6 Jul
2023
6 Jul
'23
4:15 p.m.
I’ve just pressed the 2 broken end together and measured the resistance end to end to get
an idea of the resistance. Any old trimmer of suitable value should work as a replacement
as the vdu is probably not going to be in a harsh environment anymore.
Sent from my iPhone
On Jul 6, 2023, at 15:13, Brad H via cctalk
<cctalk(a)classiccmp.org> wrote:
Thanks Rod!
I discovered an immediate problem I hadn't caught before.. two of the trimmer
resistors had actually been broken right off two of their legs.. so that may account for
strange/missing voltages. They are a CONRAC part 928237. The CRT is CONRAC too, but I
still don't think this is a CONRAC terminal. Anyway, I only found one source for the
exact resistor, an aerospace company, and they want $80 per unit (I think they just want
me to go away).
So far in testing I haven't found any shorts. My main worry is the PSU sending
incorrect voltages to wrong place. In addition to the broken resistors I also discovered
some broken solder joints on the PSU PCB.. those at least are repaired. I'm trying to
figure out the resistance the two resistors were set to so I can put a replacement in with
same, hopefully that gets me close to what should be there.
Brad
-----Original Message-----
From: Rod Smallwood via cctalk <cctalk(a)classiccmp.org>
Sent: Wednesday, July 5, 2023 8:48 AM
To: Douglas Taylor via cctalk <cctalk(a)classiccmp.org>
Cc: Rod Smallwood <rodsmallwood52(a)btinternet.com>
Subject: [cctalk] Re: 1974 No Name Terminal
I worked on VDU's as an engineer in the UK before joining DEC to sell volume
VT100's in 1975
There's a mention of block on one of the cards so a block mode terminal.
That means enter data and press a key to send the lot.
The card cage could mean its emulating something.
I'd test as many capacitors as possible. PSU first and replace as required.
Run PSU and check voltages.
Check each board for power rail to ground shorts.
If ok give each board +5v on its own and see if the TTL is alive.
If theres a clock gen start there (look for a crystal can)
Loads of fans might indicate an industrial environment
At this age some TTL will have failed plus capacitors.
Rod Smallwood
On 05/07/2023 16:28, Douglas Taylor via cctalk
wrote:
At first glance it reminded me of the Hazeltine 1000, I owned one in
the early 1980's. Brutally simple terminals, I remember getting a ROM
from Jameco which allowed the terminal to display lowercase letters.
Pure luxury.
Doug
On 7/4/2023 6:57 PM, Brad H via cctalk wrote:
Hi there - not sure how much overlap there is with vcfed's forum, but
thought I would reach out here in case. I have a terminal from 1974
(based on date codes I've found on the motherboard). I'm unable to
determine manufacturer and that would be handy for diagnostic
purposes. The terminal casing is made out of foam, and although there
are some serial numbers stamped around, nothing really lines up. The
fans inside have zero dust or dirt, so I'm thinking this may not have
seen much use, or may be a prototype or pilot for something. It does
have RS232 capability. Interestingly the screen is set down below the
keyboard so that only half of it is visible.
My main issue right now is the PSU - I am trying to determine if I'm
safe to attempt powering up the board (the PSU so far seems to be ok,
although some voltages on a couple of pins are mysterious).
Anyway, on the extremely off chance anyone has ever seen one of these
or something like it.. any tips would be appreciated. If I can find a
manual I'll feel a lot safer about turning it on.
Some pics here:
https://drive.google.com/drive/folders/1-2uEFbi3OKBYr06y6yHnygDiLMtw2
Qkj?usp
=sharing
Brad
brad(a)techtimetraveller.com