Trouble-shooting Speedball LEDs

[Loquah]

I'm helping a friend of a friend with a Crack that's lost one channel of sound. It's been slightly modified with some output caps and switched resistor mods on the small Speedball boards, but I think the issue lies elsewhere.

On first inspection, the front 2 LEDs on the large SB board don't light (closest to the HP socket). Steps tried so far:

1. Resoldered all large board joints
2. Reversed the board and it is still the front LEDs not working (i.e. the original dark pair of LEDs lit in the other orientation) so I gather this means the fault lies outside of the large SB board
3. Checked continuity between the 4 leads feeding the large board and there is continuity to the associated terminals for all 4 "feeder" leads

I've measured the voltage arriving via the red lead to the large SB board and there is 200V on that lead.

Where should I look next?

[mcandmar]

If you have power then the issue must be the ground, check across the black jumper wire on the PCB itself for continuity.

[fullheadofnothing]

Did the Speedball work before the switch mod?

Have you reverted the Speedball to stock?

[Paul Birkeland]

Post photos and look for irregular voltages.

I would suspect a bad solder joint on the "G" or "B+" jumper could cause this issue, as could a bad solder joint elsewhere on the board.

Are you getting 0V at the "O" terminal on the bad side or something pretty high?

[Loquah]

Thanks all.

After checking continuity on the red and black jumpers to find no errors, I measured the voltage at "O" on the big board where it wasn't lighting and was seeing only 1.5V. It turns out that the lead from T9 to the tube socket had snapped and was just barely making contact.

I replaced the lead from T9 to the tube socket and presto!

Thanks for your help!!