Pioneer SA-9500, Preamp warmup

notch

New Member
After fixing my power supply (damn Zener's), I now have a problem with the pre-amp.

When the amp is cold, one channel on the preamp fades in and out. After the amp has warmed up, there's no problem. It also reacts to tapping on the Stereo switch.

I have re-soldered EVERY joint on the preamp PCB (even the dodgy looking Plated Through Holes), and cleaned the stereo selector switch. Now I am left with a component problem. What's most likely to cause an issue? A transistor? or a cap? What should I replace first?

Cheers,
Nick
 
Notch

Have you tried to bypass the mode switch with a short wire, in the channal which fades ? tapping on the Stereo switch cures the prob indicates the switch is the prob or close at :scratch2:
 
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I have to really yank on the switch - i think the PCB flex's a little as the switch has good leverage on the pcb.

I will try bypassing it - but to me it seems wierd that the problem goes away after 10 mins on time reliably..... the only thing I can see would be temperature rise?

Cheers,
Nick.
 
Thats why i believe the switch to be the source of the problem, metal expand when heated ....but on the other hand an "unvisible" broken copper trace could also re-connect by warm up over time .... you will for sure locate the problem :yes:

Regards :)
 
Not to revive an old thread and all, but I am experiencing the same problem with my sx-1010. It is the amp section that is causing the problem though, not the preamp section. My right channel will fade out until a certain volume level is reached, then it will pop back in. Once its warmed up though its fine. I recently replaced a bunch of caps and the bias pots, and did not find any bad solder joints, although I did not resolder any connection (minus the caps I replaced).

Does anybody have any idea? There's no switches or anything in the amp section, so is there a way I could find out which part is misbehaving? Any help would be appreciated.
 
tschanrm
The output/protection relay often make this problem...if you wank the volume up and the connection becomes good by that ..you have a located the prob ;)
 
:thmbsp:

Thanks for the advice PMik, I'll take a look at the protection relay and see if anything is messed up.
 
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