LED out troubleshooting help

[Paul Birkeland]

Point taken re the Speedball standoff install, I will have to tweak the red wire a fraction to move it sideways a little.

I wouldn't move it.

2L needs to be reheated so that the solder flows into the hole of that terminal.

Since banging the chassis brings things back, I would try poking around with the wooden chopstick again to see if you can find which joint is causing this issue.

 

[elmoe]

Looks like 10U and 4L could use more solder

 

[aphays]

No dice - reheated 2L, problem still persists. Just out of curiosity, could this condition occur due to a bad component? I realize that a bad solder is much more likely, but is it possible that one of the resistors or capacitors was damaged by a short due to a bad connection early on that is now fixed? The first bad solder I found was at 20U, and I found it becuase I saw it spark. Could that have damaged either the resistors or the capicitor that are connected there?

 

[Paul Birkeland]

No dice - reheated 2L, problem still persists. Just out of curiosity, could this condition occur due to a bad component?

This is exceptionally unlikely.

I realize that a bad solder is much more likely, but is it possible that one of the resistors or capacitors was damaged by a short due to a bad connection early on that is now fixed?

No, this would give a completely different set of problems.

The first bad solder I found was at 20U, and I found it becuase I saw it spark. Could that have damaged either the resistors or the capicitor that are connected there?

No.

I'm sorry to say but when you tap on the chassis and that restores operation, that means you have a joint that isn't well connected.  We recommend poking around with a wooden chopstick to determine where this joint is so you can effect repairs.  I don't mean to sound like a broken record, but when I'm finished with a build, I will knock on it really hard to see if and LEDs shut off as a way to test that the joints are secure.  You have a loose wire, or a bad solder joint, or a broken wire somewhere in your amp. 

A shorted capacitor will cause billowing smoke and terrible stench from your amplifier.  You do not have that. 

A shorted resistor will either raise the B+ a little if it's one of the 270 ohm resistors, burn the 270 ohm resistors up entirely if the 270K shorts, red plate and draw the B+ down if one of the 3K resistors shorts, or leave high voltage at terminals 1/5 with the LEDs lit if one of the 22.1K resistors shorts.

Keep poking around with the chopstick at everything that has a solder joint.

 

[aphays]

Will do. Thanks man. This definitely helps clarify things.

 

[aphays]

Just wanted to follow up, as I finally got this sorted. Traveled and was working much of the summer, so I had to put this down for a while. I must have gone over every soldered connection in the amp 3 or 4 times to no avail. Replaced the LED's, no change. Over time I became suspicious that the issue was in the area of A8. Finally decided it had to be a bad 12au7 tube or a bad socket connection. Ordered both. Tube arrived first. Replaced it. Amp is working great. Both LED's come on together now instead of in a staggered delay. And they stay on. So glad to finally get this sorted out! Can't believe it took me that long to figure out it was an issue with the tube itself. Now finally looking forward to just listening.