Speedball voltage checks passed but small board OA and OB different [resolved]

[JohnnyT]

When doing the small board voltage checks for the Speedball, both OA and OB are within the stated ranges (60-90V) but are somewhat different. OA was about 62 VDC and OB was about 81 VDC. The kit passed all checks and sounds great, but I just wanted to double-check. Is this a cause for concern or will it affect sound? Thank you.

 

[Paul Birkeland]

Is Q1 installed properly on both sides?  The 62V would have me looking to be sure there isn't a backwards PN2907.

 

[JohnnyT]

Is Q1 installed properly on both sides?  The 62V would have me looking to be sure there isn't a backwards PN2907.

I believe they were, but you can check the photo here. I also just remembered the LED just below IA looked noticeably dimmer than the other 3. It was still glowing and visible in the dark but appeared dimmer. Could this be related?

 

[Paul Birkeland]

You have a backwards PN2907.

 

[JohnnyT]

Ah, I see it now. Silly me. Thank you!

 

[JohnnyT]

I flipped the PN2907 transistor the right way around, resoldered, and now OA is reading 69.7 VDC and OB is reading 78 VDC. Also, all 4 LEDs have similar brightness (no more dimness in the top left one). I guess that's an improvement.

I also resoldered the 6" black wire from 12L to the headphone jack lugs to get rid of the popping when inserting a headphone jack, it was actually loose at 12L.