Converting a 220 VT320 to a 120 VT320

From: Chuck McManis <cmcmanis_at_mcmanis.com>
Date: Wed Nov 15 18:41:49 2000

At 10:13 PM 11/15/2000 +0000, Tony wrote:
>I seem to remember there being 2 PCBs in these terminals. One contained
>the logic, monitor circuitry, etc. The other was the PSU (and is the
>smaller board).
>
>I would be _very_ suprised if there's any differences between the 120 and
>220V models other than the PSU board (and it may even be possible to
>convert one PSU into the other). If you've got both flavours of PSU, and
>if they seem to have the same output connector (so you can trivially swap
>them) then IMHO it's safe to try it.


Well, as it turns out after taking one apart (is there any way to avoid
that horrible "crack!" sound when you disconnect the front?) the PSU in the
international models had a post marked 120V and one post marked 240V and
moving the plug from one post to the other converted them to 120.

That was pretty cool and now I have two really nice VT320's. The third
still did not power up after this change so I tried swapping out the PSU
from one that had a burned tube. There was a bit of a difference in that
the power harness connector was "upside down" (its polarized and a molex
connector so it could only go one way, but with the reverse polarization I
had to try reversing it) I would have nibbled the connector back to make
this work however my test with this PSU showed that the terminal worked but
the display was not correct. So no doubt there was a change at some point
in the power supplies. And being good DEC engineers the new supply won't
plug into the old connector and vice-versa. (Ya gotta love hardware version
control!)

Anyway, for anyone else contemplating this, the PSU in the 320 is a snap to
remove, you pull the top off, then disconnect to ground connections to
spade lugs, one Molex connection to the logic board, and then what I did
was compress the press-in on/off switch so it came out as a unit. The whole
thing literally pops out when you press the one plastic retaining "tooth".

So some powering of the terminal showed me that it has a fine tube and so
I'm probably going to keep it, pull the CRT out and replace one of the
somewhat burned ones with a nice new CRT and get bright ambers once again.

Personally, I prefer green, but heck one can't always be a chooser. One
thing I prefer about the "international" ones is that they have an IEC
connector on the back rather than a built in line cord. That is nice as the
cord is always getting in the way during transport.

The other nice thing in this batch was a DECStation 5000/260 which seems to
be in good shape. (there was also a /240 but I ended up raiding the 240 to
make a nice 260. If anyone wants the motherboard of the 240 and chassis its
free-for-shipping-and-packing (I don't have a box that will fit it so
figure $20 to buy one + foam)

--Chuck
Received on Wed Nov 15 2000 - 18:41:49 GMT