Yeah, it's a bit of a bugger, I thought I'd found a short, then find out the way it's connected is electronically correct. Bah humbug. So annoying, this machine powered on 6 months ago.JezC wrote: ↑Fri Jul 31, 2020 10:34 pmWhen I used to have to design circuits with ECL logic (especially when interfacing with TTL/CMOS logic) it was a nightmare working out what signals were active (and what polarity that was)...no chance of the logic analyser sorting it out, so we had to rely on a 'scope!
At least the majority of modern electronics (and I'm generously including the ST and Amigas in that category!) don't have that pesky-5.2v supply to confuse things further!
Even just using PECL made a world of difference...
One thing I did notice today was that with the logic board plugged in, the 5v rail drops to 4.75v, so I think maybe I need to tweak it again with the logic board connected. Supposedly there is also a CNY75GB OPTOCOUPLER on the PSU side which can cause problems, so I think I will also check that out.
Time to look at the schematics again.