HP41CV Repair - Keyboard PCB Reassembly

[cesarb94]

Hello, I'm currently repairing a 41CV.
From what I can see there was a large battery leak and might have gotten under the keyboard.

I would like to know if anyone has experience with the reassembly process, after removal of the keyboard PCB. Is it possible to install small screws where the rivets were located? Or are there better options?

Thanks in advance.

[BillBee]

For a 15c, which also used the plastic rivets, I clamped the keyboard tight and used a "dab" of E6000 jewelry glue on each spot. No problems so far. Nice and tight key presses.

In my case the calc came that way. For your case there are other options. I have read (on this site) use of an ultrasonic cleaner and/or a keyboard bath (vinegar soln IIRC). Though I recommend some reading for confirmation.

For specific keys I have used DeOxit and a small wire to fix intermittent 41c keys. Be gentle.

Hope that helps until some pros pop by.

-Bill

[AndiGer]

(05-24-2021 01:50 PM)BillBee Wrote:  I have read (on this site) use of an ultrasonic cleaner and/or a keyboard bath (vinegar soln IIRC). Though I recommend some reading for confirmation.

I think - didn't check further - the bath should take place the calculator standing upright. Don't put the display under liquids. I once bathed an HP-11C upright and was careful with the LCD.
Let dry sorrowly.

[Dave Britten]

(05-24-2021 01:50 PM)BillBee Wrote:  For a 15c, which also used the plastic rivets, I clamped the keyboard tight and used a "dab" of E6000 jewelry glue on each spot. No problems so far. Nice and tight key presses.

In my case the calc came that way. For your case there are other options. I have read (on this site) use of an ultrasonic cleaner and/or a keyboard bath (vinegar soln IIRC). Though I recommend some reading for confirmation.

For specific keys I have used DeOxit and a small wire to fix intermittent 41c keys. Be gentle.

Hope that helps until some pros pop by.

-Bill

I did something similar to fix a TI FIA with dirty key contacts. That thing has enough heat stakes to make an HP 28 blush. Place the calculator face down on a board, and use Irwin clamps to hold the PCB in place. I used JB Weld Plastic Bonder so it took about 24 hours of gluing some stakes, waiting a couple hours for the epoxy to cure, moving the clamps, gluing more stakes... Might have to try E6000 and see if it's a quicker process.

[ijabbott]

(05-25-2021 02:01 PM)Dave Britten Wrote:  I did something similar to fix a TI FIA with dirty key contacts. That thing has enough heat stakes to make an HP 28 blush. Place the calculator face down on a board, and use Irwin clamps to hold the PCB in place. I used JB Weld Plastic Bonder so it took about 24 hours of gluing some stakes, waiting a couple hours for the epoxy to cure, moving the clamps, gluing more stakes... Might have to try E6000 and see if it's a quicker process.

I wonder if UV curing resin would work?

[BillBee]

(05-25-2021 02:01 PM)Dave Britten Wrote:  

(05-24-2021 01:50 PM)BillBee Wrote:  For a 15c, which also used the plastic rivets, I clamped the keyboard tight and used a "dab" of E6000 jewelry glue on each spot. No problems so far. Nice and tight key presses.

In my case the calc came that way. For your case there are other options. I have read (on this site) use of an ultrasonic cleaner and/or a keyboard bath (vinegar soln IIRC). Though I recommend some reading for confirmation.

For specific keys I have used DeOxit and a small wire to fix intermittent 41c keys. Be gentle.

Hope that helps until some pros pop by.

-Bill

I did something similar to fix a TI FIA with dirty key contacts. That thing has enough heat stakes to make an HP 28 blush. Place the calculator face down on a board, and use Irwin clamps to hold the PCB in place. I used JB Weld Plastic Bonder so it took about 24 hours of gluing some stakes, waiting a couple hours for the epoxy to cure, moving the clamps, gluing more stakes... Might have to try E6000 and see if it's a quicker process.

