Magic Smoke Escaping from [edit]Sound*Craft PSU -Schematic!-

http://www.geocities.com/northsiderap/MicrophoneLand/SmallPSU.pdf

The magic smoke is escaping! Help!

I got this on EasterBate as 'untested' which really means 'broken.'

I opened up the hood and flipped the switch. R8 and TR2 promptly released their magic smoke. (in that order)

The transformer and switches measure OK. Rudimentary testing of the caps says they are OK too. Hmmmm. :? Signs of water spillage in the PSU.

[edit] I'm away from home, but a friend's meter says 14V AC on every output pin. :?:

Someone help me get started into intermediate power supplies. I probably will end up just replacing everything, but I'd rather know what's going on. What's happening here?

I know the basics of PSUs and transistors pretty well, but am looking for deeper insights... Would love for someone to give me some topology buzzwords to look up, or explain what's happening.

Thanks

Can't help but I enjoyed your avatar .... :shock:

Bottle up the smoke and send it to me. I'm pretty good with analyzing cooked electronics smells.

But seriously, I hate it when that happens. The schematic you posted is for a Soundcraft power supply, not an SSL. Did you post the wrong schematic?


PS: watch out, your avitar is smokin' too!

Is there a short across C12 (the output) ?

For testing unknown power supplies I prefer the following approach:
* disconnect the transformer secondaries and measure the AC voltage
* connect a lab PSU with suitable current limiting and voltage instead of the transformer to the input(s) to test each output independently

You might use the second part of this procedure to gain more info on the case at hand, e.g. if really all outputs are defective or if the +/-17 V simply follow a short in the 48 V line.

Samuel