16 Jun
2009
16 Jun
'09
8:30 p.m.
On Tue, Jun 16, 2009 at 4:14 PM, Pontus<pontus at update.uu.se> wrote:
Vertical hold problems are what I would describe as scrolling and
looping. Horizontal hold problems are where the picture breaks from
left to right and tears diagonally.
Tony Duell wrote:
>> I'm sorry for hi-jacking this topic but,
>>
>>> (VT220s have a common fault that takes out horizontal hold)
>
> Most of the time it's just a bad contact at the wiper of the horizontal
> hold preset inside.
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 you can't get the picture to lock by adjusting the preset, then you
have a more tricky fault to find :-)
My memory served me wrong, or I read the post to fast. Is the symptoms
of a "lost" horizontal hold that the picture will scroll, looping around?
This vt220 in front of me has no picture at all. I was
using it and
between the blink of my eyes the picture disappeared, no bang, no smoke,
just gone. I think the logic still works, judging by the led indicators
on the keyboard and the satisfying beep it "boots" just fine.
Any ideas where I should start looking?
Me? Besides checking for reasonable voltages at the digital board?
Not really. I'm just fine with diagnosing digital logic, but not so
good with video.
-ethan