Thread: Zx81
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Old 15th Mar 2020, 8:40 am   #69
Slothie
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Join Date: Apr 2018
Location: Newbury, Berkshire, UK.
Posts: 1,104
Default Re: Zx81

Inside the RAM pack there should be a 22uF electrolytic across the supply rails. If this has gone bad then it wont be supressing all the noise generated by the 12v inverter circuit used to supply the DRAM chips. This is likely the source of your interference.

Schematic & info:
https://www.myprius.co.za/ZX81.htm
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