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Posted By

Majikeyric
on 2022-09-28
20:06:26

Video interferences

Hi,

Any idea why I get video interferences when hooking up a PI1541 or a SideKick264 to my C16 ?

Is it because there is no "paper" shield protection inside the C16 ?

Thank you

Posted By

SVS
on 2022-10-01
07:06:59

Re: Video interferences

Maybe yes, if the interferences slow down if you move the video far from the C16.

Posted By

MIK
on 2022-10-01
07:18:06

Re: Video interferences

I believe Commodore 'may' of stoped using the cardboard shield in later C16's as they realised the C16 keyboard does the same thing due to the amount of metal it's made up of? Some later 64C's also removed it - cost cutting maybe?

The obvious thing would be to try a different power pack on your C16. It may be a lack of amps to power every thing? Some cheap modern day adapters can cause interference with old tech, an old Casio keyboard I have gained a lot of hiss gritty sounding feedback out of the speakers because of the modern day 9volt AC adapter I tried on it... I stoped using it and use one from the era the keyboard was made and all was fine.

Maybe these devices your using are not grounded properly to the C16??? Sadly I'm not an expert on these things so can only guess.

If these devices are external try holding some tin foil between them and the C16 to see if it does anything.

Posted By

TLC
on 2022-10-02
16:39:48

Re: Video interferences

A friend of mine has experienced similar problems when he powered one of his computers from a cheap modern wall-outlet SMPS.

The story probably goes like this. The SMPS produces some amount of periodic high frequency noise, which (the HF components, that is) would be superponed to the signals inside the computer, including video out. Modern displays have inputs of very high bandwidth, picture properties are only controlled by particular sampling frequency and later (post-A/D, digital) stages, but not analog input bandwidth limit filters. Some of the high frequency noise content gets past the A/D stage undersampled (i.e. spreading then over the entire useful video band), and ends up displayed as an interference-type noise.

I believe that this case here should probably be similar to that one. The SMPS of the RPi adds some HF interference. The devices are grounded together, consequently, the HF noise should be found everywhere in the whole system.

(No particular safe bets from me to solve that, sorry. If I had problems like that, I'd try to get rid of the HF noise off the power supply voltage. Maybe I'd look for some solution to filter the PSU voltage of the RPi, a different RPi PSU, maybe, an old linear (non-SM) PSU, which is known not to produce HF interference.)

Posted By

MMS
on 2022-10-05
15:22:57

Re: Video interferences

Please doublecheck you use the same wall socket. There could be (corr) potential differences between the wall sockets, and this voltage may generate problems. Once we measured 28V between two sockets at the hostel.

Posted By

MIK
on 2022-10-02
19:15:05

Re: Video interferences

One more thought... keep mobile phones well away.
My woman's phone used to mess up the picture for a few seconds on an old digital TV box when a text arrived if the phone was 2-3 meters away from it. Ever since then I try to avoid having a mobile phone near older tech when it's powered on.

Posted By

Majikeyric
on 2022-10-17
09:10:21

Re: Video interferences

Thanks for your help.

I have tried different C16s, different PSUs, different Rpi PSUs, on the same wall socket, with LCD or CRT, with or without a tin foil.
But nothing does unfortunately, even if I move the video far from the C16.

Posted By

javierglez
on 2022-10-16
16:23:32

Re: Video interferences

Now I recall that the PSU (a new one) of a 1541-II ruined the picture on my LCD TV. If I used a CRT or I used an original 1541-II/1581 PSU, it didn't happen. Back then I'm pretty convinced I was using a Plus/4 with an original PSU, checking some demos, Pet's Rescue, Alpharay, before SD2IEC versions were available.

A similar situation happened when I put a C128 PSU (or maybe stacked a couple of them) on the table next to a 1084P, disappeared when I moved it under the table.

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