HI All,
I have just "completed" a build of an 8800c with a front panel board set, a reproduction CPU and an FDC+ and I am sorry to say that it is not working. I have the 9 slot Motherboard with 5 S-100 connectors installed (1,3,5,7 & 9). PSU voltages are good on the motherboard.
With only the front panel and the interface installed, the D0-D7 LEDs on the front are lit and all the rest are off. Is this expected behaviour? Switches do nothing, which I imaging is correct.
Adding the CPU card, all the voltages (+5, -5, 12) on the 8080 are correct. I have not yet been able to source a 74L00 and so I am using a 74LS00. Could be the issue?
When I power on; D0-D7, A0-A15 and INTE are lit. If I do a reset (STOP & RESET) INTE goes out, D0-D7 and A0-A12 are lit and A13-A15 flicker. If I use my iphone slow-mo camera it looks to me like the address lines are cycling backwards through a count. Stop doesn't do anything, in fact none of the switches do anything except reset. If I add the FDC+ I have the same behaviour.
I have messed for hours with the clock and have it as close as I can make it to the spec. (I am able to stop all activity if I take the clock out of spec.) I have checked for bent IC leads, bad solder solder joints, correct chips (other than the LS00 noted above) and chip orientation. I have even employed the "shotgun troubleshooting method" by replacing all the chips on the CPU board.
Does anyone recognize the symptoms or have any suggestions?
Thanks, Mark