(Topic ID: 285613)

LOTR flipper transistor blowing


By Pinballjimmy

6 days ago



Topic Stats

  • 17 posts
  • 5 Pinsiders participating
  • Latest reply 3 days ago by Pinballjimmy
  • Topic is favorited by 1 Pinsider

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#1 6 days ago

I know there are plenty of posts about this but I'll tell how this happened and what I've done troubleshooting.

This started with having an weak left flipper. It would make shots but when the ball lands on it coming from the left loop the flipper would bounce down slightly and bounce back. Sometimes when the ball is travelling especially fast would cause the flipper to collapse. While holding the flipper button down I could push the flipper down with one hand. Then the flipper would act as if it only had the hold power until I released and pressed in again the flipper button.

I rebuilt the flippers; full kit, EOS switch properly gapped, new sleeves, new bat bearings. Everything new but coils. This did improve snappiness but the weak issue remained.

I went into test mode and the EOS switches register properly. I swapped sides on the flipper buttons and nothing changed. I pulled the wiring from the flipper coils and ran alligator wires from the left wires to the right coil and this made the right flipper behave weak just as the left side had been. I ran alligator wires from the right flipper wiring the the left flipper coil and it was strong. I put everything back the way it should be.

From this I feel I had felt I eliminated in the cabinet and there was a problem on the board. From this assumption I pulled the board and replaced Q15 with a transistor IRL540N. Put the board back in and the flipper was immediately strong as it should be. It was just as strong as the one on the right. However it immediately blew the resistor because the flipper would not go back down after I let the button go. It would drop back down when I opened the coin door so its not a mechanical bind.

At this point I replaced the diode on the coil ensuring I did not reverse it. I replaced the transistor again. I buzzed out the legs on the new transistor to the proper points on the board and there is continuity. Turned on game. Flipper is strong but again immediately blew the transistor. Flipper locking up when the coin door is closed.

The flipper coils are the 090-5020-20T. Left resistance is 3.2 ohms. Right is 3.4 ohms. I've triple checked and wiring to the coils is correct. I did not reverse anything pulling and replacing the wires to the coil lugs.

Side note, the original transistor I pulled was not the original transistor to the game as there was evidence it had been replaced.

#2 6 days ago
Quoted from Pinballjimmy:

I know there are plenty of posts about this but I'll tell how this happened and what I've done troubleshooting.
This started with having an weak left flipper. It would make shots but when the ball lands on it coming from the left loop the flipper would bounce down slightly and bounce back. Sometimes when the ball is travelling especially fast would cause the flipper to collapse. While holding the flipper button down I could push the flipper down with one hand. Then the flipper would act as if it only had the hold power until I released and pressed in again the flipper button.
I rebuilt the flippers; full kit, EOS switch properly gapped, new sleeves, new bat bearings. Everything new but coils. This did improve snappiness but the weak issue remained.
I went into test mode and the EOS switches register properly. I swapped sides on the flipper buttons and nothing changed. I pulled the wiring from the flipper coils and ran alligator wires from the left wires to the right coil and this made the right flipper behave weak just as the left side had been. I ran alligator wires from the right flipper wiring the the left flipper coil and it was strong. I put everything back the way it should be.
From this I feel I had felt I eliminated in the cabinet and there was a problem on the board. From this assumption I pulled the board and replaced Q15 with a transistor IRL540N. Put the board back in and the flipper was immediately strong as it should be. It was just as strong as the one on the right. However it immediately blew the resistor because the flipper would not go back down after I let the button go. It would drop back down when I opened the coin door so its not a mechanical bind.
At this point I replaced the diode on the coil ensuring I did not reverse it. I replaced the transistor again. I buzzed out the legs on the new transistor to the proper points on the board and there is continuity. Turned on game. Flipper is strong but again immediately blew the transistor. Flipper locking up when the coin door is closed.
The flipper coils are the 090-5020-20T. Left resistance is 3.2 ohms. Right is 3.4 ohms. I've triple checked and wiring to the coils is correct. I did not reverse anything pulling and replacing the wires to the coil lugs.
Side note, the original transistor I pulled was not the original transistor to the game as there was evidence it had been replaced.

Was the original one that seemed weak an IRF540 instead of IRL540?

Double check the coil wiring and diode polarity is consistent with other coils. Make sure the diode on the coil is truly in circuit. Make sure you get IRL540 from an authorized distributor. Power mosfets highly faked. Seems common that they take a weenier Chinese transistor like nce0117 and mark it as a IRL540 which cannot take the abuse of the flipper coil.

IRL540 should be the preferred part. Stern had issue for a little while where if someone held a flipper button down a long time it would kill the original specified mosfet that could handle less current than IRL540. IRF540 may not fully turn on all the way. It seems to work in some boards but is weak in others.

#3 6 days ago

The original one pulled is a p22ne10L.
I took pics of the flipper wiring and diode before working on them and compared and they are the same before and after.
I did test both diodes old and new before installing the new one and both out of circuit and both tested good. Still installed new one.
How do I test to see if the diode is actually in circuit?
I will have to do some back checking to see where I purchased the transistors as it has been a while.

#4 6 days ago

I'd check through board and across board continuity of each transistor leg to a spot away from the repair area. A broken or cracked trace could be blowing the new transistor.

LTG : )

#5 6 days ago

Ok it sounds like I am not missing anything on the playfield side as far as diagnosing. Outside of possible bad batch of transistors I will start tracing out the board.

#6 6 days ago

Actually I did use my DMM to buzz out from each leg to the next connecting point of the trace (resistor, ground and the last one I can't remember. Those were good. I did forget to check for continuity between legs. I can check that later but I doubt it. I'm pretty good with my soldering.

