Transistor chasing for a Sony SQR-6650 left rear power amp

[Vintage_Dutch]

Hi guy's
Some might have read about it ... if not no problem... I restored a nicotine "Rich" Sony SQR 6650
It needed maximum cleaning, Full recapping, and and and and...

I was happily test driving this super sounding receiver in 4 quadro mode.. up till (after four days of problem free playing) the moment I heard left rear lots of sputtering, crackling etc... After rapidly running the controls and came to the conclusion that the power amp is at fault.(it has four as you might know )

Last night after some diagram printing etc...I opened it up and sure as hell, the transistor type mentioned in the diagram where replaced factory standard by others...
Found some Euro type BC182 replacements but I'm not happy with them... they are not the A spec and this amp is sensible to the right specs components..
So I need advice how to go about getting the amp back with "original replacements" components

from Sony or Panasonic if possible.

I do stand my ground on repairs but also eager to learn from the more Quad amp repair experienced knowledge
In the picture below the circuit...I want to replace all but the power transistors...

I found the 2sc632A was factory standard replaced by the 2sc1362
The 2sa678 is still in there
The 2sc1124 is also there.
Still I want to replace them, creating a running amp witch still can be used problem free for years to come.

So I need Pinning equal replacements for the 2sc633a, or the 2sc1362 and a pinning equal replacements for the 2sca678 and the 2sc1124.
Does anyone advice me on types and sources to get them?

I want to do this faulty amp first and then slowly the other three power amps...

Then there are those Diodes 10D-05 (In the diagram D902) I found they are 1.5 / 2 Amp diodes... any ideas on replacements? Could not find any (yet).

This is the actual power amp (left rear) circuit.. so referral is easy to the q number if needed..

Would be great to from the knowledge"bank" on Quad.com

Thanks for the response .

 

[Vintage_Dutch]

Strange.... writing my own first reply

Found a clue on the Sony original replacement component site...
the 2SC1362 could be replaced by the 2SC537G witch is replaced by the 2SC2785

 

[par4ken]

I don't see the need to replace all the transistors and diodes if they are still good. I would search eBay and Ali-express for transistors, if you need them. I used to get parts from MCM, but they were bought up by Newark.

The electrolytic capacitors should be replaced. Use film types if you can fit them or get some audio grade electrolytic capacitors.
I'm using Nichicon Audio Gold https://www.mouser.ca/Search/Refine?Ntk=P_MarCom&Ntt=196672736

 

[Vintage_Dutch]

Hi All,

The problem is solved.... Found out that the green 2SA678 (Q904 in the Circuit diagram) was the culprit.
After a long search I found that the 2SA1175 is a nice replacement and readily available.

Ordered them... put 1 in...and was surprised by the silence...

Yesterday night I brought it back in my living from my workshop and it is now playing as never before...

Totally happy!


While waiting on parts to arrive....I also fixed an Kenwood / Trio TK350-u (Real Stereo Vintage from the mid 60ties), found an Kenwood / Trio TK60 also Vintage stereo from the early 60ties...

On that TK 60 I need a solution for flaky Dail paint.....does anyone has a Hi Res picture of that Dail?
I know It is not 4 ch related, but never the less it never hurts to ask.....

Many thanks in advance

Regards Auke