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I can swap the CTC. I installed a new one just in case I'd broken the old one, and I have another brand new spare. I'm a little bit untrusting of the current set of LS244 chips as they've been through a lot during the troubleshooting. I've a complete set on order which, like everything else, should ...

But it works fine when the RS232 board is not fitted? OK, I have found one issue. The machine's stable when in BASIC and running games. The machine boots into the CFX menu fine and as long as you enter BASIC within about 10 seconds everything is fine. If I leave it any longer then the machine will ...

Hopefully you have the board back in the case? The regulator heatsink really needs to be fixed to the case to allow the heat to dissipate. That said, even when running normally, things get pretty warm, particularly the VDP With lack of use, the keys do get a bit “jittery”, they often get better jus...

Having had the machine burning in running Andy Key's "Reveal" (loaded from the CFX interface) all afternoon it's been stable. It smells a bit warm, but that might just be the new components evaporating off the volatiles as they get gently roasted by the power circuitry and VDU. I hope the ...

Dave wrote: ↑12 May 2019 16:10 But it works fine when the RS232 board is not fitted?

Yep! Despite the keyboard issues I've managed to load "REV.RUN" and "KILO.RUN" (I can't load any .BAS or .MTX as the 'B' and 'M' keys are not functional.)

64K RAM (TI chips). The LK6 links have been changed but LK7 hasn't. However, Andy's GAL code ignores that input anyway.

P.S. I can't try CP/M mode as the 'C' key is one of those which isn't operational until I get a replacement 74LS273, which probably arrives on Tuesday.

I'll probably have to do that anyway as as soon as you run "ROM 5" it crashes to the PANEL. That's if the machine starts at all.

I can't actually see any ROMs. There's the Z80 DART, a bunch of 74LS chips, the PAL and three 75XXX chips and that's it.

Oops! Sorry. I'd not noticed that.

Now that I have my original MTX500 almost fully functional I thought that I'd try my spare CFX board fitted externally. Unfortunately it doesn't seem to work with the RS232 board fitted. It either doesn't start or goes directly to BASIC. It works fine with the RS232 board disconnected. From the info...

My machine is from after October 1984 so should already have the modification.

I've just noticed that I need to change Link 7 though!

P.S. Having checked the GAL programming this isn't necessary as that pin is ignored anyway.