Transistor Testing: Am I doing this right?

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I am testing a non-working STERN Solenoid Driver board out of the
machine. It is nearly identical to a Bally AS 2518-18, as is found on
early 80's games. At Q1 to Q 19 there are a series of SE 9302
transistors (to be replaced with TIP 102). I put the BLACK lead of my
DMM on the tab and the RED lead to each of the outer legs in turn.
Except for 2 of them, I get a NULL reading on the right leg and .5 to
..7 on the left leg. On two of them I get .6 or so on the right leg
also. Can ALL 17 of these transistors be BAD ? Or have I done something
wrong?

On the Lamp driver board, I get diode readings of .700 to .720 or so
on the MCR-106-1 transistors. Is this acceptable ?

Oh BTW, thanks LTG, I'll bet you answer this one first. :eek:)
 
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The reason you normally get a .700 or so reading with black on the tab,
red on the right lead is you are reading the internal diode in a TIP102
that goes from C-E. SE9302 does not have a diode so you should read
open on that reading. The base is the left lead, only readings you
should get is red on left, black on either of the other 2 leads. (or
tab which is same as center lead). This all out of circuit, in circuit
no telling what you may read, but 95% of time if no shorts are read,
the transistor is OK.
 
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Thanks Ron. I may have explained myself a little unclearly. I did NOT
test a TIP 102, just the SE 9302 on the board. Two of them did give me
a reading of .5 or so on the right leg. Are these BAD ? ALL the other
gave a NULL reading on the right.

The MCR-106-1 on the LAMP DRIVER board gave me .7 , a separate
issue. SInce the Marvin guides say .4 to .6 I was wondering if that was
out of spec and should be replaced.
 
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What Ron said may be correct, i am not sure. But Just measure another
known working transistor mounted on the board as a comparison.

I just worked on a silverball mania with the same driver board.
i had a SE9302 transistor not working. i did just as you described,
black DMM lead on the center trans leg, red on the outside legs.
top leg showed .5 volts. Bottom leg nothing null. I compared this
to the SE9302 next to it, which showed .5 volts on both outside
transistor legs. I replaced the transistor with a TIP102 and BINGO
solenoid worked. Hope this helps.

RonKZ650 wrote:
> The reason you normally get a .700 or so reading with black on the tab,
> red on the right lead is you are reading the internal diode in a TIP102
> that goes from C-E. SE9302 does not have a diode so you should read
> open on that reading. The base is the left lead, only readings you
> should get is red on left, black on either of the other 2 leads. (or
> tab which is same as center lead). This all out of circuit, in circuit
> no telling what you may read, but 95% of time if no shorts are read,
> the transistor is OK.
 

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