exxos's Atari, Amiga & retro forum

Just having an interesting discussion over at Atari Forum about repairing an SM124 that has had the 13-pin DIN connector cut off.

https://www.atari-forum.com/viewtopic.p ... 17#p463417

My experience of other electronics is that cables, especially captured cables, don't always follow a standard internal colour coded wiring. Is that anyone else's experience?

It should be possible to work out which is the audio pretty easily by trial and error but the other 3 wires (Mono + HSync + VSync) there are 8 combinations. And I don't know what would happen if you connect up the wrong ones.

While I don't like recommending opening up monitors I think that would probably be the easiest way?

https://docs.dev-docs.org/htm/search.php?find=sm124

The MT-21 revision of SM124 has two connectors one (P301) for Mono video the other (P602) for Audio, Hsync and Vsync
The MT-9 revision of SM124 has one connector (P301)

There is a hint in this post of the wiring colour for an MT-21

https://www.atari-forum.com/viewtopic.php?t=42084

P602 = Red, Yellow, Green and Shielding
P301 = Coax with mono being the core and shielding being ground

Anyone experience with servicing SM124? Maybe has one open on the bench now?

Someone in the other thread posted links to better PDFs than I included so I've deleted the attachment

alexh wrote: 09 May 2024 09:28 My experience of other electronics is that cables, especially captured cables, don't always follow a standard internal colour coded wiring. Is that anyone else's experience?

I can't even remember having any cable which followed any sort of colour coding. Last cables I worked on were PS2 cables. Even if they had the same coloured wires, they would vary where they went batch to batch. Sometimes all but 1 colour would be the same, but even that would never tally.

Personally I never use colour coding as a guide as it seems to be the case that manufacturers use 'the cheapest cable available at the time of assembly', leading to mismatches between the varying versions.

I would always buzz out based on schematics and pinouts and connect appropriately.

What you're writing is my experience too. NTSC (Never twice same colour) applied to cables as well as TV pictures :D

But I was just curious if anyone had one open on the bench what theirs is like?

alexh wrote: 09 May 2024 10:35 What you're writing is my experience too. NTSC (Never twice same colour) applied to cables as well as TV pictures :D

:lol: Very true!

alexh wrote: 09 May 2024 10:35 But I was just curious if anyone had one open on the bench what theirs is like?

Sorry, I don't have much in the way of CRT stuff these days, just not enough space.