Sun GDM 20E20 CRT H-Sync Issue

Tete85

Aug 11, 2022
6
Joined
Aug 11, 2022
Messages
6
I need help with a very particular sync problem I'm having. I repaired a Sun Monitor with a Sony Trinitron tube which doesn't have a service manual, which makes things difficult.

The problem I have is that it loses horizontal sync both in the post and in most games (it's a Retro PC). It only looks good in Windows and running Quake 2 (800x600)...I tried differents frames rates (60-70-75 on windows...works fine) but half life, windows safe mode , and other similars test games the Horizontal lose sync. I've already tried changing capacitors on the sync board and I also changed a regulator.

The only thing I need to try is to change the 3w13 Cable. But I'm not sure that's the problem. The monitor was working fine last year and now it loses synchronization in standard resolutions as I already said in Bios, Safe mode windows and Games except Quake 2.. (Quake1 lose sync too).

Has anyone ever seen something like this? Any help would be appreciated.
 

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73's de Edd

Aug 21, 2015
3,730
Joined
Aug 21, 2015
Messages
3,730
Well . . . . . . its like this . . . . . . on your first picture, the monitor has properly phase checked and synced in and produced that stable picture.
HOWEVER . . . . on the second and third pictures . . . . . that videos incoming horizontal sync frequency is being at approximately 16 times higher than the first pics locked in horizontal sync frequency.
 
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