(Topic ID: 150388)

Twilight zone jet bumper not working

By dzrossi

5 years ago


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  • 13 posts
  • 4 Pinsiders participating
  • Latest reply 5 years ago by GRUMPY
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#1 5 years ago

I am looking for ideas. I just bought a twilight zone the lower jet bumper is not working. Upper bumpers work. At coil I have 70 volts at each prong which indicates I have power and I believe coil is good. Power board is rotten dog replacement. Q52 transistor test good. No errors reported by game. When I test nothing happens. When I test Switch it works. I am out ideas. Should I try swapping coils to make sure coil not bad. Should I replace transistor ?

#2 5 years ago

Whats the number on the transistor?

#3 5 years ago

i believe it is q52 which is the solenoid 12 circuit. I check connectivity of the wire running from coil to 127-5 connector to board. It appeared to be good.

#4 5 years ago

If you ground the metal tab of the transistor, does the coil fire?

That will test everything from the transistor to the coil. If yes, then the problem is either with that transistor or the pre-driver transistor or the address decoder on the power board. If the coil does NOT fire, then the problem is that transistor through the molex connector to the playfield.

#5 5 years ago

Reseat connects on boards worked for me I had similar issue.

#6 5 years ago
Quoted from Coyote:

If you ground the metal tab of the transistor, does the coil fire?

If its a TIP, I wasn't sure if the board was original or not. That's why I asked for the number on the actual transistor.

#7 5 years ago
Quoted from GRUMPY:

If its a TIP, I wasn't sure if the board was original or not. That's why I asked for the number on the actual transistor.

Ah! Good point, I missed that. I'm so used to working on the older boards. Sorry!

#8 5 years ago

When I check connectivity of wire I did reseat the J 127 connector. No luck. The transistor is a TIP102. I did not ground when machine was powered on. I did when it was off. There was no connectivity which I believe indicated transistor is not shorted out. Coil is not engerizing at all so not surprise by result. I am apprehensive about completing circute when powered on as it is 70 volts DC. Is there a way to test pre transistor. Is there a way to test address decoder (never heard of that) Board is a Rotten Dog after market so I assume it is good

#9 5 years ago
Quoted from dzrossi:

I am apprehensive about completing circute when powered on as it is 70 volts DC. Is there a way to test pre transistor. Is there a way to test address decoder (never heard of that) Board is a Rotten Dog after market so I assume it is good

When you 'complete' the circuit, you're grounding it, not applying 70 volts. It's a perfectly fine test, back in the 90's, that is what was done to verify problems.

Since it's a RD, you'd have to check their schematics..

#10 5 years ago
Quoted from dzrossi:

Board is a Rotten Dog after market so I assume it is good

Why, everything can break.

Quoted from dzrossi:The transistor is a TIP102.

Then you can briefly ground the tab completing the circuit and firing the coil assuming the wiring is good.

Quoted from Coyote:Since it's a RD, you'd have to check their schematics

This a good idea!

Quoted from dzrossi:Is there a way to test pre transistor

Yes, but need RD schematics which I don't have.

#11 5 years ago

thanks for everyones suggestions when I get home from my current business trip I plan to test the coil and transistor as suggested above.

#12 5 years ago

Update. I grounded the q52 transistor and the bumper coil energized and did not shut off. I called Jim at Rotten Dog to confirm what transistor was on the board. I am glad I did Jim was extremely helpful. As it turns out transistor was not a TIP102 it was a IRL520. There are no pre transistors on the board so that is all I have to replace. Jim suggested I replace coil as that might have caused the issue to begin with. Better safe than sorry. So I order transistor from great planes electronics. And coil from marco specialties.

#13 5 years ago
Quoted from GRUMPY:

Whats the number on the transistor?

This is why I asked for the number.

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