STfm without video signal through the DIN port.

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Atarieterno
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STfm without video signal through the DIN port.

Postby Atarieterno » Sun Jan 13, 2019 7:36 pm

Hi guys;
An Atari STfm does not send a video signal through the DIN port, but it works correctly with the RF port connected to a TV.
Can anyone help with a possible solution to this fault?
Thank you.
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Atarieterno
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Re: STfm without video signal through the DIN port.

Postby Atarieterno » Mon Jan 14, 2019 9:11 am

Any ideas to start?
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Re: STfm without video signal through the DIN port.

Postby Arne » Mon Jan 14, 2019 9:25 am

  • do you own an oscilloscope?
  • did you connect an SM124 (or compatible) or SC1224 (or compatible) to the DIN plug?
I have a 1040STFM board currently on my workbench so I could send you specific screenshots of my oscilloscope on certain test points.
Get the schematic and check where the signal path splits into one for the RF and one for the DIN. Then check from there on to the DIN plug for valid signals.
And check that HSYNC and VSYNC tracks on the PCB are not broken to the DIN plug.
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Re: STfm without video signal through the DIN port.

Postby tteclado » Mon Jan 14, 2019 9:28 am

Hi Atarieterno

I imagine, that you have checked with several devices.
If you can, use scart cable, a/v or vga adapter.
I, personally, would clean with a fine needle, the DIN female, in case something prevented the connection.
I hope you have luck with your checks

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Re: STfm without video signal through the DIN port.

Postby joska » Mon Jan 14, 2019 10:08 am

Arne wrote:Get the schematic and check where the signal path splits into one for the RF and one for the DIN.


Composite video is generated by the RF-modulator. There are no components between the modulator and pin 2 on the monitor socket.

So possibly a problem with the RF modulator, or maybe the video cable. Atarierno, are you sure that you are picking up the video signal from the correct pin? It's very easy to use the wrong pin if you're looking at the wrong side of the plug. Believe, I've done it myself more than once.

composite_out.png
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Re: STfm without video signal through the DIN port.

Postby Arne » Mon Jan 14, 2019 10:17 am

Atarieterno wrote:(...) not send a video signal (...)

What exactly do you mean with video signal? Composite video, RGB or Mono video?
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Re: STfm without video signal through the DIN port.

Postby Atarieterno » Mon Jan 14, 2019 1:32 pm

Many thanks to all for the answers, your help is very much appreciated.
The computer is not in my house, it is a young musician who has decided to start in the Atari world to control their electronic instruments and compose their music; but it has started with a bit of bad luck.
Data:
- Atari 1040 STfm (without mods).
- Video cable for high resolution, manufactured by "Retrocables" (http://retrocables.es/tienda/index.php? ... &id_lang=1).
- The computer with that cable was working correctly, but after moving the computer: says the boy who does not turn on the monitor now.
- I told him to try an RF cable to verify that it was not a problem with RAM or power supply: it actually works correctly with the RF cable.
- Unfortunately he does not have an oscilloscope, but all your indications will be what he will write down and deliver to an electronics technician in his city.
I do not know if this fault is typified or is common in the ST, I have searched and can not find much information, but I believe that with all your advice given to the electronics technician he will be able to resuscitate the computer.
Checking the video adapter cable is also a good idea, because previously it worked but I have met people who have even connected the DIN upside down ...

Thank you very much, guys, I take note and send to him all the information we collect.
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Re: STfm without video signal through the DIN port.

Postby Greenious » Mon Jan 14, 2019 2:49 pm

Well, if RF is working (indicating that there's nothing wrong with the video circuit), and the monitor port was working before the move... before hunting for more... complicated faults...

I'd bet that careless removal of the monitorcable broke the din-socket (much like the mouse/joystick port(s) eventually need resoldering), possibly because it was badly soldered from the beginning, or manhandling the cable broke the cable itself.
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