In switch test mode, are your flipper buttons showing up?

I think he said flipper button boards do not register in test

Do you have 14 Volt on Gray-Yellow wire ?
If not Check J116,117,118 on PowerDriverBoard.
cree-flbt.jpg

Most likely the Gray-Yellow wire to the flipperbuttonboards is broken somewhere. If there was no power at all from the 12Vunreg., the machine would have other errors (too).

Try the original setup without the mod and measure TP1, should be around 14Vdc.
Opto's/Flipperbutton/Vuk could be related to each other except for the "boing" sound, looks like the soundboard is resetting....check 5Vdig on TP2 and 12Vreg on TP3 as well.

Ah, I was thinking powerup 'boing'.

In that case it looks like 12Vunreg is too low, maybe bridge rectifier BR5 has lost a segment and is working on half power.

If you measure 12V unreg and it seems low you can do a quick test with board still in machine to see if rectifier is ok. The reading can vary some mV.

Machine 'OFF'
DMM in diode-test
unplug J112

Red pen on GND:
(test1) -Black on J112-1 ..read 460mV ?
(test2) -Black on J112-5 ..read 460mV ?
---------------
Black pen on TP1
(test3) - Red on J112-1 ..read 460mV ?
(test4) - Red on J112-5 ..read 460mV ?

If one of these 4 tests is 'open', BR5 is broken

Had the same issue. Ended up being a poor connection to GROUND WIRE wire coming from connector on driver board. Voltage tested 1-2v (should be 14v) at the flipper optics. Metered the 12v pin from the optic board to the ground straight to the cabinet braided wire strapping (which showed 14v) to determine the faulty ground on the flipper optic boards. this forum was very helpful. thanks all.

Replace fuse F116

Voltage test points on power driver board - see if any are low or missing.

LTG : )

This is not an issue, both LED2 and LED3 can be ignored.

check the diodes across the affected switches.

a bad diode can blow the corresponding transistor.

check the switch matrix and solenoid tables from the manual

Yes, I do know this; however, in your case as described, the transistor is not the problem. Whenever the transistor fires it literally shorts your 50V connected through the coil to ground, the fact that you blow a fuse when it fires tells me the transistor is working perfectly. While its extremely rare for coil winding to short without melting the coil, I strongly suspect your coil is either bad or is miswired.

WHY?
If the transistor was shorted you game would blow the fuse at power on as the coil would lock on as soon as the game was powerd up and causing the fuse to blow. This is the typical failure mode for this transistor.

If the transistor could not operate (burned open), the coil would never fire AND the fuse would never blow as no current would be pulled across this coil.

Now to answer your original question...and show you how to find it in your manual:

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Ancient Proverb: “Give a man a fish and you feed him for a day; teach a man to fish and you feed him for a lifetime.”

Dig around the thin wires from the coil windings to the coil lugs. A crack or break can be hard to see.

LTG : )

Sorry for digging this one back up but I have the same problem on my IJTPA (flippers not registering in switch test but they work in coil test). I'm not great with electronics but performed this test and found test 1 (black on J112-1, red on GND) to be open. I replaced F116 just in case with same resuts. Just wanted to confirm that this would mean BR5 is indeed bad and needs to be replaced. I would assume this also means that the board needs to be taken to a pro to do the job.

For background I have not recently made any changes to this machine - it had been working well as is for the prior year+.
Also, noted that BR5 has a sticker "tested by John H" that the other BRs do not have. This machine has a Rottendog flipper board installed if it matters (May 2019 - just previous to my purchase).

That indicates something is wrong. To be sure you will have to take the board out and measure directly on the legs of the rectifier.
It could also mean that one leg of the bridge rectifier has lost connection to the board.

When you have still an open reading from (-) and (~) on the rectifier, then in needs to be replaced.

Tested BR5 and thats what I have - open between - & ~
From here I'll probably need someone with more experience and tools than me to fix it.
Thanks for the help!

I just had this problem happen on a Fliptronics II. Left flipper did not operate on The Shadow. Switch test indicated good. Discovered the hold coil lug thin coil wire was broken off and the WRONG fuse on the Fliptronics board was blown. Scratched my head on this as that fuse indicated another flipper based on the stapled up fuse sheet in the backbox. (Turns out there was an error on this, which was obvious) Repaired the coil wire and replaced fuse - when powered up the flipper activated with no impulse. Immediately shut it down and knew it was a transistor. Turns out a 4th upper left flipper is indicted for Shadow, but it is a 3 flipper game. We also had no TIP 36C transistors in stock. So I took the transistor from the unused section of the board and put it where the blown one was. But before I powered it up, I wanted to replace both diodes in the flipper coil as a preventative measure. Sure enough as soon as I started to clip the old diodes out, the center lug both leads leading to the diodes was already sheared off.
My theory: Diodes sheared off, destroyed transistor, locked it on, burned the thin holding wire and blew fuse. Only the Shadow really knows.

It's a no-brainer (for me at least) to just shotgun replace all of the bridge rectifiers on the pre-wpc95 games. There's almost no risk because you can cut the old ones off from above the PCB and easily remove the remaining legs, and they are like $5 each. Put new ones in and forget about them for another 30 years.

Would this be a diy job for a guy with rudimentary soldering skills? I'm not afraid to try but would probably defer to a pro if theres a chance of ruining the board with a bad solder job.

Hard to say...I cut the old bridges off from the top of the board leaving a good bit of the legs sticking up. Then add some fresh solder to each and gently pull them out of the board. Use a solder remover gun/pump to remove the old solder and install the new bridges.