PN2907A transistors damaged?

shoopdelang · 1332

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Offline shoopdelang

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on: December 02, 2017, 04:53:27 PM
When I was adding the speedball upgrade I initial soldered the PN2907A transistor backwards. To remove it I had to put the soldering iron on the leads for quite some time. I have since finished the speedball upgrade and everything sounds good but I'm paranoid that somehow I damaged the transistor with the extra heat needed to remove it. Is it possible for the circuit to still function with a faulty transistor, just not optimally, or does the transistor just either work completely or not at all? Please forgive my ignorance on electronics, just hoping to learn :)
My measurements for the small board are:

OA 81V
IA 190V
B-A/B 0V
IB 190V
OB 78V (Should this be the same as OA?)

For the large board:

OA 113V (this is more than 10% of the accepted range. Could this be caused by the transistor? Is this a cause for concern?)
OB 113V (Same issue)
G 0V
B+ 189V



Offline Paul Birkeland

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Reply #1 on: December 03, 2017, 05:23:58 AM
Your voltages look OK. 

-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline shoopdelang

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Reply #2 on: December 04, 2017, 06:26:44 AM
Out of curiosity then, does a transistor just work completely or not at all or can it gradually degrade in performance?



Offline Paul Birkeland

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Reply #3 on: December 04, 2017, 07:01:06 AM
If you damage one, they usually short closed, so you would see more like 189V instead of 78.  Transistors do degrade over time, be prepared to think about replacing them in 50 years.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man