Televideo 912 terminal problems

From: Sark <ian_primus_at_yahoo.com>
Date: Fri Oct 25 20:58:00 2002

Well, I was searching on Richard Shuford's wonderful website about
video terminals, and I came across a bit of useful information.
Apparently the power supplies and picture tubes are interchangeable
between Televideo 910, 910+, 912, 912C, 920, 925 and 950 terminals. I
had a 950 in the basement with a power supply problem, so I pulled the
logic board out and stuck it in the 912, and connected the 950's
external keyboard. It worked perfectly. This means there is something
wrong with the 912 logic board. I closely inspected the 912 board,
cleaned the dust off and reseated the socketed chips (the EPROM chip
seemed to have some bent pins), but it didn't help. I noticed that the
912 board appears to have been modified. One or two things look like
factory changes. The others look home hacked. Here are the changes that
I can see:

Those that look factory made:

Green jumper wires on the bottom are connected between:
        Pin 1 and 4 of chip A77, an LS74
        Pin 4 of chip A28, an LS74, and pin 8 of A44, an LS04
        Pin 9 of A44, an LS04, and Pin and a solder point to the right of A51

Those that look home hacked:

Cut traces on the top
        W8
        Pin 11 of A77, an LS74 and Pin 3 of A28, an LS74
        W28
        W26
        
W6 seems to have a clumsy looking scrap of wire bridging it.

W31, W32, W33, W34 look as if something was desoldered between all four

The printer port seems to have been replaced or removed at time,
judging from the brownish colored solder joints. The same goes for the
S3 (printer baud rate) dip switch block.

There are four white empty 18 pin DIP sockets on the right hand side of
the board (RAM upgrade option?)
There may be other modifications, but that was all I could find.

Any ideas? Was this some upgrade, or was there supposed to be another
module with this?

Thanks!

Ian Primus
ian_primus_at_yahoo.com

On Friday, October 25, 2002, at 06:29 PM, Sark wrote:

> I just got a Televideo 912 from an ebay auction. It seems to work
> fine, it feeps, and a cursor appears in the upper left. I have tried
> to connect it to my Linux computer in place of my regular terminal (a
> DEC VT100),and it didn't work. I noticed that after the terminal had
> been on for a minute or so, the cursor disapears from the screen,
> regardless of wether it was connected to the computer or not. Then, if
> I turn it off and on again, the cursor reappears, and then goes away
> again. I have tried setting the baud rate, etc. according to the
> manual I downloaded from vt100.net. Any suggestions? I really want to
> get this terminal working.
>
> Thanks!
>
> Ian Primus
> ian_primus_at_yahoo.com
>
Received on Fri Oct 25 2002 - 20:58:00 BST