Hi
Testing a Microsoft 16k card in a known working Apple II Plus. When I plug it in and attach the ribbon cable the machine will not start - no beep to action. Thoughts on trouble shooting this?
If it was a ram problem I'd think it would still start. There is one cap on the board would that prevent the computer from starting if it were bad?
TIA
Michael
Easy check - keep the card in but unplug the ribbon cable. If the machine still won't start up then check the power rails.
If you're not getting any life at all, then check the resistance across the rails with and without that card plugged in. There may be a component causing a dead short and the PSU is shutting down to protect itself.
If it's a tantalum cap, they're notorious for that. If it is a dead short, and the cap isn't the culprit, just pop out the chips one by one and measure resistance from the ground pin to the power pin. GND is usually bottom left (assuming notch to the top) and power is top right. (EPROMS are different. The power pins tend to be in the middle)
Hope some of these get you repaired!
Without diagnostic instruments it can be tricky.
Does the machine power up? Any garbage on the screen? Or is it just dark?
With the tantalum capacitor issue in mind (there are two - one by U20 and one by U13), remove one chip at a time from the card turning on the computer after each removal, until the machine turns on.
That chip will probably be your issue.