Kaypro keyboard fault

[MikeS]

I did - that's why I quoted it in my Post #57. What I want to know now is: do you think the method I explained in Post #57, will work? (Tez has a Model 100, you see).

Philip

D'oh! I really must read more carefully; that's twice...
Gee, I was asking *you!*
If it's really standard 300bd serial then I don't see why not, unless the polarity is reversed. The M100 uses +/- 5V, but the -5 pulldown resistor is ~25K so I don't think that'd be a problem, and if the keyboard output is normally low and goes high then it oughta work.

But the usual disclaimer: use at your own risk - I ain't responsible! (Actually, "irresponsible" is the word my girlfriend uses...)

 

[dave_m]

It may be this large serial controller IC in the keyboard itself. I've looked and looked for a spec sheet for this IC without success. Anyone know of any? The IC is labelled M5L8049-109P-6. The 8049 seems to be a "class" of chip but I can't find pinouts.

Tez, you asked this question when you thought you had a keyboard problem. The 8049 is part of the wonderful old Intel MCS-48 single chip microcomputer family. I think this family was the first of its kind to contain a CPU, a little RAM (8049 had 128 bytes), 1K or more ROM (the 8049 had 2K of mask ROM), an 8 bit counter/timer, and about 20 lines of programmable I/O all in one chip. I used the 8748 (EPROM version of 8048 ) in avionics applications way back in 1980. It was easily powerful enough to be programmed to control a keyboard and perform the function of a serial UART at 300 baud.

When you get some spare time, look at the spec sheet. It successors such as the 8051 and follow-on are still used today.

http://home.mnet-online.de/al/mcs-48/mcs-48.pdf

 

[tezza]

You are correct. The crystal Y3 is only for the SIO baud rates.

Thanks for verifying that. I now know why this crystal is as much a suspect as the 8116.

Tez

I now own a logic probe. It will be utilised tonight.

 

[tezza]

Tez, you asked this question when you thought you had a keyboard problem. The 8049 is part of the wonderful old Intel MCS-48 single chip microcomputer family. I think this family was the first of its kind to contain a CPU, a little RAM (8049 had 128 bytes), 1K or more ROM (the 8049 had 2K of mask ROM), an 8 bit counter/timer, and about 20 lines of programmable I/O all in one chip. I used the 8748 (EPROM version of 8048 ) in avionics applications way back in 1980. It was easily powerful enough to be programmed to control a keyboard and perform the function of a serial UART at 300 baud.

When you get some spare time, look at the spec sheet. It successors such as the 8051 and follow-on are still used today.

http://home.mnet-online.de/al/mcs-48/mcs-48.pdf

Thanks Dave,

No wonder some documentation on the Kaypro keyboard I found on the web called this IC a "microcomputer". For it's time, it would have been amazing.

Tez

 

[tezza]

8116 tests

8116 tests

Right. I wriggled the Xtal but this didn't make a difference. Using the new logic probe I probed and found there IS indeed a pulse sent to line 12 on reset. So it would seem the 8116 does get a wakeup call (it just doesn't wake up). Other 8116 readings verified what I'd found before namely:

1 - (Xtal) - L
2 - (+ve) - H
3 - (to SIO TxCA/RxCA) - L
4 to 7 (data bus) - Pulsing
8 - (from U73 - BAUDA) - L
9 - (not connected?) - L
10 - (not connected?) - L
11 - (ground)
12 - (from U73 - BAUDB) - L
13 to 16 (data bus) - Pulsing
17 - (to SIO RxTxDB) - L
18 - (Xtal) - L

How's this for a method to verify the 8116 - assuming the xtal is fine and all connections to the 8116 are fine - plus the fact that another 8116 isn't around for a swap. Try manually pulsing STBT on the 8116. Do this by grounding momentarily pin 3 of U73 to simulate /BAUDB pulse. ..... A working 8116 should start showing waveform of *some* frequency at output Pin 17 (probably won't be the correct frequency as it depends on what was on the data bus at the time which determines frequency.)

I tried this suggestion of Philips. I certainly got a pulse on 8116 pin 12 from the U73...I saw it on the logic probe...pin 17 though stayed stubbornly quiet at L.

So....I gather this means a failed Xtal or 8116 (or both!). Do you guys agree?

If so, is there any way I can determine which one before I order components in?

Oh Dave, the Xtal is a small silver rectangle about the length of a 5 pin TTL chip and about as wide as its socket.

Tez

 

[cosam]

So....I gather this means a failed Xtal or 8116 (or both!). Do you guys agree?

If so, is there any way I can determine which one before I order components in?

My hunch would be the crystal, seeing as you didn't get anything resembling a clear signal at its pins. That said, just poking it with the scope probe may have been enough to mess with it. If the probe has a 10X setting, maybe try with that and see if it makes any difference. I can't say I've ever actually had to test one, but maybe someone can help you out with that. At the end of the day, though, a new crystal isn't going to be pricey, so it's probably worth a punt.

