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Need help with Televideo Personal Terminal

Chuckster_in_Jax

Chuckster_in_Jax

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Feb 28, 2006
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Jacksonville, Florida
I've had a small Televideo Personal terminal for a while now and can't seem to get it to connect with anything. I can't find any manuals for it anywhere.

It has the following ports on the rear:

2 telephone ports(in & out)
25 pin d-sub Printer Port
25 pin d-sub labeled Main

I connected a null modem cable to the "main" port of the terminal and the other end to a 9-pin console port on an IBM RS/6000. Can't get any output on the display.
The RS/6000 is set for VT100 terminal emulation

I can type characters on the screen OK. I don't see any menu to select a terminal emulation. Do I assume it only does TTY?

Chuck
 
The Televideo Personal Terminal is just a normal RS-232 terminal. If you're seeing characters echo back, then you either have it in local mode (not online/communicating), or half-duplex mode.

To quickly check the communications, use a paper clip or bit of wire and jumper pin 2 and pin 3 of the main port together - this loops TX back to RX. Now, with the terminal online and in full duplex mode, you should see characters echo back when you type - pulling out the jumper will result in no characters echoed back. If that works, then there is nothing wrong with the terminal.

-Ian
 
RetroHacker_ said:
The Televideo Personal Terminal is just a normal RS-232 terminal. If you're seeing characters echo back, then you either have it in local mode (not online/communicating), or half-duplex mode.

To quickly check the communications, use a paper clip or bit of wire and jumper pin 2 and pin 3 of the main port together - this loops TX back to RX. Now, with the terminal online and in full duplex mode, you should see characters echo back when you type - pulling out the jumper will result in no characters echoed back. If that works, then there is nothing wrong with the terminal.

-Ian
Click to expand...

I tried your test and it failed. Always echos everything typed at the keyboard. In the setup there is a setting that is listed as "edit". The 2 options are duplex and local. I tried both settings with the same result. There is also a mode setting I have set at "Block" The other 2 options are HDX and FDX. DUH!!! While I was typing this it occurred to me that HDX and FDX are half duplex and full duplex. Unfortunately I have the unit torn apart in my kitchen now. I was checking to see if maybe it had a bad connection somewhere. I'll put it back together and test it again.
 
Turn off block mode. You want FDX.

If you genuinely are not getting echoed characters when you connect RX and TX, then you've probably got a blown line driver. Very common on older terminals - and it's easy to kill them with static electricity when plugging and unplugging cables "hot". There is a pair of chips, near the communications socket - 1488 and 1489 - transmitter and receiver, respectively. If one or both are blown, you won't get any communications. If they're socketed, try swapping them out - if you don't have any spares, then check other parts/devices you might have - any RS232 device will have them. IIRC, they're usually socketed on Apple SSC's.

If you connect a simple crossover cable with another terminal (or computer with terminal emulator) you can see if you can send or receive data. Alternatively, if you have an RS232 tester, you can look at the lights.

-Ian
 
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If its realy a Televideo Personal Terminal it does a sort of cut down Televideo emulation. There is a very similar device the PT100 which does VT100/ANSI emulation. Do you know which you have. I have user guides for the pT100 and some copies of some pages from the manual for Personal Terminal detailing the emulation. If I can get my SPARC U60 to work I also have termcap and reminfo entries for the Personal Terminal.
 
Got it all back together and jumpered pins 2 & 3. Works like it should with mode set to FDX. Hooked it up to the RS/6000 and nothing. Since the computer is setup for VT100 terminal, that may be the problem. I may have to redefine the console "type".
Also, there are several versions of the null modem cable so there may be a problem with the cable I've got( 25 pin d-sub to 9-pin d-sub).

http://www.lammertbies.nl/comm/info/RS-232_null_modem.html

More research to do. At least I know the terminal is working.

Edit: Currently I'm using a laptop and terminal emulation software that is working fine on the RS/6000. I really want to find out if the Televideo terminal is working OK. It's an unusual design.

