Speedball upgrade issues

[jaytee]

I have a newly installed SB installed into a perfectly good working crack. The symptoms are both tubes light up, input led's light up, output led's don't and the 270ohm resistor from 16-21 gets hot as hell. DC voltage at #1=3-4vdc and at #2=45vdc which are way off. I've verified that I have the small transistors in the correct spot and with the correct orientation. I've retouched all connections, found one of the 100uf caps with a bad joint but now I am stuck.  Any help is greatly appreciated...

[Paul Birkeland]

Pull the 6080 tube and run the amp, then check to see if your voltages pop back up on terminals 1, 2, 4, and 5.

You have a short somewhere, which is sucking current down.  In these situations, we tend to see builders that leave off the shoulder washers on the TIP-50 transistors, which shorts them to ground and causes this issue.

-PB

[jaytee]

Thanks for the reply Paul,
Pulled 6080 and at #1=80vdc, #2=220vdc, #4=220vdc, 5=0vdc. 270 ohm wasn't hot, led's still dark. Are you referring to the fiber washer on the tip50's? Leaving those off would do this? Isn't the screw going thru the tip to the heatsink going to ground the case of the tip anyway?

[Paul Birkeland]

Yeah, that confirms a short that nearly has to be on the larger pc board.

That fiber washer and the insulator pad keep the Tip50 from touching the heatsink.  If you leave either off, you can potentially roast the board.

[jaytee]

I'll check that out tomorrow. Thanks Paul.

[jaytee]

Took me a while to get back to this but I did as you said Paul and still have voltage issues, just not the same. I removed the mounting screws from the tip50's, took measurements and still got zero volts at #5 and a fluctuating 53-66vdc at #9. All other voltages were OK, just a bit higher than they should be. All eight LED's were lit on the SB boards but one led on the bottom of the 12au7 socket was not lit. Thanks for your help...JT

[lordnikon]

There should be 8 red LEDs for the Speedball upgrade

[jaytee]

There should be 8 red LEDs for the Speedball upgrade

Thank you lordnikon. fixed it...

[Paul Birkeland]

It might be a good idea to post some photos of the build, there may be something amiss that we can spot from pictures.