Resistance check 7, 9, B3, B6 O.L. after breakdown [Resolved]

[monsterdonkey]

A year or so ago I blew up my Crack. I installed large output capacitors on sticky pads for whatever reason. The pads failed and allowed the capacitor attached to 6 and 7 to drop down and cause an intermittent short. This took a while and I allowed it to continue for several minutes. I suspected my headphones were malfunctioning and I went to grab a new pair instead of immediately powering down. A little smoke was released and I have not plugged it in since.

Anyway I finally got the time and initiative to check it out. No readily apparent scorch marks. The fuse is good. I have the Speedball installed.

I took the tubes out to perform the resistance check. All other terminals ok except:

7 O.L.
9 O.L.
B3 O.L.
B6 O.L.

Is it possible to deduce what is fried from this?

Thanks!

Rob

 

[Paul Birkeland]

The resistance checks change when you install the Speedball, so these resistances aren't an issue.

Can you tell which part let the magic smoke out?

 

[monsterdonkey]

Yes. I just found the spot. The arm of the capacitor attached to 7 touched the heat sink of the Speedball and burnt off a bit of paint there.

I’ve also discovered a broken solder joint on 6 while moving the cap out of the way to put a screw through the sticky pad. Maybe this turns out well.

 

[Paul Birkeland]

You may not have anything that needs to be replaced.

 

[monsterdonkey]

I’ve got it back together and running. The caps are resoldered and screwed in instead of hung by sticky pads. There might be something loose in or around the small tube socket since It took a few tries to seat the tube properly, and I got some loud crackling when I wiggled the tube (an antique RCA 12AU7) and the sound faded out after a few minutes of this. I poked and wiggled everything and plugged it in again without actually fixing anything. So far so good. I suspect the cap falling and the thing with the tube combined to freak me out and shut it down but really everything is fine.

Thanks for being available for questions. It seems it’s often the same answer: Check solder joints! but it’s still encouraging to know you chaps are there.

Now for some music.

Rob

 

[Paul Birkeland]

You may still have a loose joint up by the 9 pin socket.