16-06-2026, 07:51 PM
Thank you for your reply and pointers.
I just want to add that I have measured the signal on the solderside with the coreboard attached. Also I was mistaken with the crystal, it's a 13.5Mhz and the readings matches 13.5Mhz (it's a Danish configuration with Danish keyboard and character rom).
I have a schematic, but only for the original kit, so it's not accurate for the main board and for the core board it's very different. Unfortunately I haven't been able to find one for Rev H or similar.
I did clean all the socket but I did not think to clean the coreboard pin strips. I've done that now and measured all >0.6ohm on all pin connections between coreboard and mainboard now.
Status now is that I do see MREQ RD cycles (on both CPU and 25 pin connector) but no IORQ activity. JLATCH (pin 6) is high and there's activity on the 74ls245 pins. But as I'm self taught in these matters, I'm not quite sure what to look for next. Would it make sense to replace IC19 (74LS245) and IC33 (74C74)
I just want to add that I have measured the signal on the solderside with the coreboard attached. Also I was mistaken with the crystal, it's a 13.5Mhz and the readings matches 13.5Mhz (it's a Danish configuration with Danish keyboard and character rom).
I have a schematic, but only for the original kit, so it's not accurate for the main board and for the core board it's very different. Unfortunately I haven't been able to find one for Rev H or similar.
I did clean all the socket but I did not think to clean the coreboard pin strips. I've done that now and measured all >0.6ohm on all pin connections between coreboard and mainboard now.
Status now is that I do see MREQ RD cycles (on both CPU and 25 pin connector) but no IORQ activity. JLATCH (pin 6) is high and there's activity on the 74ls245 pins. But as I'm self taught in these matters, I'm not quite sure what to look for next. Would it make sense to replace IC19 (74LS245) and IC33 (74C74)