(Topic ID: 21343)

pop bumper locks on when machine is powered up. Now fixed!

By boostedskex

7 years ago

Topic Stats

  • 40 posts
  • 11 Pinsiders participating
  • Latest reply 7 years ago by Betelgeuse
  • Topic is favorited by 3 Pinsiders


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#1 7 years ago

Hi guys. One of my pop bumpers pulls down and locks on when the game is powered up. Let me give some background. A few months ago I smelled something and then saw smoke so I turned the machine off. I found a burned coil on a pop bumper and burned transistor on the power driver board. So i installed a new Rottendog power driver board and finally today I installed a new coil from marco. I turned the machine on and saw the pop bumper lock on so I immediately turned off the machine. This is on my HS2. Can anyone shed light or give me play by play what to check.

-I looked at the switch and it isnt touching to cause it.
-the new coil is a AE-26-1200

#2 7 years ago

Usually this is a transistor problem but if you swapped driver boards and the same thing still happens then the problem might be the CPU board or something else. I've never heard of something like this not being solved by swapping a board.

#3 7 years ago

First I would check the wiring to your new coil. This would mean verifying you have the wiring correct in relation to the polarity of the coil diode. Always applied power should go to the striped end of the diode lug. Controlled ground from the driver board should go to the diode end lug that doesn't have the stripe. The other thing is to check that the diode is OK by lifting one end or cutting the diode away from the lug so you can check that diode is OK.

If the coil wiring and diode check OK, I would pull one of the coil lug leads off. Put the game into diagnostics and check for switch closure associated with this pop bumper.

#4 7 years ago

i put the 2 purple/ornge wires onto the side that is labeled 50+VDC and the brown/grn on the other side.

#5 7 years ago

here is a pic of it.


#6 7 years ago

Minnesota/Boosted.....check the manual/schematics. I'm almost 100% certain that there is no diode on the coil itself in this assembly, only on the switch.

The manual that IPDB has is extremely readable, I was just looking at it.

#7 7 years ago

Your wiring is correct and no, WPC coils of this era have no diode....

Open up the coin door which kills the high power voltage, go into diagnostic switch edge test, and make sure that the pop bumper switch is not showing made and toggles correctly each time....

Also, is the pop bumper locking on as soon as you power up the game (in attract mode) or only when you start a game. If the former, then you have a ground short on the coil, or a locked on transistor again (something in the PF may be taking out this transistor). If the latter, then likely a switch issue or less likely an MPU issue.

#8 7 years ago

Buzz out your wiring and power driver board with power off of course. My money is on a ground short in the wiring.

#9 7 years ago

thanks guys, hopefully with your help ill get this figured out.

As soon as I flip the switch to power the machine the pop bumper locks on. Should I open the coin door and turn it on?


#10 7 years ago

You say you switched out the coil later. Did you maybe leave the cooked coil in when you put in the new board? You may have shorted transistor on the new board if you did.


#11 7 years ago

If it's coming on as soon as you flip power on then you have a constant ground to the coil....Either a short or bad transistor. To determine which, pull the connector that goes to the coil from the driver board and power on. If it still comes on, then a playfield ground short. If not, then likely the transistor again.

#12 7 years ago

i disconnected the coil for that pop bumper and it plays perfectly fine just that one pop bumper then doesnt work. If that helps determine anything.

Oh OK ill pull that plug from the board and report back with what I find.

#13 7 years ago
Quoted from robertmee:

To determine which, pull the connector that goes to the coil from the driver board and power on.

Just to be sure, do you want me to pull the plug that has the thin brown/grn wire from the board? not the purple/orange wire.

brown/green wire is in plug J127.

#14 7 years ago

Correct...reattach coil wire and pull that plug. If it stays off on power up, then your board transistor may be bad again.

#15 7 years ago

OK i pulled plug J127 and at power up the pop bumper did not lock on. Now what? I appreciate the help robertmee

#16 7 years ago

Check your transistor on the board...With power off, DMM on continuity/ohms, put red lead on metal tab of transistor for that coil and black lead on ground strap or grounded mounting screws on board. If you have continuity/0 ohms, transistor is bad.

Another test, is pull the connector from the MPU to the driver board....Power up. If coil doesn't lock on then transistor is coming on due to erroneous signal from MPU. If coil still comes on, it's from circuitry/transistor on driver board.

#17 7 years ago

ok I did the second test for now. I pulled the ribbon cable from MPU to driver board. I powered up the machine and the pop bumper locked on. I will have to pick up a meter and do the first test. I guess its begining to look as if I am going to have to try and replace a transistor.

#18 7 years ago

Two demerits for owning a pin and not a meter

#19 7 years ago

I had a really nice one that I spent stupid money on from Snap-on but the supposed rechargable battery went bad and my snapon rep couldnt get a replacement hahah.

Ill take the lashings for not having one now though!!!

#20 7 years ago

I think robertmee is on the right track here. You have eliminated the CPU board by removing the ribbon cable between the power and cpu board. I would be testing that board transistor next. I'd also be wondering if there's something in the wiring that caused both transistors to get shorted.

