driver part:
The loading motor driver part is constructed for use as a bridged dual power operations amplifier (OPAMP). It can supply max. +/0.8A output current. The output current is limited to approx. 0.7A by the internal resistance of the loading motor (18 Ohm typ.) (start-up or motor is blocked). B