Crack 1.1/Speedball Issues (w/ voltages) (RESOLVED)

[RandomTox]

Started with a happily working Crack 1.1.

AC voltage shows as 118V

Built and installed the Speedball.  Small board passed voltage checks, resistance checks passed, large board did NOT pass voltage checks:

Small Board:

OA - 80V
IA - 194V
B-A/B - 0V
IB - 194V
OB 77.3V

Large Board:

Resistances:

OA = 14.3M ohms
OB = out of range (high)

Voltages:

OA: 107.8V
OB: 125V
G: 0V
B+: 192V

...

All LEDs are lit.  The two on the front/left side of the large board light about 5-10 seconds after the two on the back/right side.

6080 is lit appropriately.

12AU7 does not appear to glow/or is extremely dim and only on one spot.

Any help, suggestions gratefully received!

 

[Paul Birkeland]

I would flip the big board over and resolder all of the solder joints on it.  That 125V would indicate to me that 30mA isn't passing through the 6080 on that side of the circuit, which is most likely the result of an iffy joint on the board.

 

[RandomTox]

Thanks for the super-fast response!

I re-did all of those joints, initially only change I saw was that on the large board, OB is now 165V.  Now it's reading 190V and the two right-most LEDs on the small board are out.

I checked continuity/resistance between OB, U7 and back to pin 3 on the tube base, and that's good (at 0.5 ohms ... which is the same reading I get if I just short the probes on pin 3).

 

[Paul Birkeland]

You need to go back in and resolder them again.  The change that you see is now the problem getting worse.  If possible, try posting some photos of the top and bottom of your large Speedball board and we may be able to point to specific joints. 

-PB

 

[RandomTox]

I re-did all the joints, twice more, with only small variations in the voltage at OB.  All the joints are (and were) bright, shiny, nicely formed.  So I pulled the board out again, and checked every individual joint on my meter; all were good.  Then checked from each pad along each trace on the PCB and found a damaged trace there (high resistance, but not totally broken).  Jumpering/patching that trace fixed it ... OB now is 106V, and all is working fine.

Thanks!