(Topic ID: 237728)

TIP-102 Fires When Grounded, Doesn't Work in Test

By herbertbsharp

3 years ago


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Topic Stats

  • 16 posts
  • 9 Pinsiders participating
  • Latest reply 2 days ago by Gorgar666
  • Topic is favorited by 1 Pinsider

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#1 3 years ago

I've got a solenoid not firing in game, I've got continuity and power, and when I ground the TIP102 the solenoid fires. It doesn't fire in the game or in test mode. Does this mean the TIP102 is bad or should I look elsewhere? The ones I've seen go bad ground out and lock on.

Thanks!

#2 3 years ago

Use the multimeter and see if you get voltage when the transistor is supposed to fire.

If yes, the problem is somewhere between the transistor and the coil.

If no, I would go up the logic path and look at the chip that drives the transistor. Sometimes those can fail.

#3 3 years ago
Quoted from ForceFlow:

If no, I would go up the logic path and look at the chip that drives the transistor. Sometimes those can fail.

Cool, thanks! I'll dig into it. I'm leaning towards this

#4 3 years ago

Grounding the tab of the transistor only verifies the connection between the transistor and the coil, it does not test the transistor itself.

Transistors can fail open, so I would check that first.

#5 3 years ago
Quoted from dothedoo:

Grounding the tab of the transistor only verifies the connection between the transistor and the coil, it does not test the transistor itself.
Transistors can fail open, so I would check that first.

Thanks! I tested the transistor according to pin wiki and it looks good, I think . I think everything is good between it and the solenoid too, so I guess it must be upstream from the TIP-102. I'm going to try breaking out the schematics book to see if I can follow it

#6 3 years ago
Quoted from herbertbsharp:

Thanks! I tested the transistor according to pin wiki and it looks good, I think . I think everything is good between it and the solenoid too, so I guess it must be upstream from the TIP-102. I'm going to try breaking out the schematics book to see if I can follow it

Did you check the switch that tells the solenoid to fire? It could just be that the switch is bad...

What coil is the problem?

#7 3 years ago
Quoted from PinMonk:

Did you check the switch that tells the solenoid to fire? It could just be that the switch is bad...
What coil is the problem?

In test mode, you can just fire the coil from the menus.

#8 3 years ago

Perhaps time to pull out that digital probe and see where the circuit is breaking down. All the solenoid boards work with similar circuits. Scroll down to the part about the driver board:
http://homepinballrepair.com/index.php/how-to-use-a-digital-logic-probe-for-pinball-repair/#bally

#9 3 years ago
Quoted from ForceFlow:

In test mode, you can just fire the coil from the menus.

Right, I forgot he said it didn't fire in coil test. That would eliminate the switch.

Knowing what coil it was would help...

-2
#10 3 years ago
Quoted from dothedoo:

Grounding the tab of the transistor only verifies the connection between the transistor and the coil, it does not test the transistor itself.
Transistors can fail open, so I would check that first.

Grounding the tab of the transistor does in fact test the transistor, otherwise it would not fire the coil. If it failed open, it would lock the coil on and likely blow the fuse. Grounding the tab basically confirms that everything is good between the transistor and the coil. Since it does not work in coil test mode, that says to me that it's upstream from the TIP102. Next 2 things to check are your pre-drive transistor and then if you get good readings on the pre-drive transistor with your meter, my money would then be on the 74LS374 chip that drives it.

#11 3 years ago
Quoted from PinMonk:

Right, I forgot he said it didn't fire in coil test. That would eliminate the switch.
Knowing what coil it was would help...

It's the Thing kickout on an TAF, looks like Q67 & 68 to me, grounding Q67 fires the solenoid properly.

Quoted from lhammer610:

Perhaps time to pull out that digital probe and see where the circuit is breaking down. All the solenoid boards work with similar circuits. Scroll down to the part about the driver board:
http://homepinballrepair.com/index.php/how-to-use-a-digital-logic-probe-for-pinball-repair/#bally

Oh cool I've never seen that, thank you. That looks like a very good test procedure. I don't have a logic probe, I'll have to look into grabbing one.

#12 3 years ago
Quoted from RazerX:

Grounding the tab of the transistor does in fact test the transistor, otherwise it would not fire the coil. If it failed open, it would lock the coil on and likely blow the fuse. Grounding the tab basically confirms that everything is good between the transistor and the coil. Since it does not work in coil test mode, that says to me that it's upstream from the TIP102. Next 2 things to check are your pre-drive transistor and then if you get good readings on the pre-drive transistor with your meter, my money would then be on the 74LS374 chip that drives it.

Thank you, I'll look at that one. I'm thinking you are probably right.. ughh... chips... I knew I'd have to do one sooner or later.

#13 3 years ago
Quoted from herbertbsharp:

Thank you, I'll look at that one. I'm thinking you are probably right.. ughh... chips... I knew I'd have to do one sooner or later.

If you replace the chip, socket it. Probably won't be the last time it needs replacement.

#14 3 years ago

I had similar problem with Corvette. Turned out to be a bad contact on ribbon calble between cpu and driver board. You might want to check input and output of LS374 before changing it.

#15 3 years ago
Quoted from RazerX:

Grounding the tab of the transistor does in fact test the transistor, otherwise it would not fire the coil. If it failed open, it would lock the coil on and likely blow the fuse. Grounding the tab basically confirms that everything is good between the transistor and the coil. Since it does not work in coil test mode, that says to me that it's upstream from the TIP102. Next 2 things to check are your pre-drive transistor and then if you get good readings on the pre-drive transistor with your meter, my money would then be on the 74LS374 chip that drives it.

Well, if the tab of the transistor is tied directly to the pin that goes to the coil (which it is) then grounding it will absolutely fire the coil if the wiring is all okay, you are completing the circuit for the transistor. To actually test the transistor (since it's an NPN transistor) you would have to apply positive bias voltage to the base sufficient to cause the Collector to Emitter current flow. Also if the transistor fails open it will never fire the coil, failing shorted will lock on the coil and blow a fuse / melt a coil.

3 years later
#16 2 days ago

How to test a loose Tip102 with a multimeter. What should the reading be? Actually bought a batch at a really good price and I want to test that they’re not counterfeit.

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