HP 97 Keyboard issue

[wmax351]

I have been working on repairing an HP 97 I rescued from electronics recycling for a bit now.

In the past, it had worked, however, the keyboard has started not responding to anything entered on the right side (with the numbers). The left side, with the functions, appears to work well.

What should my next step be? I might also just part it out on the forum/ebay if there isn't a fix.

[teenix]

(01-19-2020 08:15 PM)wmax351 Wrote:  I have been working on repairing an HP 97 I rescued from electronics recycling for a bit now.

In the past, it had worked, however, the keyboard has started not responding to anything entered on the right side (with the numbers). The left side, with the functions, appears to work well.

What should my next step be? I might also just part it out on the forum/ebay if there isn't a fix.

I cant see any logical reason why that side of the keyboard would have failed. The key circuitry is intermingled with those on the left side.

Do any of these keys work?
Have any failed on the left side?
Do they work in program mode?

There might be corrosion on the keys circuit board or on the connecting pins between the keyboard and CPU board.
Someone spilt coffee on the side of the board at some time and the keys there need cleaning.

Search for the HP-97 service manual on the web. It might help.

cheers

Tony

[wmax351]

That's what I was wondering when I was looking at the service manual. The rows definitely are connected. I'll open it up and see if there's any break in a trace or something like that.

[BobVA]

Not much help, but I had exactly the same malfunction on my 97 several years ago. One day I turned it on the the right side of the keyboard didn't work.
I believe I "fixed" it by swapping in a good logic PCA out of a parts unit, but never figured out what the underlying fault was. (I was guessing it was a faulty ROM or PIK.)

[teenix]

(01-19-2020 09:50 PM)wmax351 Wrote:  That's what I was wondering when I was looking at the service manual. The rows definitely are connected. I'll open it up and see if there's any break in a trace or something like that.

Those rows and columns are used with other keys as well so unlikely to be the problem.

Do the DSP and BST keys work?

All of the keys produce an 8 bit value that is used to calculate the address in microcode to jump to and process the key.

8 bit values can also be expressed as two 4 bit hex nibbles, an upper and lower nibble. Eg DSP key is 72 in decimal or $48 in hex, 8 being the lower nibble.

The only logical explanation I can find is that all of the keys on the right side of the keyboard have lower nibbles less than 8, ie. bit 3 = 0.

The two exceptions are DSP which has 8 and BST (in the left half) which has 6.

If this is the case then as mentioned by Bob, maybe a ROM has failed.

cheers

Tony

[wmax351]

I will put it back together and see what that does. I'm curious, even though the calculator is likely needing parted out either way.

[teenix]

(02-12-2020 12:13 AM)wmax351 Wrote:  I will put it back together and see what that does. I'm curious, even though the calculator is likely needing parted out either way.

The printer and card reader need not be attached for the test.

cheers

Tony

[jftman]

AnyOne trace the problem? Mine started doing that but overall all I been doing is working on the gummy wheel.
Before I began that ,on the first day I received it it acted up by not turning off and numbered key side sputtering. Worked initially, put it away then for a brief time no responses on that right side. Then by itself started working.

Well I fixed the card reader and the machine wasn’t turning off.
I started to disassemble the keyboard level thinking the switches are similar to ho67. Believing I could clean the contacts.

While I tried to maneuver the keyboard apart I gave up because it looked as though if I flipped it out, seeing a ribbon cable from the top, at the display I figured I would stop, not knowing how to proceed, and spray tge switch with CRC, safe for plastic.

Behold the switch is now working, but the whole right side of the keyboard is nonresponsive.

What might I try now?b I am hoping someOne has solved this issue given it happenes and also is frustrating!

I believe the card reader ribbon cable is inserted enough. I followed the procedure of pulling it out of the slot and testing the card reader before full assembly. I hope it is not now so old that it did not like being bent much.

Is there any connection through that bridge board, and might I be able to find a replacement ribbon cable? Just throwing out tge process of what I did. Pic of ribbon cable into the card reader.    

[jftman]

I found something at the last moment before quiting with trying to get the ENTIRE right side keyboard to respond.

I put finger pressure between tge function key and the roll down key and everything works!
If I move it a bit higher or lower it stops responding..
When I was futzing around removing a screw here and there to remove the keyboard PCB I did remove the center screw below the display circuitry.
I remember not snugging it down for fear of cracking the board.

I surmised that this screw being a central screw might dish the whole thing if too tight.
I now must experiment with it, and the rest of any pressire points that make it work.

