Hello everyone,
I have a 80B Hollywood Heat machine that instantly burns out the fuse to the popbumper. I have tried a number of fuses, replaced the pop bumper driver board, and beeped out all the grounds. My machine has the grounding mod (wirenut all the ground wires to the transformer case). I even verified the coil was good by directly powering it via a DC power source (it pops in that case) and checking the resistance (it was a nominal 4.5 ohms)

I feel like I have tried everything.

The popbumper semantic shows two grounds across it. (see attached image) Pin 6 and Pin 2 should effectively be the same ground, however when using each one as a reference I get a ~.25 volt discrepancy when reading to pin 5. Could this be causing the issue? Should I just short these two grounds together? Why would the "DC Ground" and the "Solenoid Ground Bus" be at a different potential, and why even have two different grounds in this case?

Please advise.

Screenshot from 2022-11-29 22-52-26 (resized).png

I shorted the two grounds together; same issue (burned out fuse). As I beeped the other coils (flipper, etc) I noticed that they are able to beep to ground... is this expected? Those coils still function in game. So strange!

I am not sure how to test the +5 sagging when it pops, as I can only make it pop with an external power source (rest of the game is off)

It looks like all the coils I tested against have a lead to ground. (see attached screenshot)

None of the coils appear to "lock on", and other than the pop bumper everything works. When I ran the direct power source to the coil the device read a load of about 2.5 amps, a bit more than the 2 amp that the fuse is rated for. Could the coil be "a little" shorted? How bad would it be to try a 3 amp fuse?

Screenshot from 2022-11-30 16-22-30 (resized).png

Hi Chris,
I took out the pop bumper coil and measured the ohms - it was right on spec. I also verified that it pops when out of circuit with an external power source. For good measure I replaced the diode too.

After putting it all back together I got a few weak pops, then another dead fuse. There must be a short somewhere but I can't seem to figure out where it could be...

Gentlemen,
I have solved the mystery. It was deep, dark, and maybe a little silly.

I had recently purchased this machine. It ended up that someone before me had attached the pop bumper coil diode in the wrong orientation. This in turn fried to the driver board which caused the coil to lock on causing the fuse to fail. After I replaced the driver board I very quickly had the same issues again. (and another dead transistor on the driver board)

After this I removed the coil and examined the diode - it was reversed from how it should have been in the semantic! So, I bought ANOTHER driver board and decided to get a new coil for good measure.

Now it all works!

Moral of the story: If your coils are acting strange check the diode orientation... you never know if some silly goose before you turned it around!