Voltage Regulators

How does one test a voltage regulator to tell if it's fried, or if there's just a short somewhere in a circuit? I built SSLTech's power supply point-to-point using a lower voltage transformer, and 15V regulators. The + leg is working, but the 48V and - leg are both coming out at 61V and -30V which are what's going into them from the rectifiers.

I suspect there's a short at the regulators, since their leads are so close, i probably accidentally got solder on two legs at the same time but just can't see it. I've checked wiring and it all looks right compared to the schematic and the board traces.

Daniel

Well there may be a difference between how one does it, and how I do it =), but....

If you suspect a short, I would hit it with a DMM, if the resistance is 0 between pins( or you have a continuity test), then *ding ding*, you've got a short =)

If that's not it, If I recall when I first built this supply, I put all the regs in backwards, the heatsink side should be facing the edge of the board where the outputs are.

If'n that don't get me there after I've checked for no shorts ( I always DIY in the nude :shock: ) and correct part values, swap the reg in question for a new one. =)

Regards

ju

No, the heatsinks of the TO-220 should be nearest the capacitor.

Like this.
http://www.fivefish.net/diy/powersupply1848/default.htm

Ok,

I'm doing mental gymnastics now, cuz in comparing, I etched my boards in reverse. :shock:

So, don't do what I did, listen to owel, you'll be fine :green:

ju

Make sure that you have a load on the output of the regulators when you measure them. Many three terminal (IC) regulators need to be loaded with at least 10 ma before they'll regulate.

Cheers,

Well, even after desoldering the connections, I get continuity between the input and output pin on the LM317 and LM7915 (which would be normal right?), but no continuity between any of the pins and ground. So that's good right?

I hooked up the Green Pre board, and it dropped the 60V to 58.x , and the -30V to -28.x.

So is it probably just a couple of shot regulators? Should I run out to my RadioShark and see if they've got any cheapo's I can replace?

Thanks,
Daniel