Amiga 1200 / Red Veil Screen

Hello friends,

Since a while now, my Amiga 1200 is displaying a red veiled screen as you can see in the following screenshots :

http://i.imgur.com/IxVBO2Y.jpg
http://i.imgur.com/rOIswIp.jpg
http://i.imgur.com/KtCSMje.jpg

A friend of mine is trying to fix the problem and for now he hasnt find the solution, here is a brief of all modifications and test he did :

- Every resistance of port DB23 has been checked
- It's not the Video Chip
- It's not Alice or Lisa since everything else is working
- It's not the DB23 port
- The capacitors have been replaced
- The video cable is working, problem persists with other cable.

Any ideas ? Any help would be greatly appreciated ! I really need my Amiga 1200 back in shape. Thanks a lot !

[Zapotek]

Hi.

I had a similar problem with yellow, not red.

Just recently I had my board in for recapping and cleaning. At the same time I asked if he could find out why this yellow colour was present and if he could fix it.

I am not sure what the following means, and it is a direct translation to english (not sure what the correct terms in english are and it might appear as complete gibberish..). Maybe it has already been checked, I don't know:

He was able to fix it and it turned out to be an "error in the driver step / one of the steps in RGB amplifier had to be exchanged"

[demolition]

The green channel is missing, so I would follow the green channel backwards from the DB23 to Lisa.

Do you have the same problem with the composite port?

Also, you don't write if you have tried another monitor.

Hey friends, transfered your impressions to my friend, as soon as I have some feedbacks, I'll post them here, thanks a lot for your replies

[Jope]

Time to start checking the area around the transistors near the IDE port, and the transistors themselves.

This is what the "driver step" thing is referring to.

[Daedalus]

Yes, I've seen that before, where capacitors have leaked and destroyed some of the traces around the video circuits, resulting in one of the colour channels disappearing. If that happened before the capacitors were replaced, that won't have fixed the problem. Following the RGB lines from Lisa to the port should find your problem pretty quickly. Also, checking the composite output to see if that has proper colour might help to narrow down the fault.

@Jope
The A1200 doesn't have the video driver stage the same way the A600 does, so there are no transistors to check. The drivers are in the A1200's DAC instead.

[Jope]

Ah, thanks for pointing that out, seems I can't work off my memory any more. :-)

I've also seen a broken CXA1145 mess with the colour output sometimes.. Not immediately obvious, but worth checking if the other components between the DAC and the RGB port seem to be ok.

Thanks for your new feedbacks, my friend will check it out and hopefully will find out the problem. I'll post the result here of course. Thanks again !