[sdiy] odd behavior of transistors

[Gene Stopp]

Just last week I had an imput transistor on on Oberheim SEM envelope
generator triggering on gate rising edge and gate falling edge. The
flip-flop set pulse comes in thru a cap, and the flip-flop was flip-ping for
both positive and negative pulses thru this differentiator. I poked all over
with the scope and finally shrugged my shoulders and replaced the
transistor, fixed the problem.

- Gene

-----Original Message-----
From: mark verbos [mailto:a0284520 at addcom.de]
Sent: Tuesday, October 15, 2002 1:32 PM
To: synth DIY
Subject: [sdiy] odd behavior of transistors


In my current project I have used a 2N3904 at the trigger input. I 
noticed today that this transistor was responding backwards to the 
triggers! That is it was opening with a ground and closing with a gate.

I pulled the part out and put another in. Problem solved. Does this happen?

Has anyone in Germany noticed a high margin of bad parts in orders form 
Reichelt? I have found at least one bad chip on each channel of my new 
sequencer. That's 5 chips that didn't work from the onset. When they 
were replaced by chips from another source, everything was fine. They 
have been 4067, 4514 so far, plus the 2N3904. Am I the one who's crazy? 
I guess that's why they're cheap.

mark