jimh@ultra.com (Jim Hurley) (01/16/90)
I have an Atari monochrome display that's about 5 months old. Recently, it's gotten the jitters and they're getting worse. The symptom is a jittery screen display, but only the top half of the display is affected. The symptoms appear only after the unit warms up. The unit was rock-steady when new. My guess is that it's a heat-related horizontal sync problem. I have noticed this problem on at least one other monochrome monitor. Anyone know the cause and cure? If I had schematics I'm sure I could troubleshoot. Thanks in advance. -- Jim Hurley domain: jimh@ultra.com UltraNetwork Technologies Internet: ultra!jimh@ames.arc.nasa.gov 101 Daggett Dr. uucp: ...ames!ultra!jimh San Jose, CA 95134 (408) 922-0100
econadm5@watserv1.waterloo.edu (BENTLEY BH - ECONOMICS) (01/17/90)
In article <1990Jan15.182430.2495@ultra.com> jimh@ultra.com (Jim Hurley) writes: > >I have an Atari monochrome display that's about 5 months old. >Recently, it's gotten the jitters and they're getting worse. >The symptom is a jittery screen display, but only the top half >of the display is affected. The symptoms appear only after the >unit warms up. The unit was rock-steady when new. I have fixed several Monochrome Sm124 or SM125 models. I even have the schematics for both of them. When I was having similar problems with my monitor I found it was the IC that controls Vhold and Hhold. On some models its the IC601. I found near the back of the unit when your looking at it from the back. I simply replaced this IC and my problems were fixed. This IC after a number of years causes several problems or symptoms 1) Mine had background was black with no checkers display and characters were white.(looked terrible) 2) On other Sm124 or sm125's screen looked fuzzy and my screen after warmup had the jitters Hhold or Vhold were out of sync? Well thats a guess. So if your good at desoldering there are three to four ICs on the older Sm 124's and one or two on the newer ones that I remember. Ps when I used an ohmmeter on this chip all signals seemed correct. So I suggest you concentrate on the ICs and the one in the middle towards the back is the one I replaced on the older model..(ill dig up the IC number for you when I get my schematics back from my former place of residence) Dave Tomesch, Super BBS (519) 749-1206, Kwest Co-Chairman, StarTrak Inc. "The Man with the Golden Gun"