Atari STE - GEM desktop flickers during floppy drive operations

[RollerDos]

Hello everyone,

I'm fairly new here and am currently working on restoring an Atari STE.
I've now purchased a Sidecar VGA adapter and a 15 kHz-compatible LCD monitor.

The monochrome mode and the other two color resolutions can be displayed with good image quality.

So far, so good—but when I'm in high resolution and the floppy drive is performing read/write operations, the gray area of the GEM desktop starts to flicker slightly.
The flickering is synchronized with the floppy drive actions. I have already tried two other floppy drives, with the same effect.

Interestingly, but I dont have this behaviour in the colour mode with both resolutions....

The STE is like new, with all original parts.
What could it be? Maybe the power supply?

Best regards,
Roland

[Steve]

Yeah load caused by the floppy drive... probably need to either upgrade to a 'modern' PSU with new parts, or get an Exxos re-cap kit which includes a better voltage rectifier.

[Darklord]

Yep. What Steve said.

At one point in time, my Mega ST4 would completely reboot whenever I accessed
the floppy drive. It was because of the floppy's draw from a weak P/S. I replaced
the P/S and the problem went away.

Have fun with your project - it sounds like you're off to a roaring start.

[RollerDos]

Hello together,

thanks for your tipps and replys. OK next step is a modern PSU.
So I guess the Sidecar VGA adapter (12V - 10-20mA) and floppy drive 12V, is a little bit too much for the STE PSU.


BR
Roland

[rubber_jonnie]

Hello together,

thanks for your tipps and replys. OK next step is a modern PSU.
So I guess the Sidecar VGA adapter (12V - 10-20mA) and floppy drive 12V, is a little bit too much for the STE PSU.


BR
Roland

The likelihood is that if you recap the PSU it'll work just fine. You may want to check the 5v output as it is adjustable, but best to test under load.

[DoG]

Only very old belt driven floppy drives uses 12V. All the other only uses the 5V line. But the PSU is regulated on the 5V so that makes sense to do a recap on it. Or buy a meanwell and plop that in instead of the original PSU PCB.

[exxos]

Display dimming and noise was part of the design goals of my psu to prevent that issue as much as possible. However I never tried mono. Unfortunately most is down to the motherboard layout. Jailbar issues can also be when display adapters don't use composite sync.