Thread: Zx81
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Old 15th Mar 2020, 9:24 am   #71
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 8,873
Default Re: Zx81

Originally Posted by John Earland View Post
I do actually have another 9v dc psu too. It powers an old Binatone Mk IV game console from the 1970s and hasn the same connection. The Binatone works well on the crt-picture a little wobbly but very usable
If two completely different RF connected devices give you a rough / wobbly picture on the same TV then I can not help but wonder if it is the TV rather than the devices which has the problem.

When swapping PSUs between different devices, beware of polarity - roughly 50% of PSUs from that era had positive on the tip of the plug, the other 50% negative on the tip of the plug. Use your meter to make sure the polarity of the Binatone PSU is the same before trying to run either of the ZX81s on it. I seem to remember the ZX PSUs are tip=negative, but don't take my word for it, check.
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