Speedball troubleshooting help [resolved]

[notphilip]

Hi all,

I successfully built and used the bottlehead and small circuit board of the speedball kit.
However, I think I may have messed up something in the large circuit board.

At first, I got 0 ohms on OA, G, and OB; and high resistance on B+.
Then after resoldering a bit, I got high resistance for OA, OB, and B+; 0 ohms on G.

When I plugged it in, the tubes lit up, but none of the leds lit up and I got about 235V on OA, OB, B+, and G.
After unplugging, then I measured resistance again and got 0 ohms on OA, G, and OB.

I desoldered the wires from 3U, 4U, 7U, and 9U then replaced them (in case I nicked any of them) just in case that would help.
Then I resoldered the pins for the transitors on both sides of the large circuit board.

Then I was able to get high resistance measurements from OA, OB, and B+; 0 ohms from G again.
Plugged in again, and got the exact same results - tubes light up, no leds light up (on small or large circuit board), and 235V on OA, OB, B+, and G.
Upon unplugging, I got 0 resistance again from OA and OB.

At this point, I'm not sure what to do or if I've damaged any components (e.g., blown out a transistor).
Any ideas?

[Paul Birkeland]

Can you go back and confirm that the small PC board is still functional?  To do this, you can run the amp with just the 12AU7, which effectively takes the big PC board out of operation.

Having such high voltage on all terminals on the big PC board indicates that there is perhaps a loose ground wire in the amplifier.  This seems to be the most common where the black wires meed on the headphone jack.

-PB

[notphilip]

Can you go back and confirm that the small PC board is still functional?  To do this, you can run the amp with just the 12AU7, which effectively takes the big PC board out of operation.

Having such high voltage on all terminals on the big PC board indicates that there is perhaps a loose ground wire in the amplifier.  This seems to be the most common where the black wires meed on the headphone jack.

-PB

Thanks for the advice.
So just to confirm, I'll remove the larger tube, power it on, and the voltages on the small board should still be what the speedball manual specifies?

[notphilip]

Yup, I realized that there was a loose ground wire after doing the recommended test. After re-flowing solder across a bunch of various joints, the small board voltages read correctly again.

Then I re-flowed solder across the large circuit board, reconnected the large tube, got high resist in OA and OB, and got all leds lit with correct voltages.

Now everything works perfectly and I'm listening to music!

But now I'm bummed that this project is over and I need to find something new to occupy my time with

[fullheadofnothing]

But now I'm bummed that this project is over and I need to find something new to occupy my time with

Crackatwoa is on sale this weekend…