Introduction; Pre-Amplifier; Main Amplifier - Marantz SUPERSCOPE BLA-545 Service Data

1. INTRODUCTION
This service manual was prepared for use by Authorized
Warranty Stations and contains service information for
the Super Scope Model BLA-545/A-545/BLA-530/A-530
Stereo Console Amplifier.
Servicing information and voltage data included in this
manual are intended for use by knowledgeable and expe-
rienced personnel only. All instructions should be read
carefully. No attempt should be made to proceed without
a good understanding of circuitry operation.
The parts list furnishes complete ordering information.
Most replacement parts should be ordered from the
Marantz Company. However, a simple description is
included for parts which can be obtained locally.
2. PRE-AMPLIFIER
Signals from the TUNER and AUX terminals are taken
to the SELECTOR SWITCH (SV01).
Signals from the PHONO terminals pass through the
phono amplifier (Q401, 0403 and Q405) where they are
amplified by 36dB and at the same time undergo RIAA
equalization, before going to the SELECTOR SWITCH
(SV01).
The signal selected by the selector switch passes through
the buffer amplifier and then is led to the mixing variable
resister RJ10.
The signal from the mic jack is amplified 36dB by the mic
amplifier composed of QJO01 and QJ02 and routed to the
mixing variable resister.
These two signals are mixed at the mixing variable resistor
and then led to the TAPE MONITOR switch and TAPE
OUT terminal.
Signals which enter from the TAPE IN terminals are
taken to the TAPE MONITOR SWITCH.
Signals which are selected by the TAPE MONITOR
SWITCH are taken to the MONO SWITCH BALANCE
and VOLUNE potentiometers, and then enter the preamp-
tifier (QEO1 and QE03). The preamplifier has a gain of
19dB and also serves as a tone control amplifier, with
the frequency response being controlled by the BASS and
TREBLE controls.
After passing through the preamplifier, the signals enter
the main amplifier.
BLA-545/A-545/BLA-530/A-530
3. MAIN AMPLIFIER
The main amplifier contains an NF type high pass filter
network which can be switched in and out of circuit by
means of the LOW FILTER switch.
4, TROUBLESHOOTING ANALYSIS
1. Excessive line consumption
a. Check for shorted O806 through O809.
b. Check for shorted transistor Q715, through Q718.
c. Check for open 0709, 0710, R717, R718.
2. No line consumption or zero bias voltage
a. Check line cord, fuse, check for shorted 0709,
Q710, 0717, O718.
b. Check for open rectifiers Q806 through O809
or open LOO1.
3. High hum and noise level
a. Check filter capacitors C808, C809, C801, C803,
Q801 and 0812.
5. POWER AMPLIFIER ADJUSTMENT
ADJUSTMENT OF IDLING CURRENT
Connect a vacuum voltmeter to between emitters Q715
and Q717. Adjust R717 until 117 mV is reached. Likewise,
adjust Q716, O718 and R718.
6. TEST EQUIPMENT REQUIRED FOR SERVICING
Table 1 lists the test equipment required for servicing the
Model BLA-545/A-545/BLA-530/A-530 Stereo Console
Amplifier. The wattmeter, AC voltmeter, and variable
autotransformer may be assembled as a test fixture as
shown schematically in Figure 1. The load resistors and
AC ammeter may be assembled into a second test fixture
as shown in Figure 2.