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.
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...
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.
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..
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.
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.
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.
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.
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...