I was given this terminal many years ago, rescued from a skip. I don't think it has been used much in its life. It is is good condition and the CRT appears to have plenty of life in it.
It actually worked as soon as I turned it on, though I did clean it up a bit and adjust the internal monitor controls a little to improve the greyscale. Some switch cleaner is very useful for this sort of thing as it really improves potentiometer operation in old equipment.
I can't find any data on it online, though there is a similar (and I suspect somewhat earlier) model described on the Computing History web site http://www.computinghistory.org.uk/. It supports an impressive number of demonstrations with (presumably) recorded Prestel and other sessions to show off its capabilities. These include 80 column mode and several levels of greyscale. The display is monochrome.
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| Real Owls Don't Like Acorns! |
I do wonder about the page shown above. The text on the bottom right says "Real owls don't like acorns!". Did someone have an issue with Acorn Computers?
Internals
The case is nicely designed, and just four screws allow the monitor section to be hinged out of the way. The power supply then simply lifts out after disconnecting the mains input.
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| Main PCB |
- MC6803P microprocessor. This is a member of the then popular 6800 family of 8-bit processors.
- UM6845EA CRT controller. This generates timings and addresses for the video display.
- SAA5055 Teletext character generator (U.S. ASCII version).
- SCN2681 dual asynchronous receiver/transmitter, for the line and printer RS-232 ports.
- CDM6264E3 8K x 8-bit CMOS static RAM.
- NMC9346N EEPROM, used to store configuration settings.
- 27256 32K x 8-bit EPROM.
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| Power Supply |
The power supply is a conventional switching unit. I imagine it provides +5 V, +12 V and -12 V. A negative supply is required for the RS-232 drivers on the main board.
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| Monitor Section |
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| Terminal With Keyboard and Keypad |
I have a numeric keypad as well. Strangely, I can't see a way to connect both. Perhaps for some applications, the keypad is all that is needed.
There is an idea lurking in my mind that could use this terminal, which was really the motivation for blowing the dust off it. More soon, perhaps!
I've just got hold of one of these too, curious to know whether the EPROM contents would be the same (I'm yet to power it on), so no idea even if it works! You seem to be the only other place I can find which mentions this specific terminal!
ReplyDeleteDid you do anything more with it? Curious to know what your idea was!
Hi Paul. The idea was to use it as a console for my homebrew Z80 CP/M machine. I wrote about that here: https://www.tech-cave.co.uk/2022/11/zarc-z80-anachronistic-retro-computer.html The EPROM on the main board gives a checksum of 64014cf9981249c29e55be143773f2bce8b48baec86ad7442e13ebc592f4d736 (using command "sha256sum -b Main.BIN"). I hope you get yours working. Good luck!
ReplyDeleteThere are a couple of other posts here about repairs. One I didn't write up was a single failed electrolytic capacitor in the power supply, C8 (100 µF 10 V 85 ºC). That caused intermittent start-up. It is next to the main switching transistor, so suffers high temperatures which are never a good idea for electrolytic capacitors.
DeleteBrilliant thanks for the pointers. Managed to get mine to power on, I did go over the PCBs first to check for any shorts or obvious faults before powering it on. There was some blackening of the CRT board in the middle beneath the mosfet, but thankfully so far the only issue I've noticed is a slight bit of jitter on the screen. I just need to figure out now how to make use of it as there wasn't a manual with it when it was found.
ReplyDeleteThat's good, now there are at least two in the world! If you press "Setup" you should have access to the menus including the demonstrations, which are quite interesting. You can connect it to a PC via a RS-232 to USB adaptor. From Linux at least you can then use it to login and run (text based) commands! I suspect Windows has a similar feature. There are numerous articles around to tell you how to do that sort of thing.
DeleteHey! Thanks so much for this post, I love keeping old tech like this alive. I also have just come across one of these however I haven't got a keyboard with it unfortunately. I'm wondering if a standard AT keyboard would work if I made an adapter to the 631A socket. Has anyone else had any luck with this?
ReplyDeleteHi Warren. Unfortunately, the keyboard interface is unusual though straightforward. You could make an adaptor using a microcontroller. The codes sent to the terminal are mainly straight ASCII, rather than PC-style key codes.
DeleteOk, thanks for the heads up, that makes a lot of sense. I think I could build something when I get a little time. I've managed to get hold of a DB25 to DB9 adapter and am trying to interface with it over a USB-Serial cable but can't seem to get any output. Do you happen to know how it want's to talk?
DeleteIf you send ASCII characters to the terminal main port (normally connected to a computer or modem), they should appear on the screen. Keys typed on the keyboard (if you had one) would be sent on this same port. It will be tricky without a keyboard as you don't know the serial parameters (Baud rate etc.) and can't access the setup menus. You are a bit stuck unless you can solve the keyboard problem, I'm afraid.
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