Thread: Zx81
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Old 23rd Mar 2020, 12:30 am   #132
SiriusHardware
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Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 7,278
Default Re: Zx81

OK, sorry, maybe I wasn't clear - I would not expect the spray to have any effect until the '81 has warmed up enough for the fault to appear. Only then is it worth starting to spray things.

I would start with the ULA (chief suspect as that is what generates the video signal and reads the keyboard) and also the regulator IC

For the difference in the way the CRT and LCD screens work, the diode and resistor mods may prove a useful line of attack. The aim of the freezer technique is to find out what it is that is going so badly wrong after half an hour regardless of the display being used (in fact, you have already proved that the machine breaks down without a display even plugged into it, thereby ruling out the displays as a possible cause).
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