Yamaha CA 710 symptom ?

Hello, I have a Yamaha CA 710 which is the same as the yamaha CA 610.

Schematic is on page 11 of the service manual here on AK.

http://akdatabase.org/AKview/albums/userpics/10007/Yamaha CA-610 II Service Manual.pdf


I replaced electrolitics and some diodes about a year ago. Also some transistors.

On A5 in the schematic, In stead of the 2 x 2SA847 I put in 2sa970 or so, but they (one) blew pretty soon. So it took me a while to trace some 2SA847. Yesterday I put the 2SA847 in and the Yamaha seemed to work fine.


But it doesn't. Somehow this channel gets a lesser signal. Then if I turn the volume up, at some point the signal is good again and can play fine for a while... on all volume levels till it after maybe an hour or so again fades somewhat. I can repeat the trick to turn op the volume till the level meter peaks and the signal is back and equal on both sides.

What could cause this symptom ? Would I be looking for another transistor that's not totally healty ? There's no crackling or so. I'm out of freeze it so can't test it quickly that way.

I thought someone might recognice this behaviour and point me to a likely culprit...

Where did you find the A847 ?

Williges Elektronik Service GmbH

Solinger Str. 13
28199 Bremen / Airportstadt
Tel.: +49 (0)421 - 50 40 21
Fax: +49 (0)421 - 50 52 43
www.williges-elektronik.de

Any ideas about the Yammy ?

Which transistors did you replace ie. TRxxx ?

Then if I turn the volume up, at some point the signal is good again and can play fine for a while... on all volume levels till it after maybe an hour or so again fades somewhat. I can repeat the trick to turn op the volume till the level meter peaks and the signal is back and equal on both sides.

Click to expand...

Next time rather than adjusting the volume , tap on the protect relay. It kind of sounds like fouled relay contacts.

Hm, it's a long time ago.

But I took all transistors out to measure with a peak atlas DCA55

If I look at the saved measurement list , just the A847.

But I also swapped a A798 (5 legged) for a homemade double A1015.

Got that trick from here or another forum. that A798 is also unobtanium.


At the time there was a problem with one of the diodes that I tracked down

with the online help of a local tech.


Elektrolyte Caps have been replaced.

Hm, it's a long time ago.

But I took all transistors out to measure with a peak atlas DCA55

If I look at the saved measurement list , just the A847.

But I also swapped a A798 (5 legged) for a homemade double A1015.

Got that trick from here or another forum. that A798 is also unobtanium.


At the time there was a problem with one of the diodes that I tracked down

with the online help of a local tech.


Elektrolyte Caps have been replaced.
All switches have been desoldered and cleaned with a ultrasonic cleaner.
All solderwork has been reflowed.

Well, the strange thing is that on the dimbulb tester both channels work fine, and then directly on the wall socket I get these symptoms. I saw that for 7 euro I could get a pair of them A798 from a local supplier. So I am doing a bet, that the A1015 dubbel is maybe not doing the job it's supposed to do. Tickin on the relay does not change matters. If I remember well, I desoldered that one and gave it a thourough clean with fine sandpaper etc.