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OK so the propellor chip arrived today and was promptly swapped in. Black screen still. Although occasionally I will get this through the composite which is new behaviour https://i.ibb.co/LCRCvQ9/IMG-3250.jpg So the extra 32K is showing up OK. Pressing Return I get the Ready prompt and can run the U...

Did you check the power patch wire?

Yep the Serial Eprom is getting 3.3v and the patch wire to it from the resistor seems to be secure

Thanks, I've erased the rom and written that version to it.

No change unfortunately. Maybe the propeller chip needs replacing? I can source a replacement through RS Components is it just a straight swap?

U5 the 3.3v regulator U5 gives 3.3v I've run some tests faking a propeller issue (by removing the serial rom that's easier to pull!) normal boot black screens after the tones as expected. Reset with C held down will produce a blue screen and "CPM boot" and then lock. Reset M for MTX mode ...

OK so with the ROM chip removed I still get no signal from the CFX so would I be correct in suspecting the Propeller chip? With the ROM removed I do get the Ready prompt and cursor through the composite output. With the ROM in place I just get a black screen through the composite output and no signa...

Thanks Dave, I'm also not sure about any VAT or GST impacts. In the meantime the sound issue I also have is making me wonder if the issue isn't something on the MTX itself. I've ordered a replacement PSG and have socketed the exisiting one. Once that arrives if the sound works then I think it'll be ...

OK so the Caps arrived today and promptly got swapped and the missing C53 fitted.

Apart from the display looking more stable (may just be me) the CFXII still does not work. I may have to try and find someone in NZ with an MTX to test the CFX out as that would identify if its the MTX or the CFX.

Yep the board is fine. No sign of insulating washers but I'll find some.

In the meantime I've got a replacement PSG on order and the caps should be here soon.

Interesting. Never seen one of those before. Now that I have a good look at it yes its got a metallic finish but is actually plastic.
I gather someone installed it to support/protect the motherboard?
Maybe I should put it back.

That green plate under the board is metal, it had insulation tape between it and the board. Looks like someone cut it out of an electric motor ID plate.

The heatsink plate that the 3 regulators bolt too is still bolted on of course.