I'm progressing with the restoration of my ebay M24. After fixing the faulty PSU, reviving the harddrive (Tandon TM502: fortunately wiping the metal tab contacting motor "spindle" on the bottom of the drive with contact cleaner was enough to make it spin again), and completely disassembling/cleaning a super filthy keyboard (yuk!) where almost none of the keys had worked reliably, it is almost perfect again. Almost...
Final issue (hopefully) is a defect with the monitor. It's color monitor for the M24, an Olivetti "DSM 2412/C":
Unlike many other Olivetti monitors this one is not made by Hantarex, but by Toshiba: its chassis has a label "Toshiba CDU 1200". The main PCB bears a type label "Toshiba PW 4269-1". This is the monitor also mentioned in this other thread.
Unfortunately I could not find any schematics for this monitor. Neither the Olivetti number, nor the Toshiba numbers result in anything useful.
The actual issue I'm having with this monitor is some defect affecting the monitor's brightness/contrast. Everything is fine when the overall screen is mostly dark. In this case the display is perfectly bright & crisp:
However, as soon as the overall screen is bright (colored background, or graphics filling most of the screen) then the monitor slowly get's brighter and shows terrible contrast (photo doesn't truely reflect the issue, but you can kind of guess):
Switching back to a screen content with mostly black background, slowly restores the picture quality to normal brightness/contrast.
I'm hoping it's going to be a simple issue - maybe a bad capacitor. I'll probably have to completely disassemble the main PCB (yes, after discharging the tube first) and see if I can find any suspicious component. If anyone had any more specific suggestions, let me know...
Final issue (hopefully) is a defect with the monitor. It's color monitor for the M24, an Olivetti "DSM 2412/C":
Unlike many other Olivetti monitors this one is not made by Hantarex, but by Toshiba: its chassis has a label "Toshiba CDU 1200". The main PCB bears a type label "Toshiba PW 4269-1". This is the monitor also mentioned in this other thread.
Unfortunately I could not find any schematics for this monitor. Neither the Olivetti number, nor the Toshiba numbers result in anything useful.
The actual issue I'm having with this monitor is some defect affecting the monitor's brightness/contrast. Everything is fine when the overall screen is mostly dark. In this case the display is perfectly bright & crisp:
However, as soon as the overall screen is bright (colored background, or graphics filling most of the screen) then the monitor slowly get's brighter and shows terrible contrast (photo doesn't truely reflect the issue, but you can kind of guess):
Switching back to a screen content with mostly black background, slowly restores the picture quality to normal brightness/contrast.
I'm hoping it's going to be a simple issue - maybe a bad capacitor. I'll probably have to completely disassemble the main PCB (yes, after discharging the tube first) and see if I can find any suspicious component. If anyone had any more specific suggestions, let me know...
Last edited: