Yup the only plausible way to horizontally shift analog video is by changing the time between the Hsync and the actual picture, it would take a spectacular cable - with active electronics to be less than several hundred meters long - to do that; you most likely have a scaler in the monitor that doesn't like the timings and/or the sync polarity very much (I also agree that the few size/position options on VGA LCDs are usually useless)

From your description, connecting the drive causes a short somewhere - I would try using only one power supply (I made a similar system, most 3.5 FDDs only use 5V and 3A should be enough for the motherboard + drive)

Unrelated, but you're using a 2mm to 2.56mm adapter cable for the FDD, right?

Not sure if it's a good idea to have different 5V supplies. If you haven't already then it might be worth making sure that their grounds are connected.

Thanks for your replies.

I'm using a combo drive (3.5" + 5.25"), so I need 12V. I'm temporarily using an AC to DC molex adapter to power the drive, like the one seen in the picture . But the idea is to end up using a 5V power supply and a 12V power supply like the ones seen in the picture. Currently, I'm using the 5V power supply to power the board.

Can I connect the grounds of both power supplies?

Yep you should be fine connecting the grounds together directly (the drive will do that for you if you simply use each half of the power connector for either brick, but better to not depend on that and do it in a "permanent" manner)

Ok. I'll try connecting the grounds and get back to you.

In regards to the H sync, as I said, I made my own cable... Actually, I made an adapter. The board has a 2x5 pin header for VGA, and I got a VGA to 2x6 cable. So I used a perforated board to reroute the pins, as seen in the pictures.

The pins are 100% where they should. I checked, and rechecked, and they make good contact, and there are no short circuits. I used a tester in continuity mode and everything is fine. But is there a chance that this kind of soldering does not agree with the high frequency signals of the VGA cable?

popcalent wrote on 2024-03-03, 14:32:

But is there a chance that this kind of soldering does not agree with the high frequency signals of the VGA cable?

That would only make the picture unsharp (ringing/trailing edges/blurry), it would take a spectacular length of the R/G/B wires compared to H to shift it without electronics 😀

Ryccardo wrote on 2024-03-04, 20:21:

That would only make the picture unsharp (ringing/trailing edges/blurry), it would take a spectacular length of the R/G/B wires compared to H to shift it without electronics 😀

So it's 100% the board not working then?

I tried a different cable on the same monitor, and I got the same issue (picture shifted to the right). Same as shown on the first picture I posted.

Then I tried on a different monitor, and the picture is slightly shifted to the left, and the bottom line is out of frame (see how the DOS prompt is not visible).

The keyboard... Sometimes works, sometimes doesn't. And I haven't been able to try powering the floppy drive with a common negative. But at this point, I'm 100% certain the board is faulty. I'll have to return it. What a bummer!!