[Speedball] Big board voltage (RESOLVED)

[Paul Birkeland]

I'm still nearly certain that this is an issue of flaky solder joints, perhaps made worse by lead free solder?

The flat rate repair service may be the most sensible option, or you can put the 3K resistors back in and replace the transistors on the PC board on the offending side.

[manolito]

The solder I use is rosin core, Sn60/Pb40, so it's definitely not lead free. The repair service does seem like an option, but I'd rather do everything I possibly can before I go for it. Having someone repair it for me kind of kills the DYI appeal. If by the end of the week I don't find what's wrong, I'll probably go for that.

Just to be sure I fully understand, what does this capacitor do and where should it discharge ? (and actually, how does a capacitor discharge ? none of the other seem to be having any kind of issue) Also, what transistors are you talking about ?

[Paul Birkeland]

On the big PC board and the half that isn't working, there's a TIP50 and a 2N2222.  I would remove and replace those two parts.

[manolito]

YAY, I'm finally getting the right voltage and the amplifier works !

Ok, just to summarize what happened. Back when I first assembled the big board, I accidentally soldered several terminals of the 2N2222 together. I tried to remove the excess with a desoldering bulb and failed miserably. I insisted when I shouldn't have and probably ended up burning the hole without realizing it. Later, I bought desoldering wick and it went much, MUCH better.
Anyway, you told me to check the transistor and so I did. Resistance was reading OL between the holes of the transistor and the next point on the PCB... So I did what I had to do and bypassed the PCB with wires. (see attached photo)

I have to say I'm not 100% confident about my approach (not that bypassing sections of PCB is unheard of), but at least it seems to be working fine now.

[Paul Birkeland]

I've had to do that once in a while, though never with all 3 leads.  If your DC voltages are where they are supposed to be, I wouldn't worry about it.