Have a weird issue with a Zaccaria that I can't figure out. Upper level stuff man.
Specific details of lamp issue.
Lamps 6000 and 8000 out. Lamps 7000, tilt, game over and 3000 on the backboard are locked on. Also at random boot-ups it will lock on 1 of 2 different pop bumpers. Sound board works, but sometimes the CPU ready signal is not sent so the sound board sometimes doesn't boot, but disconnecting the ribbon cable to the sound board allows it to boot up and work.
So the lamp issue would look to be standard driver board I/O issues, but it's not.
Replaced the 106 SCR's, replaced the 4050 buffers, swapped out the 4724 decoders.
No change. So I jumped the output signals from the decoders for the 6000 and 8000 lamps and the lights work, confirming everything down the line works. If I jumper the enable signal from one of the other fully working 4724 decoders the 6000 and 8000 lamps light up. So the decoder works just fine, which means the driver board is working correctly and somehow the MPU is at fault. The decoder chips on the driver board all receive 6 signals, 5 of which are shared by EVERY single decoder on the driver board. The only different signal is the enable line.
So this must be a RAM or memory issue somehow as all the 11 other decoders are working fine. Just to make sure on the MPU board I replaced the 3081 transistor array (used as a buffer/amplifier) at IC40 as well as the 4028 at U38 decoder chip for those enable signals. No Change.
Tried a different set of Roms (both stock and Freeplay) as well as a different 2650 CPU chip, No change.
Already swapped out the 6514 Ram with no changes. Need to try the 2101 and 2114 next.
Game is so close to being fully functional, but one little glitch somewhere is tying me up.