VT100 only showing white blocks

[trhaynes]

Hi everyone. I have my vt100 connected to a Windows 10 computer through a null modem serial to USB cable. I can type characters on the vt100 and they show up in a windows terminal program fine, but when I type on the Windows terminal program all I get are white blocks on the VT100.


I have aligned the communication settings between the terminal and my Windows computer:




I assume that since I can type on the vt100 and my windows terminal program receives it fine, that it should work in the opposite direction, too.

I have tried almost every permutation of port setup, as well as two different null modem cable configurations.

Perhaps something is glitchy with my vt100 machine? Can anybody here share any advice?

Thanks!

 

[bolex]

I would get loopback adapters for both your Windows 10 and Terminal and test both. It would be interesting to see if they both echo correctly.

 

[AK6DN]

Can you put the VT100 in local echo mode and type characters on the screen using the VT100 keyboard.
That would rule out any issues with the character memory display logic for the screen.
And as the prior post noted putting a loopback connector on the VT100 and typing without local echo, you should see what you type.
Ditto for the PC on it's serial port connector.

I am suspecting you will see a fail on VT100 with loopback connector, which might mean a bad UART chip, or bad RS232 driver/receiver.

 

[gwiley]

Can you put the VT100 in local echo mode and type characters on the screen using the VT100 keyboard.
That would rule out any issues with the character memory display logic for the screen.

I had a similar thought. Without involving the Windows PC at all, simply short pin 2 to pin 3 on the VT100 25-pin connector. This connects TxD to RxD, so whatever you type on the VT100 keyboard will appear on the screen.

The VT100 configuration menu looks right so character generators and much video logic are working.

One more thing… for this to work you need the same serial settings for Tx and Rx.

 

[trhaynes]

Thank you for the great advice!

Shorting 2 and 3 on the terminal resulted in good echoes.
Shorting 2 and 3 on the windows com port resulted in garbage echoes.
So, the problem was with my rs232 to usb adapter.

I replaced the adapter with a new.one from Amazon, and successfully got my vt100 talking bidirectionally with my Windows 10 machine!
Thank you @bolex , @AK6DN, and @gwiley for steering me in the right direction!

Now, if anybody has a source for up-arrow key replacements, I'd be very interested in talking

 

[cchhrriiss11]

Thank you for the great advice!

Shorting 2 and 3 on the terminal resulted in good echoes.
Shorting 2 and 3 on the windows com port resulted in garbage echoes.
So, the problem was with my rs232 to usb adapter.

I replaced the adapter with a new.one from Amazon, and successfully got my vt100 talking bidirectionally with my Windows 10 machine!
Thank you @bolex , @AK6DN, and @gwiley for steering me in the right direction!

Now, if anybody has a source for up-arrow key replacements, I'd be very interested in talking

Arrow-key replacements will be tricky... I had to hunt around quite a bit for some arrow keys for mine. Your best bet is to find someone who has a VT10x junk keyboard, but considering how hard they are to find normally (lots of VT10x's are sold keyboardless on eBay), that might be a tall task. About a year ago, I was extremely lucky to find a VT102 on eBay in one auction, and a matching VT102 keyboard (they're different than the VT100 keyboard) in a separate auction, it was still quite a bit of money at the end of the day, but I ended-up with a nice terminal.

The DECWriter III shares the same style key-caps, however, the DW3 never had arrow keys on it. I've got a bunch of spare keys from a spare DW3 keyboard, but can't help you in this case.

There was someone selling at complete/working VT100 recently for $500 in the for-sale section a month or so ago in the CA area.

-Chris

 

[trhaynes]

That is some good advice, @cchhrriiss11 Thank you!