Wayne Parham wrote:I had similar troubles with one of my front-panel interface boards. Mine ended up being caused by one of the NOR gates in the 74LS02 chip in location "L."
If you socketed your chips and have spares, you might swap 'em one at a time and retest. You can always break out the 'scope too, but you may find it just by swapping parts.
Thanks Wayne, I did read about the issues you had in your thread. Yes, all my chips are socketed just in case I need to swap one out. But I'm happy to say I've resolved both the issues I was having. I'm not sure what happened with the FDC+ PROM, it seems to work fine now. I may have had it disabled when I thought it was enabled. But I've tested it today and everything is working fine. PROM and RAM work fine, and disks load fine too.
The issue I was having with the 882SIOJP is a little more interesting. I've found that it has issues depending on which slot it's in. It seems that if it's positioned after the CPU and Front Panel Interface it has issues. But if I position it in slot 1 it works fine. So, I currently have a fully working 8800C, with all new boards. The slot configuration that works is:
1: 882SIOJP
2: empty
3: CPU
4: Front Panel Interface
5, 6, 7, 8: empty
9: FDC+
I don't think it really matters which slot the FDC+ is in. I tried it in several different slots and it seemed to work consistently. Not so with the 882SIOJP. I tried that in the centre and it worked a little better, but not perfect. It seems to only work perfectly if positioned before the CPU.
It'd be interesting to work out why different slot position have an effect on it? This isn't an issue in my original Altair.