Unusual semi-modern DEC terminal - "MT 505"?
ard at p850ug1.demon.co.uk
Mon Jun 15 15:22:07 CDT 2009
> I'm sorry for hi-jacking this topic but,
> > (VT220s have a common fault that takes out horizontal hold)
> I think my VT220 has this problem, is there any documentation regarding
> diagnosing and fixing this problem? I have search to no avail.
Most of the time it's just a bad contact at the wiper of the horizontal
hold preset inside.
Take off the terminal cover (extend the 'leg' all the way down, put the
terminal on it's screen, take off the 3 (?) plastic caps and undo the
screws under them).
The horizontal hold preset is marked on the paper cover on the video PCB.
Note its position, then turn it several times from one end to the other.
Put it back to the original position.
Plug the terminal into the mains and power up (you don't need a
keyboard). If the picture locks, power down amd put the cover on. If not,
turn the horizotnal hold preset until it does, and set it to the middle
of the range where the picture is locked. Power down, wait a bit, power
up nd check it locks. Then power down again and put the cover on.
If you can't get the picture to lock by adjusting the preset, then you
have a more tricky fault to find :-)
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