Re: TECH: Aux Power Drive Unit Board Caught On Fire!

Q24 is MPU 1J11-5 and controls the aux power driver board grounding
transistor (this is how Williams expanded the number of controllable
solenoids... by stacking the aux transistor with the A/C relay, thereby
multiplying the number of solenoids by 2 (almost, anyway, as one of the
original solenoids has to be used to control the A/C relay selector).

Anyway, you should test the Q24 by measuring it in all 6 combinations
of leads with the MM. Only 2 should show a .5v-.7v forward junction
voltage drop, all other conditions should read OL (or 1. in your case,
with your RS MM)

This transistor is a TIP122, a common part. In this case you can
replace with TIP122, TIP120, TIP102, or pretty much any NPN Darlington,
as this transistor is driving to ground which simply controls the Aux
Power Driver grounding transistor (which carrys the real solenoid or
flasher current), hence very little current is consumed in control of
the Aux Power Driver transistor's base.

What you originally did with the clip lead should have not injured this
part, but it could have failed previously, leading you to decide to go
in and test it in the first place.

Also, be sure that you note that the A/C relay has two sections, a 25V
section and a 50V section... Don't make the mistake of crossing
voltages on the A/C relay... i.e., connecting, for some strange reason,
the 50V line to the 25V line.

Again, grounding the tab of the Aux Driver's transistor should provide
a ground path for the flasher or pop bumper.... but the controlled
device will only be activate when the A/C relay provides power to that
controlled device... As I recall, there is a diagnostic to control the
A/C relay. If this is true on your machine, then you may be able to
select that diagnostic and provide ground for the aux driver
transistor's tab. As the A/C relay cycles, it will power alternately
the pop bumper, then the flasher...

Again, before trying this kind of test, you should have ohmed out each
part of the circuit so that you, really, know in advance, that it will
be working in some particular way when you actually do test it.

keith



PinballPoor wrote:
Keith,

First and foremost, thanks for all the information you have supplied me
here to help me get started.

I do have a DIODE test feature on my DMM. It is a Radio Shack Digital
Multimeter , model 22-171.

In diode test, the meter will read 1.000 before starting. When I put the
red probe on the 80% silver/grey side and the black probe on the 20%
black ring side, the meter reading will swing down to a .479 reading.
When I reverse the probes on the diode, it has no change from the 1.000
reading on the VOM.

I pulled J1, J4 and J5 connectors off the AUX PWR DRVR BRD and was able
to test the "flow" of the existing diodes (which all tested in the .48
to .50 range. I mounted the repl diode in D35 position. I turned on the
game briefly and the TOP left BLUE FLASHER and CENTER TOP PLAYFIELD
YELLOW FLASHER still burn too BRIGHT in attract mode so will follow the
transistor testing you mentioned tomorrow.

Thanks again....

BTW, Do you think any damage occurred to Q24 on the CPU board? D35 and
D36 both seem to be connected out to Q24 8J3-4.


keith wrote:
The diode cathode is the banded end. You can find which end is which
using a DMM set to diode test function. Black to Banded (Red to
non-banded) and meter shows the forward voltage drop across the diode,
around .7v. Reversing the leads on the diode shows OL (out of range),
or non-conduction. Once you have found which end is the banded end,
then replace the dead diode with the new diode in the noted
orientation. You can determine the proper orientation either from the
silkscreened image on the circuit board, or from the schematic. In
this case, the black ring is 'probably' the cathode as the black is the
lesser width color... I, personally, would verify orientation with the
DMM.

Not knowing this game's particulars, I cannot comment on the COLOR of
the yellow/blue bulbs... however, looking at the schematic, I see that
there are two flashers that are controlled from the same grounding
transistor as the pop bumper that you hassled the circuit on ... The
manual page 69, over to the right, shows the 04A and 04C solenoid
controls... 04A is the right pop bumper, 04C is "Top p/f + 'ES'
flashers".

This section shows that several flashers are used:
Top p/f + 'ES' flashers
Top p/f + 'TA' flashers
Flame + 'TI' flasher
etc.

My experience with the flashers is that there will be a series load
reistor on the resistor board that attempts to limit current to these
bulbs (#89 & 906 flashers, as shown by page 54 Solenoids Flashers
listing), and that when they are on solid, that they are blindingly
bright... and will probably produce enough heat to melt anything around
them if left on sufficiently long enough. They are only momentarily
turned on during play, and flash then. (Some bulbs, maybe not on this
game, are continuously powered with a minute current to preheat the
filaments so that they will flash when fully turned on). The point
here is that if you see these bulbs on continuously, then you are
assured that their grounding transistor is shorted ON, and is a direct
connection to ground, which, after all, is what turns the devices on,
when they are powered by the A/C relay (or directly in the case of
non-switched solenoids... i.e., those always have power to the device,
and the ground-side of the circuit is a computer-controlled grounding
transistor...)

So, the grounding transistor for the right pop bumber, as shown by Aux
Power Driver Board schematic page 61, J1 (Upper left in the schematic,
pin 5, is Q7, controlling solenoid 04A and 04C, depending on where
power is supplied by the A/C relay.

You need to inspect Q7 with the DMM set on diode function. There are 6
total combinations of connections of the DMM to the transistor. Only 2
of the 6 combinations should show a .6v (or so, could be .5 to .7v)
forward voltage drop. All other combinations will show OL. You can
check this transistor with the plug removed from J1, J4, and J5 (J1
goes to the MPU, J4 and J5 go, J4P Pin 6 to pop bumper, and J5 Pin 5 to
flasher)... or you can remove the transistor from the circuit board.
If you find ANY OTHER COMBINATION or VOLTAGE DROP, then the transistor
is BAD so replace it. Schematic calls for TIP36C, PNP power
transistor, a common part from many pinball or electronic supply
places.

Also, if you haven't, then visit:
http://www.marvin3m.com/sys11/index.htm

and read ALL 3 SECTIONS.

keith

PinballPoor wrote:
Thanks for the reply...


I picked up a 1n1502 diode at RadioShack to replace the destroyed 1n1501
and it looks more like a little round bullet instead of the resistor
style diode.
The only marking on it is 3a and it is predominately SILVER/GREY in
color where the 3A marking is and the top20% of it is a black ring. I
don't want to assume that this is the anode side and put it in wrong.No
info on the pachaging either. ..Have you used these types? Then see what
sort of damage happens.
I did note when I turn on the game now and cycle it in COIL TEST, the
UPPER CENTER YELLOW BULB and the UPPER LEFT BLUE BULB burn so bright at
points within the test you'd swear the bulb was just gonna burn out so I
turned off the game....


.

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