Reviving VT220?

[Peter Coghlan]

> Hi all,
>
> A colleague and I are trying to get a VT220 working again as it recently
> died on us. We are hoping to set up a few items for the mid-80s
> (including this terminal) to show the graduands what it would have been
> like if they were doing their CompSci degree 30 years ago.
>
> It looks to me like the flyback is dead. There is a lot of soot and
> there looks like there is some damage to the top of the transformer,
> better seen in the second image.
>
> http://www.cs.nott.ac.uk/~psxasj/sparse/flyback1.jpg
> http://www.cs.nott.ac.uk/~psxasj/sparse/flyback2.jpg
>

I think the soot is fairly typical of what accumulates on high voltage
components in a city environment.  I'm not sure this indicates any damage to
it but it may well be faulty without showing any signs of damage.

>
> The terminal powers on and does the usual beeping but nothing is
> displayed on the screen. Does anyone have any advice about what to do
> here? Are there any sources of compatible flyback transformers?
>

I have a VT220 which also appears to have a faulty flyback.  This results in
it drawing too much current from the power supply.  I am not certain the
flyback is faulty but I have eliminated most of the other components which
are likely to be responsible.

I have looked for replacement flybacks or equivelants but I have never found
any.  Someone mentioned that they might have VT220 parts available on the list
some time ago but I didn't get anywhere in following that up.

> 
> We have a second VT220 which exhibits the same behaviour, hopefully for
> a different reason so we can try and cobble two into one.
>

I have a second VT220 which works and I have used it to compare readings
with my faulty one.  I also tried swapping some of the suspect components
but this failed to take suspicion off the flyback.  I am reluctant to try
swapping the flybacks over in case I cause damage to the working VT220.

While the two flybacks appear likely to be electrically similar, I am not
certain of this and they are physically different - one is PCB mounted
and the other is chassis mounted with flying leads to the PCB as far as
I recall.  They have different part numbers, 16-21181-01 and 16-26299-01.

>
> Any thoughts / advice would be greatly appreciated.
>

Sorry, I haven't been able to provide much help or hope.

Regards,
Peter Coghlan

>
> Thanks,
>
> Aaron.
>
>
>
> --
> Aaron Jackson
> PhD Student, Computer Vision Laboratory
> http://cs.nott.ac.uk/~psxasj