Now that I've said that, it'll probably be the 8116... I'm not sure where you'd get a replacement for that, other than salvaging one from something else. If you happen to have an Apple I lying around, it apparently has one in it too :->

 

[MikeS]

...
So....I gather this means a failed Xtal or 8116 (or both!). Do you guys agree?

If so, is there any way I can determine which one before I order components in?

Oh Dave, the Xtal is a small silver rectangle about the length of a 5 pin TTL chip and about as wide as its socket.

Tez

A 5 pin TTL chip?? ;-)

You could try replacing the crystal if you've got one that's similar; if you then get a signal out of the 8116 (even though it's the wrong frequency) then it's a good bet that it's the crystal. There are different crystal types though, so if you *don't* get a signal it could still be either.

 

[dave_m]

Tez,
You are in a dilemma here. I think its the crystal but it's probably soldered in. So it may be easier to try the 8116 first. But will it take a long time to get, is it costly, etc, etc.

If you go with Mike's good idea, the parameters of xtal I think you want from reading a 8116 spec sheet are fundamental mode (not 3rd overtone) and series resonant. But for the experiment, probably anything should do. Hopefully you will get a clock output and then replace with the proper frequency crystal.

Look at the link for the MP050 under "Additional parts". The package size may be wrong, but this may be the electrical parameters you want. Let's see what the others find. You should have no problem finding a crystal locally.

However before you start all this, make sure it is not just something like a bad connection between the crystal and 8116.
-Dave

http://www.ctscorp.com/components/Datasheets/008-0308_C.pdf

 

[tezza]

Tez,
You are in a dilemma here. I think its the crystal but it's probably soldered in. So it may be easier to try the 8116 first. But will it take a long time to get, is it costly, etc, etc.

If you go with Mike's good idea, the parameters of xtal I think you want from reading a 8116 spec sheet are fundamental mode (not 3rd overtone) and series resonant. But for the experiment, probably anything should do. Hopefully you will get a clock output and then replace with the proper frequency crystal.

Look at the link for the MP050 under "Additional parts". The package size may be wrong, but this may be the electrical parameters you want. Let's see what the others find. You should have no problem finding a crystal locally.

However before you start all this, make sure it is not just something like a bad connection between the crystal and 8116.
-Dave

http://www.ctscorp.com/components/Datasheets/008-0308_C.pdf

Yes, I checked those 8116 <--> Xtal lines for continuity last night. They are fine.

Well, the next step is up to me. I'll try Mike's idea of just soldering any old Xtal in and seeing if I get anything. There may be one on some of my junk boards.

I'm going to have to leave this for a few days now. I've got a few family committments which need attending to and tomorrow (weather premitting) I'll be climbing over volcanoes (the Tongoriro crossing) with a friend and my oldest daughter. It's about 2.5 hours from where I live. I've done the walk several times but for those with me it will be their first.

Anyway, thanks for helping me get to the nub of this issue. Virtual beers all round! (and real beers if you ever find yourself in my neck of the woods). I'll let you know what happens when I get the replacement part (or parts), or what shows up with a shoe-in crystal.

Tez

 

[pavery]

Da Beep

Da Beep

A beep is heard with just a single keypress on the machine in its present state. This was the case even when the machine is working properly (and explained above) so it's not just an overflow signal like it is in some computers.

I have a theory on why the keyboard Beeps, even thou the CPU hasn't received any signal from the SIO/keyboard. The SIO has an output to the keyboard - pin 26 (TxDB which is labelled BEEP), and I am presuming the keyboard microcontroller monitors this line after a keystroke. I also presume this line is normally Low, but when the CPU receives a keystroke, it instructs the SIO to go Hi on TxDB for a time - at which time the keyboard microcontroller detects this and Beeps.

Now, the smoking gun... Tezza says

It was a steady 5v at the Z80 SIO output pin 26.

Arh! We now know the SIO is probably in an invalid state (it has no clock input) & a result of this is TxDB is Hi all the time! Therefore the keyboard is going to Beep after every keypress, regardless that the signal hasn't originated from the CPU - but just an inconvenient side effect of the SIO in limbo.

Philip

 

[tezza]

This sounds plausible to me Philip. Good thinking.

Tez

 

[dave_m]

I have a theory on why the keyboard Beeps...(TxDB which is labelled BEEP), and I am presuming the keyboard microcontroller monitors this line after a keystroke. I also presume this line is normally Low

Philip,
I think the TxD line is normally high when inactive as it usually interfaces with a RS-232 line driver like the MC 1488.

My hypothesis is that that Beep signal is only used for a few things like power up test or system errors or maybe as part of the beep command in BASIC. I'm guessing the key 'clicks' are probably generated by the keyboard controller. I'm not sure but how many computers of the era were so unreliable as to need "feedback" on key entries? wouldn't the fact that the character showed up on the screen be enough?
-Dave

 

[dave_m]

I'll be climbing over volcanoes (the Tongoriro crossing)

Two hours from a volcano! I think I'll stay in California where I only have to worry about a little shaking. Thanks for the link. It looks like a very interesting place.

