(Topic ID: 297612)

Gottlieb System 80B Switch Matrix ROW not Working Monte Carlo

By jk

80 days ago



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  • 4 posts
  • 2 Pinsiders participating
  • Latest reply 78 days ago by jk
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#1 80 days ago

I have a Gottlieb Monte Carlo with clean boards that boots and will play if I move the ball out of the trough outhole but there is a full row of switches that won’t register (strobe 6: #2 #4 #7 #9 drop targets, left return rollover, trough outhole) . In test mode with pinballs removed, all switches show open. Is this a board issue? (one of the Z chips) or should I be looking for something else like connector, wire continuity, under playfield wire, diode board etc? Thanks I’m not familiar with the 80B boards. I don’t have a scope. Is there a certain Z Chip associated with this switch matrix row that I can try to change? I don’t see any broken wires associated with any of these switches. Any help would be appreciated thanks.
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#2 80 days ago

I would suspect the 7404 at Z11.
A logic probe would help you know with certainty.
You can also "diode test" that chip with a meter.

Meter on diode check.
Board out of game or connectors removed.
Red on lower left pin.
Black on other pins one at a time.
.4-.7 should be the reading on each pin except the upper right pin.

--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#3 80 days ago
Quoted from ChrisHibler:

I would suspect the 7404 at Z11.
A logic probe would help you know with certainty.
You can also "diode test" that chip with a meter.
Meter on diode check.
Board out of game or connectors removed.
Red on lower left pin.
Black on other pins one at a time.
.4-.7 should be the reading on each pin except the upper right pin.
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

Thanks ChrisHibler, with the board removed I used diode test on my meter on Z11 and some legs of that chip are reading .184 and others are .526. One leg (2nd down from top left) is reading “0”. I’ll try replacing the 7404 at z11.

#4 78 days ago
Quoted from ChrisHibler:

I would suspect the 7404 at Z11.
A logic probe would help you know with certainty.
You can also "diode test" that chip with a meter.
Meter on diode check.
Board out of game or connectors removed.
Red on lower left pin.
Black on other pins one at a time.
.4-.7 should be the reading on each pin except the upper right pin.
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

Thanks ChrisHibler, I removed z11 and socketed in a new 7404 and everything works great!

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