Misbehaving Sansui 4900 Amp

[RolyShoes]

This is a shot in the dark - I'm new to this group and audio repair so please be kind!

For a few years now, my Sansui amp has been kicking off intermittently. It currently is emitting a ferocious crackling and popping through the left speaker whilst the right one is okay. This can carry on for weeks then randomly stops again and all is well until next time, although the good periods are getting shorter!

I opened it up six months ago and found the capacitors were a bit leaky so I replaced them but it didn't solve the problem. I assume the speakers are not the problem as when we plug headphones into the socket, we get the same terrible noise. I tried changing the speaker cable but that didn't make any difference.

I've had this amplifier for years, it's mostly great and I'd like to keep it rather than starting again. I've not been able to find anyone local confident in fixing it so thought I'd keep trying to repair it myself.

Does anyone have any thoughts/suggestions/advice for me?

 

[RolyShoes]

Oh, and I have tried outputting from both sets of speaker connections but the growling is still there.

 

[audiojones]

That's the classic symptom of failing transistors in the amp or preamp section. You might want to post this over in the Sansui forum along with some more information for accurate troubleshooting (what settings are when symptoms occur etc.) that way many experienced eyes will see it and I'm sure you will get some help. This is a very common failure with vintage gear and it involves replacing some aging transistors with modern equivalents. Can be a little tricky but not very hard with some guidance. I wouldn't recommend continuing to use it in that condition, it can lead to bigger problems.

Welcome to AK and good luck with your amp!

 

[RolyShoes]

That's great. Thanks for your reply, I'll try the Sansui forum (if I can find it).

 

[vinnx]

http://audiokarma.org/forums/index.php?forums/exclusively-sansui.39/

I hope you find a fix! I have a 4900z as well, it's a pretty sweet sounding amp : ) But keep in mind, the Z series isn't too coveted, so you may be able to find a replacement pretty cheaply.

 

[slimecity]

Worth fixing for sure. Find the service manual and start from there. I'd be looking at isolating which section of the amp the issue is in, and then removing and checking relevant small signal transistors.

http://www.hifiengine.com/manual_library/sansui/au-4900.shtml

 

[RolyShoes]

Thanks for all this guidance. I wish I'd come on here a year ago!

 

[Hyperion]

It would be best to clarify exactly which model you have - there is 4900z (a Receiver) and AU-4900 (an Integrated Amplifier).

"Sansui 4900 Amp" could possibly be either?

 

[RolyShoes]

I messed up - mine is the au 2900 integrated amplifier. I started a new thread over in the Sanusi specialist forum with the correct machine. Thanks for your feedback though.

 

[Hyperion]

ok - good stuff