Order the right transistor (someone chime in here - TIP102?) or two and take your board to Mike Chestnut, who lives 30 minutes north of Nashville. He (or his dad) will replace the transistor and you won't have that issue again. Might as well have him replace both Q15 and Q16 so you don't have that issue again.

I don't think a transistor can do that - I wonder if the coil/diode didn't short and take out the transistor in the first place?

Yes. Pull the board and have somebody who's a little more experienced have a look at it. Could also be a bad replacement part, but more likely a poor soldering job.

The NTE2987 is an acceptable replacement. Not easy to find, but acceptable.

Holding a flipper up for a minute is getting to be the typical MO for these. Hopefully with the new board system they'll upgrade those transistors.

Did you check the the coil plunger to make shure its not binding? Mambe you heated up that coil and melted the coil sleeve some? Also is the eos switch working properly?

Coil sleave is a plastic bushing between the coil and the plunger. The only reson I brought up the eos was to make shure it was adjusted properly because if its not then that's how you heat up your coils because they get too much power when you hold the flipper on.

This happend to me in the past. Got it all fixed up no problem.

http://pinside.com/pinball/forum/topic/stern-mosfet-transistor-part-check

a heated up coil may have partially shorted within, would sure make it a weaker electromagnet, and if it heated enough to warp or partially collapse the sleeve, its gonna drag to rob even more flip power. might or not be anything to do with the driver transistor, but if its physical mechanical like that ^ its putting a real strain on the new transistor.

If the fuse blew, but the flipper didn't stay locked in the up position first (before the fuse blew), I would look for a short somewhere in the wiring. Your first post sounded like the typical locked on transistor, but now it sounds more like a short somewhere. It could also be a problem on the driver board, but I'd check the wiring first. Follow the wires from the flipper coils all the way back to the boards looking for any problems. Could be as simple as pinched wires between the head and the lower cabinet.

Could you have done that with the soldering iron or was it there before? The plastic where the wires feed in look ok, so does the wires, just looks like the plastic on the board is melted, mambe you touched it by accident with the iron. Try playing a game for a while and see if the coil on your weak flipper is hotter than the one that's not weak. Mambe you could take a pic of your weak flipper assembly And post it on hear mambe someone can see something wrong.

yea I have been waiting for parts since Wednesday.

Seems like I've been waiting for parts my whole life....for one thing or another!

Glad to here you got it! Play on kmerrell.

As an FYI, stern has been using better transistors recently than the Irl540n. So I wouldn't be proactively swapping these. On some cases you may be downgrading.

???
What better transistors?
I would think a 26 amp, 100V FET would be more than enough for any load they use.

The issue isn't whether not its enough. The OP proactively replaced also working Q15. Off top of my head on part numbers , old boards used 22NE10L, also "enough". The IRL540N is an improvement to this. New boards use I believe 44NE10L, which are a bit beefier than the IRL540N. So enough or not, it's not smart to proactively replace working 44NE10L with downgraded IRL540N

Proactively changing FET's, yeah, no need... especially going to an NTE ("well... the part we offer should be a replacement"). But not really a downgrade if going from 40NF10Ls to IRL540s.

The 40NF10L as only used in a few places. For the most part, they are still using IRL540's and equivalents. Actually the IRL540 is a closer replacement to the 40NF10L's as a replacements then as a replacement for the older 20N10L's and 22NE10L's.

Major points between the two:
Both have a VbrDSS of 100 (not to exceed voltage).
The IRL540 is rated 26 to 36 amps depending on temperature.
The 40NF10L is rated 25 to 40 amps depending on temperature.
Hopefully the installed fuse isn't this high...

The things that kill these = VbrDSS (induced by magnetic field collapse of coil - think of missing coil diode), dV/dt (resulting from insufficient gate slewing -- cap used by Stern is fine but other replacement boards out there have -none-), excessive ID (a shorted coil or diode can take out either one with a very high and very fast current spike) and ESD. There's not really enough difference between the IRL540 and 40NF10L to make one better than the other in any of these.

It isn't an issue of whether or not it's enough - it's a matter of what they got a better deal on when buying parts.

good to know...