AU-3900 Loud static crackle pop - right channel

[clogish]

Hi folks - I've been searching the internet and it seems that almost all roads lead to AK, so here I am.

Probably good to know that I'm somewhat technically minded but know very little about the inner workings of audio equipment - but I'm also not afraid to wield a screwdriver and such!

I recently bought a Sansui AU-3900 for a very nice price - very clean looking - but untested. Today I hooked it up to some speakers into group A, and as soon as I turned it on, there was a very loud bunch of static and crackling through the right speaker. Not great.

First things I did was switch the speaker cables over, and sure enough, when I turned it one, the left speaker produced the same problem instead. So, likely not the speakers, or the cables. Then I tested speaker group B, and had the same issue.

No input devices are connected. Volume control doesn't have any impact on the noise.
I've tried pushing all buttons, twisting all knobs, and flicking all levers a few times - no difference.

At this point, I'm guessing this means that something internal has blown, come loose or died - but have no idea where to start with "the obvious things" before I take it to a specialist.

Does anyone have any suggestions for things I can easily check, poke, wiggle or stare really hard at over the weekend?

Thanks in advance!

 

[LBPete]

Welcome to AudioKarma Exclusively Sansui. You have joined a long list of members drawn here seeking technical help. Have you cleaned the controls? Always the best place to start. Some of the small signal transistors can get noisy. There are threads discussing the usual suspects.

- Pete

 

[EastPoint]

Probably the 2SA798 dual transistor in that channel. I had one of those amps that had the same issue, and that’s what it was. You can replace it with a pair of KSA992s (Google around time find out exactly how) or find a new one on eBay. I’d replace both as long as you’re in there. It’s possible that the issue is something else, but I bet it’s the dual transistor.

 

[slimecity]

Agree with the above - look at the 2SA798 first.

There are also a plethora of other failure-prone small transistors in the pre stage to this amp. Ive managed to leave all mine in there in my own 3900 with no problems (so far) so you may be OK too. The 2SA798 is however more likely to be your culprit.

 

[EastPoint]

I rebuilt mine with all new caps and transistors. It was pretty easy. They’re nice little amps.

 

[clogish]

Thanks for the welcome and input, I'll check out the things suggested.

 

[petehall347]

Today I hooked it up to some speakers into group A, and as soon as I turned it on, there was a very loud bunch of static and crackling through the right speaker. Not great.

First things I did was switch the speaker cables over, and sure enough, when I turned it one, the left speaker produced the same problem instead.

i would say its the speakers or cables . i suggest you try one speaker at a time in left then right and see what happens then .
just thought you may have left the speakers in the same positions if so its a problem inside the amp .