RESOLVED Issue with Speedball LARGE board...one LED Dark, other very Bright

[jthomp27]

Installed Speedball Small Board last week and everything functioned correctly.
When I installed the Large board and turned it on, he two LEDs on the "B+" side of the board were glowing normally, but on the "G" Side of the board, the one closest to the center is dark and the one on the outside is REALLY bright.  I also heard a low hum in the background (my crack has always been whisper-silent.

Measurements on Large Board:
OA= 91.6V Expected=60-90v
OB= 7147.8V  Expected=60-90V
B+= 171V (OK) Expected170-195V
G = 0V (OK) Expected=0V

After I measured the voltage, I checked the soldering (everything looked good), and tried to power the crack again, but it will not power on.  I noticed a red mark on the board at Q2A (see picture on top).  Thoughts?  Did I fry my Crack?  I checked resistance on OB and OA, and they were both over 100 Ohms.

[Paul Birkeland]

It would be very strange for your meter to read 7,147V, something else must be going on there. 

Can you post a clearer photo of the bottom of the PCB?  It looks like there might be a solder bridge between two pads, but it's hard to say.

When you say "the amp doesn't turn on", is the fuse blown? 

[jthomp27]

Strange update....checked the fuse, and it is fine.  Crack powers up, there is a slight low hum in the background.  The one LED is still extremely bright. Left channel does not sound as loud as right (they were perfectly balanced up until I installed the large speedball board). Unit plays, but has a slight burnt electronics smell after 10 mins (no visible smoke, but quickly unplugged unit).

Thoughts?

[Paul Birkeland]

There is absolutely no reason that you should ever listen to or use an amplifier that hasn't passed its voltage checks.  This is a great way to damage your headphone or other equipment, and please refrain from doing so until the voltage issue is sorted out.

On the bottom of the big PCB, you need to trim the leads of those components back considerably, then I would recommend reheating all the joints on the board.  It looks like two pins of one of the 2N2222 transistors may be touching each other.

-PB

[jthomp27]

Paul - you were right, and all voltages measure correctly and the Crack sounds great!  How do I do about buying you a virtual beer?

[Paul Birkeland]

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[jthomp27]

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