20 amp and 36 amp transistors? What parts are you specifically talking about? You said you did an exact replacement what is the part number. Do you mean the TIP36c at Q80?

Coils don't normally need to be replaced. If the driver transistor locks the coil on it may heat up and get damaged. The wire coating getting scratched can cause a short. Shock might break a connection in lug.

Coils usually last forever until some solid state part fails and overheats them.

Coils are, for the most part, fairly robust. Besides the most common failure of a short between windings, heat is the next biggest destructive force for coils. As temperature rises, resistance also rises, increasing electrical losses and causing further heat build up. This phenomenon is a primary cause of coil failure. If you get a momentary coil that gets stuck on longer than it should, the first thing you may notice is the coil getting warm, or even very hot. If the problem is not addressed, this most certainly will kill the coil eventually.

Transistors do fail. The IRL540 is a better (beefier) replacement for the 20N10L.

The problem is when they fail closed and lock the coil on as soon as the game is powered on. I've had smoke come out I gets so hot.

Is Q80 normally a power FET? I thought these drivers were normally TIP36C (around 25A collector current and should be more than sufficient for this circuit I would think)

OK, I wasn't sure...I'm not by any means an expert on WPC, I've never owned one.

The initial inrush surge on a momentary coil circuit can certainly be in excess of 20A, remember this is not a continuous duty current - it's a very brief surge. This is why time delay fuses are used in coil circuits.

I am having a similar issue on my Whitewater at Q76. Rottendog has been very supportive and sent a replacement board. Both boards fail after a few games at Q76 (lockup popper). I took similar steps in confirming there were not shorts or bad connections. I replaced the 20N10L with the exact one used on the board sent by Rottendog. It works for a while, then fails. What could be causing this? Q76 is only controlled by the Power Driver board, all the wires come directly from it, all other coils on the circuit work, as well as all flashers. Is using a beefier transistor the only answer? Will with have any negative effects long term?

Would this work?

http://www.mouser.com/ProductDetail/International-Rectifier/IRL540NPBF/?qs=sGAEpiMZZMshyDBzk1%2fWi5%252bqVgN3%252bWS88iBXP4BpZM0%3d

Also to note, everything (minus the GI and reset, why I decided to replace in the first place) works as it should with the original board. This is how I concluded the problem was with the transistor in the first place.

I am having the same issue on my Whitewater. Q76 lockup popper tranistor blew last night while I had family over playing so Whitewater was done for the night. What transistor did you use to replace it the old one with?

Back in the day, when i was working on Route use machines, 90% of the time a coil fried when the transistor failed closed. If coil showed signs of damage, either looked burned, or swelled up, standard op was replace coil, transistor, and pre driver transistor. if damage was bad, maybe a diode and resistor, because i didn't want to pull the board 2 or 3 times.