Newbie question on Lynwood Scienctic Developments Ltd computer or terminal

[veroniacthecow]

Hi, first time posting so hi everyone.

I brought this the other day and was told it was working but it won't even switch on.
I have searched the Internet for ages and can find nothing like it but have made some guesses from the little info I found.
It may be a computer but my guess is it's more likely a dumb terminal possibly from an old police system or other bespoke system.
I could not track down any info about the big chip on the keyboard (78372C-007)

If any one has an idea of age or use of this I would be much appreciated.
Thanks, Tony

 

[1980s_john]

Hi Tony, welcome to VCF forums!

Looks like a dumb terminal. have a read of:

http://vt100.net/lynwood/

What connectors are there on the back, is there any label with the model number or mains voltage?

Do you have much experience in fixing electronics, a dumb terminal is a combination of a CRT with a high-voltage power supply (over 10kV) plus some digital logic boards probably working at 5V. Best to fix the power supplies first. If the fuse is blown always replace with the correct rating and type.

What tools do you have? CRTs are best tested with a series light bulb and a variac, with a mains power meter to check how much current is being drawn, should be a mains rating plate telling you the maximum (eg 150W).

Without a circuit diagram it is very hard to fix a faulty terminal or computer, but not impossible if you have enough patience.

Regards,
John

 

[Chuck(G)]

There's a "Here is" key--it's a terminal. The use of disc ceramic bypass caps and the group of 8-pin DIPs on the only visible board tells me that screen memory is probably MOS shift register, not SRAM/DRAM. So, perhaps 1972-74. I suspect the second board contains a character generator ROM.

Start with the power supply. You can see that this setup uses TTL, so the first thing to check is for the presence of a +5VDC output from the power supply (which is probably a simple linear design). After that, you look for +12/-12 outputs (or something in that range).

If you find those outputs, then check to see that the CRT filament is lit (in a very dark room, look at the small end of the CRT to see if you can see an orange glow).

Hope this helps.

 

[veroniacthecow]

Hi 1980s_john and Chuck(G) many thanks for your replies.

http://vt100.net/lynwood/ has been useful cheers. I used to do electronics about 20 years ago but don't have much equipment at the moment (or time, or money 8-) so it probably won't get fixed sadly.
I tracked down some of the big chips.

an AY-5-1013 high speed UART (A blistering 22.5kB)

a TMS 2501 NC ASCII character generator

and a couple of N74154 4-16 demultiplexors

There is a bank of 30 x 7437 quad 2-input NAND buffer on one board and some mh0026cn dual 2 phase clock drivers which I guess is about comms or display? (it has a metal backing plate I thing to help shield the comms part.)

I have found a date of 1974 on a board which is good. I was hoping that it was an actual early computer rather than just a terminal but that's they way it goes.

Useful to know about the "Here is" key,thanks.

Paul Williams of http://vt100.net/lynwood/ was kind enough to get back to me with some info about among other things. "The 78372C you took a picture of is just a ROM, I think," which was the one chip I couldn't track down.

" The use of disc ceramic bypass caps and the group of 8-pin DIPs on the only visible board tells me that screen memory is probably MOS shift register, not SRAM/DRAM. So, perhaps 1972-74. I suspect the second board contains a character generator ROM."
Very good guess, I wondered quite what that patch was doing.

The earliest I really worked on was a 8080 used on a control board in the late 70s then build a ZX81 from the kit. From elctroics I moverd to computers and now to organic farming, funny how things change.

Best wishes. Tony

 

[Chuck(G)]

The 30x7437 doesn't sound right--are you sure that's not the date code?

 

[veroniacthecow]

30 x 7437 = 30 times 7437 chips, sorry. 8-)

 

[Chuck(G)]

But that's what I'm saying. 30 of a generic NAND doesn't make sense. I suspect those chips have other printing on them and that the 7437 refers to the 37th week of 1974 production.

 

[veroniacthecow]

I see what you mean S2103, thanks.
S2103 Specifications
Generic Number :
Military/High-Rel : N
Tech. : PMOS
Number of Words : 1k
Bits Per Word : 1
t(acc) Max. (S) : 300n
tW Min (S) : 580n
Output Config :
P(D) Max. (W) : 350mВ
Nom. Supp (V) : 16
Minimum Operating Temp (шC) : 0
Maximum Operating Temp (шC) : 70
Package Style : DIP
Mounting Style : T
# Pins : 18
Description :

 

[Chuck(G)]

It's an AMI chip alright--the DIP molding says as much. My catalogs don't show the 2103, but I suspect it's probably about the same as the Intel 1103, with dual 16/19V power supplies.

Good luck with these old DRAMs--they're not very robust and very sensitive to stray static fields.

 

[veroniacthecow]

Hi Chuck(G) many thanks for your help in tracking these things down, as soon as I saw the 74 I made a n assumption, that will teach me 8-)
best wishes. Tony