SG-1000 buzzing sound... HELP!

[kschafer2598]

RESOLVED! See last post below.

Hey all,

I recently picked up an SG-1000 which I was very excited about.

Problem is when I power it on, with any game, I get this over-powering noise that drowns out any other sound from the game. I've done multiple things to get this working,  nothing so far has helped:

1) Normal RF box on old TV
2) Different known-good AC adapter
3) Bypassed power switch completely with jumper wire
4) Tapped sound directly from sound chip and entry point to the RF box

I'm out of ideas. There was one glimmer of hope, where someone with a colecovision was having a similar problem but the thread did not come to a conclusion. IIRC the CV and SG-1000 use the same sound chip (sn76489).

Here's the thread I mentioned earlier:

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCcQFjAA&url=http%3A%2F%2Fwww.digitpress.com%2Fforum%2Farchive%2Findex.php%2Ft-17266.html&ei=Lfs1T-WfDefa0QGe3sGmAg&usg=AFQjCNFwYWTmpiCsQ9KuLhbnNyGYJmrolg

Any help is appreciated, please help me enjoy my console!

Karl

[ApolloBoy]

If you're in the US, I'd suggest using one of these instead of an RF switchbox: http://www.ramelectronics.net/audio-video/adapters/rca-to-f-adapters/f-009/prodF009.html

[kschafer2598]

Thanks man, I've tried two different RF boxes (sega, nintendo) with the same results. I also was able to tap sound directly from the sound chip and got the same result.

Sound is there, but its extremely overwhelmed by buzzing and other noise.

I've been wondering if its something in my home's wiring, which would be weird because I don't get this with any other console. I've been thinking about trying it with a battery attached for DC power instead of the transformer.

[kschafer2598]

Help!

[phreak97]

Have you tried with a battery yet? I'm thinking dead capacitors in the power area..

[kschafer2598]

I did try a battery pack from a sega nomad, it powered on and was "normal" but the sound was no different - so I was able to rule my residential power as the source of any interference.

I have to crack open the case again and see what caps there are on it, worth a try replacing them.

Would it be worth replacing the sound chip itself? I need to find one first though...

[kschafer2598]

I opened her up again, there aren't many caps on the board  but they don't look like they are original so who knows if the values are right.

Anyone out there with a working sg-1000 willing to open theirs and write down the cap values?

[kschafer2598]

Hey, great news! I finally resolved this problem.

Turned out that the sound chip was bad after all. I got a replacement TI SN76489, desoldered the old one and popped the new one in. Sounds great now!

Thanks all who helped!