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@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@classiccmp.org> > Sent: Wednesday, July 5, 2023 8:48 AM > To: Douglas Taylor via cctalk <cctalk@classiccmp.org> > Cc: Rod Smallwood <rodsmallwoo...@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 >>> >>> b...@techtimetraveller.com >>> >>> >> >
