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Stern Solenoid/Driver Board - RevC

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Sinbad79:
Hi Guys
Last night picked up a Stern Galaxy - powers up, GI lights OK, just not booting.
While i havent had the time to systematically work through diagnosing the electronics, i did notice that the under playfield fuse was removed, i'm assuming becuause the driver board was locking up coils - tested it and yep, that was why.

So i removed the solenoid/driver board - which is the rev-C type and started to test the transistors - herein is my question.
The voltage readings when using a DMM with red lead to GND and black lead to TOP of Transistor are mostly around the 1.4v - the information on the net suggests that these should be around 0.6v.

Do my readings suggest that there is something else wrong on this board or do these voltages sound OK?
Additionally, Q10 on this board (as an example) was reading a lower voltage 1.05v - which is known bad because the pop bumper coil was humming (locked on - reason why under playfield fuse was removed)

Any suggestions?

Homepin:
I wouldn't bother with EXACT readings as there are too many variables to stipulate a precise figure.

What you are looking for is a SHORT circuit (0 (zero) ohms) between the collector and emitter of the transistor. The transistor acts as a switch and when ON it basically shorts C to E - when OFF C to E read open circuit.

With power removed - if a transistor reads zero ohms between C and E it is stuffed and the coil will lock on as if the transistor switched it on.

That's what you need to understand and go from there.

Sinbad79:
ok, didn't know that, thats helpful.

Sinbad79:
Ok well according to that suggestion, all transistors are fine, which begs the question, why caused the coil to burn?

Sinbad79:
Couldn't modify previous post, so here's another one, lol.

Tonight i spent some time on the machine to take a more systematic approach to diagnosis.
Began with testing voltages on rectifier board, both with J3 connected and not.

Results as follows:
TP.     J3 off.     J3 on
1        5.8vdc.   5.85vdc
2.       146vdc.  218vdc
3.       10.9vdc. 13.2vdc
4.       5.6vac    5.6vac
5.       44.3vdc. 44.0vdc

How do the above voltages compare?
TP3 which converts to the +5v regulated source seems fine, TP4 is low and outside of spec, TP2 seems low (backbox displays dont power up)

Does anyone have any direction or suggestion as to which components on the rectifier board are at fault?
What i'd really like is a components list, so i can replace everything.
Thanks

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