• Please review our updated Terms and Rules here

Need help with "unresponsive" Teletek FDC-1C all in one computer-on-a-board.

This is not the "DCE" you speak of; pin 3 goes to the 1489. There are only two traces up there sorry to crop too much image off earlier today, rushed it.


Bruce

qhZWH.jpg
 
Last edited:
Must find the light

Must find the light

I am apparently going to have to get a scope and start looking for signals, instead of hoping they are there. Been since about 1971 in Turkey with ASA that I used them very much.

I would be appreciative of any recommendations for books on S-100 designs, and IEEE 696, known to be good standards.

I've looked a bit, and scopes range from about $300 for brands I don't recognize, +/- $700 up to $3K and more for the ones I know. Do I need dual trace?

If anyone here has an old scope that might have been supplanted by an upgrade, and would part with it, let me know, I'll see if I can manage it.

You would have the satisfaction of knowing that you helped nudge one of the great unwashed toward knowledge and enlightenment in the cryptic arts and cloaked practice of S-100ness.

Bruce
 
You may not need a scope--just a simple inexpensive logic probe may do the trick for you. Here's an example.

It's one of the most useful tools in my toolkit; I've had it for decades. Some years ago, I replaced all three red LEDs with blue (pulse), green (low) and yellow (high)--now I need only note what color is on without having to read the legend.
 
USASAgencyman said:
I am apparently going to have to get a scope and start looking for signals, instead of hoping they are there. Been since about 1971 in Turkey with ASA that I used them very much.
Click to expand...
A scope is definitely invaluable when you really get into it, but even a multimeter or logic probe can help with the signals we're dealing with here.
I would be appreciative of any recommendations for books on S-100 designs, and IEEE 696, known to be good standards.
Click to expand...
At this point it would probably make more sense to read up on the RS-232 standard ;-)

Looks like there's a 20 pin header plug that connects to a DB25 somehow, probably with a partial ribbon cable that leaves the upper pins unused.

Your pin numbering is correct for a dual-row header, but not for the corresponding RS-232 pins; they would be numbered 1 to 10 up the left side and 14 to 23 up the right side, so that pin 2 does indeed go to the 1489, pin 10.

Google the RS-232 pinout if you're not sure how they are numbered.

Check all your connections end-to-end, from the terminal connector to the 1488 &1489:
Pin 2 of the terminal should go to pin 10 of the 1489
Pin 3 of the terminal should go to pin 8 of the 1488
Lift pins 9 and 10 of the 1488 and connect them to pin 8 of the 1489 (use a socket in between if you're worried about breaking the bent-out pins)

With hardware handshaking turned off and the terminal in full duplex mode, that should echo what you type on the terminal.
 
Chuck(G) said:
You may not need a scope--just a simple inexpensive logic probe may do the trick for you. Here's an example.

It's one of the most useful tools in my toolkit; I've had it for decades. Some years ago, I replaced all three red LEDs with blue (pulse), green (low) and yellow (high)--now I need only note what color is on without having to read the legend.
Click to expand...

Therefore I shall shortly have one in hand... I'm in the Prime of course!

B.
 
MikeS said:
A scope is definitely invaluable when you really get into it, but even a multimeter or logic probe can help with the signals we're dealing with here.
At this point it would probably make more sense to read up on the RS-232 standard ;-)
Click to expand...
I'll buy that course, (-of action). Who knew cable pin assignment was a freestyle sport?

However, if I am to be testing address lines, (wherever those are!), for my voltage stability with the reset button pressed, don't I need to have some S-100 info? OTOH, maybe I'll just see if there's a description of the purpose of each of the 100 contacts at Wikipedia.

There will be a slight delay, with appropriate space/time fabric distortion, while I get up to speed on S-100ness. My soon to arrive logic probe will sure speed me on my quest. :D

B.
 
Well now, that's where we differ. The first thing I'd concentrate on is getting the board to talk to itself. It's supposed to be a single-board computer that will interface to the S100 bus, but why complicate matters if the basic board can't do a "Hello world" ? In other words, I'd be peeking at the chip signals to see if they made sense. After I was satisfied that things looked okay, I'd then concentrate on the S100 bus signals.
 
Chuck(G) said:
Well now, that's where we differ. The first thing I'd concentrate on is getting the board to talk to itself. It's supposed to be a single-board computer that will interface to the S100 bus, but why complicate matters if the basic board can't do a "Hello world" ? In other words, I'd be peeking at the chip signals to see if they made sense. After I was satisfied that things looked okay, I'd then concentrate on the S100 bus signals.
Click to expand...
Obviously I agree; we're at 67 posts and still don't know whether the RS232 I/O is working and wired/configured correctly, or whether the CPU is actually running...

Some faults on the bus could cause problems but as Chuck says I'd worry about that later; just make sure the voltages are OK.

For all we know the board works fine and just needed a 'borrowed' RAM chip replaced.
 
