My Gottlieb System 80B Hollywood Heat had been working fine. The first symptom of a problem was the display would not come on some times at power up. After that, usually solved by powering off and turning on again, it would stop registering certain switch closures, like the capture saucers and outhole. I discovered the labels had fallen off the EPROMS. I have been told that would likely not have been the problem. I bought a used but "pulled from a working game" Swemmer MPU. Jumpers are set properly for Hollywood Heat. I swapped EPROMS to the new board and installed (checked power supply and it was right at 5V). Not it has a slam switch warning at power up (which I can defeat by momentarily closing the switch-did not need to do this with the MPU that had been in there), and the video shows what happens.

It is as if the switches are are all rapidly closing. It seems like it is playing an invisible game.

I do not have a logic probe. On the Swemmer board, all the ICs are socketed.

Has anybody seen this before?

Thanks,

Zap

Ground mods had been done.

To be extra sure, I ran a wire from the transformer chassis in the bottom cabinet to a post in the backbox where the ground straps mount, and both the driver board (Rotten Dog) and Swemmer MPU have ground wires going to this point too.

No change in symptom.

A repair expert I respect told me corrupted EPROMS are very unlikely.

I used a DMM to check diodes on boards, and they appear to all have about the same value. None are open or shorted.

I have ruled out corrupted EPROMS. I bought new ones and installed, and it is the same. It happens with the audio board disconnected, and it happens with the display disconnected. I guess I will try to find where the credit switch wire goes to the MPU, disconnect the switch matrix from the MPU and put a jumper wire from the credit button input to the pad on the MPU, that way I can see if it is some issue in the playfield, or in the MPU itself.

ts4z

Switch test shows all switches open, except two drop targets which fall in the test right before the switch test.

It acts like multiple switches are activating, because different lights turn on reflecting different lane switch closures, etc..

sparky672

I tested all the diodes on the boards underneath the playfield. I am going to replace all of them this weekend, even though they read about all identical.

I will report back once I've done that. I bought new boards to mount them on too.

Thanks!

Isochronic_Frost I have checked all the switches. They appear to be gapped correctly.

PinballAir It does change lanes, but it is not stuck closed.

Due to shipping delays, diodes did not arrive until today. Put all new diodes on new diode boards and installed. Now, it won't start a game. It acts like it is waiting for the balls to register. I will look closely at the trough switch, and see if there is anything that could be wrong there.

I got the game working with an old original Gottlieb System 80B MPU.

When I put the Swemmer 8T-B MPU in, it still goes crazy as seen in the video.

Something is really off about this MPU.

I swapped new ICs (some were purchased as good pulls) at U1, U4, U5, U6, Z5, Z9, Z13, Z14 and Z33.

It still does the same thing.

I also replaced component at Q1.

I could keep spending money blindly swapping ICs, but at this point, I think it is cheaper to send it to somebody for repair. Maybe it is one of those tiny surface mount components I do not have the skill to replace.

Thank you to everybody that attempted to help and offered advice!