Degraded video quality with 1040 STF (C070523-001 REV.D)

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Re: Degraded video quality with 1040 STF (C070523-001 REV.D)

Post by rubber_jonnie »

exxos wrote: Wed Sep 05, 2018 1:36 pm
sandord wrote: Wed Sep 05, 2018 1:19 pm I'm thinking of making the CO70789-001 REV. C1 my favourite motherboard, since it has the best features:
The CO70789 type are my favorite styles. Versions without the modulator (STF) are same board, even ones with SMT DRAM, basically same board. So really any similar style board of the CO70789 should be a good one.
Also my favourite boards too, the ability to upgrade the RAM relatively easily, and also the Blitter, make it a good board to get up to a decent spec.

The only trouble I had was that some I've run into have the vias filled with solder, so you need to desolder before you can upgrade anything! 340 holes to desolder isn't fun.
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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: Degraded video quality with 1040 STF (C070523-001 REV.D)

Post by KyleB »

What's the story behind these weird boards? I've had single side drive 1040s that didn't have them, and neither did any of the 520STFMs with rainbow TOS that've passed through my hands. Seems they showed up for a bit in the middle and then went away again.
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Re: Degraded video quality with 1040 STF (C070523-001 REV.D)

Post by exxos »

KyleB wrote: Wed Sep 05, 2018 4:11 pm What's the story behind these weird boards?
No idea. There does seem to be rather a lot of them. Even the CO70789 with its revisions, while they look the same, I found the MMU can be like 1cm to the left on one revision than another.. bizzare..
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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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Re: Degraded video quality with 1040 STF (C070523-001 REV.D)

Post by tzok »

On mine I did this (it is not perfect, but much better):
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Re: Degraded video quality with 1040 STF (C070523-001 REV.D)

Post by exxos »

tzok wrote: Fri Sep 07, 2018 1:36 pm On mine I did this (it is not perfect, but much better):
What did you patch wire up ?
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.
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Re: Degraded video quality with 1040 STF (C070523-001 REV.D)

Post by tzok »

5V rail... from the main cap near PSU connector directly (almost - via the factory choke coils) to Shifter, MMU and DMA, and I've added a 100nF cap under the Shifter.
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Re: Degraded video quality with 1040 STF (C070523-001 REV.D)

Post by SolderGirl »

tzok wrote: Fri Sep 07, 2018 3:08 pm 5V rail... from the main cap near PSU connector directly (almost - via the factory choke coils) to Shifter, MMU and DMA, and I've added a 100nF cap under the Shifter.
Did that improove the quality?
I also have those vertical stripes on my 520 STm.
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Re: Degraded video quality with 1040 STF (C070523-001 REV.D)

Post by tzok »

I've got a lot of signal phase variations, which were visible on a VGA monitor in ST-High, these wires helped to minimize this effect, and the stipes on color modes also disappeared. But I still have a problem with first 10-15 lines being noisy and "skewed" in HIGH mode. I found that the video signal is very dependent on 5V rail, increasing or decreasing voltage on this rail by 100mV results in shifting the whole image by 1-2 pixels left or right. I also have to mention that I have no PSU for this unit, and I'm using really cheap PSU from a 3,5" USB disk enclosure (but I've also tested it on lab supply with more or less same issues). I've ordered a MeanWell RT-65B PSU...
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Re: Degraded video quality with 1040 STF (C070523-001 REV.D)

Post by Cosmic Puppet »

I also have this issue. Have any of you tried them on an original Atari colour CRT?

I'm wondering if it looked like that when originally sold or whether it's only on more modern displays?
US Atari 520 STFM (C070523-001 REV.D1) , Exxos PSU, 4MB Marpet Upgrade, Exxos 6 Chip TOS 1.04 USA, EmuTOS 20211020, Ultrasatan, PP Driver, Original Floppy Disk Drive, NEC Multisync EA193Mi Monitor, Star LC-10c Printer, iMP C100110-001 DMA.
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