My results:
Code: Select all
Test PSU Draw Heat sink temp
16K comp* ZX81 Sinclair UK700 290mA Quite hot
16K comp* ZX81 9V regulated 290mA Only a bit warm
16K comp* with WESPI 9V regulated 490mA Uncomfortable to grasp
1) Does anyone have a power draw figure for an unmodded 1K ZX81? My guess is that removing the modulator and consolidating the RAM might have lowered the current draw a bit.
2) Should I convert to a switching 1A DC-DC regulator for a machine containing a WESPI? Presumably the Sinclair design anticipated a fair amount of heat inside the case, however that did bring notorious reliability problems back at the time didn't it?
My guess is that while it could run hot with the WESPI on a regulated 9V supply, if someone used an original Sinclair PSU it could be hazardous. I want to sell one of the two machines I'm restoring so I need it to be safe. I guess I've convinced myself...
3) How much current headroom do you need to leave (for the DC-DC regulator) to power a ZX Printer to avoid having to give it its own PSU? I have one that I got restored by Mutant Caterpillar so it would be fun to try it without risking a restored Zeddy. I think I'll probably buy a 2A PSU for the ZX81 that I keep for this reason. Will I need a 2A rated regulator?
4) Where's a good place to buy one? All the electronics suppliers seem to have shipping or handling charges that just make small orders non-viable. Retroleum has the 2A Traco, but not the 1A version and it's quite pricey coming in at nearly £15 shipped. Do Chinese fakes of these components exist?