Coil Stuck On - Baby Pac-Man


By pinmods

4 months ago


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  • 11 posts
  • 4 Pinsiders participating
  • Latest reply 4 months ago by Biffbar
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#1 4 months ago

Restoring my Baby Pac-man and ran into an issue when powering it up for the first time...

The center of the 3 coils on the 5 post drop target goes instantly to on right when I powered up.

I turned it off to prevent any damage and replaced the coil. Powered up again - same problem.

Thoughts?

#2 4 months ago

Bad transistor? Or did you check them already? In the past when I had a coil energize when I powered the game on it’s been a bad transistor

#3 4 months ago
Quoted from Bigbad:

Bad transistor? Or did you check them already? In the past when I had a coil energize when I powered the game on it’s been a bad transistor

I THINK I checked it correctly. Q33

Schematics here:
https://ia601409.us.archive.org/0/items/ArcadeGameManualBabypm/babypm.pdf

#5 4 months ago
Quoted from vid1900:

Check transistor like this:
https://pinside.com/pinball/forum/topic/vids-guide-quick-bally-driver-board-repair-bulletproofing

Or just send you the board for you to bulletproof?

#6 4 months ago

.575 on one side
.667 on the other

#7 4 months ago
Quoted from pinmods:

Or just send you the board for you to bulletproof?

Might not be the board.

-

Pull the Coil fuse and then put the game in Switch Test.

Make sure there are no balls installed.

Are there switches stuck on? Do all the switches give back the correct switch number?

-

Is the new coil wired in reverse? Look at the band on the coil diode, as they can be soldered on either way.

#8 4 months ago
Quoted from vid1900:

Might not be the board.
-
Pull the Coil fuse and then put the game in Switch Test.
Make sure there are no balls installed.
Are there switches stuck on? Do all the switches give back the correct switch number?
-
Is the new coil wired in reverse? Look at the band on the coil diode, as they can be soldered on either way.

No stuck switches. Coil diode on all coils(I have 3 spares from a parts machine) are facing the correct direction.

I changed all the connectors on the wiring harness and thought that maybe I had a wire in the wrong spot. Triple checked and they are all correct.

It's gotta be something on the board.

#9 4 months ago

Not sure if it helps but when I pulled off the J8 connector, the coil releases...

#10 4 months ago

Replaced the transistor. It lasted 3 power ups before blowing again. Thoughts?

#11 4 months ago
Quoted from pinmods:

Replaced the transistor. It lasted 3 power ups before blowing again. Thoughts?

First thoughts: Could have been a bad transistor to begin with, then it became a coil diode issue (back EMF). The wiring to the coil terminals got mixed up, or the diode polarity was mixed up (coil was recently replaced).
Other thoughts: Perhaps too much current being drawn from a short in the wiring or in the coil winding. Is the correct solenoid circuit fuse in place (why wouldn't the fuse blow)? Was the game playing ok with the new transistor, up until it failed. Miss-marked or re-marked transistor, try another one. Something upstream of that transistor is locking it on.

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