24 Dec
2003
24 Dec
'03
1:06 a.m.
I just unearthed a VT320 terminal at the very back corner of one of my
store rooms.
Before I go any further... should it work with a VT220 keyboard? There
was no keyboard when I found it years ago, but I do have a couple of
VT220 keyboards lying around.
Secondly - it doesn't seem to be getting any HT output to the tube. The
green LED D509 is pulsing about once every second.
Is there a common failure mode for these things?
I'm not too fussed about fixing it as I have a couple of VT220s that I
can use as 'real' terminals anyway. If anyone wants it for spares
they're welcome to it (I'm in Cambridge, UK)
cheers
Jules
24 Dec
24 Dec
3:06 a.m.
Jules Richardson wrote:
I just unearthed a VT320 terminal at the very back
corner of one of my
store rooms.
Before I go any further... should it work with a VT220 keyboard? There
was no keyboard when I found it years ago, but I do have a couple of
VT220 keyboards lying around.
Secondly - it doesn't seem to be getting any HT output to the tube. The
green LED D509 is pulsing about once every second.
Is there a common failure mode for these things?
90%+ The flyback transformer. They used really cheezy ones in these
terminals. Often takes out the horizontal transister too. If you replace
those two components, it will likely come back to life.
I'm not too fussed about fixing it as I have a
couple of VT220s that I
can use as 'real' terminals anyway. If anyone wants it for spares
they're welcome to it (I'm in Cambridge, UK)
7:24 a.m.
I just unearthed a VT320 terminal at the very back corner of one of my
store rooms.
Before I go any further... should it work with a VT220 keyboard? There
Yes. The LK201 keyboard works with the VT320. It will also power up (and,
IIRC display a faillure message) with no keyboard if everything else is
working.
was no keyboard when I found it years ago, but I do
have a couple of
VT220 keyboards lying around.
Secondly - it doesn't seem to be getting any HT output to the tube. The
green LED D509 is pulsing about once every second.
Aha....
Is there a common failure mode for these things?
YES! This is a very common failure.
What happens is that the flyback transformer develops shorted turns (and
sometimes takes the line output transistor out as well). This overloads
the PSU, which owing to the design _increases_ the voltage on the 5V rail
(I am not joking!). The crowbar fires, and the PSU trips. The cycle then
repeats. If you pull the case and look at the flyback transformer, you'll
propably see a crack in the casing with gunge coming out.
-tony
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ard＠p850ug1.demon.co.uk -
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