Restore a Pioneer keyboard (27s)

[franz.b]

Hi everyone, we talked about the topic some time ago but in a discussion about the 48, so I thought it was better to open a new one.
I am repairing a 27s (a pioneer model), I had to disassemble the keyboard because some dirt got between the membranes and some conductive tracks were degraded. I have repaired the degraded tracks with a conductive marker and it looks like a working solution.
Obviously I had to cut the plastic rivets. How do you advise me to close the keyboard? I have seen images I think of a voyager in which metal pins have been inserted, and then drops of epoxy resin, but this method does not inspire me confidence because I think that the resin can run on the underlying plastic films and degrade them forever.

I received 2 suggestions, but incomplete.
The first is to use 3D printer wire, but first I don't know which material works best, then I don't know whether to add it to what's left of the pegs or to drill the keyboard, insert the wires and melt the heads on both sides.
The second suggestion says to use jeweler screws, but I don't know whether to make small pre-drilled holes in the original pegs and screw the screws into them (in this case they would be self-tapping screws with a diameter of less than 1mm) or whether to drill the keyboard and use nuts and washers ... anyway I don't know where to find both types of screws.

[Dave Britten]

I've had pretty good results just using a plain old hot-melt glue gun. Squeeze the metal keyboard plate into place, apply small dots of glue to a few of the posts, and hold until it sets firmly enough to move on to the next few. I've done this with Pioneers and Voyagers, and it's turned out quite well.

[BillBee]

E6000 jewelry glue is one type I have used. The Calculator Store had that tip in their 41C book. Something to consider.

-Bill

[franz.b]

I closed the keyboard. The touch is great and it seems that all the keys are working. I forgot to photograph the tracks before closing, I reinforced some with a conductive marker because they were ruined by the water that had entered years ago. You can see the first two tracks on the right retouched and another on the left, but for those on the right I had to go back a few centimeters with the conductive paint.
I discovered that the plastic films that make up the keyboard are 4 and not 3 as is often described on the web.
It was very difficult to handle the microscopic screws, I made a pre-hole with a hot needle before inserting them.
Unfortunately 2 keys do not work: down arrow and shift.
From the layout of the keys they have a common track but this is in common with other keys that work, so, if I think well, the problem must be in the contact under the buttons ... I'll have to open everything again! ? but luckily I didn't use the plastic welding or glue method!

[franz.b]

HP27s repair part 2 (bis)
I reopened the keyboard and immediately identified the non-continuity of a track. The repair with a conductive marker looks positive with the tester, it took several coats of paint to ensure continuity. The ink is very liquid and spreads, it would take a denser one, but by wetting the tip of a toothpick I managed to be quite precise, even if at that point a huge stain that connects the tracks to the same potential would also have been functional.

[ijabbott]

Would it be possible to transplant a keyboard membrane from a cheaper model (such as a HP-10B)?

[franz.b]

(02-18-2021 09:18 PM)ijabbott Wrote:  Would it be possible to transplant a keyboard membrane from a cheaper model (such as a HP-10B)?

I suppose so, there are several Pioneer models in these links but the membrane looks the same.

https://www.keesvandersanden.nl/calculat...wasa7LsPJM

http://www.finetune.co.jp/~lyuka/interes...c/pioneer/

[Terje Vallestad]

(02-18-2021 09:26 PM)franz.b Wrote:  

(02-18-2021 09:18 PM)ijabbott Wrote:  Would it be possible to transplant a keyboard membrane from a cheaper model (such as a HP-10B)?

I suppose so, there are several Pioneer models in these links but the membrane looks the same.

https://www.keesvandersanden.nl/calculat...wasa7LsPJM

http://www.finetune.co.jp/~lyuka/interes...c/pioneer/

Hi Franz,

The keyboard matrix for a 17BII is the same part number as your photo. I have just used one such from a 17BII to repair a 32SII. Works fine

Cheers, Terje

[franz.b]

(02-19-2021 11:05 AM)Terje Vallestad Wrote:  Hi Franz,

The keyboard matrix for a 17BII is the same part number as your photo. I have just used one such from a 17BII to repair a 32SII. Works fine

Thanks, great confirmation news! I suspect it is the same for all Pioneer models.

