Denial

Gyro Gearloose wrote: ↑Mon Dec 26, 2022 10:56 am I am confused. I am also highly hung over and drinking again so who knows ...

I think this is from having two different people experiencing nearly identical video issues with third-party power supplies.

The one I have is this:

C64 PSU Modern Black US - Replacement Commodore 64 Power Supply, US Plug

I since added a review, as did my wife as we bought the thing under her Amazon Prime account. I figured it would be treated as a verified purchase that way.

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 test with a 64?

Gyro Gearloose wrote: ↑Mon Dec 26, 2022 6:44 pm Can you test with a 64?

I need to find one first.

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)?

JonBrawn wrote: ↑Sat Dec 31, 2022 11:10 pm 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 supply I feel pretty ticked off about it.
When I bought this VIC-20 about 4 years ago, the original PSU was non-working so I wasn't able to fire it up until I had bought the after-market one from Electroware on Ebay. When I finally got it and turned it on and saw the video noise, I merely assumed that it was the video circuit since it hadn't entered into my head that a brand new PSU could cause the issue.

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.

sean_sk wrote: ↑Sun Jan 01, 2023 6:09 pm

JonBrawn wrote: ↑Sat Dec 31, 2022 11:10 pm 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 supply I feel pretty ticked off about it.
When I bought this VIC-20 about 4 years ago, the original PSU was non-working so I wasn't able to fire it up until I had bought the after-market one from Electroware on Ebay. When I finally got it and turned it on and saw the video noise, I merely assumed that it was the video circuit since it hadn't entered into my head that a brand new PSU could cause the issue.

I think this is a grounding issue, or what should be called "earthing", or called frame or chassis ground in power supply circles. The 5V switching module used in these supplies is likely a Class II supply meant for things like razors, chargers, LED lights, stuff like that.

The noise I am talking about is generated on the AC side of the 5V switcher. Because of the way they are designed, they dump noise on to the DC side, there is a capacitor for that on purpose.

My working hypothesis, which could be wrong until I see the actual hardware, is that this problem could be solved by putting in a supply with a earth ground connection and connecting it to the mains earth/ground/whatever it's called in your country...

And the fact that this video issue apparently doesn't exist on the 64 reinforces my hypothesis. Until I see real hardware of course.

Here's something that may or may not help to explain

https://www.heliosps.com.au/wp-content/ ... lation.pdf

Maybe you can look for that symbol on the module?

Here are some pics I took of the power supply.
This is a 240v PSU for the Australian region. It has the round 7-pin DIN connector for the VIC-20.

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 ... plies.html

I believe this is a grounding issue.

"OK Gyro you've said that a million times , now what?"

Don't know yet. Let me think about this some more. This appears to be a European version, I have to go take a look at the electrical system over there.

Does anyone know if this VIC-20 issue happens everywhere on Earth? Does it happen with other types of after-market power supplies?

I have a Kellog c64 power supply (din style, USA) works fine on my C64, horrible interference just like the original poster on my newly acquired Vic-20.

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? Does it have an old-timey RF input? Antenna? What kind of power connection does it use? Two or three prong?

And is everything connected to the same AC mains? Like on the same power bar or somehow maybe the monitor is plugged with a 30 foot extension to the next room? With this type of issue, gotta know that.

And is the maker of this supply aware of the problem? Do they acknowledge it? Are they working on it?

My theory, for what it's worth, is that the VIC-20/monitor combo is showing on the screen the noise that the 5V module is injecting into the DC side rather than draining it on the AC ground/earth side.

Perhaps page 4 of this will explain

https://www.mornsun-power.com/public/up ... 3BxxR2.pdf

The AC side of a switching power supply is quite noisy in the electrical sense, you can consider it like a small AM radio transmitter sending out a noisy signal that consists of the frequency of the switching power supply which can be in the 100s of KHz these days, maybe even close to 1MHz (maybe not in these cheaper modules but still).

For many applications it is acceptable to dump this energy on the DC side and it's fine.

But as you can see in the very analog world of NTSC video hooked up to a monitor, there is no difference between the noise and the real video signal and the TV shows it as a hum bar or herring-bones or whatever crap.

The only way to really handle this is with the circuit from page 4. It's either a re-design of the supply or a rework of the present one.

I think by adding an earth ground to the power supply and the right filtering, the issue can be solved but you will need to dig in the supply and add some parts. And from what I see it's a tight fit ... yikes.

Gyro Gearloose wrote: ↑Sat Jan 07, 2023 10:24 pm Can you tell me what monitor you are using? CRT or LCD? Does it have an old-timey RF input? Antenna? What kind of power connection does it use? Two or three prong?

And is everything connected to the same AC mains? Like on the same power bar or somehow maybe the monitor is plugged with a 30 foot extension to the next room? With this type of issue, gotta know that.

My AC mains plug is 3 prong so it includes an earth. My video cable is component cable. Not using RF.
Unfortunately, it doesn't matter where the PSU is plugged into, whether it's the same powerboard or plugged in a socket in another room, the video noise always manifests itself. Also, doesn't matter what monitor is used, LCD or CRT.

Gyro Gearloose wrote: ↑Sat Jan 07, 2023 10:24 pm And is the maker of this supply aware of the problem? Do they acknowledge it? Are they working on it?

I'll let him know, but I don't expect much to come out of this. I'm just annoyed I didn't pick up on this when I got the PSU 4 years ago, because I just assumed it was an issue with the video circuit. But going on similar experiences with other users who have new power supplies and the fact that I have replaced just about every part in the video circuit, it's now obvious the PSU is the problem.

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.

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?

Yeah unsure about that.

Anyway, I have a relative who has infinitely superior electronics knowledge to me. I'll get him to check the PSU with an oscilloscope and see if there is a way we can filter it, if possible.