Televideo PC Keyboard Pinout/Adapter

[Cooccoo]

Thank you.

It’s true that I don’t want to spend lot of money, specially for any keyboard that it’s not the original 803. I will try to fix my pcb as I don’t have other solution for now. Thank you about the futaba information. I didn’t know the type as I am not so much a keyboard guy.

I am in progress already. I remove the switches from pcb. I add the 2 ic’s that was missing. 7414 & 74ls145. I found about 5-6 traces damaged. I am gonna replace and the 2x electrolytic capacitors.

Here some photos:



















I don’t know if it is better to start new topic or post the progress here.






Again thank you very much!

[Polecat]

Thank you.

It’s true that I don’t want to spend lot of money, specially for any keyboard that it’s not the original 803. I will try to fix my pcb as I don’t have other solution for now. Thank you about the futaba information. I didn’t know the type as I am not so much a keyboard guy.

I am in progress already. I remove the switches from pcb. I add the 2 ic’s that was missing. 7414 & 74ls145. I found about 5-6 traces damaged. I am gonna replace and the 2x electrolytic capacitors.

I don’t know if it is better to start new topic or post the progress here.

Again thank you very much!

It looks like you're well on your way to having a working keyboard. I'm just a junior member here, but I'd suggest starting a new topic and posting a link to it in this thread.

[Cooccoo]

Just a question please. I just finish on the original pcb keyboard. All traces now are ok. New capacitors, new 1N914 diode and other thinks. But keyboard don’t work. Do nothing…

Have something special to work? or it is like we say "plug and play"?

Thank you

[Polecat]

From what I remember the Televideo PCs will give a keyboard error when you fire one up without a keyboard. But from the link I posted the 803 supposedly has an "integrated terminal", and that might respond differently. I used many, many terminals back in the day, but I don't remember ever powering one up without a keyboard connected. Is the computer booting to a command prompt when you power it up?

[Cooccoo]

Yes. In command prompt, after loading the OS from floppy disk.



As you can see for some reason in "almost" Greek language.

But I got no error if I have the keyboard disconnected. Nothing change if is connected or disconnected. Some times if unplug the keyboard when the system is running I got this 2-3 characters like this: " [^". But nothing else. I check the cable and it is in working order:



Next step is to remove all keyboard IC,s and test them if are in good working order.

Update:

Keyboard IC’s tested with my Tauntek ic tester

2x 74ls145
1x 7414
1x 4040




All passed the test.



What I can’t test is the D8749H:




Also 5.7143 MHZ crystal works:

[jsheradin]

Are you sure all the missing IC spots were supposed to have chips in them? Depending on the system some of them might have been purposefully left unpopulated.

If you have an oscilloscope can you check if there's any activity on the data lines? Are there any scan strobes on the matrix? Are all chips getting regulated 5V?

The manuals mention a few DIP switch settings. Have you checked that they're in the default positions?

Your 8749 looks to be one with a UV EPROM which unfortunately tend to bit-rot over time. It would be a good idea to compare the ROM contents with that of a known good chip (if you can manage to find one).

[Polecat]

Yes. In command prompt, after loading the OS from floppy disk.

As you can see for some reason in "almost" Greek language.

But I got no error if I have the keyboard disconnected. Nothing change if is connected or disconnected. Some times if unplug the keyboard when the system is running I got this 2-3 characters like this: " [^". But nothing else. I check the cable and it is in working order:

Next step is to remove all keyboard IC,s and test them if are in good working order.

Update:

Keyboard IC’s tested with my Tauntek ic tester

2x 74ls145
1x 7414
1x 4040

All passed the test.

What I can’t test is the D8749H:

Also 5.7143 MHZ crystal works:

As jsheradin says the 8749 has an onboard EPROM, so a replacement will have to be programmed to match what was there originally. As long as the window is covered the contents are probably ok. Regarding the two missing chips it's obvious that the 74LS145 came there, but I can't tell on the 7414.

With the amount of damage to the PC board I'd check for more broken traces. It sounds like you have experience with troubleshooting. They're not always visually obvious, so check carefully with a multimeter to be sure.

