exxos's Atari, Amiga & retro forum

Hello,
I have a naughty 1040STf with video that is jumping; the picture keeps rolling off the screen. I just completed a recapping, and replacement of the pullup resistors yet still have the same problem. Where should I look now? :?

It might be your monitor ? ST video isn't "ideal". If you monitor has V-Hold present then tweak that.

What screen are you using?

Is it vertical or horizontal rolling, is the rest of the picture fine?

It may be that your hsync or vsync have a bad connection.

Hsync and vsync can be traced straight from the glue to get monitor socket, so a real quick check could be to remove the glue, clean and straighten any pins and then see if that fixes it.

exxos wrote: 14 Jul 2021 22:04 It might be your monitor ? ST video isn't "ideal". If you monitor has V-Hold present then tweak that.

For video, I use an upscaler board into a VGA which seems to work well with my other ST's monitor output. That other machine, yet to be re-capped, also begins skipping, but after 15-20 minutes of use.
Perhaps it is my upscaler and monitor but I doubt it since I've used two monitors, and my 2nd machine is an stfm which behaves the same with a television.

So I removed my Shifter, deoxed it and the connectors, and found continuity between IC pins 2,20, & 21 and monitor #12 (vsync). replaced the Shifter and now I've got the White Screen of Death. :stars: Though I've got your diagnostic cartridge, I'll have to wait for a null modem cable to get here.

PhilC wrote: 14 Jul 2021 22:07
It may be that your hsync or vsync have a bad connection.

Hsync and vsync can be traced straight from the glue to get monitor socket, so a real quick check could be to remove the glue, clean and straighten any pins and then see if that fixes it.

I couldn't find continuity to Hsync, but perhaps I had the wrong pin on the monitor out. Still exploring that avenue. Things have gotten worse since I reseated the chip, so maybe a trace or joint. I wish I had schematic for this 70523 board.

@PeckPeekPoke with regard to the GLUE, MMU and Monitor Socket you can use any ST schematic as the pin layouts are the same.

As a for instance Vsync & Hsync are on pins 37 and 38 on the GLUE and go to 12 for vsync and 9 for sync on the 13 pin monitor socket.