Help with Atari STf with no video / RGB

[walterg74]

Today I decided to test (among other things), a recently acquired Atari 1040 STf NTSC I purchased from ebay. I had two other STs (a 1040 STFM and a 520 STe w/4MB) but both were PAL and I wanted to also have an NTSC machine.

 

The computer was listed as "pristine" and shown working with the Atari monitor, but for convenience, shipping,etc. I made an offer and purchased just the computer.

 

Ok background set, here is what happened.

 

My initial tests were with a Commodore 1084S-D2 monitor, and an Atari ST RGB-SCART cable plus a SCART/DB-9 adapter cable.

 

I first tested a 520 STFM, and a 520 STE. Both worked just fine, I tested a few games, ran sysinfo etc., so I know both the monitor and cables work ok.

 

When I went to test the 1040 STf, I did not get a picture. All I got were some rolling horizontal stripes that seemed to be made up of red, white, black, etc. (the computer itself did power up, and loaded the disk, etc. )

 

I decided to go a different route, and pulled out a Sony PVM (that I had to test anyway), along with a SCART-BNC cable.

 

Since this has more options to play around with, I managed to learn some more. Connected properly, the screen stays black, and monitor says it's not receivng sync. Playing around with the inputs for the RGB, selcting "composite" (it's not actual compiste) Imdo see the screen but in a weird red tint, then goes away.

 

I tested the same setup with other consoles and computers (I had a lot to test pending anyway!) and all these worked fine with the same SCART-BNC cable (and their respective RGB-CART cable): The previously tested Ataris, ZX Spectrum 128 +2, Playstation, Neo Geo CD, Saturn, Super Nintendo. Everything works fine, it is only the STf that refuses to cooperate...

 

So... Finally... WTF is wrong?

 

- I know the STf doesn't output composite video, but is it also missing the Composite / Composite video Sync on pin 2 and that's why I get nothing?

 

- How does the Atari Monitor work then? Does it use H-sync and V-sync signals instead?

 

- if I wanted it then to work with the Commodore Monitor, would I have to make my own cable and use the separate H-sync and V-sync signals?

 

- If I want to use the PVM monitor, that only has ONE external sync input, then what? How would I have to produce such input?

 

Thanks!!!

Edited August 27, 2016 by walterg74

[walterg74]

Hmm 2 months, 168 views, and nobody know/cares to comment?

[Android8675]

First guess, your PSU is failing. I have a 1040 STf that works for a while, but starts to crash and fails to start after being on for a few minutes. Drive spins up, but the system usually produces random number of bombs and stops before starting.

 

Can't be sure without a photo of the output, but I suspect you're seeing a crash screen. As for all your other non-ST monitors, I can only point you to other articles about ST video. I think ST uses some weird H/V Combined Sync signal. There are cable pinouts you can look up via Google. I tried to figure it all out a while ago, but finally broke down, got a Best VGA cable and never looked back.

 

Might want to test the PSU to make sure the system is getting enough voltage. Exxos's website might have hints on how to do that.

 

Might just open the ST up and look at the PSU for distended capacitors or other tell taile signs of PSU failures.

 

Good luck,

-A.

[tjlazer]

Try reseating all socketted chips too. Or perform the Atari Universal 4" drop on it.

[atarian1]

Do NOT perform the 4" drop!

[walterg74]

First guess, your PSU is failing. I have a 1040 STf that works for a while, but starts to crash and fails to start after being on for a few minutes. Drive spins up, but the system usually produces random number of bombs and stops before starting.

 

Can't be sure without a photo of the output, but I suspect you're seeing a crash screen. As for all your other non-ST monitors, I can only point you to other articles about ST video. I think ST uses some weird H/V Combined Sync signal. There are cable pinouts you can look up via Google. I tried to figure it all out a while ago, but finally broke down, got a Best VGA cable and never looked back.

 

Might want to test the PSU to make sure the system is getting enough voltage. Exxos's website might have hints on how to do that.

 

Might just open the ST up and look at the PSU for distended capacitors or other tell taile signs of PSU failures.

 

Good luck,

-A.

Thanks, but I don't think that's the case...

 

I recently had some good luck and managed to find an SM-124 monitor. I hooked it up and the picture comes up just fine...

 

So att his point I think maybe it's just the cables are not compatible with this model, maybe missing some resistors or something. Will make my ow and see what happens...

[walterg74]

Try reseating all socketted chips too. Or perform the Atari Universal 4" drop on it.

Do NOT perform the 4" drop!

Don't worry, I'm not THAT stupid! I know the drop only works for Amigas...

[krupkaj]

check 12V rail of the PSU. It drives MC1377 which mix the composite / composite sync signal.

Edited November 27, 2016 by krupkaj

[walterg74]

check 12V rail in the PSU. It drives MC1377 which mix the composite / composite sync signal.

I will check the PSU, but this model doesn't have composite signal...

Edited November 27, 2016 by walterg74

[vattari]

It does have composite sync just not composite video

 

 

Sent from my iPhone using Tapatalk

[walterg74]

It does have composite sync just not composite video

 

 

Sent from my iPhone using Tapatalk

Yes, I know.. but as he said "composite / composite sync signal", since the second is obviously sync, the first must mean composite video, which it does not have...