Mystery (unusual) 1973 terminal
bhilpert at shaw.ca
Fri Feb 12 13:08:48 CST 2021
On 2021-Feb-12, at 6:08 AM, Paul Koning via cctalk wrote:
>> On Feb 12, 2021, at 7:50 AM, Jules Richardson via cctalk <cctalk at classiccmp.org> wrote:
>> Hopefully the following link works, but someone over on one of the Facebook vintage groups has this oddball terminal from 1973 that they've been looking for any information on:
>> ... it's somewhat unconventional in that half the CRT is hidden from view within the machine, i.e. it only actually displays the top half of the display to the user - I've no idea if that's because it had a specific application where space was limited, or if it was simply that memory at the time was horribly expensive and so it was designed to only use a few lines (I know some vendors did that, although I think they typically presented the whole CRT and at least had the option of RAM upgrade to more lines).
>> The blower assembly seems a little on the homebrew side, but on the other hand the PCBs and case construction make it seem like a professional product.
>> The owner says the only label anywhere on the thing is the one on the CRT saying "Mfd in Japan for Conrac", but that's presumably just the CRT itself and not the entire machine.
> I remember Conrac as a well known CRT maker from that time. I think they were used in PLATO III terminals (mid 1960s).
>> I don't believe there's anything resembling a microprocessor in the system, it's all just TTL logic (the large white ceramic IC is an ACIA).
>> Oh, I believe the owner's in Canada, so it may be it was made there and never exported to other parts of the world.
> The photos are not particularly helpful; they show parts of the device but not close enough to tell the details, while much of the case is not shown. Is there any manufacturer label or serial number tag on the case?
> One of those boards is full of rather sloppy ECO wires, which makes it feel like a home made job, but the rest look like decent quality commercial pieces. And yes, the blower is rather curious, it's hard to see how a device like this might dissipate enough power to need that kind of air mover.
Between google and the browser I'm using, the photos didn't display properly, so I downloaded them (upper right corner),
which unzipped to high-res versions.
The board with the white ECOs is the memory, it has 5 1402's (256*4 shift register), 3 of them from Intel and 2 replacements from MIL (Microsystems International Limited) which is the only place Canada appears to come into it.
Not clear how they would be organised for the screen .
The main board has a Fairchild 3258 64*7*5 character generator, along with the 1602 UART/ACIA.
The blower is probably targeting the pass transistors for the linear power supply, to avoid requiring a giant heat sink.
Most/many terminals from that period had a large heat sink for the pass trans.
I don't think the CRT is half-hidden, rather just a high-aspect-ratio CRT (very wide rel to height).
Interesting that aside from the Intel/MIL memory chips, a couple of specialised clock drivers for those, and a couple of other chips, it's entirely Fairchild 9xxx series stuff.
In terms of design & construction it looks pretty typical for its period; nonetheless a cool unit to be working on.
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