Atari ST 1040 - restarts due to video cable malfunction

[tonata]

Hi,

I have an Atari ST 1040 STe. I use it together with SM124.

I have a problem with the video cable. If I move the cable just a little bit (where the connector for the Atari is), the computer seems to either make short-circuit or it restarts without being able to boot. The screen becomes either white with unsuccessful attempts to load TOS or completely dark. Or it flickers a lot.

Maybe it is a known problem? Is it the connector inside the Atari ST?

 

[mbliss11]

I would open it up to inspect the socket on the board and then consider using a new cable if it’s not the socket. I have a 520st and definitely does not do that. I wouldn’t keep doing it either there is 12v on pin 8 of video port that could cause some havoc on the board if that is bridged to another pin

 

[Timo W.]

Pin 4 is the monochrome display detect pin. I'm pretty sure (un)connecting that while the power is on results in a reset, or even in a crash.

So yes, could very well be the cable. However, it can be the socket, too.

 

[tonata]

I tried with another cable that I use for the small/medium resolution with my TV. It was stable.
So it must be the male connector of the SM124 cable?

 

[Timo W.]

Seems so, yes. Or a broken wire near the connector, which isn't that uncommon.

 

[tonata]

Thanks. So I should shorten the cable a little bit near the male connector to hopefully cover this case as well.

 

[tonata]

Here are some photos of the internal connector.

 

[PPC_505]

Those look pretty corroded. Perhaps it's time for a toothbrush and some vinegar to see if you can't clean those up?

 

[tonata]

This is the back of the connector on the motherboard. Problem is that it is not possible to clean inside the connector (the other side). What we see is probably OK as long as it does not touch???
I will try first replacing the male connector on the Atari cable. I already ordered one.

 

[Zare]

I tried with another cable that I use for the small/medium resolution with my TV. It was stable.
So it must be the male connector of the SM124 cable?

SM124 uses MVIDEO pin for signal, the low/mid res screen uses RGB pins. Stable over RGB doesn't mean MVIDEO is ok.

This is the back of the connector on the motherboard. Problem is that it is not possible to clean inside the connector (the other side). What we see is probably OK as long as it does not touch???
I will try first replacing the male connector on the Atari cable. I already ordered one.

IMO you need to clean up the ST connector as best as you can.

 

[tonata]

You mean clean the female port on the ST?
How do I clean inside these tiny holes ... without making it worse?

From here https://info-coach.fr/atari/hardware/interfaces.php#atari_video_connector I see that I need to clean top left pin (pin 4 monochrome detection) when looking at the back of the Atari ST.
Question is what tool to use.

 

[seat safety switch]

You could try a bottle brush. I think I would probably spray Deoxit in there to start and then plug and unplug a cable a bunch of times.

 

[g4ugm]

You mean clean the female port on the ST?
How do I clean inside these tiny holes ... without making it worse?

From here https://info-coach.fr/atari/hardware/interfaces.php#atari_video_connector I see that I need to clean top left pin (pin 4 monochrome detection) when looking at the back of the Atari ST.
Question is what tool to use.

I don't think its the holes, but its more likely the joint between the actual socket in the housing, and the riser pin ringed here in the picture.
I wonder if its possible to replace the socket?
As for cleaning I would spray with "switch cleaner and lubricant" and push the plug in and out several times...

 

[cjs]

I wonder if its possible to replace the socket?

Sure, though how difficult it will be depends on the the layout of the PCB pads. (I've only ever seen one pinout that I recall, though.)

The page you linked claims that the connectors are "very hard to find," but perhaps he just didn't know about Amazon and AliExpress (whether local or overseas or wherever).

 

[seat safety switch]

The port is definitely replace-able, but swapping out DINs on a board is a huge pain in the butt. Especially if you don't have a lot of soldering experience: there's a lot of thermal mass to heat up there and awkward pads to clear.