Speedball large board connected wrong, what could be damaged?

Pflugshaupt · 333

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Offline Pflugshaupt

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I did some cap rolling on my Crack+Speedball unit I bought and built a few years ago. When I was done I noticed the right channel was about twice as loud as the left one. When I looked at everything inside again I found I made a mistake reconnecting the large speedball board. I had accidentally switched the B+ and OA cables. When I measured I read 190V on OA and 105V on B+, which is quite wrong. The amp has been running this way for maybe one hour overall.

I then corrected the mistake and now all voltages are in order again and the channel imbalance is gone. However now I get quite a lot of distortion that wasn't there before. It's ok for very low levels but already at the center volume position, distortion is very audible on both channels. (= every bassdrum distorts vocals clearly).

Now I wonder whether I could have possibly damaged some components when hooking it up the wrong way. What would most likely break from this misconfiguration? I have quite a few spare parts, but I don't even know where to start looking. Voltages do look good and all leds do light up. Switching both tubes makes no difference. Can anyone help me troubleshoot? Many thanks in advance.



Offline Paul Birkeland

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Reply #1 on: February 21, 2020, 05:06:09 AM
If the voltages are OK, then the Speedball is probably OK.

In the process of installing new caps, I bet you disturbed a solder joint that wasn't 100%.  The one I see on about 50% of the Cracks that I get in for repair is the solder joint on the headphone jack where the black wires meet.  I frequently find that one of the wires is soldered to the jack and the other is just floating loosely in the hole.  This will make your amp sound pretty terrible too.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Pflugshaupt

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Reply #2 on: February 21, 2020, 06:54:32 AM
Thanks for the help! I'll do some more resoldering and hopefully the distortion will be reduced.