(Topic ID: 31266)

TECH: Bally Star Trek - Coil Mayhem


By pinball_faz

8 years ago



Topic Stats

  • 10 posts
  • 4 Pinsiders participating
  • Latest reply 5 years ago by barakandl
  • Topic is favorited by 2 Pinsiders

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Linked Games

#1 8 years ago

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

But...
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]
knocker works

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
the game.
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.
TIA,
faz

#2 8 years ago

Try re-pinning the j4 connector on the MPU board.

If u don't have the pins/tools to do it, try cleaning the header and extract the pins from the connector and clean them up with some 400-600 grit.

Start simple, then move on to more complex trouble shooting. Transistors, the U11 pia chip on the MPU board, bad sockets, fun stuff like that.

Most times, a good cleaning of the connector pins will do the trick temporarily until you can re-pin them.

#3 8 years ago

Well, I feel silly.

I tore through Clay's guide and saw the part about checking J4. But since I was in solenoid mode...I was working with J4 on the solenoid board.

I saw your note and said....OHHHHHH the "MPU" board.
Nuts... I was traveling last week; I just had a chance to try it out.

A quick reseat of the connector ...and it all works fine.

I pulled the connector again and gave all the pins a brush with some 600 grit paper. All good.

I don't have any pins...I'll order some with my next parts order.

Thanks for the note...you got me in the right direction!
faz

2 years later
#4 5 years ago

Hi. I am having the same exact issue as described by the OP, but on my KISS. Same set of wrong coils are firing when the switches are pressed. I have an alltek MPU and J1 and J4 are repinned on the MPU. game was working great and then I moved it and now it's all messed up after reconnecting.

Do you think I should try and swap the alltek board with another?

Something else to note. when J5 on the SDB is plugged in, the kickout does not work properly... instead the game fires something else. When J5 is unplugged, the kickout works, but the other coils don't obviously b/c they are unplugged. that makes me wonder is it something under the PF?

I need help big time. thanks.

#5 5 years ago

oh, also I swapped out the SDB and no difference. I had it with me, so tried, but no luck.

#6 5 years ago

any thoughts?

#7 5 years ago

MPU J4 connector pins male or female.

Driver j4 female connector pins

#8 5 years ago

I redid the entire plug and the alltek board is new. so that leaves me with little idea. I will redo all the wires that go off the j4 on the SDB and hope the problem is fixed... I wonder what the nature of the issue. if one wire is broken, let's just say cut. would this cause the symptoms. I find this logic hard to figure. thanks. at least I have one idea.

#9 5 years ago

i put it a new alltek sdb and that solved the problem. strange that two different orig sdb did not work. one came from a working machine. I have always questioned how good alltek mpus are with orig sdb. i prefer to pair either orig or alltek together. I should have stuck to my previous thinking. thanks for the help.

#10 5 years ago
Quoted from Anshiin:

i put it a new alltek sdb and that solved the problem. strange that two different orig sdb did not work. one came from a working machine. I have always questioned how good alltek mpus are with orig sdb. i prefer to pair either orig or alltek together. I should have stuck to my previous thinking. thanks for the help.

your driver board j4 has broken solder joints on it.

I will buy your MPU and driver board you replaced with Alltek.

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