#7 5 days ago

I'm getting 75 volts at the gray-yellow wire for the left flipper and same voltage on blue-yellow for the right flipper. I buzzed out the orange-gray from the other lug of the left flipper coil back to J9-8 and all the way to the middle leg of Q15. No bleeding over anywhere It shouldn't be.

Replaced the transistor again. I buzzed out from the bottom leg C248 and R15. Buzzed out the middle leg to J9-8 and C256 (blank pad). Buzzed out the top leg to ground. Buzzed between all legs and all crossing paths if there were to be any. Buzzed out to legs on Q16 and no shorts other than ground leg of course.
I logic probed U2 16 and 19 (left and right flippers respectively) and both probed out correctly and identically with their respective flipper buttons. I had the coin door open to avoid throwing voltage through the coils.

I pulled the wires off the flipper lugs. I put it test mode and single coil mode. Still door open. Put it on the left flipper. Hit run and nothing. Transistor still good. Pushed the coin door switches in and hit run. Blew the Q15 and fuse F6. Replaced the fuse with my circuit breaker for testing. Did the exact same steps on the right flipper and no blown transistor of kicked breaker. Flipper worked as it should once I placed the wires on the lugs. Of course once I placed the lugs on the left flipper it locks on when power applied.

I'm at a loss at this point. I'm ordering a new batch of transistors in case this batch is bad. How unlucky would that be? I've burned through 3 of them.

I'm considering removing C248 as although it doesn't buzz out to ground from the side that is connected to Q15 the other side does go to ground. I'm wondering if this capacitor is somehow grounding me out when signal is applied and load hits.

#8 5 days ago
Quoted from Pinballjimmy:

I'm getting 75 volts at the gray-yellow wire for the left flipper and same voltage on blue-yellow for the right flipper. I buzzed out the orange-gray from the other lug of the left flipper coil back to J9-8 and all the way to the middle leg of Q15. No bleeding over anywhere It shouldn't be.
Replaced the transistor again. I buzzed out from the bottom leg C248 and R15. Buzzed out the middle leg to J9-8 and C256 (blank pad). Buzzed out the top leg to ground. Buzzed between all legs and all crossing paths if there were to be any. Buzzed out to legs on Q16 and no shorts other than ground leg of course.
I logic probed U2 16 and 19 (left and right flippers respectively) and both probed out correctly and identically with their respective flipper buttons. I had the coin door open to avoid throwing voltage through the coils.
I pulled the wires off the flipper lugs. I put it test mode and single coil mode. Still door open. Put it on the left flipper. Hit run and nothing. Transistor still good. Pushed the coin door switches in and hit run. Blew the Q15 and fuse F6. Replaced the fuse with my circuit breaker for testing. Did the exact same steps on the right flipper and no blown transistor of kicked breaker. Flipper worked as it should once I placed the wires on the lugs. Of course once I placed the lugs on the left flipper it locks on when power applied.
I'm at a loss at this point. I'm ordering a new batch of transistors in case this batch is bad. How unlucky would that be? I've burned through 3 of them.
I'm considering removing C248 as although it doesn't buzz out to ground from the side that is connected to Q15 the other side does go to ground. I'm wondering if this capacitor is somehow grounding me out when signal is applied and load hits.

Where did you buy the mosfet transistors from? IRL540 is a target part number for fakers. Fake ones may appear to be fine until you fire once with a decent load and then go short drain to source.

#9 4 days ago

I can't remember where I got them. Whenever I buy components its from one of the pinball parts suppliers (Marco, Pinball Life, PB Resource) or Mouser or Tay Electronics. They are stamped as IR for International Rectifier. I've placed a new order from Mouser and expecting arrival shortly.
I'm going to check the voltage coming across the resistor going to the gate and compare that to the other flipper. I'm kind of at a loss of what to check next.

#10 4 days ago

I had a similar problem once on Monopoly, also a Whitestar. It ended up being the driver chip, in this case U2, which is an HCT273. Good luck, you'll figure it out!

https://www.greatplainselectronics.com/proddetail.asp?prod=74HCT273

#11 4 days ago

Please continue to post. I have the same situation but with the diverter gate coil. I replaced Q8 with an original type transistor but have bought IRL540 under the impression they are more robust. In my case swapping the transistor didn't help.

#12 3 days ago

There may be bridges of time when I post. Working full time and regular life you know.
I checked the voltages from U2 all the way to the transistors. Flipper side that is working (right) voltages are 0.458 between U2 and resistor and 0.457 after the resistor. Flipper side that is blowing the transistor (left) is 0.440 between U2 and resistor and 0.439 after the resistor. So there is a difference. I may do ahead and swap out U2.

#13 3 days ago

Placed order of new U2 and should be here Monday.

#14 3 days ago
Quoted from Pinballjimmy:

Actually I did use my DMM to buzz out from each leg to the next connecting point of the trace (resistor, ground and the last one I can't remember.

I had another thought. Might not be anything.

Any of those pulling ohms yet still showing continuity ? Weak trace maybe ?

LTG : )

#15 3 days ago

U2 to resistor is Left 0.3 ohms. Right is 0.2. Resistor to gate left is 0.2. Right is 0.1.

#16 3 days ago
Quoted from Pinballjimmy:

U2 to resistor is Left 0.3 ohms. Right is 0.2. Resistor to gate left is 0.2. Right is 0.1.

That doesn't seem to be a problem. Worth a quick look see just in case.

LTG : )

#17 3 days ago
Quoted from LTG:

That doesn't seem to be a problem. Worth a quick look see just in case.
LTG : )

Agreed. Not sure what else to check at this point. U2 be here Monday. Likely that evening I can pull the old and socket the new. See what jappens.

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