520STFM Playing Blind/Sync Issues

[AtariShrimp]

Morning all!

I've got my old 520STFM back and it appears to be (almost) a worker, except with problems in displaying an image. It is booting, disk drive is working and I can hear/see that it is loading software (Chicago 90 in this case). However, via RF i get sound/black screen and, if I use my RGB Scart cable (Retro Computer Shack) to my CM8833ii, I get a picture, but appears to struggle with Sync. The board is a Rev.F C070759-001 and it's running (iirc) TOS1.4. The TV for RF and the CM8833ii have been tested with other outputs without issue.

Given the symptoms (And my limited skills/understanding of ST hardware) where would be the most obvious places to start? GIven it is behaving impeccably on everything else, I feel like it's probably something fairly innocuous so wondering where the best/obvious place would be to start looking

Thanks!

[exxos]

There are two types of RGB cables. Both depend on when exactly what ST you have and what monitor along with how the cable is wired.

Some older STs don't have combined vertical and horizontal sync over composite, which cables use in general. Aside from that your monitor may not support composite sync.

So the first step is to see what motherboard you have.. "Rev.F C070759-001" I assume is a typo ?

[AtariShrimp]

I'm off to a flying start there Apologies, it is; C070789-001 rev F

The people responsible for writing the first post have been sacked

[exxos]

You have one of the later boards then we should be fine. As you struggling with RF and RGB, you really need a scope to check the V & H syncs are being output from the GLUE and continuity check those points right back to the RGB socket. Also check the socket is not physically damaged as well.

[AtariShrimp]

Ace, thank you! I have a friend with a scope so we can go from there. Will report back on progress

[rubber_jonnie]

Can I ask what TV you are connecting to with RF? Some modern TVs just don't get along with RF from older computers. It's also worth remembering that RF and composite use similar cables, but are not cross compatible.

I've seen a few things recently on FB where people have connected RF to composite on the display and the results were not as expected.

I'm pretty sure the C070789 supports composite so long as it has a modulator installed, so it might be worth trying a simple composite cable too.

[AtariShrimp]

Can I ask what TV you are connecting to with RF? Some modern TVs just don't get along with RF from older computers.

I'm pretty sure the C070789 supports composite so long as it has a modulator installed, so it might be worth trying a simple composite cable too.

Sure, it is the now archaic Hitachi C14-P216. I never threw it away and was the TV I used with this ST from 1989 to 92. #Nostalgiawaves

[rubber_jonnie]

Can I ask what TV you are connecting to with RF? Some modern TVs just don't get along with RF from older computers.

I'm pretty sure the C070789 supports composite so long as it has a modulator installed, so it might be worth trying a simple composite cable too.

Sure, it is the now archaic Hitachi C14-P216. I never threw it away and was the TV I used with this ST from 1989 to 92. #Nostalgiawaves

OK, cool.