"Estrada 101" 4 channel soviet amplifier, 1st channel problems.

[Deactivated-1]

I'm having problems with my Estrada 101 amplifier, when I turn it on, sometimes the 1st channel protection light doesn't turn off, but after around 3 minutes it turns off. at first, I thought it was just a sticking relay, but then after around half an hour, I hear a pop and smell something burnt, the amplifier 2nd channel (which I was using at the time) was still working, none of the protection lights came on.

so I turned it off, and the first thing I did was pull the 1st channel block/preamp out and look for anything there, and I saw the R39 resistor burnt, and nothing else.

when looking at the schematic I would think that there is no way for the R39 resistor to be blown with the correctly sized fuse F2, the fuse would've just blown.

maybe if pin 5 on the preamp block, if that gets shorted to ground maybe then, but I examined the rest of the amplifier and saw no place that it could be shorting.

Maybe I should take it more apart and look closer at the first channel circuitry

the protection light problem followed the amplifier 1st channel, not the 1st channel preamp board, so the problem must be in the amplifier
also, all the fuses are original ones and the proper value.

I've attached the schematics of the amp

[Chris56000]

Hi!

Is there any chance you could scan all the pages of the book you got that from please?

There's a lot of useful additional information in Soviet manuals, including coil and transformer winding details, full voltage tables and layout diagrams, etc!

This would assist me in rendering an English diagram for you!

Chris Williams

[serg-el]

https://forum.cxem.net/applications/core/interface/file/attachment.php?id=448053
http://rt20.mybb2.ru/viewtopic.php?f=5&t=50600
http://offtop.ru/dustyattic/v1_720390_19_.php

http://radionet.com.ru/forum/viewtopic.php?t=16494

http://rt22.ru/viewtopic.php?f=5&t=55489

Check and solder the connectors.  Replace capacitors K50-6 (aluminum barrels).  Check power supply and output transistors.  The voltage map is in the circuit.

[serg-el]

So does the relay turn on / off? Is the protection lamp still on?
R9 in the amplifier sets the output zero balance. R26 sets the quiescent current. It is imperative to adjust the balance, otherwise the protection will work.
Check / replace C3 and C5 in the protection circuit.
C3 power-on delay. C5 delay during protection operation.

And without replacing electrolytic capacitors, repairs are pointless. They are 100% defective.