Thread: Zx81
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Old 21st Mar 2020, 10:17 am   #118
SiriusHardware
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Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 7,280
Default Re: Zx81

And this also happens when you don't have a RAM pack connected?

Sounds like a thermal-related problem. The best way to hunt for this would be using freezer spray - let the unit run until the faults appear and then spray each major component - regulator, ULA, Z80, memory IC, one at a time to see if that makes the fault disappear. Any electroyltic capacitors in the unit are also a possibility (spray those too).

Freezer spray made for the purpose of diagnosing thermal electronic faults is usually quite expensive but if you take a look at this thread, someone has just discovered more or less the same product being sold for an entirely different purpose, and much more cheaply.

https://vintage-radio.net/forum/showthread.php?t=164937

If you can bring yourself to buy some of that, that should work quite well for the purpose.

Last edited by SiriusHardware; 21st Mar 2020 at 10:38 am.
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