Right now neither the 7 under tge cover or 6 in the cover are in.
But center pressure makes the keyboard come back to life! Yessssss.

[jftman]

Ha, one minute later……….I tried cornor pressure and other places around the outer edges.

Nothing, the alas, back to the ‘sweet spot’ and NOTHING! Arrrgggg.
But this must mean something……

[jftman]

I have been able to repeat getting the right side keyboard to work with center finger pressure.

I don’t know what this means exactly.
But it has my interest, and I like it.

[teenix]

In the keyboard assembly, there are some spacers sandwiched with the gold switch contact sheet. If the screws aren't tight enough, these spacers might be looser than normal and the small gold contact fingers may not be contacting the traces on the circuit board.

cheers

Tony

[jftman]

I never got the keyboard removed as in the lower pic.
The screws I did remove, checking for extraction progress are marked.

But since at receipt I had the problem intermittently should I concentrate on the screws in tge upper or lower pic?

Or more specific, if only the numbers side, or the left side in the lower pic, is nonResponsive, which screws would have the effect of some finger pressure making it work in the center of the machine while operating the keys?

[teenix]

The 6 screws on the lower image hold the keyboard together.

If these screws are tight and there appears to be no warping of the circuit board, then maybe there is something wrong inside.

After opening and possible disassembly, the spacers inside have to be replaced exactly as found, or you may have a situation where the contacts are too close or too far away from the mating circuit board. You might be able to adjust the right side so the contacts are closer to the circuit board.

Once disassembled, the keys can be removed for cleaning by removing the round discs which are clipped to the end of the keys. However, unless there is a real need, like suspecting dirt or similar is under the key face, I would avoid doing this. The plastic keys and discs are old and there might be an issue with cracking the hole in the disc or breaking the bulb off the end of the key shaft.

cheers

Tony

[Hiwi]

(12-05-2023 12:01 PM)jftman Wrote:  Is there any connection through that bridge board, and might I be able to find a replacement ribbon cable? Just throwing out tge process of what I did. Pic of ribbon cable into the card reader.

Hi regarding the ribbon cable, there is no direct replacement.
But the cable is robust even bend it will not fail.
You could measure the reisistance of the cable from pin to pin.
The main issue is, that many people do not use the HP cable tool, so they damage (the contacts) the female connector on the pcb. Try to pull out the cable a bit and fix it with hot glue, that helped for me in some cases.

If the ribbon is totally damaged you can solder a pcb connector or self made connectors (13 pins are unusual) from precision IC sockets. The pitch is 2,54mm, so you have a great choice on the market.

If one side is Ok, you can solder the male part directly on the ribbon cable and a female socket on he PCB

Ralf

[jftman]

I am making progress. Did get the keyboard separated from the top and connected it with the bottom plate. Held it together with the battery installed and it works.

I put electrical tape accros some contact points that had old scotch tape on them.
I was getting failure when I held it down in some areas.

I thonk the tape may have helped.
Gotta get the top back on and solder the printer wires.
But last! When I get some screws back in it, Hopa Hopa

[Hiwi]

Here is a picture of the ribbon replacement.
The female part has to be soldered on the pcb.
That works perfect, when there is no chance to get the ribbon cable into the socket or the contacts are bend to much, so there is a contact problem.
Ralf
   

[jftman]

It is now working and plate and back screws all gingerly snugged. No point in reefing them.
After the work of gummy wheel, and applying tape and being careful in routing wires so not to crimp them, she is happy again.

The ribbon cable having been out and in a couple times will be tested by using the card reader.
I think it is OK, bcuz I did read a couple of cards and the display said Crd. Asking for side B and it read several the same way.

I haven't used a game or math program yet though.
I am not always sure which keys are defined as utility within the loaded program.

I have noticed the printer was printing on the paper but now, after all the futzing the head moves and it sounds OK but nothing is printed on the paper. Maybe a heat element is not getting power?

Well this is for sure. The calculator keyboard now is working. What needs to be known is .....when opening it for more trouble shooting will the keyboard actup the same as before.

The last 'fix' was when I put pressure on the battery it would lose the right side. I opened it and put electrical tape over both battery contacts. Pressure did not reoccur with failure. I buttened it all up and each time checked with every screw put in, the plate and back cover.
Still OK. That's a WIN

[teenix]

I've found a manufacturer for this type of cable and asked for a quote. If it is reasonable, I'll get some made.

cheers

Tony