Firepower credit knocker problems

(Topic ID: 238390)

Firepower credit knocker problems


By mdhawkeye

6 days ago



Topic Stats

  • 12 posts
  • 4 Pinsiders participating
  • Latest reply 14 hours ago by Schwaggs
  • Topic is favorited by 1 Pinsider

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#1 6 days ago

Refurbing a Firepower I bought a few weeks back. It's my first pinball, but I've done several other similar projects (jukebox, helped my son on a Blackout, etc) so am somewhat familiar with the workings. The credit knocker solenoid was toast...completely fried, dark brown and the knocker stuck in the sleeve. I'm assuming in a past life the sleeve got dirty, the knocker stuck and burnt out the coil. Replaced the solenoid and still nothing. When I pulled the driver board, I noticed the trace for the solenoid (#14-> pin 4 on SJ9) was totally burnt out of board...YIKES!!!! I replaced EVERYTHING in the path of that circuit...the resistors R68, R69 and R70, and the transistors Q40 and Q41. I used a tiny jumper wire to go from the emitter of Q41 to pin 4 to replace the trace. So far I've blown 3 TIP122 transistors. I figured the first was sloppy soldering on my part, the second I pulled because it was getting REALLY hot during the solenoid test, and the third sparked and cracked in half during power up :-O I tested voltage as best I can with a digital multimeter coming out of the resistors and the Q40 BEFORE Q41 and all seems to be in spec as best as I can tell (hard with DMM in the back box...suggestions welcome). Voltage off of pin 4 all over the map again because of my tools but off the emitter of Q41 when I can reach it seems correct, between 32-35V. I know the ICs in the path are doing the correct thing (used a logic probe to see that they were pulsing properly). I've looked at most wiring coming from board to molex, and molex to knocker and dont see anything obvious. I'm kinda lost now, and would appreciate the expertise of those who have been here before.

Thanks
Andy

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#2 6 days ago

I had a similar problem on a Wms driver board. Read the resistance between the legs of TIP 122 transistor, and compare those readings to a few of the other transistors.

What I found was a carbon path between two of the legs of the TIP 122, with the resistance low enough to keep the solenoid energized, which it turn, burned up the TIP. I ended up removing the carbon (burned up) portion of the board to remove the path. Once that was done, I used two part epoxy to fill the hole I created. During the entire evolution, I kept checking the resistance reading to make sure I cleared the problem, and that I did not create another problem in the process. I was fortunate in that I did not have to remove the eyelet in the thru hole. If yours is gone or removed, there are methods you can use to "stitch" around the missing eyelet. There are a few threads somewhere on the site - look up solder stitching or eyelet repair - I don't remember which.

I remember this was an extremely frustrating issue, and only one of two drive me nuts issues with that particular machine. Let us know what you find.

#3 6 days ago
Quoted from mdhawkeye:

Refurbing a Firepower I bought a few weeks back. It's my first pinball, but I've done several other similar projects (jukebox, helped my son on a Blackout, etc) so am somewhat familiar with the workings. The credit knocker solenoid was toast...completely fried, dark brown and the knocker stuck in the sleeve. I'm assuming in a past life the sleeve got dirty, the knocker stuck and burnt out the coil. Replaced the solenoid and still nothing. When I pulled the driver board, I noticed the trace for the solenoid (#14-> pin 4 on SJ9) was totally burnt out of board...YIKES!!!! I replaced EVERYTHING in the path of that circuit...the resistors R68, R69 and R70, and the transistors Q40 and Q41. I used a tiny jumper wire to go from the emitter of Q41 to pin 4 to replace the trace. So far I've blown 3 TIP122 transistors. I figured the first was sloppy soldering on my part, the second I pulled because it was getting REALLY hot during the solenoid test, and the third sparked and cracked in half during power up :-O I tested voltage as best I can with a digital multimeter coming out of the resistors and the Q40 BEFORE Q41 and all seems to be in spec as best as I can tell (hard with DMM in the back box...suggestions welcome). Voltage off of pin 4 all over the map again because of my tools but off the emitter of Q41 when I can reach it seems correct, between 32-35V. I know the ICs in the path are doing the correct thing (used a logic probe to see that they were pulsing properly). I've looked at most wiring coming from board to molex, and molex to knocker and dont see anything obvious. I'm kinda lost now, and would appreciate the expertise of those who have been here before.
Thanks
Andy[quoted image][quoted image]

When these transistors are burning, is the knocker firing?

