I'm having a weird issue with several backbox lamps pulsing or strobing when I turn on the game. The problem seems to be on the driver board, as I currently have this driver board in Firepower, but when I put it in Gorgar, it does the same thing. In this video, you can see that the P2, P3, P4, Tilt, Shoot Again, and other controlled lamps start flashing as soon as the game is turned on, and continues when a game is started.

I've switched out the lamp matrix PIA as well as the 7408 IC 14 since it seems that most of the lamps that are flashing are from column 8. The driver board has had the 40-pin board interconnect connectors replaced, as well as new sockets for the PIA's.

Anyone else ever see something like this, or have any thoughts on what to check next?

Works fine during the tests. The displays aren't really scrolling like they appear in the video, the camera picks up that effect, like the video camera is out of sync with the refresh rate of the plasma displays or something.

It's the flashing lamps on the right side and bottom of the backbox that are the problem. I swapped with another driver board, and the lamps work fine, so it is definitely something on the driver board causing this.

Just a follow-up in case anyone else has this problem, I finally figured it out.

The TIP42 (Q77) in the lamp matrix was shorted between the C & E legs. I just figured a shorted transistor in the lamp matrix would result in the lamps in that column being locked on. Not in this case, the lamps in that column flashed like crazy, that's why I kept going back to the PIA and 7408. I replaced that TIP42, all is well again.

Hope this helps someone else out in the future!