I'm not familiar with how the 803 is laid out internally. Since it has an "integrated terminal" there will be a point where the terminal connects to a serial port on the computer. If you can disconnect it there and loop the terminal back to itself you can see if it's sending and receiving. On a DB25 connector that means connecting pins 2 and 3, but it may be hardwired on the 803 instead of using a DB25.

[Cooccoo]

I will post soon. I have problem with internet connection.

A sort answer is that for sure the 7414 is a part of the pcb. The only optional ic’s are the ds8867 & 74ls164.

All ic’s got 5v and ground.

Dip switches are in default position.

About the eprom it is very difficult to read it. My eprom programmer can’t.

And no. I don’t have lot of experience with electronics . I just got an oscilloscope but don’t know how to use it correctly.

[Polecat]

The 8749 isn't just an EPROM. It's a microcontroller with an EPROM onboard to store the firmware. And that firmware is specific to the Televideo. You would need a programmer specific to the 8749 to read or write to the EPROM, and reading it wouldn't tell you anything unless you had a good one to compare to, or at least a checksum for the file.

The reason I suggested testing by looping back the terminal connection is that will tell you if the problem is with the terminal section or the computer section. The most common problem with terminals is the line driver and receiver chips for the RS232 port. The receiver is working because the characters the computer is sending (the command prompt) are showing up on the screen. So if you loop the terminal's send pin back to its receive pin that will tell you if the keyboard is sending characters. What you type should show up on the screen when you do that. If so the problem is on the computer board. If not it's in the keyboard or the send part of the terminal section.

[Cooccoo]

The reason I suggested testing by looping back the terminal connection is that will tell you if the problem is with the terminal section or the computer section. The most common problem with terminals is the line driver and receiver chips for the RS232 port. The receiver is working because the characters the computer is sending (the command prompt) are showing up on the screen. So if you loop the terminal's send pin back to its receive pin that will tell you if the keyboard is sending characters. If so the problem is on the computer board. If not it's in the keyboard or the send part of the terminal section.

Hello!

To be honest I didn’t understand that part how to do it. Little my bad English, little that I never did it again…

Can you please show me the way?

Thank you!

[Polecat]

Hello!

To be honest I didn’t understand that part how to do it. Little my bad English, little that I never did it again…

Can you please show me the way?

Thank you!

Your English is probably better than mine, and I have no excuse.

I don't know how the 803 is laid out internally, but there will be a connection someplace between the "terminal" (keyboard and CRT) and the "computer". On computers with separate, external terminals that connection usually goes to a DB25 connector (RS232 protocol). To test or loop back a RS232 connection you connect pins 2 and 3 together on the terminal. When you do that whatever you type should show up on the screen if everything is working correctly, regardless of whether or not the computer is working.

The Televideo 803 may have the connection between the terminal and computer hard wired. To loop that back you'll need to find that connection and figure out which pins are receive and transmit and connect them together. That's what "loopback" refers to. You're looping the transmit back to the receive to allow the terminal to test its receive and transmit lines.

[Cooccoo]

I will try to find the schematics. But are we sure that the 803 is terminal based machine and not just a normal computer? Sorry if my question sounds stupid.

















Edit:

I found the technical manual: http://bitsavers.trailing-edge.com/pdf ... _Jul84.pdf

[Polecat]

There are no stupid questions, only stupid answers. I'll try to keep mine to a minimum, but no promises.

The link I posted above says the 803 came with an "integrated terminal". The User's Manual you found on bitsavers doesn't use those exact words, but describes the character generator as the one from the Model 925, which was a very common Televideo RS232 terminal. Scanning the manual quickly I see a few interesting things.

First, the book says the 803 uses a "970-type" keyboard. (p. 1.1) So my previous guess about that was a lucky one.

Second, the 803 keyboard is described as "9600 baud" and runs through the DART chip. (p. 3.11) So you could probably connect a different serial (RS232) device there to test or even to use the computer. To do that you'll need to know a couple other things in addition to the baud rate - the number of data and stop bits, parity, and the type of handshaking if any.