Do not solder the jumper wire between the pins of the transistor. Scrape the solder mask off the remnants of the burned trace, directly above the transistor. Leave the leg of the new transistor long and bend it towards the center of the board, following the old trace. Solder the long leg to the old trace and the patch wire to the long leg.

Power up the board with the driver board connector that runs to the coils removed and see if the transistor still burns or over heats. If it does, you have a problem with the board.

While you have the connector removed, measure the power to the knocker coil and make sure you have power connected to the banded side of the coil. The other wire on the coil runs to the connector on the driver board you have removed.

If all this checks, and the transistor does not burn up with the driver board connector removed, turn the game off, re-connect the driver board connector and turn the game on. If you hear the knocker energize, quickly turn the game off. This means the coil is still locking on and we need to troubleshoot further.

#4 6 days ago
Quoted from Schwaggs:

When these transistors are burning, is the knocker firing?

Nope, it never engages at all

Quoted from Schwaggs:

Power up the board with the driver board connector that runs to the coils removed and see if the transistor still burns or over heats. If it does, you have a problem with the board.

One of the attempts I made yesterday, I did just this, and No, it did NOT get hot

I plan on looking at this again this afternoon. Will post the results. Thanks for your help!
Andy

#5 6 days ago

FRIED ANOTHER ONE ! hope there wasn't collateral damage to neighboring bits. This one came complete with smoke!

schwaggs - Tested with the plug OFF the board. Transistor did NOT get hot, maybe warm but not like yesterday. I had it firing on the self test for quite a while. I don't think it got any hotter than the one next to it when I was testing it as well. Voltage at the knocker coil with the plug removed was ~34VDC.

When I powered up, I did NOT hear the coil energize or see the plunger get pulled up. I DID see smoke almost immediately coming off board. I pulled the board again to take a look. I don't see any apparent damage, but will replace the things in that circuit again.

I'm all out of spare TIP122, so will have to wait for my order from Mouser to arrive to try again. Any pointers appreciated.

Andy

#6 5 days ago

Did you confirm the power wire is soldered on the correct side of the knocker coil (banded side of the diode)? It sounds like you have power on the wrong side of the coil (diode) which ends up looking like a direct short to the transistor.

Get TIP 102s. Slightly more power carrying capacity at virtually the same price.

#7 5 days ago
Quoted from Schwaggs:

Did you confirm the power wire is soldered on the correct side of the knocker coil (banded side of the diode)?

Yep...the wire coming from the connector (pin 4, brown/blue) is connected to the banded side of coil

Already ordered TIP122s Next time!

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#8 5 days ago

Well there you go. Schwaggs for the win (as usual). Here's mine.

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#9 5 days ago

Oops. Double.

#10 5 days ago

Thanks for the picture travish ! As they say a picture is worth a thousand words.

mdhawkeye - Power is the red wires, the driver board wire and associated transistor grounds the coil, turning it on. Reverse those coil wires and you should be all set.

#11 22 hours ago

Thanks for the help...finally got back to this (life gets in the way of the important things... )... Swapped the wires, plug the board back, and KABOOM! Blew it again, but really bad this time. I had unfortunately closed the backbox so i could lift the table to see if the solenoid got energized....Thus I missed the explosion and the small fire that ensued! Obviously something more going on than just my stupidity in wiring the power backwards.

The little incident took out quite a few other nearby components. I replaced a bunch of resistors and a few transistors in the vicinity. and verified that everything back to where I started except that now I have aboard with quite the scorch mark. I probably need to dremel it out and fill with epoxy.

Before I do anything else though, I need to figure out root cause. I can only think that something in the wiring from the board to the solenoid got screwed up when the original solenoid went bad. I'm going to have break open that bit of harness and inspect more carefully.

Other options I can think of: 1) Do nothing, live without credit knocker (that doesn't fit my anal retentive personality) 2) repair board 3) send board OUT for repair and diagnosis 4) Is it possible to re-use one of the UNUSED solenoid circuits on this board that firepower ignores (i think 2,3,4 maybe). That would mean nasty jumper wires but I have one of those anyway.

All suggestions welcome. Thanks again for the assist.

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#12 14 hours ago

Its not a problem with the board since the transistor does not blow when you have the connector removed that leads to the solenoids.

Check the diode on the coil, it may be failed shorted from all the current that ran through it when it was connected backwards.

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