Chuck
 
The computer doesn't care about the terminal type at this level. It doesn't matter what you called the terminal, it'll still send the same login prompt. The terminal type only comes in to play with things like cursor positioning, screen clearing, and text attributes.

Are you sure you've got the line in /etc/inittab commented out that references that serial port? Similarly, did you tell the computer to reread it after changing the line? (init q). The most basic null modem cable just swaps receive and transmit. On a DB25 connector, receive is pin 3 and transmit is pin 2. On a DB9, receive is pin 2 and transmit is pin 3. Therefore, if you simply connect pin 2 to pin 2, and pin 3 to pin 3, and be sure you have a signal ground connection (DB9 pin 5, DB25 pin 7), it should work fine. The extra lines should also be accounted for to allow for proper flow control, but the basic three wire setup is quick and lets you confirm it.

-Ian
 
Just a thought: are you sure the RS/6000 expects a DCE null-modem connection? It's been quite a while but ISTR that my old RS/6000 used straight-through connections to its terminals.

Maybe try swapping pins 2 & 3 ?
 
Well, I know the terminal works. Hooked it up to my Morrow MD-3 and it works fine.

So it must be the cabling. The cable I'm using to successfully connect my laptop to the RS/6000 has pins 2 & 3 crossed. 9-pin female on both ends.
 

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Chuckster_in_Jax said:
Well, I know the terminal works. Hooked it up to my Morrow MD-3 and it works fine.

So it must be the cabling. The cable I'm using to successfully connect my laptop to the RS/6000 has pins 2 & 3 crossed. 9-pin female on both ends.
Click to expand...
So the TV<>RS/6000 cable is 25-pin to 9-pin with pins 2-2, 3-3 and 7-5, correct?

Does the TV talk to the laptop with that cable?
 
OK. Hooked up a straight through cable to the Televideo and RS/6000 and it works. Must be some difference between the laptop(Thinkpad 770Z) and the Televideo terminal's RS-232 pinouts.

I don't have a straight through cable with DB-9 on both ends to see if that would work on the laptop.

I'm going to take retrohacker's advice and get one of those rs232 testers. I would make troubleshooting a lot easier.

Televideo Personal Terminal 002.jpg
 
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Chuckster_in_Jax said:
OK. Hooked up a straight through cable to the Televideo and RS/6000 and it works. Must be some difference between the laptop(Thinkpad 770Z) and the Televideo terminal's RS-232 pinouts.
Click to expand...
You might have missed that pins 2 and 3 have opposite functions on a DB25 and a DE9, so a null-modem DB25<>DE9 cable connects 2-2 and 3-3 (and 7-5). Going DE9<>DE9 or DB25<>DB25 you have to swap pins 2 and 3 for a null-modem, although your Morrow probably expects a terminal (DTE) and a straight-through 25<>25 cable.
 
RetroHacker_ said:
On a DB25 connector, receive is pin 3 and transmit is pin 2. On a DB9, receive is pin 2 and transmit is pin 3. Therefore, if you simply connect pin 2 to pin 2, and pin 3 to pin 3, and be sure you have a signal ground connection (DB9 pin 5, DB25 pin 7), it should work fine.
Click to expand...

MikeS said:
You might have missed that pins 2 and 3 have opposite functions on a DB25 and a DE9, so a null-modem DB25<>DE9 cable connects 2-2 and 3-3 (and 7-5). Going DE9<>DE9 or DB25<>DB25 you have to swap pins 2 and 3 for a null-modem, although your Morrow probably expects a terminal (DTE) and a straight-through 25<>25 cable.
Click to expand...

Definitely missed that. It became apparent when I hooked up what I thought was a straight through DB25<>DE9 cable and it worked, there was some difference with the pinout.
Well, this was a lesson learned. Hopefully others will read this and won't make the same mistake.

Thanks everybody for the help!

Chuck
 
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