Hey guys, I have an issue that I'm guessing is pretty common, and am hoping one of you ca tell me right quick what the issue is before I do too much digging.

I just put my Mr. and Mrs. Pac-Man Pinball back together, and it booted fine, though I had no solenoids functional, as the under-the-playfield fuse was removed. I've got a couple lamps locked on, but nothing major.

When I plugged the displays back in, they came up just fine, and worked for about ten seconds, before the fuse on the solenoid driver board blew.

Any thoughts as to what would cause this?

I subsequently replaced the playfield fuse, and the solenoids all work fine, for what it's worth.

Thanks in advance!

Collin

#2 8 years ago

CNK

CNKay

Pinside member

East Aurora, NY

14y 72,050 3,444 11 10

I guess I would add one display at a time waiting a few minutes before adding an additional display. Until you find the display that causes fuse to blow. Then undo all and try that one first again. Of course you will waste two fuses but.

#3 8 years ago

CDF

Collin

Pinside member

Columbus, OH

10y 113K 5,183 29 64

Will do. So you think it is likely tied to a single display?

I know that seems logical; I've just never had a display blow a fuse before, let alone on the driver board. Plus, nothing in this game is 'tried-and-true' as I just got it thrown back together tonight. I half thought I had a connector wrong or something, though that seems unlikely, as stuff is basically working.

#4 8 years ago

CDF

Collin

Pinside member

Columbus, OH

10y 113K 5,183 29 64

Definitely seems like CNKay has steered me in the right direction.

I have plugged in two different displays individually. Each time, it has blown a fuse. On each display, the first comma has lit up VERY bright; I'm guessing whatever drives this is the source of my problems. Seem feasible?

#5 8 years ago

RIK

Meteor_Rick

Pinside member

Birmingham, AL

8y 39,650 28 11

your High voltage regulator circuit might be bad and is in an overvoltage condition. stop trying. you might permanently damage the displays. do this to check: unplug the displays and measure the test points on the regulator/driver board. make sure your DVM is set to measure 300v range. TP4 should be 230vdc or so. TP2 is the output to the displays and should be no more than 190vdc. BE CAREFUL PROBING THIS CIRCUIT! THE VOLTAGE IN THIS AREA IS HIGH AND IT HURTS! Rick

#6 8 years ago

CDF

Collin

Pinside member

Columbus, OH

10y 113K 5,183 29 64

I tested the voltages before plugging the MPU in, and they were within reasonable tolerance (I want to say 200-220v, and 180v or so)

#7 8 years ago

RIK

Meteor_Rick

Pinside member

Birmingham, AL

8y 39,650 28 11

OK good. Then make sure your display connectors are keyed correctly and not plugged in backwards. Been a long time, but theres something thats ringing a bell about the commas being on like that. Like maybe using Stern 7 digit displays or maybe 6 digit displays mixed in with the 7's. I dunno. its late and I cant think anymore! Will check on it tomorrow.. Good night and good luck. Rick

#8 8 years ago

CNK

CNKay

Pinside member

East Aurora, NY

14y 72,050 3,444 11 10

OP
Quoted from Collin:
I have plugged in two different displays individually.

I was expecting one display to pop a fuse but all others to work. Not two different displays popping fuse.

Rick is totally correct the fuse 1/10a in the driver board is for HV so be careful.

Might want to double check the connection on the driver board. Ie off by one pin etc.

Just seems to be connection issue or something easy.

#9 8 years ago

AMS

barakandl

nvram.weebly.com

11y 130K 10,219

Take each display. Measure resistance form the high voltage test point to ground and five volt test point. Look for one that is shorted.

I rarely find these display get shorted internally. 9 times out of 10 it is a soldering mistake from a reflowing the header pin.

The comma is driven with out specific logic from a decoder. There are two diodes that allow the comma to turn on when the appropriate digits are lit up. Check the diodes for shorted condition if the comas are locked up (in a game up condition, not until after it boots).

#10 8 years ago

CDF

Collin

Pinside member

Columbus, OH

10y 113K 5,183 29 64

Quoted from barakandl:
Take each display. Measure resistance form the high voltage test point to ground and five volt test point. Look for one that is shorted.
I rarely find these display get shorted internally. 9 times out of 10 it is a soldering mistake from a reflowing the header pin.
The comma is driven with out specific logic from a decoder. There are two diodes that allow the comma to turn on when the appropriate digits are lit up. Check the diodes for shorted condition if the comas are locked up (in a game up condition, not until after it boots).

Would you suspect a header pin soldering mistake on the SDB? Or on a couple of the displays?

#11 8 years ago

AMS

barakandl

nvram.weebly.com

11y 130K 10,219

The driver board is typically going to either work or have a shorted HV section. A shorted HV section just makes the +185 read at +230. It won't blow the fuse on the driver board.

The small fuse on the driver board (0.1875a to 0.25a fuse) only blows when the short/ over current is past regulation (ie short on display). Plug in the displays one by one and see which one blows the fuse, or do the resistance check i mentioned in my previous post. A display the blows fuses is probably has a 185 to gnd short.

#12 8 years ago

CDF

Collin

Pinside member

Columbus, OH

10y 113K 5,183 29 64

I tried two different displays, one at a time, and both of those blew fuses

#13 8 years ago

---

ForceFlow

Pinside Moderator

9y 236K 29,431 267 1 18

OP
Quoted from Collin:
I tried two different displays, one at a time, and both of those blew fuses

Could be a problem on both of them--it doesn't necessarily have to be restricted to one.

#14 8 years ago

ZDG

gutz

Pinside member

9y 76,050 1,667 27 2

OP
Quoted from Collin:
Would you suspect a header pin soldering mistake on the SDB? Or on a couple of the displays?

In my infancy, I had a solder bridge across the SDB header (on the top right) that caused the HV fuse to blow immediately.

#15 8 years ago

AMS

barakandl

nvram.weebly.com

11y 130K 10,219

OP
Quoted from Collin:
I tried two different displays, one at a time, and both of those blew fuses

Did you repin the top right connector of the the driver board? If so double check for problems.

#16 8 years ago

CDF

Collin

Pinside member

Columbus, OH

10y 113K 5,183 29 64

Resolved! It turns out I had swapped two of the connectors that go to the display board. I think this may be a game-specific issue that wouldn't be feasible on other Bally games.

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