Not sure what I did

nickj · 569

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Offline nickj

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on: April 13, 2020, 02:31:07 AM
I built my stock crack about a month ago, then added Speedball after a couple weeks. No issues, worked great and sounded great. However, I was finishing the wood chassis this week and left the amp flipped upside down with the tubes taken out on a shelf. This morning before I set it back up I noticed that the screws mounting the speedball were a bit loose so I gave them a little tighten, but that's just about the only thing that I'm actually aware of changing on the amp. When I powered on and plugged my headphones in, I heard a loud buzzing/hum which quickly shifted back and forth between L and R channels before settling into a loud hum/buzz in the R channel. The volume pot had no effect on this noise, nor did removing the RCA inputs. I powered off, tried re-seating the tubes, checked the fuse, no change. I powered down and unplugged the power cord, waited about 20 seconds and I actually got a jolt while removing my headphone jack.

I started reflowing some of the joints that maybe looked a little suspect. While reflowing 9U there was a loud pop and spark, it was the one joint I felt needed the reflowing. Everything else I think looks okay but I reflowed some others anyway. I went back to measuring the resistance at OA and OB. However, on doing the voltage check, the LEDs on the speedball boards are not lighting up and the voltages are not measuring correctly. The LEDs on the small socket are lighting up, and both tubes light up.

OA 220V
OB 220V
G 235V
B+ 225V

Would appreciate any help here. Thanks!



Offline nickj

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Reply #1 on: April 13, 2020, 04:35:07 AM
Well - I just went back and continued to reflow some of the solder joints, seems like I'm back in business! Voltages check out and all the LEDs are back on. I was worried I might have damaged something after getting that pop and spark while soldering on 9U.



Offline Paul Birkeland

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Reply #2 on: April 13, 2020, 05:00:31 AM
If 9U sparks, the solder joint on the headphone jack where the black wires meet will need attention.  Specifically it's likely that one of those wires isn't captured by the solder.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man