Speedball - I goofed, but what did I damage?

Bungwu · 1042

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Offline Bungwu

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on: June 20, 2015, 06:59:21 PM
So I had the Crack assembled and working and began the speedball upgrade

I am new to DIY soldering and circuits and I failed to recognize that the 2N2222A and 2N2907A transistors were different despite the big red warnings in the manual. I thought it was referring to the resistors, not transistors.

Anyways, a quick run down of what I did:

  • one 2N2222A on the bottom right small PC board
  • one 2N2907A  on the large PC board
  • finished assembly, powered on...Tubes lit up, powered off to test voltage
  • powered on to test voltage, noticed not all LEDs were on... little bit of smoke... powered off
  • removed PC boards from Crack, checked all solder points(re-did a few)... reassembled, powered on, same  problem as before: tubes lit up, some LEDs on, and a  little bit of smoke
  • removed PC boards again, noticed the swapped transistors
  • desoldered the wrong transistors from the small and large board, soldered them in the correct location
  • reassembled, powered on... and here is where it gets weird
    • Tubes turned on
    • LEDs on the smaller boards were all on
    • LEDs on the large  board were off
    • LEDs and Tube light begin to  slowly fade out until they are completely off
  • I now can no longer get the Tubes or LEDs to power on

I am going to go ahead and assume I fried the 2N2222As and possibly the 2N2907As, is there anything else I should check and/or be worried about? 
« Last Edit: June 20, 2015, 07:11:28 PM by Bungwu »

Offline Paul Birkeland

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Reply #1 on: June 21, 2015, 06:51:55 AM
I would replace all of the transistors on all of the boards.

Generally a swap like this doesn't smoke the amp, so be prepared for additional diagnostics once everything is in its proper place.


Paul "PB" Birkeland

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Offline Bungwu

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Reply #2 on: June 21, 2015, 03:54:44 PM
Ok, I ordered the transistors.  I am guessing the bit of smoke was from a really bad solder point at 15 that I went back and fixed after my first set of problems.

Offline Bungwu

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Reply #3 on: June 25, 2015, 06:45:43 PM
Ok, I replaced all the transistors and the fuse and I have a different result now. 

-left most LEDs off
-bottom right small board's LEDs are both off. 

 I have no idea where to go from here.  Picture and voltages below.

1   70
2   188
3   16   
4   188
5   185
6   0
7   110
8   16
9   186
10   0
11   16
12   0
13   187
14   0
15   206
20   0
21   222

« Last Edit: June 25, 2015, 06:48:15 PM by Bungwu »