I was really hoping I could do this one myself. Digging through Clay's guide, I'm at a loss where to go next.
Coils are not behaving.
All TP test per spec on MPU and Solenoid Driver Board
48.1 V at both lugs of all coils
ball launch coil will not fire
lower(center) popper swich fires left sling kicker coil, lower (center) popper coil does not fire
left(upper) poper switch fires RIGHT (upper) poper, left (upper popper coil does not fire)
right sling switch activates drop reset, right sling kicker does not fire
right(upper) popper switch fires right (upper) popper coil [correct function]
Left sling switch activates left sling kicker [correct function]
In test, left (upper) and center (lower) coil do not fire. Right (upper) coil fires twice.
saucer eject coil works
both flipper work
Clay's guide specifically calls out my issue..explaining the cause, but these are what I would call "fun facts". Any clues on how to fix?
Quoth the guide...
"Wrong Coil (or No Coil) Energizes.
This is an interesting problem that isn't very easy to diagnose. For example when a slignshot
switch closes, the drop target bank resets. Or perhaps one particular coil never engergizes in
This is often due to the PB0-PB3 encoded lines that come from MPU PIA U11 or the line
select. These four bits are encoded by the PIA, sent to the Solenoid Driver board (SDB), then
unencoded by the SDB U2 74154 chip, and the appropriate solenoid is energized. If one of
these four bits is lost in the data path between the MPU and the SDB, the unencoded number
will be wrong, and the incorrect solenoid (or no solenoid) is energized.
Another test of this problem is to put the game in coil test. If coil(s) fire twice (same coil for
two solenoid numbers), or does not fire at all, there is potentially a problem with the
PB0-PB3 encoded lines."
I should note, the game was working just fine. One day, it stopped working.