Quote:
Originally Posted by Techman
I've put it all back together for the time being, as I don't want bits to get lost or damaged and I've got a lot of other things on the go at the moment. However, if anyone has any ideas on this particular fault condition, I may have another look at it in the future, although I seem to remember there was some thoughts that this particular type of fault could be a main processor chip fault.
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I did have another look at the machines a few days ago and nearly had the 2020 working. So having proved that one had a good processor board, I removed it from the machine, unsoldering and removing its dodgy looking back up battery and fitted it into the 2022 machine, and it brought it immediately back to life. From the previous comment regarding some still visible corrosion that the camera had picked up on the original board, I gave them both a good clean with IPA, but the original board still had the fault after the cleaning and exhibited the same fault in both machines.
I repaired the broken tape, it had come off the end of the spool. It was a bit chewed at the end, but still had the silver foil strip intact, so I decided not to shorten it and stuck it back on as it was. It played the tape (and others) fine, but this was short lived, as another fault then developed, in that the machine will not go into play mode and just sits there in pause, with the only way to view video being in fast picture search. Guessing that this was yet another processor board fault, I swapped the board back into the 2020 machine where it exhibited the same fault, thus proving my guess correct.
It crossed my mind that running these boards without any backup battery installed could perhaps be causing some sort of over voltage spike that's knocking out the processor chip. Another test that I could have done would have been to swap over between boards the main socketed 8049C processor to narrow down what was happening, but at this stage I decided to call it a day!
Pictures below show the board in the 2020 before having its battery removed and being cleaned and fitted to the 2022 machine. Also the innards of the 2020 and some batteries that I was given the other day that might have fitted as replacements and shown next to one of the removed yellow originals - perhaps I should have fitted one before running the board in the 2022 machine without one? I was using a small CRT portable B&W TV as a monitor before the machine packed up yet again. I remember these machines always being very unreliable, possibly worse than the 15/17/1750 models. I also remember a work colleague back in the day, after doing much research, buying the Grundig version brand new, and I remember him eventually giving up with it and dumping all his recordings and the machine when it went wrong and he couldn't fix it - or perhaps couldn't be bothered to fix it any more - he was a qualified TV engineer.