reversed transistors.

[tomg]

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> From: Reverend bluE <djblue at asu.edu>
> To: DIY <synth-diy at mailhost.bpa.nl>
> Subject: reversed transistors.
> Date: Monday, January 18, 1999 6:59 PM
> 
> 
> I'm still wondering the bad stuff that would happen when I hooked up one
of
> the 2N3904's and the 2N4392 backwards.  I've fixed these problems
(re-soldered
> the parts the way they *should* be) but I still only get a radio station
and
> no waves in the outputs...
> 
> so could I have blown an op-amp, the tranny itself, or a cap in this
process
> of powering the things wrong?  should they be replaced?  is there an easy
way
> to test the bits?
> -b
The fet should be ok. Test the npn like this...
-Set your multi-meter on RX1 and zero the meter. Digital diode-check
mode is the same kind of thing. Look for a good reading to be .6 or .7.
leads may be reversed on some meters just make sure it tests good one
way or the other.
-Put the neg-lead on the 2N3904s base the meter should move about 1/3
of the scale when the collector or emitter is connected to the pos-lead.  
-Put the pos-lead on the base and the meter should not move at all when
putting the neg-lead to the collector or emitter, if it does it's leaky.
-Last test the collector-emitter junction both ways the meter should not 
move at all, if it does it's leaky.
-At any point if the meter deflects full scale the transistor is shorted.

In circuit working adjust the cv so 120mv is on the base of the input 
transistor, it should be close to +10 on the collector side of the 1K5 
resistor, about -.55mv on the emitters and near .4mv at the collector
hi-scale trimmer junction.