Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: JulianBaynes on December 13, 2017, 03:23:55 AM
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I built the base crack without issues and have been listening to that for over a week. When putting the speedball upgrade together I installed the MJE350 Transistors backwards on the small board. I didn't notice this until I did the voltage checks on the small board. I have since removed and correctly installed the transistors. The lower two leds illuminate, but the upper two(closer to the IA and IB terminals) do not. These are my current voltages:
OA - around 100mV
IA - 186V
B-A/B - 0V
IB - 186V
OB - shows an open loop, climbs into the 100s of mV and returns to open loop. This process cycles.
I'm sure I need new MJE350s and probably two new leds. Am I better off getting a whole new small board? Hoping I didn't break anything on the crack itself.
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A replacement small board isn't a bad idea.
If you want to repair it, a new pair of MJE350s and a new pair of PN2907s should do the job. The LEDs do not need to be replaced.
-PB
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A replacement small board isn't a bad idea.
If you want to repair it, a new pair of MJE350s and a new pair of PN2907s should do the job. The LEDs do not need to be replaced.
-PB
Thank you for the reply. So you think I'm better off ordering a new board and set of parts than desoldering and installing new transistors?
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What I would do is cut the transistors off close to the plastic. Now you can desolder one leed at a time, putting less stress on the PCB. When you are done you will be in a better position to judge if the board cad be saved...John
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The issue with component level repair is that a lead (particularly the rectangular transistor leads) can catch and pull up a trace when being pulled out. This is most likely if the lead is pulled after the reheated solder begins to cool. Solder wick or a desolder pump will help to get that excess solder away from the lead so it can be pulled out without yanking up a trace.