Take care on the hike, lad, we need you back on the computer.
-Dave

 

[pavery]

Philip,
I think the TxD line is normally high when inactive as it usually interfaces with a RS-232 line driver like the MC 1488.

Arh, ok.

My hypothesis is that that Beep signal is only used for a few things like power up test or system errors or maybe as part of the beep command in BASIC. I'm guessing the key 'clicks' are probably generated by the keyboard controller. I'm not sure but how many computers of the era were so unreliable as to need "feedback" on key entries? wouldn't the fact that the character showed up on the screen be enough?
-Dave

I guess we'll know for sure when Tezza fixes this Kaypro. I'm sure he'll be happy to make the extra measurments to solve this puzzle. Thanks Dave.

Philip

 

[dave_m]

Philip,
You're right, when everything is working again, he can get to the bottom of our mystery beeps.

This Kaypro problem has really been fun. Leave it to our lad to come up with interesting problems. He is lucky to have you near to help out with equipment and expertise.
-Dave

 

[tezza]

Advice on replacements

Advice on replacements

Hi Guys,

Well, we are not on our mountain walk today as the weather forcast was for cloud around the peaks. The last thing you want if you are going to expend that effort going up there is no view, so it's postponed until next week. Things are flexible at work at the moment so I can take a day off at a day's notice so to speak. Next week I'll be watching the forcast every day.

Anyway...back to the Kaypro.

I found an old 3.something crystal in a junk apple clone keyboard and soldered it in. No change in pin 12 and no sign of crystal activity on pins 18 and 1. But as Mike said...that doesn't necessarily means anything as the replacement Xstal could be too incompatible. It still could either be the crystal OR the 8116.

I've been looking around on the web and it seems I can get both a replacement Xtal and 8116 from various places. However with shipping etc. cost does mount up. The 8116 is in the U.S...shipping costs unknown at this stage but it's never cheap from the U.S. The Xstal can be imported through a local supplier BUT you have to order at least $15 worth of stuff.

As all the ICs seem to be socketed in the Kaypro II, I wonder if it would be worth putting a request out for a whole Kaypro II mainboard, someone might be prepared to sell. Assuming the Xstal and 8116 were ok I could swap them out of this board, and also have one for parts in case something else happens, or even for a supply of ICs.

My point is, it might be no more expensive getting a suplus board from someone with a broken kaypro (drives stuffed, screen stuffed etc.) than importing two separate components.

Of course it depends on what people want for the board AND there is the risk that those very components might be damaged on replacement board too. There are one or two Kaypro boards on eBay but they are way (way!) too expensive.

I haven't been following prices of the likes of Kaypro mainboards (or even Kaypros) so I'm not sure of the going rate. I know Kaypro IIs were relatively common in North America so I imagine there are a few junk units around. Do boards for sale come up now and again? Does something like $25 US (excluding shipping) seem reasonable or unrealistic? If the latter, I'm probably better off ordering the separate pieces.

Otherwise I might put a request on the "Wanted to Buy" section. Any thoughts?

Tez

 

[pavery]

No change in pin 12 and no sign of crystal activity on pins 18 and 1.

Tez, just making sure you know what a good crystal looks like on the scope. A very fast & low power waveform. Suggest you measure the master timing crystal - Y2 which is 20MHz. This will show you, and give the scope settings, of a good crystal.

Philip

 

[dave_m]

No change in pin 12 and no sign of crystal activity on pins 18 and 1.

Tez,
The signal on 18 & 1 may just look like a little noise as Philip said, and you should be looking for any pulse activity on output pins 3 and 17 of the 8116 chip. Pin 12 is not important right now.

Since the outputs of the 8116 (pin 3 & 17) are mostly independent and both were inactive, I thought the probability was that the crystal was bad. However if the amplifier for the crystal in the 8116 is bad, it would have the same symptoms as a bad crystal.

 

[tezza]

Philip, Dave,

Ah. Ok, points noted. I'll do what you suggest (I'll have to solder out the old one and solder in the test one again..damm!)

Tez

 

[tezza]

Tez, just making sure you know what a good crystal looks like on the scope. A very fast & low power waveform. Suggest you measure the master timing crystal - Y2 which is 20MHz. This will show you, and give the scope settings, of a good crystal.

Philip

Right, I tried this Philip and I see what you mean. A VERY OBVIOUS sin-type waveform.

No, there is nothing at all coming out of the 5.0588 Mhz crystal like this. It's completely dead at 0v

>Since the outputs of the 8116 (pin 3 & 17) are mostly independent and both were
>inactive, I thought the probability was that the crystal was bad. However if the amplifier
>for the crystal in the 8116 is bad, it would have the same symptoms as a bad crystal.

Does this still hold Dave? Now I know what I'm looking for it seems to me this Crystal is COMPLETELY dead. I guess if the 8116 isn't feeding it any power is could seem completely dead though? Is there anyway to tell if it's dead or not, out of circuit somehow? Put a few volts through it perhaps? Or is special circuitry needed for oscillation.

Sorry, I'm not sure how these things work?

Tez