Atari 1040stf screen on off on low and medium resolution high ok

[mathias_matschke]

hi forum,

I need your insight pls.

I have acquired a 1040stf with SM124 and wanted to try the color modes and connected the computer via SCART to my TV. The picture in low and medium is surprisingly good. However, in both color resolutions the screen goes black and after a few seconds comes back the cycle time is not regular. The same thing does not happen in high which I connected via VGA to the same TV.

Any idea if this a shifter issue or the TV has issues with the Video signal from the ST. Is there any other easy way to get low resolution mode running. I also have an Atari 13pin to RCA cable which I fed into my retro upscale me which outputs HDMI but no success

thanks for your insight.

BR

mathias

[stephen_usher]

Is this an LCD TV?

This sounds like it's switching between RGB and composite video on the SCART input as the select voltage the SCART cable is marginal.

[rubber_jonnie]

hi forum,

I need your insight pls.

I have acquired a 1040stf with SM124 and wanted to try the color modes and connected the computer via SCART to my TV. The picture in low and medium is surprisingly good. However, in both color resolutions the screen goes black and after a few seconds comes back the cycle time is not regular. The same thing does not happen in high which I connected via VGA to the same TV.

Any idea if this a shifter issue or the TV has issues with the Video signal from the ST. Is there any other easy way to get low resolution mode running. I also have an Atari 13pin to RCA cable which I fed into my retro upscale me which outputs HDMI but no success

thanks for your insight.

BR

mathias

If you have an STF then it has no modulator, so IIRC there is no composite out and your 13 pin to RCA cable wont work unless you install some additional components where the modulator would normally be.

Apologies, but I can't recall what these components are.

I think it likely it is most likely a problem with the TV or the cable is missing some necessary components. Not all SCART cables are made equally.

Do you have a SCART input on your upscaler? If so I'd try that (I have one on my OSSC)

Is your VGA adapter mono only? If it is switchable you can try low and med res via VGA.

[mathias_matschke]

Hi all,

yes it is an LCD TV.

My upscaler has only RCA input and HDMI Out.

I also tried to connect an ATARI 13 pin to the RCA input of the upscaler to see if this brings up an picture via the HDMI input of my TV, but no picture.

So, what could be the solution here. I don't want to add any components to the SFT without M and get low res color preferably on my LCD TV.

Two more question:

1. Would an RCA to SCART adapter work, so s this all kinda hopeless? I understand that as there is no composite coming out of the computer this would be useless and no viable option.

2. So as last resort, where I can I obtain a SCART cable that has a bigger likelihood to work then my current one please.

Thanks all for your support. Appreciated. Have a good Thursday :)

[stephen_usher]

If your STF doesn't have composite sync then you will either need an adapter board which generates it or a special SCART cable which includes the same circuitry as TVs can't handle separate horizontal and vertical sync.

An example of a simple circuit is here: https://www.retrorgb.com/building-a-pas ... biner.html

Passive-Sync-Combiner-1536x856.png

[rubber_jonnie]

Hi all,

yes it is an LCD TV.

My upscaler has only RCA input and HDMI Out.

I also tried to connect an ATARI 13 pin to the RCA input of the upscaler to see if this brings up an picture via the HDMI input of my TV, but no picture.

So, what could be the solution here. I don't want to add any components to the SFT without M and get low res color preferably on my LCD TV.

Two more question:

1. Would an RCA to SCART adapter work, so s this all kinda hopeless? I understand that as there is no composite coming out of the computer this would be useless and no viable option.

2. So as last resort, where I can I obtain a SCART cable that has a bigger likelihood to work then my current one please.

Thanks all for your support. Appreciated. Have a good Thursday :)

You aren't going to be able to use RCA without modding the STF to add the missing components, and if you aren't prepared/able to do that, then you probably need to set aside any ideas of using the RCA output either with an upscaler or with a SCART adapter. No composite out means RCA won't work no matter how you plug it in.

Personally I use a VGA adapter that can be switched from lo/med res to hi res, though your display would need to support 15Khz to support lo/med res. These are available in the store and are relatively inexpensive, but I have no idea if your TV will support 15Khz so can't say if it'll be appropriate.

The other way I display is using an upscaler with SCART input, in this case I have an OSSC which takes SCART and works great. However OSSC's are not the cheapest and require a decent PSU to prevent on screen interference.

As far as a 'better' cable goes, I always use Coolnovelties.co.uk, however I can't state specifically if their cable is suitable, you'd need to ask them before ordering. Other suppliers can be found online, such as Retrocomputershack, another supplier of great cables, however the same caveat applies, you'd need to check what's in the SCART lead with them to be sure.

I would say that there is a new SCART cable that @exxos has been working on that contains a circuit similar to that which @stephen_usher has described and that I will be testing soon, so if you are able to wait then that may be the cable for you.

[exxos]

I did have problems with my uncle's TV back in the 80s going black intermittently. I remember spending hours with the cables in breadboard just endlessly screwing around until I found something which helped. I still use the same cable 30 years later. I'm not going to publish those changes online, but my current cables have those mods. But indeed it can be quite a complicated problem is there was no real proper scart standard.

As already said, some TV's can get confused between composite video and composite sync. So the switching pins need to be correctly done. I do have a couple cables from the places mentioned, one cable had a early version number on it which works reasonably well, and then to some reason I purchased another cable years later which has a updated version on it which has issues with my TV. So I think they were trying to fix some problem but inherently created another problem. I won't say which company this was. But they were "standard" composite sync cables.

I have got made up a load of standard cables which should work better for most people but it is never a guarantee unfortunately it will work with all TVs. I remember talking to a company back in the 80 who said there was three types of cables. If I remember rightly SONY TVs had to have a different cable but I don't know what those changes were.

Indeed the cables I'm prototyping currently don't use composite sync. A lot of STs simply don't have it. So these new cables should offer the maximum compatibility with is realistically achievable. The standard cable should be in the store over the next couple of weeks. Though the more advanced cables, I really want to try and solve the background interference problems first. Generally this needs individually screen cables but such cable does not seem to exist any more, and I even posted about this several years ago as well. There only overall screened. I won't hijack this thread with all the technicalities anyway.

@rubber_jonnie should be getting the new type cable to compare on his TVs soon. My original cables worked on my TV but the mods didn't work on his. So I redesigned the cable which hopefully will now be compatible with his TVs. Though before anyone gets excited, these are quite problematical to build up. So it could be some months before I can finalise the design and they hit the store.

Indeed he could simply try one of my standard cables when they get into the store soon. They do have more mods and wide slightly differently than other people's cables. But again it is really difficult to guarantee any sort of success with so many TVs out there all doing different things.

[JezC]

I'm sure that I have an external modulator box (with composite output) for my UK spec 1040STF...never opened it up to see what was in there though.

That 1040 (bought in April 1987 with a SM135 monitor) had red LEDs, the long button floppy and the 'silly' motherboard with the RAM under the keyboard (and no Blitter socket) - and I still have it in a working state (but upgraded to 4Meg, 6 chip TOS 1.04 and a replacement floppy drive)

If I can find that external modulator I'll open it up & post some pictures, just in case it helps.

[mathias_matschke]

Hi Forum,

Thanks for your insight. I ordered the st2vga adapter and will find myself a new 15khz monitor. Will report how it went when I am ready.

Thanks.

[rubber_jonnie]

Hi Forum,

Thanks for your insight. I ordered the st2vga adapter and will find myself a new 15khz monitor. Will report how it went when I am ready.

Thanks.

Good stuff, will be interested to see how you get on.