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TEAC AUSTRALIA
TECH MEMO #TV#
05.08.94
Model: CTM511/5S, CTM631/5S, CTM711/5S - Stereo Televisions
Symptom: The instability of the Stereo Identification Signal on some high quality live stereo
TV programs will cause split-second Sound distortion that may be confused as
`Sibilance'. Replacement of C015 will improve filtering of the ID signal and remove
any interference causing the effect. Stereo LED indicators may or may not switch
off when distortion is audible. However, re-transmitted programs from
overseas, movies and alike will not show any symptoms.
Instruction: Incoming RF signal must be clean, high quality live transmission to verify if a TV is
effected (use the NEWS or ABC Kids programs for example).
Check Stereo ID signal (~117.5Hz) present on [TP001] Pin 5 of TDA 3803A (IC001).
The sinewave found should be at least 7.0 Vpp (AC) and may vary slightly in
amplitude from station to station. Instability of this wave is synchronised with speech
and music and will show as a milli-second collapse.
Carefully remove Stereo PCB, disconnection all connectors and the link to the main
PCB (going to R633). Replace C015 from the original 10nF with a 1nF Capacitor .
Reconnect all connectors and the link, check [TP001] again.
Distortion on [TP001] must be peaked to its
V. rising shoulder. maximum amplitude with
T001 and thereafter readjusted
to a more stable waveform
with a shoulder distortion, as
shown typically 6.5Vpp and
Perfect symmetrical 8.5ms , (use a suitable
waveform on negative adjustment tool and
half do not readjust any other
T
potentiometers on the Stereo
PCB).
Please note that the correct adjustment of T001 must result in a distinctive `shoulder
distortion' on the positive rising edge of the sinewave, the falling side is undistorted. This is
not the maximum amplitude adjustment as outlined in the service manual!
Should you require any more information, please fax your enquiry on (03) 646 5554 to the
attention of the Technical Manager.
Zoltan Sekula
Technical Manager
TEAC AUSTRALIA
TECH MEMO
23.07.94
Model: CTM511/5S, CTM631/5S, CTM711/5S - Stereo Televisions
Symptom: All sets have in common a 12 Volt Zener Diode ((ZD 402 - 12V/1W) short and
limiting Resistor (0.68 and/or 6.2) open, or vertical collapse (TDA 3653B)
and/or Horizontal output transistor (2SD1555 or 2SD1547) short.
Confirmation: Check B+ as 112V/(143V respectively CTM 7xx) up by ~ 30 to 40Volts
Check 12 Volt rail and if not there....
Check Zener Diode (ZD 402) for short (near Vertical heatsink)
(CTM511/515) Check R423 open
(CTM631/635, CTM 711/715) Check R435 open (near EHT TRX)
Instruction: Replace all faulty components and the following Capacitors in the Power supply.
CTM CTM CTM
Old Value New Value 511/515 631/635 711/715
47uF/25V 47uF/63V C909 C910 C910
10uF/50V 10uF/100V C910 C908 C908
Also check the B+ rail capacitor and replace it if the powersupply failed as outlined above.
Model Location Original: Replace with:
CTM511 or 515 C915 47uF/160V 47uF/160V
CTM631 or 635 C926 22uF/160V 22uF/160V
CTM711 or 715 C925 100uF/150V 100uF/160V
Special Note:
When a unit is repaired for the symptoms as described above and the Capacitors are not
replaced, because it is not apparent that they are faulty, it will result in a repeated
breakdown within days after completion of the repair.
It is imperative that all Televisions with the above model number, irrespective of the
original complaint, have the outlined power supply Capacitors replaced as a matter of
preventative service.
Should you require any more information, please fax your enquiry on (03) 646 5554 to the attention
of the Technical Manager.