Hooray !! finally cracked it. It’s all working again. Thanks for the suggestions and help.
This all came about because although my Printer fired up and I could slew the print head and heat the bed and nozzle, the printer refused to start a print.
So I started fault finding, but I had no info. The printer was cold, and threw up a TO sensor error. Brought printer to a warmer place but still no joy, even after 24 hours.
So I went through all the internal electrical multi connectors, and disconnected and cleaned each one with contact cleaner. Now it recognised an old SD card. But not the new one……
In the meantime, I had erased the new SD card several times and recopied the Cura file onto it several times. The printer still would not read the new SD card. Very confusingly, if I put the SD card back into the MAC, it WOULD read the SD card, and I could see the file and all the G code, but the printer obviously couldn’t see it.
Then I learned that when you erase an SD card with Apple MAC disk utilities, it gets reformatted as well – didn’t know that. But what I also didn’t know is that the default MAC SD format is, unsurprisingly, an Apple MAC format. This was not recognised by the printer – it knew an SD card was in the slot, but would not read anything on it.
Once I realised about the formatting, I tried several formats for the SD card – there are five available in the MAC. The one called by Apple “MS-DOS FAT”, is the one that speaks the same language as the AnyCubic.
So now all is well, printer is behaving very well – all those multi connectors I took apart and cleaned has obviously helped as well, (I did them all, not only the SD reader multicore cable, but all the fans, extruder and stepper motor connectors as well, and it has made the machine much more responsive. It seems turbo-charged now compared to how it was. Clearly a bit of resistance had built up in the stepper motor drive connections).
Normally of course, one should only change one thing at a time when fault-finding, but I didn’t really have the luxury or the time for that, especially with no information to go on. Unfortunately, I created another problem by unknowingly reformatting the SD card into a format not recognised by the printer !!!
And, finally, what was so urgent that needed printing ?………..Ermmm, well…..it was some replacement plastic doll’s dummies for two of Mrs Doe’s old dolls that she wants to sell on eBay………………..Ho hum.
But I have learnt a lot, and rejuvenated my printer, so not entirely wasted time.
Oh, and the printer bottom plate had been fitted 180° the wrong way round, so underneath where there should have been vent slots for the fan which cools the stepper motor drivers; there was sold metal, starving the fan of air. I had to drill two new holes to fit the plate the right way round – the makers had obviously put the plate in the hole punch press the wrong way round.