So what did I blow up

[ssssly]

While I have done some bonehead things before building things I think this one takes the cake.

When I received my Paramount kits they were missing the 10k ohm trimmer potentiometers. I emailed Eileen and she mailed them out to me right away. In the meantime I figured I would finish the builds minus the potentiometers, slap them in when they got here and call it a day.

So I spent all day yesterday building the first one. Then promptly forgot that it didn't have the potentiometer. Fired it up for a voltage check and low and behold something started smoking. I shut it down but then noticed that the voltage then shot up to about to about 450v dc at t18. At which point I unplugged it and immediately realized that the trimmer pot was missing.

So what did I probably fry and how should I test for it? Resistances still look good other that B2.

Thanks all

 

[Paul Birkeland]

Replace the entire PCB, all its components, and the string of zener diodes in that amplifier (especially the zener diodes).

 

[ssssly]

Which PCB?

 

[Paul Birkeland]

The soft-start PCB. 

 

[Paul Birkeland]

Eh, scratch that, I think you probably blew up one TL431 regulator, the one on the A side.

I'd try replacing that and installing the 10K trimmer.  If you continue to get explosions, another board is in order.

 

[ssssly]

Will do.

Thanks CB.

The smoke came from the general area of the Zener string. So I'm guessing that is where the genie was released.

Will get the 431 and the Zeners replaced, the trimmer installed and see what I get.

 

[jrebman]

"I'd try replacing that and installing the 10K trimmer.  If you continue to get explosions,
another board is in order."

Nominated for quote of the month.

 

[Grainger49]

So, Jim, do you like the subtlety of it?

 

[4krow]

SMMMMOKIN!      Brother, it isn't just you. I smoked a tranny a couple day ago because of a mis-wire. And I have done MUCH worse, but we won't go into that just now.