So my TSPP which was working fine before we very carefully moved it to another room. No cables were pinched, nothing is loose in the head. Checked all connectors to make sure that they were all seated properly.

Now when I power it up, I get GI, but no boot. On MPU L204 and the +5V LEDs are both lit when the game is powered on.

Fuses on driver board all test good.

+5 is present on MPU, +12/-12/+5 are all present on both driver board and MPU, and within spec. (Yes, I know the watchdog won't take the MPU out of boot if there is, say, +4.75vDC or less on the +5 logic line and there is +5.08V there).

If I disconnect the MPU from the driver board, L204 will flash (blanking LED), if I connect the MPU, L204 goes out (which indicates that the MPU is holding the driver board in "reset" state).

After powering on if i disconnect the DMD, the DMD will boot and display the boot rom (A.500). As near as I can tell with my cheapie 'scope, I have the 6MHz and 24MHz clock signals on the test points on the MPU.

No acid damage from batteries on board (always new batteries in it, and a replaced battery holder (old one had one of the - terminal springs break off of it). VBatt is present when board is powered off and all 3 batteries test good.

Any suggestions to test before I send it off to Jerry?

TIA

ok, so here's an update. After spending an hour meticulously looking at the solder connections on the MPU/sound board, I figured I'd reinstall it and measure more voltages. Lo and behold the game boots up fine. But only for about 3-4 minutes, and then L204 goes out (it's solid when the game is running), and all that's left are the GI on. I can generally get it to boot up if I turn it off and let everything go cold.

Thermal failure? But what is causing it? I watched the +5 dc on my scope, and it doesn't change at all, even when the mpu drops into reset (and L204 goes out)

Urg.