Third, the book says that the 803 keyboard uses an Intel 8048 microcontroller, not the 8749 that's in your keyboard. Perhaps there was a design change, or maybe your keyboard isn't the right one for the 803? (p. 3.11)

There's probably more good info there, but that's all the time I have right now.

edit - the ebay link I posted to what was supposed to be a Televideo 1605 (which was a MSDOS computer) appears to actually be a Televideo 970 terminal, and that would explain the 970 keyboard as part of the listing. There's no way a 970 keyboard would work with a 1605 computer, as I mentioned before. It might be worth a note to the seller and/or a lowball offer of what the keyboard is worth to you if they're willing to sell it separately.

https://www.ebay.com/itm/143715760478

[Cooccoo]

I will read it!

Thank you very much for your time!

[Cooccoo]

At page 47 you can find the schematic about 970 keyboard. The A6 ic have 2 types. 8049 / 8749. So, maybe it is a design change as you told.

http://www.bitsavers.org/pdf/televideo/ ... ration.pdf

[Polecat]

Looking at the 803 schematics there's apparently a direct connection (5 volt serial) between the keyboard and DART chip, so no line drivers or receivers and no RS232 interface. If I had to guess between the DART chip being bad and the keyboard itself I'd say the keyboard. Again with the amount of physical damage I'd be checking for bad traces with a multimeter. Or (patiently) searching for a replacement 803 or 970 keyboard. You might be able to get a different Televideo terminal keyboard to work, like the 925 or 950, which were much more common, but the connector on those is different and research would be needed to determine if the interface is the same.

The keyboard controller was probably a design change as you suggest. The 8049 and 8749 in the 970 schematic were pin-compatible, with the difference being that the 8049 had onboard ROM (not erasable) while the 8749 had an EPROM, so was reusable. The 8048 as shown in the 803 schematic was the ROM version of the 8748, but I don't remember if it was pin-compatible with the 8049 and 8749. What really matters is that your keyboard is the right one for the 803 computer.

[Cooccoo]

You are so helpful!

I will do a serious reading my self too and I report back.

Again thank you very much polecat.

And just realize that forgot to make a new topic and keeping destroy your great work about the adapter.


For Moderator:


Please if a moderator can move all that posts about my try to fix my keyboard I will appreciate it!

From here if you can:



And you can name the topic:Televideo ts-803 resurrection.

Thank you!

[Muirium]

You can rename the topic yourself: edit your first post.

[Cooccoo]

You can rename the topic yourself: edit your first post.

Hello and thank you. I renamed my post. The post I want the new topic to begin. What I want is to separate all posts after my first that I renamed, to a new topic please. The reason is because is not helping polecat topic.

Is that possible?

[Polecat]

No need to move anything on my account. It is a related topic, and possibly useful to anyone else with an 803 or other 800 series Televideo computer. I'm good with it either way. I'm going to edit the start of the thread to confirm the 800 series does not work with the adapter. What matters is getting your 803 working, and hopefully that will happen. It's refreshing to me to see the older hardware. I'm just another dumb user with the new stuff.

[Cooccoo]

If you don’t have a problem then fine for me!

[Cooccoo]

Polecat there is a RS232 behind.

Not started reading yet but I post that because you wrote that is not RS232 interface

[Polecat]

Polecat there is a RS232 behind.

Not started reading yet but I post that because you wrote that is not RS232 interface

There is a serial (RS232) port on the computer, but that is not used for the keyboard. The most common use for that was to run a serial printer, which was preferred over a parallel interface if you needed to run a long distance.

The keyboard itself connects directly to the DART chip, which is not an RS232 connection. Instead it appears to be a 5 volt 9600 baud serial interface. That isn't really important, because my idea of breaking and connecting to the "integrated terminal" connection to test whether the problem is the keyboard or the computer doesn't apply now that we know it's not a simple RS232 connection.

[Cooccoo]

Thank you polecat. Today I will do a good reading of schematics. To be honest I am a bit confused cause I am not good knowledge of terminals. Not at all.

By the way here is a photo behind the computer:

https://www.dropbox.com/s/jnnoamvvi6sw3 ... 0.jpg?dl=0

Have both parallel for printer and rs232 port.

[Cooccoo]

The only thing that work in my keyboard is the hard reset. By pressing ctrl with reset keys together. This make system reboot.

I order a pair of 2 dart ic’s MK3884N-4 cause I can’t thing anything else.

I check about 3-4 times every trace on my keyboard with multimeter. Everything looks ok.

[Cooccoo]

Metal switches holder fixed from the crash!