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Atari ST low res not working?


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Hi,

 

I recently bought a STfm including the monochrome monitor and cubase which is working perfectly.

I'm totally new with the ST so maybe i'm asking a very stupid question...

 

I made a composite cable to hook up to my philips, as this is a STfm composite should be available on the videoport.

Problem is, the only thing i get is sound and a white screen followed by a black screen, when i plug in my hi res monitor (with the atari booted up) it's running in high res.

Is this normal behavior ? Can i force it to low/medium res to test my cable or do i need to load a game disk ?

 

 

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It should be left open. Can you draw a diagram of how you have the cable wired?

----------Video-----> connected to pin 2 next to the audio. The spaces are removed on this BB

|

OOOO-----Audio---->

OOOO

OOOO

O--------ground---->

 

Pin 1: audio

Pin 2 ground

Pin 13: ground

Edited by edwinvanpoeijer
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It should either boot (by default with no desktop info) in low res (with a colour monitor) or high res (with a mono monitor). The boot resolution is entirely determined by whether that pin is there or not on the original ST. What TV/ monitor are you using for low res? It might be having problems synching to the low res and only notices when there is a change in sync. Perhaps you need to fiddle with the monitor settings some more if it is a modern LCD.

 

Occasionally a chip fails on the ST (although it mainly seems to effect the STe) which causes it to be stuck in mono, but as you have achieved colour this would seem to be ok.

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It should either boot (by default with no desktop info) in low res (with a colour monitor) or high res (with a mono monitor). The boot resolution is entirely determined by whether that pin is there or not on the original ST. What TV/ monitor are you using for low res? It might be having problems synching to the low res and only notices when there is a change in sync. Perhaps you need to fiddle with the monitor settings some more if it is a modern LCD.

 

Occasionally a chip fails on the ST (although it mainly seems to effect the STe) which causes it to be stuck in mono, but as you have achieved colour this would seem to be ok.

 

 

I'm using a CM8802, when i boot with this monitor the screen flashes white and then becomes black.

If i then plug in the high res monitor i have instant image of the desktop so it looks like its stuck in high res unless a game/program switches to low res.

 

At least it's working and i can play some games on this nice machine.

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Ah a Phillips. Ok have you tried fiddling with the button on the back left side (if you are looking at the back (the RGB button I think), and the video button?

 

I also noted from the manual that if you have two RGB inputs in at the same time one (through the scart and the RGB port) takes priority over the other. Do you have anything else plugged in there?

 

Other than that I can only think there is a cable problem somewhere (probably something minor by the sound of it).

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Ah a Phillips. Ok have you tried fiddling with the button on the back left side (if you are looking at the back (the RGB button I think), and the video button?

 

I also noted from the manual that if you have two RGB inputs in at the same time one (through the scart and the RGB port) takes priority over the other. Do you have anything else plugged in there?

 

Other than that I can only think there is a cable problem somewhere (probably something minor by the sound of it).

 

 

It's not a cable problem, the Atari always starts in high res mode, if i plug in the philips (without any other computer attached) it will show a white screen and after that a black screen with some distortion.

If i then remove the philips and plug in the SM124 i have high res image (instantaneously without reset of the atari).

If i then load a game the atari switches to low res manual.

So it looks like the monochrome sense is stuck in high res mode?

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That is odd, I always thought changing the monitor caused a reset. In that case you might want to check chip U504 (if this is the same in the STFM as it is in the Mega STe/ STe). You will have to desolder it and replace if it is faulty, so it depends on your skills on that front. On the Mega STe you can cut pin/ leg 7 on that chip to force the computer into low res to test it (but you won't be able to get mono back unless you reconnect it or replace the chip). I wouldn't like to say whether the leg cutting will work on an STFM though. I don't think I could get the STe to boot in low res with a game when I had this fault however, so maybe the fault lies elsewhere.. and is even more obscure.

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That is odd, I always thought changing the monitor caused a reset. In that case you might want to check chip U504 (if this is the same in the STFM as it is in the Mega STe/ STe). You will have to desolder it and replace if it is faulty, so it depends on your skills on that front. On the Mega STe you can cut pin/ leg 7 on that chip to force the computer into low res to test it (but you won't be able to get mono back unless you reconnect it or replace the chip). I wouldn't like to say whether the leg cutting will work on an STFM though. I don't think I could get the STe to boot in low res with a game when I had this fault however, so maybe the fault lies elsewhere.. and is even more obscure.

 

 

I think the STFM doesn't have the U504, pin 4 of the monitor connector is directly linked to the MFP 68901. I think that is where my problem can be found.

I have all the necessary tools to desolder it luckily :) , i only need to find a new part.

The game i tested was Outrun and that game switched to low res, tried also some other games but these didn't start because of the high res mode.

 

Thanks for your help :)

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