Incorrect voltages after installing Speedball [resolved]

[Adelz]

Okay, thanks.
 
I've continued to check every connection and joint and I can't find anything wrong. I've resoldered everything and the problem remains the same. Also, now it appears that two of the LEDs on the large PCB are not lighting up during operation either. There must be a defective or dead transistor or something . . . or else I'm completely out of ideas.

[Paul Birkeland]

It sounds like other connections have been disturbed... Could you post as many photos as possible of your build?

[Adelz]

Sure. I'll post some soon.

[Adelz]

http://imgur.com/a/St4vU 
 
Above is an image album of some photos of my amp. I currently don't have the small PCBs in the amp so if you want pics of those installed I can put them back in. I still have the large PCB in the amp, however the two LEDs closest to the 9 pin socket are no longer lighting up at all. If you want any additional pictures I'll take them right away. 
 
Edit: I don't know what went wrong with the two LEDs but I replaced them and those are lighting up now. Still the same buzzing with the small PCBs, though.

[Adelz]

I'm still stuck with the buzzing. I've replaced and resoldered the red and black wires that attach to the small PCBs just in case but those didn't seem to be the problem either. Have you looked at the photos yet (if you want to see anything else I'll take some)?

[Paul Birkeland]

One thing you might try is moving the wiring from the input jacks to the pots as close to the edge of the panel as possible.

Those little Speedball boards do make the amp a little more sensitive to certain things, though we rarely see an issue like this when the voltages are spot on.

-PB

[Adelz]

Moving the wiring between the input jacks and the pot didn't change the buzzing at all. After all the resoldering and rewiring I've done I'm fairly certain that the problem must be on the small PCBs themselves. The amp is completely stock minus the resistor mod and the startup voltage modification for the 1/4" jack in the stickied thread, but I'm guessing those small changes wouldn't be the cause of the problem.

[Adelz]

I think I'm going to get some replacement transistors for the small boards. At the moment one of the boards works but still causes buzzing and the other board's LEDs will not light up (tried fresh LEDs as well, so it's not them, and tried the board in both channels), nor will the corresponding LED in the 9 pin socket. I've resoldered all the wires and capacitors around the transformer and replaced and resoldered the wires that attach to the small PCBs. I figure that having the resistors switched at the start must have damaged the transistors on the small boards. 
 
Also, the large board is currently installed, and with the 22.1k resistors, it works fine. The problems caused by the small boards occur whether the large PCB or the 3K resistors are installed, so I believe that the large PCB is functioning correctly.

[Paul Birkeland]

What voltages do you have with the iffy small board?

[Adelz]

I installed the iffy board on the standoff nearest the headphone jack. Regardless of the side it's on the two LEDs do not light up (plus one of the two in the 9 pin socket). All voltages are normal except for zero at Terminal 1 and 50 at Terminal 7.

[Adelz]

Do you have any recommendations as far as what I should do next? I'm fairly certain it isn't a bad solder joint due to all the resoldering and reflowing of solder that I've done. Would more photos be useful?

[Paul Birkeland]

Zero volts at terminal 1 indicates a fault in the small C4S board feeding that terminal.

-PB

[Adelz]

Yep, that would be the 'iffy' small board where the LEDs aren't lighting up, I'm assuming a transistor is defective. Can I get a free replacement through Bottlehead's replacement parts email?

[Paul Birkeland]

Yes, but please replace both the 2N2907 and MJE350.

[Paul Birkeland]

I did some testing this morning, and it looks like some counterfeit transistors made their way into our inventory.  We will be shipping out replacements when we receive a replacement batch shortly. 

Replacing the 2907 will cure this issue.

-PB