Though the BERR logic seems to stop the thing from booting up :shrug: Answers on a postcard... "A" is the ROM_CE line, so we know that works. /RW. So on WRITE that will be low. /AS will be low on bus access. "Y" will be low on all those conditions and set BERR low on a tri-state...

I have to admit my knowledge of floppy disks is more the 5.25" variety. Maybe 3.5" ones dropped the 12V. Seems odd that Atari, who if they could cut a corner did, actually left the 12V wire in the cable if it wasn't needed!

On your previous thread you mentioned only a 5V power supply to the external drive, that will work with the Gotek, but most (all?) real floppy drives need 12V in as well. That may be your problem. Or may not, I'll go back to lurking!

I certainly did. I also wrote a basic compiler, to speed up writing some of the non timing critical game code. I'd write chunks of code in basic and then optimise the assembler code and incorporate into the game. It's all lost now, the only copy of Dr Frankie I have is running in the Memotech emulat...

So many memories there in that picture. I had an MTX512 and the FDX box. The FDX was huge and connected with a really ungainly giant ribbon cable out of the back of the MTX where your MFX is now sitting (it also gave the MTX the two 25way RS232 connectors that were listed on the connection panel). I...

Hmm yeah to be honest I am afraid to work on it because it is AC. I might contact Ultrawave and see how much it'd cost to just swap the board. I checked that IC and it's unobtanium, so the manufacturer of the machine is probably the only ones with stock. I spend all day finding components for work ...

Thanks for the circuit and explanation of R101. Looking back at that picture from page 11, pin 1 of the MC4044 looks extremely janky, and that is a critical element of the feedback loop to the LS629. Might be worth looking at DOT-CLOCK and seeing how stable it actually is? Otherwise I got nothing. P...

I haven't read the whole thread (TL;DR ) and I know next to naff all about C64s, but that last picture of the VIC chip, there is a resistor jammed into the left side of C86, that doesn't have any silk screen reference I can see. Just wondering if that's been ruled out as a cause?

The RAM timings must be very comfortable to mix and match the memories in one bank so much. I'd never risk mixing device families like that in my designs! I used to use all sorts of packages back in the 80's - my favourite were the SDRAMs in ceramic packages with gold lids. You could take the lids o...

That's a wacky bunch of sdram chips, 6x Mitsubishi, 1x with early Micron logo and 1x Fujitsu part! As for the video noise, I'd probably replace all the caps (not just the electrolytics) in that area if you know the values. Even ceramics from that age will likely have drifted too far from design valu...