Speedball some LEDs not lighting [solved]

[sjeffrey]

I just completed my speedball upgrade.  The crack has been working for a couple weeks.
I tripled checked everything and all parts should be in correct place and orientation.
My symptom is, when I turn on the Crack A3 and A8 LEDs light up, with A3 lighting up faster.  Then the 2 small board light up and only the LEDs at top portion of the larger board light up.  After a few seconds A3 dies out and the other LEDs that had turned out are all very faint.  So after about 10 seconds A3 and the bottom LEDs on bigger board are not lit.  Oh and both tubes do light up.

I haven't done a voltage check because I don't want to damage the amp.  If I can get some guidance on where I should mesure based on my symptoms that would be great.

Thanks!

 

[Paul Birkeland]

Perform the voltage check, but wait a few minutes for the amp to settle before you do.
-PB

 

[sjeffrey]

Here are my readings, I excluded the 0s where they were expected to be 0.
T1 47
T2 53
T4 53
T5 7
T7 47
T9 0
T13 53
T15 119
T21 183

A1 7
A3 Starts at 1.5 but decreases over time
A6 47
A8 1.5

B1 47
B2 53
B3 43
B4 7
B5 57
B6 0

I also noticed the transformer is buzzing.  From the little I know it would appear to me that something is shorted to ground.

Thanks again,
Stephane

 

[Paul Birkeland]

Yeah, you are losing voltage like crazy.  If you run the amp long enough, something will either pop or smoke due to the current it is trying to demand.

I'd carefully check your soldering to be sure there aren't blobs of solder touching each other under each PC board.  Also triple check to be sure that the transistors are all properly placed.

You can also remove the black wire from the "G" pad of the large PC board, remove the 6080, then test the amp with just the 12AU7 installed, which will let you see if the voltages on T1-T5 stabilize.

 

[sjeffrey]

Well this is embarrassing, it turns out I had a T9 going to the wrong place on the big board.
I was a bit confused last night when I got to that part and I was getting tired.
Today with a fresh set of eyes and review all the steps I saw the mistake.
I had T9 going to the left side ground where the black wire bridges both.

Can I ask another question?
Why are the T7 and T9 connections black?  I assumed all black wires had something to do with the ground?

Thanks for the help!
Stephane

 

[Paul Birkeland]

When we created the Speedball kit, we really wanted to include the teflon wire, as it's totally bulletproof and easy to use on a retrofit kit.  At the time, we only had black and red in stock for other kits, so that's what got included. On a kit like the Mainline, you would find white teflon wire in places like that.  Since the outputs of the larger PC board are essentially a load from the ground up, we opted to use black wire.

-PB