I have a vintage Macintosh Plus recently removed from long-term storage. It seems to be working well and I added a BlueSCSI emulator which boots fine into Systems 6 and 7.
I have one minor problem I noticed when it was running for a while. The screen, which on boot-up was nicely crisp, bright, and centred, began to move horizontally ever so slightly left of centre after about an hour of use.
I know there are controls on the Analog board to adjust the CRT picture and one of those controls manages centring the desktop image. So I’m guessing some part of that circuit is drifting with time and temperature. It’s still acceptable after an hour but I’m not sure if running longer will cause the screen to move even further left. Although I’m unlikely to have it running for such a long time I’d like, if only for aesthetic reasons, to have it centred and stable. I did the 'Diode Mod' on the logic board to power the BlueSCSI from the SCSI port and took a look at as much of the analog board I could see at the time and the capacitors seemed in pretty good shape, with no obvious bulging or leaking.
I’m not a techie, or an electronic engineer, but I have a common-sense approach to troubleshooting and problem solving. Can anyone advise on how I might go about fixing this problem? Or point me at a link about the circuitry controlling horizontal centring of the Macintosh Plus display? And, if there’s a better forum to post this question in please let me know. Thanks!
I have one minor problem I noticed when it was running for a while. The screen, which on boot-up was nicely crisp, bright, and centred, began to move horizontally ever so slightly left of centre after about an hour of use.
I know there are controls on the Analog board to adjust the CRT picture and one of those controls manages centring the desktop image. So I’m guessing some part of that circuit is drifting with time and temperature. It’s still acceptable after an hour but I’m not sure if running longer will cause the screen to move even further left. Although I’m unlikely to have it running for such a long time I’d like, if only for aesthetic reasons, to have it centred and stable. I did the 'Diode Mod' on the logic board to power the BlueSCSI from the SCSI port and took a look at as much of the analog board I could see at the time and the capacitors seemed in pretty good shape, with no obvious bulging or leaking.
I’m not a techie, or an electronic engineer, but I have a common-sense approach to troubleshooting and problem solving. Can anyone advise on how I might go about fixing this problem? Or point me at a link about the circuitry controlling horizontal centring of the Macintosh Plus display? And, if there’s a better forum to post this question in please let me know. Thanks!