You're definitely doing the right thing by powering off that machine as soon as you discover the coil issue. Also, if you replace one transistor, may as well fix both boards at same time

#21 7 years ago

Did you power up the game with the old coil and new board?

#22 7 years ago

Opps, sorry I had High Speed on my mind rather than the WPC version II that has the diodes for each coil remotely mounted.

#23 7 years ago

I picked up a meter and I feel I am checking the correct transistor for the pop bumper but I am getting a reading.


The brown/green wire wich is the 4th wire from the left on plug J127 comes from the pop bumper. I put my red lead on the transistors center post, trace goes to that part of transistor, and the black lead on the cabinets braided ground and I am getting a reading of 1.1

Am I doing something wrong or whats my next step?


#24 7 years ago

In ohm mode test impedance from the center lug to the ground pads or screws on the board. You get what? And compare it to a working one next to it. Then remove the solenoids connectors from the power board and test again.

#25 7 years ago

Yes, what markmon said....

#26 7 years ago

I tested the one in question and it shows 1.1 where as the others above it show 23.2 . I then pulled the plug and tested them again and the brown/grn still shows similar numbers at 1.4 and the others show around 5.0

Does that make sense to you guys or give you any idea where the problem may be stemming from?

Much appreciated

#27 7 years ago

Yes. Usually when you get a shorted transistor you get 0 ohms. But 1.1 is way too low. But the part after pulling the plug doesn't make sense. I'm not sure what the plug is. The solenoid connector into the board is what I'm suggesting you remove. Try to isolate the board from the wiring.

Or better yet, disconnect the power board entirely and out it on your work bench. Then retest the transistor tip to screw plate. Is it still 1.1? If so, replace it. After replacing it, test it again same way. Is it like the others? Reinstall everything. If the solenoid still fires up locked on, test the transistor again. If its now at 1.1 or shorted then you know something in your wiring is blowing the transistor. I guess we should start there and move forward.

#28 7 years ago

when I said plug i meant the J127 plug. I pulled that plug off of the power board. I tested the brown/grn wire at the power board plug (unplugged from the board) and then put the other lead on the VDC side of the coil (2purple wires) and I am getting close to 11.0 I then tested from one side of the coil to the other and I am still close to 11.0

Does that help with anything?

#29 7 years ago

I now have the board out. I ordered a few new transistors. Anyone have any other ideas on things to check before i put the board back in?

#30 7 years ago

And with the board out, the transistor shows 1.1 ohms from top to ground? If so replace it.

#31 7 years ago

On this rottendog board it uses 13N10L transistors. When checking them should i put red lead from meter on center leg of the transistor and the black lead on one of the outer legs or do i put black lead to the board where mounting screws go?

#32 7 years ago
Quoted from boostedskex:

On this rottendog board it uses 13N10L transistors. When checking them should i put red lead from meter on center leg of the transistor and the black lead on one of the outer legs or do i put black lead to the board where mounting screws go?

Sorry but I'm not sure how those test and I don't have a board here to look

#33 7 years ago

13N10L is an NPN, so put the positive lead on the middle leg and test to the outer legs. You should get .05 to .08 volts. Then put the negative lead on the middle leg and test to the outer legs. You should read an open.

#34 7 years ago

That'd be .5 to .8

#35 7 years ago

Correct, thanks. My 0 key sticks.

#36 7 years ago

Hi guys I received the transistors that I ordered from marco today. I removed the original transistor from the Rottendog board and compared to my new transistor and found they have different numbers on them.

Original transistor: 13N10L FQP 1B21AA
New Transistor: 13N10L FQP 1B16AL

When I ordered them I only saw the 13N10L number and didnt see the others. Are the new transistors compatible with the original transistors?

#37 7 years ago

A couple corrections to keep in mind here.
Rottendog does not use transistors for coil drives, they use FETs. The original Williams design used TIP102 and/or TIP36 darlington transistors.

To determine if a trans or a FET is bad, it's best to use the diode setting of your meter (not ohms.) Center leg (metal tab) on a FET or TIP gets the black DMM lead, red DMM to either leg. For TIPs you should get .4 to .6. On FETS i can't remember... just check it relative to the FETs next door. Different values indicate a problem.

Also HS2 does not have a coin door coil power interlock switch (that started with Twilight Zone.)

The new replacement transistor from Marco will work, but it's not as robust as the original. It can sink 16 amps, where the original can sink 21 amps. Not that it matters, but i always go with IRL540 transistors myself as replacements.

Also this all happened because you installed the new Rottendog board without replacing the original coil first. If the coil was shorted (which no doubt it was, due to the smoke), that will immediately fry the driver TIP or FET. So that's why this happened. It's always a good idea to check coil resistance with your meter when in doubt. Anything below about 5 ohms (this is a 50 volt game, 30 volt games can go a bit lower), and you need to replace any given coil.

#38 7 years ago

Thanks for a lesson cfh! Im always all ears! Ill install it and report back later tonight.


#39 7 years ago

I want to say thank you to all who had some input! I replaced the transistor and it is working as should now.


#40 7 years ago
Quoted from Betelgeuse:

You say you switched out the coil later. Did you maybe leave the cooked coil in when you put in the new board? You may have shorted transistor on the new board if you did.

I guess this would have been a 'yes'.

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