A 28 blush? Yikes! I took only one 28s apart (corroded beyond repair and I needed to explore) and it was robustly staked. I want to blame your TI threads for the nice 58Cs I have here - now I hope there is never a need for surgery.

Edit: TheCalculatorStore's book on 41 repair is what put E6000 on my radar. Good intro book for contemplating 41 repairs.
-B

[Dave Britten]

(05-25-2021 03:26 PM)BillBee Wrote:  A 28 blush? Yikes! I took only one 28s apart (corroded beyond repair and I needed to explore) and it was robustly staked. I want to blame your TI threads for the nice 58Cs I have here - now I hope there is never a need for surgery.

Edit: TheCalculatorStore's book on 41 repair is what put E6000 on my radar. Good intro book for contemplating 41 repairs.
-B

Ha, at least the 58 and 59 are super easy to dismantle (and reassemble!) should the need ever arise. Actually getting underneath the key contacts to clean them is another matter, though - you'll typically need a soldering iron and new cellophane packing tape. Fortunately mine have needed almost no maintenance in that regard.

The FIA was kind of an oddball; it's the only TI I've come across so far with a heat-staked PCB. It's also got a really strange key design that tries to mimic the click-and-roll HP keys and comes close enough to succeeding that it's not unpleasant to use. I think I prefer the 1st-gen 36X Solar and TI-85 keyboards though, if we're talking TI's rubber contact membrane designs.

Looks like Michael's carries E6000. I'll have to grab some to have on hand, and maybe do a little work on my 15C LE.

[rprosperi]

(05-25-2021 04:08 PM)Dave Britten Wrote:  Looks like Michael's carries E6000. I'll have to grab some to have on hand, and maybe do a little work on my 15C LE.

E6000 is good stuff! It's not as strong as 2-part epoxies, but is good enough for many repair jobs you likely use epoxy for, and far more convenient to use:

Open cap
Squeeze
Close cap

Give it a try on something that doesn't matter, you'll get a better feel for its viscosity, application and cure timing. Better to know that from direct experience before dabbling with a calculator repair.

[BillBee]

(05-25-2021 06:27 PM)rprosperi Wrote:  

(05-25-2021 04:08 PM)Dave Britten Wrote:  Looks like Michael's carries E6000. I'll have to grab some to have on hand, and maybe do a little work on my 15C LE.

E6000 is good stuff! It's not as strong as 2-part epoxies, but is good enough for many repair jobs you likely use epoxy for, and far more convenient to use:

Open cap
Squeeze
Close cap

Give it a try on something that doesn't matter, you'll get a better feel for its viscosity, application and cure timing. Better to know that from direct experience before dabbling with a calculator repair.

For posts I angle cut the ball off a que-tip and grab a wee bit of E6000 from the end of the tube. One does not need a lot just the "post-nub" and a bit around. Be sure to clean the end of the tube and threads to save the rest of the tube for wife friendly projects.

-B

[cesarb94]

Thanks a lot for the information. I did not know how tough the E6000 was. Got a tube of it online, it should arrive on friday. It's going to be a fun weekend.

[cruff]

(05-25-2021 02:27 PM)ijabbott Wrote:  I wonder if UV curing resin would work?

I've had good luck using the Bondic brand UV resin for a number of repairs, including a broken glass dragon figure that a supposed "glass/ceramic glue" wouldn't hold on. The nice thing about it is you can build it up in layers to gain additional strength.

[cesarb94]

Haven't yet fiddled with the keyboard PCB, but after some extra cleaning and adding come spacers at the bottom posts, I got something to show on the display. However pressing on/off does nothing, it stays like this the moment batteries are inserted.

[cesarb94]

Ok, so the problem was actually the zebra connector. I've replaced it and now the calculator is alive!

I'll probably will have to disassemble the keyboard some day, the Program key is not responding very well.

Thanks a lot for all the suggestions!