[franz.b]

HP27s repair part 3
it works. operation almost completed because I applied the sheet of the keyboard with thin double-sided tape, then I doubled the strips compared to the photo, but it does not adhere well: suggestions? I would not use the spry glue because it gets very dirty ...
The keyboard works well, I just applied a thin piece of paper under the "exit" key because it generated an annoying "click" sound, probably due to a slight deformation of the metal support, perhaps forced when opening.
To avoid twisting of the hooks I have inserted wire pieces so that a possible reopening is not fatal, this because they do not know the duration conductive ink that I applied.
I'm happy because this tank has been underwater.

[franz.b]

Hi! after fixing this HP27S everything seems to have gone well.
But there is a strange problem: if I leave the calculator unused for a long time (a month? Two months?) It will no longer turn on unless a reset (ON-C) and when I turn it back on all the memories, date, time and settings are lost... How come? it's normal? the batteries are in excellent condition.

Thaks in advance

[striegel]

(05-05-2022 10:20 AM)franz.b Wrote:  ...leave the calculator unused for a long time (a month? Two months?) It will no longer turn on unless a reset (ON-C) and when I turn it back on all the memories, date, time and settings are lost... How come? it's normal?...

No, that is not how my 27s behaves, but it will say, "MACHINE RESET" when I power it on after weeks in standby. It still retains the solver list that I have stored in it.

Alan

[GreyUser]

MACHINE RESET should not appear in normal operation, it indicates the processor was reset and register contents lost but the contents of the external ram survived. It is normal on a 42S that has been converted to ferromagnetic ram when the batteries have gone flat or removed. Replacing batteries on an fram 42S will always result in the reset message because the fram contents always survive a power loss.

The OP’s problem sounds like a leaky keyboard matrix. Any cross point in the matrix that has a resistance of even a few megohms will cause processor lockups. Pioneer and 48 keyboards (which are electrically identical) must be absolutely clean and contaminant free when reassembled. Anything conductive whatsoever will cause processor lockups that clear temporarily with a hard reset which is most easily accomplished by removing batteries and shorting the terminals together with a coin.

If the leakage is present in a single key crosspoint, most Pioneers will display the offending key name at power up. Multiple leakage paths will usually result in a blank screen. Monitoring supply current at turn on is the easiest way to diagnose. I’ve got those values documented around here somewhere if anyone needs them. Post if interested.

[franz.b]

(05-23-2022 01:58 AM)GreyUser Wrote:  MACHINE RESET should not appear in normal operation, it indicates the processor was reset and register contents lost but the contents of the external ram survived. It is normal on a 42S that has been converted to ferromagnetic ram when the batteries have gone flat or removed. Replacing batteries on an fram 42S will always result in the reset message because the fram contents always survive a power loss.

The OP’s problem sounds like a leaky keyboard matrix. Any cross point in the matrix that has a resistance of even a few megohms will cause processor lockups. Pioneer and 48 keyboards (which are electrically identical) must be absolutely clean and contaminant free when reassembled. Anything conductive whatsoever will cause processor lockups that clear temporarily with a hard reset which is most easily accomplished by removing batteries and shorting the terminals together with a coin.

If the leakage is present in a single key crosspoint, most Pioneers will display the offending key name at power up. Multiple leakage paths will usually result in a blank screen. Monitoring supply current at turn on is the easiest way to diagnose. I’ve got those values documented around here somewhere if anyone needs them. Post if interested.

Thanks, but the calculator works normally when used continuously, the problem you mention should give symptoms continuously, not just after weeks of inactivity. Is it right?
In any case, if you also want to post the values of the ignition current, I think they can be useful to those who repair these machines.