Incorrect voltages after installing Speedball [resolved]

[Adelz]

The transistors on the small board with the swapped resistor would be the ones most likely to be damaged, correct?

[Paul Birkeland]

Yes.

-PB

[Adelz]

Is it okay to test the circuit with one of the small PCBs and one 22.1k resistor? That would definitely help with confirming the problem.

[Paul Birkeland]

Yes.

-PB

[Adelz]

Both boards are causing the same buzzing sound. Do you think that there are blown transistors on each board or could something else be the cause of the problem?

[Paul Birkeland]

could something else be the cause of the problem?

Yes, I think you have an issue elsewhere.  I still believe that you have an iffy connection in your amplifier, and the Speedball constant current sources are simply more sensitive to the issue than the stock circuit. 

There could also be an environmental problem close to the Crack (computer, wifi router, etc.) that could be causing some interference.  It might not hurt to try the amp in another room.

-PB

[Adelz]

I tried a different location and interference doesn't seem to be the problem. I guess I'll go through and resolder everything again.

[Adelz]

I've once again resoldered pretty much everything. Where should I go from here? I really don't want to just continuously resolder every joint; I feel like after all of this it is almost definitely a problem with one of the components. Could the transformer itself be causing the buzzing?

[Chris65]

Could the transformer itself be causing the buzzing?

Easy to check, make the screws are all tight then add some weight on top of it. Or just push down on it with your hand, but use a piece of wood or something in between....it can be hot!

[Adelz]

Doing that test didn't affect the buzzing so it appears that the transformer is fine. I'm really stumped about what's causing this buzzing.

[Doc B.]

How long ago did you buy your speedball kit?

[Adelz]

I bought the kit on April 16th (+/- a day) during the sale. I built the stock Crack for someone I know and am now installing the Speedball on my (roughly 6 month old) amp.

[Doc B.]

OK, I was just checking to make sure this wasn't an older kit from a year or two ago. We had a few that had counterfeit transistors back then. But not in the current kits, those transistors are legit.

[Adelz]

Ah, okay. Do you have any input on what may be causing the buzzing? I've resoldered all the connections around the transformer and filter capacitors multiple times. All my voltage readings are correct. The amp functions perfectly with the large PCB installed and the 22.1K resistors instead of the small PCBs. I really don't know what to do at this point. 

[Doc B.]

Peebs is the designer and the expert on this. I am inclined to agree with his assessment that, if it isn't a miswire or bad solder joint, there may be a problem with the transistors on the small boards. Replacing them might help.

That said, it seems more likely that it would be a cold solder joint or a miswire. It's not uncommon to miswire something on one side of the amp and then unknowingly replicate the mistake on the other side during the build.