DIYbanter - View Single Post - HELP Technics SU-V60 Stereo Amplifier VC-4 distorted sound

Mark D. Zacharias

wrote:
hi there

Recently I've got the SU-V60 amplifier. It was in good shape,but it
didn't worked. I've tried to find out what is the reason. At first,
the hybrid power stage - dedicated for those AMPs, hard to find spare
parts. However, there was no burned PCB close to it, so I guess its
working properly. There were some dark areas near the current mirror
of the first power amplifier stage. I've soldered some bad joints,but
it didn't help. I also found some burned resistors, first biasing the
diode in current mirror and the other series in the positive supply
rail, which comes to the preamplifier mounted on the front panel. The
preamplifier board is also darkened, mainly around the two power
transistors and output transistors driven by the AN7062. I wonder if
there is a current or a voltage signal coming from the preamplifier to
the main power AMP. Unfortunately, the resistors are burned so bad,
that it's impossible to read the colour markings The output relay
is open all the time, voltage at both outputs of the power amp ~ minus
(50...60) V (depending on the speaker impedance switch).

Without schematic it would be very difficult to troubleshoot this amp
any further. I'd like to ask if anyone has got the schematic or
service manual. I would be very grateful. Any close-up photos from
the inside would be also helpful.

Sent the OP a PDF of the s/m.

Mark Z.