Denial

interesting. What's the schematic, and what else is plugged to the VIC-20? Monitor, RF? 1541?

Maybe it's hungry? Seriously though, if you try the command several times, does it always display pi or other characters too?

Also remove the RAM expander and try again.

Well let us know what you find. In the meantime here's something else to try: a clip-on common-mode choke on the DC cable itself, even better if you can chop up the cable and only choke the 5V and ground lines. You can buy a variety of clip-on ferrites but there's rarely any specs attached to the ch...

It's just an idle speculation. I guess it would be possible to design a VIC-20 motherboard in the SX form factor, but who would want to actually do it? A madman, surely.

Curiosity is killing me here, I was thinking of buying a Meanwell IRM-10-5 supply and see how it behaves here, but my bench is a mess.

Then the thought occurred, could there be counterfeit modules that perform poorly that ended up in these supplies?

Well the issue is fixable, it just depends how much time and energy and money you want to put into it, or just buy another supply. Surely there must be other supplies that don't have this noise issue.

Has anyone ever tried to make a SX-20? Hey at least it would be more legible on that 5" CRT. I had the same idea - SX-20 and I bought a tiny CRT a couple of years ago, but didn't get further than that. But perhaps one day 😉 Yeah it would be useless but kinda fun. Since you bought a CRT I guess...

No one? Come on. Next you'll tell me my idea for a VIC-20 to MCA bus adapter is dumb too.

Interesting. It is difficult to find the source of these types of problems even with the hardware on hand to poke at, so it's pretty much just conjecture on my part since I do not own such a supply, but I've seen these kinds of issues before. Can you tell me what monitor you are using? CRT or LCD? D...

Thanks. Well we can clearly see the Class II symbol on the DC switcher module. "Class II power supplies can be identified on the label by a symbol of a large square with a smaller square inside of it. " https://www.superbrightleds.com/blog/is-there-a-difference-between-class-2-and-class-ii...

Has anyone ever tried to make a SX-20? Hey at least it would be more legible on that 5" CRT.

Maybe the switching frequency inside the switched mode power supply is similar to one of the video frequencies (frame rate, line rate, dot clock, colour subcarrier)? Would there be any way to adjust this? I opened up the PSU and the 5v switch-mode looks pretty non-serviceable. If it is the power su...

Can you share what power supply model you are using? I'd like to look at it. Also, same question about using it with a 64.

I suspect that the same power supply does not cause the same video issues on a C64, because the 64 derives a separate power supply just for the VIC-II chip and its circuitry from the 9VAC winding, bypassing somewhat the noise injected by the 5V switcher. Would you know if this is correct? Can you te...

Sorry, I was too lazy to click on your eBay link at first because it sounded just like a "switch mode power supply that uses no Earth connection noise injection" issue. But you said "power supply I got had a ground pin on it" so I clicked the link and saw this https://i.ebayimg.c...