Atari STe video switching color/mono

[nemox]

Hi,
my atari 520 STe can't switch to color mode. switching mono / color mode does nothing, the computer does not even restart.
Pls any idea?

[rubber_jonnie]

How are you switching it?

The ST and STE are switched depending on the type of cable that's plugged in.

So either you are using a Mono cable, a colour cable, or a VGA switcher.

Please expand on how you are trying to change mode.

[Smonson]

I had a problem like this once on my STFM. The mono-detect pin in the video socket is sensitive to static electricity and can become damaged, and then it doesn't do anything anymore. It's connected straight to the 68901. I had to replace my 68901 with a new one to fix the issue. As far as I know it's the same setup on an STe.

[czietz]

I had a problem like this once on my STFM. The mono-detect pin in the video socket is sensitive to static electricity and can become damaged, and then it doesn't do anything anymore. It's connected straight to the 68901. I had to replace my 68901 with a new one to fix the issue. As far as I know it's the same setup on an STe.

In the STe, it's not connected directly to the 68901 but to a 74xx logic IC. That one often dies, as well, though, and is the most common cause for what @nemox is observing. Please see this long thread incl. happy ending http://atari-forum.com/viewtopic.php?f=15&t=38424, also as a cautionary tale to replace the IC with the exact same part number.

[stephen_usher]

Or faster version, e.g. 74ASxxx (though that is CMOS so your milage may vary).

[nemox]

Thanks
.I'll test the circuit 74xxxx