Odd OSSC interference - Has anybody experienced this?

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Re: Odd OSSC interference - Has anybody experienced this?

Post by rubber_jonnie »

exxos wrote: Fri Oct 01, 2021 1:33 am There was a similar thread not long ago https://www.exxosforum.co.uk/forum/viewt ... =23&t=3681

I don't think there is a solution as it appears the ossc itself has issues.
Yes, I remember that one, but even if the Atari isn't going through the OSSC, it's picking up interference form it when they are both plugged into the same TV. Bloody annoying.
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Re: Odd OSSC interference - Has anybody experienced this?

Post by exxos »

Have you tried putting all the shielding back ?
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Re: Odd OSSC interference - Has anybody experienced this?

Post by exxos »

Oh its 800xl, thought it was a ST.. Yeah those 8bits are built to burger and chips price.. You probably would have to build a video buffer circuit which as a built in conditioner to solve that one :( but also caps on the rgb lines may help.
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Re: Odd OSSC interference - Has anybody experienced this?

Post by rubber_jonnie »

exxos wrote: Fri Oct 01, 2021 9:20 am Have you tried putting all the shielding back ?
I can't on the Atari because of the U1MB, VBXL and Pokeymax upgrades, shield wont fit.

However I am going to try a couple of things in that area, so I will try some shielding (I have a Mega ST upper shield that should do it) over the OSSC and also the Atari, see if it helps. The Atari PSU is new, but I may just try the original, see if that helps and also try running the OSSC of one of my bench PSUs.

I can understand interference like the post you referenced when running the Atari via the OSSC, but not when they are just plugged into the same device i.e. OSSC is plugged into HDMI and has no other device connected, Atari into SCART on the same TV and there is interference when the OSSC is turned on. It 'seems' like it's the TV that is the problem, because simply unplugging the HDMI lead from the TV stops the interference.

Bloody annoying as I'm trying to cut down the cable clutter by using HDMI as much as I can and this is getting in the way.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
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Re: Odd OSSC interference - Has anybody experienced this?

Post by exxos »

So what is powering the ossc ? Are all your cables screened ? If you power up the ossc, and unplug the ossc PSU, does the interference stop as soon as the PSU is unplugged, or does it take a second to go away ?

Do you have theossc plugged into the same mains point as the TV ? Tried a ferrite ring on the HDMI cable ? Tried a shorter HDMI cable ?
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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Re: Odd OSSC interference - Has anybody experienced this?

Post by stephen_usher »

You could try reducing the Pre-Gain amplification on the OSSC. Old micros' video output is noisy at the low levels and the pre-amp stage will show the noise up.
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Re: Odd OSSC interference - Has anybody experienced this?

Post by rubber_jonnie »

exxos wrote: Fri Oct 01, 2021 9:44 am So what is powering the ossc ? Are all your cables screened ? If you power up the ossc, and unplug the ossc PSU, does the interference stop as soon as the PSU is unplugged, or does it take a second to go away ?

Do you have theossc plugged into the same mains point as the TV ? Tried a ferrite ring on the HDMI cable ? Tried a shorter HDMI cable ?
I have tried shorter better quality HDMI cables, longer ones, and just about everything in between. No difference. I don't have a ferrite ring I can add to them.

But, I have something new here from just doing some quick tests.

I loaded up a game on the 800XL that has a predominantly black background. The 800XL is plugged directly into the TV and not using the OSSC, and the OSSC is plugged into the TV using HDMI. With no other devices connected to the OSSC and it turned off, I see very faint, barely noticeable interference patterns slowly rolling up the screen. I hadn't noticed these before as they are very faint. Turning the OSSC on, the pattern becomes much stronger and visibly rolls up the screen.

Switching off the OSSC or pulling power causes the faint pattern to return immediately. If I remove the HDMI cable from the TV or OSSC, all interference disappears.

Now, if I plug my BBC B (Black background, and BBC has zero shielding by default) into the TV using SCART and have just the OSSC connected, no interference just pin sharp white on black.

Putting a grounded metal shield over the Atari or the OSSC makes zero difference.

:dizzy:
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Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
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Re: Odd OSSC interference - Has anybody experienced this?

Post by rubber_jonnie »

stephen_usher wrote: Fri Oct 01, 2021 10:46 am You could try reducing the Pre-Gain amplification on the OSSC. Old micros' video output is noisy at the low levels and the pre-amp stage will show the noise up.
I'll have a delve into the OSSC see what I can do, still getting familiar with it!
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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Re: Odd OSSC interference - Has anybody experienced this?

Post by rubber_jonnie »

stephen_usher wrote: Fri Oct 01, 2021 10:46 am You could try reducing the Pre-Gain amplification on the OSSC. Old micros' video output is noisy at the low levels and the pre-amp stage will show the noise up.
Found it in the menu, will have a play with it later on.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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Re: Odd OSSC interference - Has anybody experienced this?

Post by exxos »

I suspect you may have a grounding problem. It is why I suggested making sure you use the same power point for all items. The only way to really prove this would be to run the OSSC and Atari on battery to isolate it from the mains GND.. Simple if you have a "portable" UPSU I guess..
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
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