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SERVICE
MANUAL
. . . . . . . . . . . . . . ";;i//L
TABLE OF CONTENTS
SECTION PAGE
Introduction ............................................................... 1
AM Tuner. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1
FM Tuner. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1
AM Alignment Procedure ..................................................... 3
FM Alignment Procedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3
Test Equipment Required for Servicing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4
Parts List ......... .. ................................................... 13 ~ 17
Technical Specifications .................................................... .18
LIST OF ILLUSTRATIONS
FIGURE PAGE
1. Dial Stringing .......................................................... 5
2. Front Panel Adjustments and Component Locations. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6
3. Main Chassis Component Locations (Top View) ................................ 6
4. Rear Panel Adjustment and Component Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7
5. Main Chassis Component Locations (Bottom View) ............................. 7
6. FM/AM Tuner Assembly P100 Component Locations. . . . . . . . . . . . . . . . . . . . . . . . . . .. 8
7. FM, AM, Mono and Muting Switch Assembly P300 Component Locations. . . . . . . . . .. 8
8. Power Supply Assembly P400 Component Locations .......................... " 8
9. Schematic Diagram ................................................... 9, 10
10. Exploded Mechanical Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11, 12
TABLE
1. Test Equipment Required for Servicing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4
INTRODUCTI ON
This service m anual w as prepared f or use by A ut horized Warranty Stations and contains service
information for Marantz Model l 05B Stereophonic T uner.
Servicing inform at ion an d volta ge dat a inc luded in this manual are intended for use by the
know ledgeabl e and experienced t echnician only . All instruction should be read carefully. No
att empt shou ld be made t o proceed without a good understanding of the operation in the
t uner.
The part lists f urnish informat ion by w hich replacement part may be ordered from the
Marantz Com pa ny . A sim pl e descr iptio n is incl uded f o r parts which can be usually be obtained
th rough local suppliers.
Th e Model 1058 is a tu ner version of t he Marantz's Model 20 15 T uner/Amplifier and almostthe
sam e circu itry as used in t he Mode l 201 5 is em pl oyed except the audio Amplifier, and power
su pp ly circu it.
1. AM Tuner
A ll com po nents except ferri t e bar antenna are mounted on a printed circuit board Pl00.
T he AM signals induced in a ferrite bar antenna are appli ed to the base of converter transistor
H113 t hrough a capacitor of C171, while t he loca l osci llator voltage is injected to the emitter of
H113 t hrough a capacitor C172. Both AM sign als and oscillating voltage are mixed at the
base- em itter ju nction and converted into 45 5 KHz intermediate frequency. The resulting I F signal
is app lied to the f irst I F transform er L 1 16 co nsisting of one ceramic filter and two tuned circuits.
T he output of L11 6 is led to the tra nsisto r H 104 which in turn apply its output to the
t ra nsistor of next stage Hl05. T he fu lly ampli f ied IF output is then applied to the diode H123 to
detect aud ibl e si gna l th rou gh t he detector t ransf ormer L 117. The detected audio signal is filtered
and th e final au dio output is obtained from pin terminal J118 and applied: to the output jacks
th rough the f unct ion switch.
T he DC com ponent of the det ected I F signal is used as a AGC voltage to control emitter
current of H 104 th rough th e resistor R 185. A part of I F signal output is also applied to the diode
H 124 th rough a capacitor C1BO and rect if ied t o obtain DC current for energizing the AM signal
strengt h meter M001.
1.1 Suggestions for AM Tuner trouble shooting
Check f or broke n A M bar anten na, nex t try to tune station by rotating fly-wheel tuning knob
sl owly and observe the AM signal strength met er whether it deflects or not. If the signal strength
meter gi ves a deflection at several frequencies received, no failure may exist in the stages at least
preced ing f inal I F transf ormer L 117. Next connect a oscilloscope to the pin terminal J118 and
ch ec k for aud io signa ls w it h t he tuning meter deflected. If the signal strength meter does not
defl ect , check the local osc ill ator circu it. Norm al oscillating voltage at the hot end of the
osci llator tuning ca pacitor is about 2 or 3 volts, varying with tuning capacitor position. When
measu rin g osc illati ng voltage use a RF V TV M, no circuit tester gives correct indication. If the
local osci ll ator voltage is normal , check all vo ltage distribution in the AM circuits by using a DC
VTVM and com pare t he measured values with t hose given in the schematic diagram.
2. FM Tuner
A ll com ponents are mou nted on a pri nt ed circ uit board P100.
FM signa ls induced by a FM an tenna are led to FM antenna coil L 101.
These signals are then applie d t o t he FET R F amplifier which in turn applies its output to the
next transi sto r m ixer Hl02 th rough a h igh Q tuned circuit.
The mixer convert its in put signal into 10.71V1 Hz intermediate frequency and amplifies it at the
same ti me. The H1 03 is a local oscillator and its output is injected into the base of mixer
t ran sistor , t he inj ect ion vol tage is abo ut 40m V.
1
---......... :.:.
The 10.7 MHz front end output is led to the next IF section . The IF section consists of five
stage of I F amplifier and one stage of sub I F amplifier. Two pieces of ceramic filters are also used
to obtain high selectivity, a pair of symmetrical diode limiters are also employed for the best
limiting characteristics, improved capture ratio and good AM suppression. A part of I F amplifier
H 105 output is rectified by the diode H 115, H 116 and its DC output is fed back to the gate of
FET RF amplifier to decrease the gain with increased signal strength.
2.1 Muting and Auto-Stereo Switching Circuits
The muting circuit consisting of all solid-state electrical switching has been incorporated in the
Mode1105B.
The DC vo Itage obta i ned by rectifi ng the su b I F output signal from the H 109 is app I ied to the
base of H 11 0 and turns on it, if th e sub I F output is greater than predetermined level (muting
threshold level).
When H110 turns on, the muting switch transistor H111 is turned on, thus decreasing the
emitter collector resistance to near zero ohm and allowing emitter current path to the Final IF
ampl ifier H 108.
When the input signal is lower than the predetermined level, the DC output obtained is small
and can not turn on the H110, thus the H110 keeps its turn off state and this makes the switch
transistor keep H111 turn off, then no emitter current is supplied to the H108 and signals below
the threshold level are muted out.
The muting threshold level can be varied by adjusting the trimming resistor R 153.
The DC voltage obtained is also used to make the Auto-Stereo switching transistor H 112 turn
on and off.
2.2 MPX Stereo Decodi ng Circuit
A Non-equalized audio signal from the FM detecto r is applied through the phase adjuster
network of C148 and R161 to input termin al pin CD on the M PX decoder IC Hl14. The MPX
decoder Ie consists of a stereo decoder and postam pl ifier for the output. The right and left
channel signals decoded by the stereo decoder H 11 4, appear at pin @ (right channel) and pin
QJ) (left channel), respectively. These signals are passed through the low-pass filters and
de-emphasis networks to eliminate undesirable residual switching signals and are then delivered to
postamplifier input pin