Short on power rails (with Forssell amps on) I don't get it!

[NewYorkDave]

Reverse your ohmmeter leads. Do you still read a short?

 

[Steffen]

these are FET opamps right? and aren´t FETs conducting when no gate voltage (no supply voltage) is applied? it´s just a thought... where´s Fred?

steff

 

[NewYorkDave]

I thought of that, too, but he's not reading a short on the op-amps when they're out of circuit.

 

[Steve Jones]

If it makes you feel any better I have a similar kind of fault here with a power supply from a reverb unit. I just cannot find the short anywhere, so all that's left to do is to have a vomit and a lie down :wink: and a :guinness: :guinness: :guinness:

 

[FredForssell]

Don't worry about it. I can't say why there is measureable low impedance between the rails... I haven't given it any thought.

But I wouldn't worry about it. Power it up. I'm sure it will be fine. If you are really worried, or if you are into proper first time power-up procedures, you'll bring your design up slowly using a variac or variable DC power supply. That way you can monitor the supply current and voltages. It will be obvious if you have a problem.