MegaSTE Repair Continued - Video Noise

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displaced
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Re: MegaSTE Repair Continued - Video Noise

Post by displaced » Wed Jan 06, 2021 4:46 pm

Some of that might be my phone - it’s quite difficult to get a good picture of the screen. Had to force focus on a dark area to get it to show the interference. It looks bright, but not bloom-y in real life.

Plus, this is my usual computer monitor which is normally used with my PC. I’m a bit of a b’stard when it comes to wanting a lot of nits blasted into my face when coding :)
A bunch of Ataris and others:
Atari XEGS with RGB mod - STFM - Portfolio - Lynx Mk1 with McWill display - Mega STE - Falcon030 - Jaguar
Commodore VIC-20 CR with ClearVideo - CDTV (Wicher 8MB+IDE)
Acorn Electron - Archimedes A3020

displaced
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Location: UK

Re: MegaSTE Repair Continued - Video Noise

Post by displaced » Thu Jan 07, 2021 12:08 am

Well, whaddya know...

Wired up a Meanwell RQ85B, and here's the output (earth connected, OSSC powered via its usual USB adapter).
IMG_5889.JPG
IMG_5889.JPG (169.34 KiB) Viewed 123 times
Still a little bloom-y, but the interference pattern's gone. There are still slight jailbars visible, but they're barely visible from a normal viewing distance. Again, everything looks brighter in the photo than in real life.

Looks no worse than any of my other Atari systems (although nothing can beat the Acorn Electron - the output on that is so ridiculously crisp it looks like an emulator!)

Here's the new PSU hooked up in a nicely bodgy manner.
IMG_5884.JPG
IMG_5884.JPG (170.73 KiB) Viewed 123 times
Got a P8/P9 connector on its way, as well as a new power switch from exxos. Was going to replace the old PSU's switch anyway as it's quite bzzzty during the throw. So hopefully I'll be able to fit this nice and cleanly somehow.

Will test a few more times over the next couple of days before going ahead, just to make sure the problem doesn't rear its head again.
A bunch of Ataris and others:
Atari XEGS with RGB mod - STFM - Portfolio - Lynx Mk1 with McWill display - Mega STE - Falcon030 - Jaguar
Commodore VIC-20 CR with ClearVideo - CDTV (Wicher 8MB+IDE)
Acorn Electron - Archimedes A3020

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Re: MegaSTE Repair Continued - Video Noise

Post by exxos » Thu Jan 07, 2021 12:20 am

I thought you recapped the PSU right at the start ?
https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.

displaced
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Re: MegaSTE Repair Continued - Video Noise

Post by displaced » Thu Jan 07, 2021 12:31 am

Ah no, I hadn't -- I did post some scope traces from the existing one that didn't look too bad early on.

Should've bit the bullet and done that straight away, but the voltages were good and the machine was stable. I think geogeo_28, with almost identical interference, had recapped their PSU and motherboard, though.
A bunch of Ataris and others:
Atari XEGS with RGB mod - STFM - Portfolio - Lynx Mk1 with McWill display - Mega STE - Falcon030 - Jaguar
Commodore VIC-20 CR with ClearVideo - CDTV (Wicher 8MB+IDE)
Acorn Electron - Archimedes A3020

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Re: MegaSTE Repair Continued - Video Noise

Post by exxos » Thu Jan 07, 2021 12:35 am

Looks like he had issues with a STE looking back., says he brought a new recapped PSU.. But from who ? I've seen people selling recapped PSUs with caps worse than the originals ...

@geogeo_28 what PSU exactly has your machine got ?
https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.

geogeo_28
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Re: MegaSTE Repair Continued - Video Noise

Post by geogeo_28 » Thu Jan 07, 2021 12:56 am

exxos wrote:
Thu Jan 07, 2021 12:35 am
@geogeo_28 what PSU exactly has your machine got ?
The one from your store. ;)

I tried to remove the ground of the Atari STE and remove the Ultimate Scart Converter (HVSync to CSync) and no change.

I plugged in also my Amiga 1200 PAL and the image is way brighter in the dark area with lot of noise but different of the Atari STE (similar noise than the Atari STF).
I suspect more and more that the noise is coming from the Framemeister. At 60 Hz NTSC, the image is perfect. Not sure if the A/D converter of the Framemeister is designed for 50 Hz PAL or an hidden setting is required?

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Re: MegaSTE Repair Continued - Video Noise

Post by exxos » Thu Jan 07, 2021 1:17 am

Is the STE the one you posted with the booster ? As it looks like you have parity simms... Plus the 32mhz wire could be causing you issues..
https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
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geogeo_28
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Re: MegaSTE Repair Continued - Video Noise

Post by geogeo_28 » Thu Jan 07, 2021 1:31 am

Yes this is the STE with the booster. How do you see the RAM has parity? I will definitively try with another RAM and check the 32 MHz wire!

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Re: MegaSTE Repair Continued - Video Noise

Post by exxos » Thu Jan 07, 2021 1:34 am

geogeo_28 wrote:
Thu Jan 07, 2021 1:31 am
Yes this is the STE with the booster. How do you see the RAM has parity? I will definitively try with another RAM and check the 32 MHz wire!
Its 3 chip.. Odd numbers are parity Simms... They can oscilate causing noise and as I have shown in my videos, they can cause video and ram faults.
https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.

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Re: MegaSTE Repair Continued - Video Noise

Post by geogeo_28 » Thu Jan 07, 2021 3:02 am

Ok I tried the original 2x256K without parity and no change, same noise.
What do you suggest for the 32 MHz wire, I can try to reroute it.
Switching to 32 MHz on the fly shows more noise, white bands.
If the CPU freeze during the switch, the white bands disappear and the noise is similar to the STF.

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