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Heathkit H19 Terminal Questions

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Vercus

Experienced Member
Joined
Jul 9, 2009
Messages
123
Location
Pennsylvania
Hello,
I recently picked up a Heathkit H19 terminal and am a little confused by it. I hooked it up to my DOS PC and tried to communicate with it by typing "CTTY COM1" as I did with my DEC VT-102. The problem I am having is that communication seems to be only one way. The computer can send text to the terminal, but when I type, nothing happens. All the keys work fine in offline mode, but I can't get any text to appear when I type in online mode.

I used the manual to set the dip switches inside for 2400 baud, which is the same as the computer. Text sent from the computer displays fine. I've tried turning parity on and off, and switching from "heath" mode to "ansi", and this made no difference.

Anybody have any ideas?
-Jon
 
Try a loopback test

Try a loopback test

Jon,

Try connecting pins 2 and 3 on the DB25M on the back of the terminal. Everything you type on the keyboard should be echoed back to the display (in online mode).

If this does not work, then I would bet that the RS232 line driver is toast. It will be easy to replace, everything inside the H19 is socketed. ISTR it's a 1488. I've done component level repair / restoration of two H19s, so I'm pretty sure I could fix anything on them : http://www.vintage-computer.com/vcforum/album.php?albumid=2&pictureid=62

Lou
 
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I wasn't able to connect pins 2 and 3, however I did take a look at the terminal logic board.

Next to the serial out connection, there is a 1488 and 1489. The 1488 looks fine, but the 1489 has burnt pins, so it looks like it's toast. I'm placing on order on Mouser for caps and voltage regulators for the Horizon, so I'll check to see if they have 1488s and 1489s. I'll likely replace them both, as they're so easy to change out.

Thanks for the guidance.

-Jon
 
I ordered 2 1488s and 2 1489s, so I'll have everything I need, plus a spare of each for future projects.

I'll let you know how it works out.

-Jon
 
Well, it's good I ordered an extra 1488, because I destroyed the pins trying to get it in the socket. Replaced both the 1488 and 1489. Now, I can type text, but when I press enter, nothing happens, it just goes to the beginning of the line, acting as if it's offline. Is it just a setting I have wrong? I have the right baud rate, because I can receive text from the computer fine.

I'm also having a problem where when the terminal receives more than a screenful of information, it doesn't scroll, and I have to hit the scroll button on the terminal manually. I haven't figured out how to change this.

I'm beginning to think I'd be better off just looking for another DEC terminal instead, as they seem to be more reliable, and not so archaic.

Any suggestions would be appreciated.
Thanks,
Jon
 
There is nothing wrong with your terminal. It's supposed to behave that way!

When you hit enter, it's doing a "carriage return". The cursor moves to the beginning of the line, like it's supposed to. If you want it to move to the next line, that's called a "line feed", which is a separate ascii code. There is probably a swich inside (I can't remember) that will make the terminal send both CR and LF when enter is pressed, but right now, it's only sending CR.

As for scrolling, the behavior you see is extremely useful! When the host machine is sending data at you faster than you can read it, you want the screen to stop at one screenfull. Then, when you press "scroll" the next screen will come.

Congratuations, your terminal is working properly. It's behaving just like a 1975 dec VT52. Are dec terminals more reliable? I'm not sure. I've fixed two H19s, two VT52s, and three VT100s. I would say that they're all equally unreliable (but I still like them.)

If you want, I can read the H19 manual and look into defeating the screen hold feature and how to set the enter to send CR and LF. Or, if you have the manuals, you can do the same.

You also need to learn the trick to inserting new ICs into sockets. The pins are always flared out more than you want. You can either buy a dip inserter (a neat tool that holds the pins at the right spacing and has a plunger to push the chip into the socket) or press the whole line of legs against a table to fold them in toward the package slightly (do this evenly on both sides.)

Lou
 
Hey Lou,
Thanks for the info. I figured out how to get it to send CR and LF simultaneously, however, now when the computer sends text out, it is double spaced instead of single spaced. When I press enter, I get no response from the computer, it just scrolls to a blank line.

To elaborate, I am using it with a DOS machine, doing CTTY COM1. I get a C:\ Prompt, but when I type DIR, or any other command, and hit enter, I just get a blank line, much as it would behave in OFFLINE mode, except I have the terminal online. There is no response from the computer. This leads me to believe the terminal still isn't transmitting information, much to my confusion.

-Jon
 
Jon,

Unplug the terminal from the computer and do a loopback test. Connect pins 2 and 3 on the DB25M on the back of the terminal. In online mode, whatever you type should be echoed on the screen. The is the fastest way to test a terminal.

Lou
 
Vercus said:
I am using it with a DOS machine, doing CTTY COM1. I get a C:\ Prompt, but when I type DIR, or any other command, and hit enter, I just get a blank line, much as it would behave in OFFLINE mode, except I have the terminal online. There is no response from the computer. This leads me to believe the terminal still isn't transmitting information, much to my confusion.
Click to expand...
If you just replaced both the 1488 and 1489, chances are the terminal is fine.
Of course, if you don't do a loopback test like Lou suggested (twice!), you won't ever know for sure.

Try disconnecting the serial cable from the DOS computer,
flip Switch S401 position 7 to the UP position (half duplex on)
and see if typing anything shows up on the screen.

If that works, then your cable is probably bad.

Andy
 
Well, if you can't even stick a paper clip into the plug to loopback 2 & 3 like we've been asking all along then we probably can't help much ;-)

How is your cable wired? RTS and DTR will have to be connected in addition to Tx and Rx if you want to run CTTY.
 
Sorry if I annoyed you guys by not doing the loopback test! I just forgot is all. No need to get upset. I'll try it today and report back.

-Jon
 
Hmm, how do I figure out which pins are 2 and 3? I've never had to mess around with connectors before, as I've no doubt demonstrated..lol.

-Jon
 
Vercus said:
however, now when the computer sends text out, it is double spaced instead of single spaced.
Click to expand...
Possible cause:

Some systems are set up so that when the ENTER/RETURN key is pressed, the sending end only sends a CR (i.e. no LF following the CR), and the receiving end upon seeing a CR not only performs the CR but also then performs a LF (i.e. an implied LF).
If one end is then misconfigured to send a CRLF instead of only a CR, the other end ends up performing two LFs: CR (perform a CR followed by an implied LF) then LF (perform a LF)
 
Wasn't the 24-line feature in the H19 an option? ISTR that the base version of this terminal was 12 lines.

Edit: Or maybe not. Try changing the setting of SW4.
 
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I hooked the terminal up to the Horizon today and it works just fine with it. So, the terminal is fine, it just doesn't like CTTY for whatever reason. So, that's good news.
 
Vercus said:
I hooked the terminal up to the Horizon today and it works just fine with it. So, the terminal is fine, it just doesn't like CTTY for whatever reason. So, that's good news.
Click to expand...
As I said in a previous post, I suspect the "whatever reason" is that your cable doesn't connect DTR and RTS, but I expect you couldn't be bothered to try that either...
 
The Zenith version, the Z-19 (same thing as the H-19), is my go-terminal for almost any computer that needs a terminal. Extremely reliable and with the internal switches adjustable. Mine is always set up and ready to test, to remove the "does my terminal work" variable from the restoration process. The manual is online (not sure where but I have found the manual before by searching. There is nothing special or weird about this terminal or the cabling. Very generic.
Bill
 
I have the manual for mine, which was helpful in setting the dip switches correctly. I believe I did have a bad cable as well.

Now if I can just get my N* Norizon memory board to cooperate as easily!
 
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