MegaSTE Repair Continued - Video Noise

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geogeo_28
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Re: MegaSTE Repair Continued - Video Noise

Post by geogeo_28 »

New picture of the noise:
IMG_0409.jpeg
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exxos
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Re: MegaSTE Repair Continued - Video Noise

Post by exxos »

displaced wrote: 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).
BTW if that PSU is better, have you tried moving it closer to the motherboard ? Also wondering if the video is picking up interference from the PSU.. and as you have the meanwell "out" of the way... was just a thought anyway..
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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Re: MegaSTE Repair Continued - Video Noise

Post by exxos »

Also the problem may be on the RGB drivers .... May need better caps...

Capture.PNG
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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.
geogeo_28
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Re: MegaSTE Repair Continued - Video Noise

Post by geogeo_28 »

I replaced all the caps with new ones but I should definitely test them again. I have an Atlas ESR70 to help. I have to check the diodes also.
Is it possible that the floppy controller adds noise on the bus? Definitively, I know that I have issue with this controller and it needs to be replaced.
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Re: MegaSTE Repair Continued - Video Noise

Post by exxos »

The whole motherboard is a noise generator..
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https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
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.
geogeo_28
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Re: MegaSTE Repair Continued - Video Noise

Post by geogeo_28 »

Unfortunately, switching to another shifter did not solve the problem.
The motherboard has a bigger issue... Keep you posted if I make progress..
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displaced
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Re: MegaSTE Repair Continued - Video Noise

Post by displaced »

exxos wrote: Tue Jan 12, 2021 4:22 pm BTW if that PSU is better, have you tried moving it closer to the motherboard ? Also wondering if the video is picking up interference from the PSU.. and as you have the meanwell "out" of the way... was just a thought anyway..
I didn’t try this I’m afraid - got caught up in other stuff. But in the meantime, I received one of your recap kits for the MSTE PSU and fitted it. There’s slightly more noise than with the Meanwell, but not enough to be a problem. Could be, as you say, proximity related. Still well within what I get with my other old machines, so I’m happy with it.

Got an Epson SMD-340 on the way to go with the AJAX and HD-capable GAL in the machine. Then I just need to wait for the weather to warm up so I can respray the case.
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
geogeo_28
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Re: MegaSTE Repair Continued - Video Noise

Post by geogeo_28 »

@exxos Sorry to revive this topic. By curiosity I saw a post https://www.atari-forum.com/viewtopic.php?t=27647 where you mentioned the possibility to create a buffer for the RGB lines to clean the signal.
Do you have a schematic or could you give more details about this circuit?
Thanks a lot!
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Re: MegaSTE Repair Continued - Video Noise

Post by exxos »

geogeo_28 wrote: Sun Apr 11, 2021 8:05 pm @exxos Sorry to revive this topic. By curiosity I saw a post https://www.atari-forum.com/viewtopic.php?t=27647 where you mentioned the possibility to create a buffer for the RGB lines to clean the signal.
Do you have a schematic or could you give more details about this circuit?
Thanks a lot!
The project was abandoned a long time ago.. too much noise on the motherboard, and even if you buffer everything and make everything look perfectly fine on the scope, the route across the motherboard will pick up noise anyway. If you want better video you will have to wait for the next batch of H5 motherboards where all these problems have been fixed.
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
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.
geogeo_28
Posts: 59
Joined: Fri Nov 06, 2020 12:55 pm

Re: MegaSTE Repair Continued - Video Noise

Post by geogeo_28 »

I guess I will wait for the next batch of H5 motherboards. :)
Proud owner of:
- Atari STF (US).
- Atari STE (UK).
- Atari Falcon030 (US).
- Amiga 1200 (UK).
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