Don't worry about the number of posts. There's threads with way more posts and way more straying off-topic. I think the major stumbling block is most folks think you should stick with confirming if the serial port works and getting that working before you move on to S100.
Look at it this way, you can make serial communication happen with just a couple of wires, but with S100 you've suddenly got almost 100 signal lines to worry about. Best to walk before running.
patscc
 
Some of us here have the attitude that if the stuff hung around for 30 years or more, a week or two won't make much difference. By all means, howeever, check out places such as JDR Electronics and Jameco for your needs. They're old time vendors to the hobbyist trade. BTW, you ddin't say where you were located...Ouagadougou, perhaps?
 
Chuck(G) said:
Some of us here have the attitude that if the stuff hung around for 30 years or more, a week or two won't make much difference. By all means, howeever, check out places such as JDR Electronics and Jameco for your needs. They're old time vendors to the hobbyist trade. BTW, you ddin't say where you were located...Ouagadougou, perhaps?
Click to expand...

No, but one of the guys on my very modest Folding team, #187 in the world, at Kitguru lives not far from there...

My domicile in space and time is located a long time away, and far, far ago in a little townlet called Fernandina Beach, FL., about 2000' from Peter's point, on the Atlantic. "Dogs on the beach" for us means Brats and adult beverages right about there. Come on by sometime.

Bruce
 
MikeS said:
Pin 2 of the terminal should go to pin 10 of the 1489
Pin 3 of the terminal should go to pin 8 of the 1488
Lift pins 9 and 10 of the 1488 and connect them to pin 8 of the 1489 (use a socket in between if you're worried about breaking the bent-out pins)

With hardware handshaking turned off and the terminal in full duplex mode, that should echo what you type on the terminal.
Click to expand...

Now we know that pin numbers 2 & 3 go where they should.

Tying 9 & 10 on 1488 to 8 on the 1489 did not result in echo to screen.

Here are the voltages on the two that are associated with S-IO A. The connection between 4, 5, 20 from the D25 monitor cable, (and its numbering scheme), has been made, as unequivocally instructed by Teletek's manual. Key inputs and even letting a key repeat seem to not affect these voltages.

I found a contact on the motherboard slot (fourth from right on back side of board), that goes from 2.16 up to 3.32V when I push the reset button. Thought that was curious. :confused: I figured that with that switch grounded anything that changed would go down.

I may be ready to put this up as classic computer art on the wall. You guys have been patient, but this is ridiculous.

Bruce

1488.jpg
1489.jpg
 
USASAgencyman said:
I may be ready to put this up as classic computer art on the wall. You guys have been patient, but this is ridiculous.
Click to expand...
Nah, don't give up. This is par for the course when doing this sort of remote diagnostics; it's great to have several people looking at your problem but it can take a while, not just because of the back and forth delay and misunderstandings but everyone has a different approach to troubleshooting which can leave you wandering all over the place.

Stick with it; we've got a pretty good record on this forum for bringing the old iron back to life and we're almost as eager to get it working as you are.

mike
 
Last edited:
Worst case, you could send it to one of the troubleshooters on this forum and save a whole bunch of money and trouble, if you don't consider this electronics stuff fun...
 
USASAgencyman said
that goes from 2.16 up to 3.32V when I push the reset button
Click to expand...
Try measuring pin 26 on the Z80 (the reset line ), it should read a logical high, then press and hold the reset button, pin 16 should go to low, and back to high when you release.
patscc
 
Last edited:
Chuck(G) said:
Worst case, you could send it to one of the troubleshooters on this forum and save a whole bunch of money and trouble, if you don't consider this electronics stuff fun...
Click to expand...

1. I didn't know there were any here for hire. That would be good news. But not yet! I mentioned I tried to get in touch with Arthur Sittle, he posted a year or two ago he was using a Teletek to program CPM with, I thought he might have been my last hope, especially if he had the right software, -he didn't specify.

I worried if the EPROM that makes this board a computer with a monitor was lost into the ether...

2. I'd rather do it myself, and learn how to actually fix it! My logic probe will be here tomorrow, and if it takes a scope I go there. The only reason I was talking up the idea of retiring it was to get you guys off the hook.

BTW, I don't know how many boards do this, but with 25V external power applied, it will program the 2716s. I am only guessing that being able to actually communicate with this thing will help though. :D :D

Thanks,
Bruce
 
patscc said:
USASAgencyman said

Try measuring pin 16 on the Z80 (the reset line ), it should read a logical high, then press and hold the reset button, pin 16 should go to low, and back to high when you release.
patscc
Click to expand...

I hope you mean Z-80A CPU voltage with my kinda-trusty Fluke. 2.93V and it does not even change the last digit when I press reset. Maybe Teletek had a "different" idea on pin assignment? Or Q&T, re; the motherboard, had a different idea on the reset current path.

Tried pin #26 and got 3.6V drop to 0V when reset is pressed.


However:
The #66 contact in the mobo slots, also goes up with the reset button, 2.36V to 3.30 bizarre! The #75 goes from 2.74 to 0V relative to chassis. I think I just discovered it is called "Reset"!!! Finally found a pretty good list of all the contacts. Remember that cartoon I found...

Bruce
 
Last edited:
You must log in or register to reply here.
Back
Top