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

[rubber_jonnie]

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.

[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.

[exxos]

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..

[tzok]

On mine I did this (it is not perfect, but much better):

[exxos]

On mine I did this (it is not perfect, but much better):

What did you patch wire up ?

[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.

[SolderGirl]

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.

[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...

[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?