Started by Cwiiis, 00:02, 29 July 21
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Quote from: Bryce on 16:26, 31 July 21If you have a logic analyser you can connect it up to the ASIC keyboard outputs and observe what happens. It should run in an endless loop of all bits high except for one going low. ie:111111101111110111111011Bryce.
Quote from: RetroCPC on 10:15, 01 August 21Hi,Its a chance that the ASICS Joystick / keyboard port has been Damged by ESD (Joystick cable).I can confirm condition of the ASICs internal ESD protection diodes with lab equipment here and no problem to swap the ASIC SMD IC if required (I have full SMD rework equipment) - trouble is during these covid times I'm based in Czech Rep. so shipping is not so easy post Brexit... but happy to do the work for free if you cover the shipping costs...
Quote from: Cwiiis on 15:29, 01 August 21Ok, one last desperate idea... Would it be possible to bypass the ASIC for keyboard handling using a 74LS145 like on the non-Plus models?I can't work out from the schematics if it's possible and what exactly you'd need to bodge where to do it, but it seems like it might be vaguely possible? I suppose that if you could figure out what corresponds to the 4 input lines on that chip, you could cut the traces for KY1-10 on the ASIC, connect those 10 lines to the 74LS145 (along with the 4 inputs, assuming they have corresponding lines somewhere), find points for VCC/GND and that'd work around the ASIC for input?
Quote from: Cwiiis on 15:43, 01 August 21It's a shame to sacrifice a GX4000, but I'd rather have the home computer than the console...
Quote from: eto on 15:44, 02 August 21but what if this doesn't work or if you fry the other Acid? If you buy a broken Plus or GX, it's fine, but please don't kill a very rare working machine.
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