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Dave Britten · 01-25-2018, 01:50 PM

You've probably seen me and several others gripe about the 30b keyboard quality, and how it's the weak point of the otherwise excellent WP-34S. Mine had a number of reluctant keys, which made me reluctant to use it for "real work". Well, figuring I had nothing to lose, I tore mine apart and did some cleaning.

It's the typical "adhesive laminate layer with a bunch of metal domes" keyboard design. What I did was peel up the laminate from the bottom, stopping halfway (just above the XEQ row). Then I used a cotton swab dampened with 91% isopropyl alcohol (i.e. what I happened to have sitting on my desk) and scrubbed the metal contacts on the PCB. After that, I did the same with the dry end of the swab to mop up. Then I dampened another swab, making sure it wasn't dripping wet. I carefully scrubbed the inside of each metal dome, including the little "legs" at the corners. After letting them dry for a few moments, I visually inspected them for debris/residue, re-swabbing as needed until they looked clean (watch out for cotton fibers sticking to the laminate). I resealed the laminate to the PCB, then peeled from the top, repeating the procedure with the top 3 rows of keys.

After that, mine is working flawlessly, with all keys responding with no hesitation. I can probably get some actual use out of this thing now, though I suspect it's long overdue for a firmware update (gotta dig out my programming cable).

aurelio · (This post was last modified: 01-25-2018 07:51 PM by aurelio.)

Hi Dave, do you have any pics to share of this upgrading treatment?
It should be helpful in better understanding the "issues" removed.
Happy to know you are appreciating more your calculator now
Thanks for sharing

brickviking · 01-25-2018, 08:39 PM

Nice job! That's always been a reservation of the WP-34S, the quality of the underlying 20b/30b. Yes, we'd love to have seen pictures, as that gives the rest of us a better idea of what we'd have faced to do the same job ourselves. It's clear there's some other kit needed.

(Post 161)

Dave Frederickson · 01-25-2018, 09:08 PM

A little dab of DeoxIT Gold on the contacts should help keep the switches working.

Dave Britten · 01-25-2018, 09:17 PM

(01-25-2018 09:08 PM)Dave Frederickson Wrote: A little dab of DeoxIT Gold on the contacts should help keep the switches working.

I'll have to pick up some of that stuff for this and other things. I've heard it mentioned more than once.

I didn't think to snap any pictures of the insides, mostly because it was so straight-forward. Remove the five screws on the back of the case (two are under the bottom rubber strip), use a small screwdriver to carefully pry the clips in the seam between the front and rear case halves, then deal with lifting the board out of the front case. You might need to work it off some heat stakes, but it's not as bad as doing a Pioneer or a 48. Just be careful of the flex cable holding the LCD to the board, since it's all one piece.

jebem · 01-26-2018, 07:19 AM

(01-25-2018 09:17 PM)Dave Britten Wrote: I didn't think to snap any pictures of the insides, mostly because it was so straight-forward. Remove the five screws on the back of the case (two are under the bottom rubber strip), use a small screwdriver to carefully pry the clips in the seam between the front and rear case halves, then deal with lifting the board out of the front case. You might need to work it off some heat stakes, but it's not as bad as doing a Pioneer or a 48. Just be careful of the flex cable holding the LCD to the board, since it's all one piece.

Thanks for sharing.
How did you fix the pca back in place after having the heat stakes undone?

Dave Britten · 01-26-2018, 12:05 PM

(01-26-2018 07:19 AM)jebem Wrote: Thanks for sharing.
How did you fix the pca back in place after having the heat stakes undone?

A hot glue gun is usually my go-to heat stake tool. Put enough pressure on the board to hold it in place, and put a little cap of glue on the stake. Hold the board in place until the glue has set up enough to hold (doesn't take long). Everything fits snugly enough in the 30b that you don't have to be completely perfect to get good results.

I've used the same approach in repairing the keyboard on a 32S, which was far more arduous than doing the 30b.

cjmcc · 01-26-2018, 01:44 PM

(01-26-2018 12:05 PM)Dave Britten Wrote:
(01-26-2018 07:19 AM)jebem Wrote: Thanks for sharing.
How did you fix the pca back in place after having the heat stakes undone?

A hot glue gun is usually my go-to heat stake tool. Put enough pressure on the board to hold it in place, and put a little cap of glue on the stake. Hold the board in place until the glue has set up enough to hold (doesn't take long). Everything fits snugly enough in the 30b that you don't have to be completely perfect to get good results.

I've used the same approach in repairing the keyboard on a 32S, which was far more arduous than doing the 30b.

Let me also say thanks for sharing. I have several non-operational HPs that I would like to fix (48 and 49 series), but I haven't had the time or the nerve to dig in yet. It's nice to hear from others to help feed the mantra, "It's not that hard."

Dave Britten · 01-26-2018, 02:01 PM

(01-26-2018 01:44 PM)cjmcc Wrote: Let me also say thanks for sharing. I have several non-operational HPs that I would like to fix (48 and 49 series), but I haven't had the time or the nerve to dig in yet. It's nice to hear from others to help feed the mantra, "It's not that hard."

I will say that the 48 is definitely trickier than the 30b, since the case itself is held together with large heat stakes rather than screws. But if you can manage that part, then the keyboard itself should be the same deal as most other models.

jebem · 01-26-2018, 04:08 PM

(01-26-2018 12:05 PM)Dave Britten Wrote:
(01-26-2018 07:19 AM)jebem Wrote: Thanks for sharing.
How did you fix the pca back in place after having the heat stakes undone?

A hot glue gun is usually my go-to heat stake tool. Put enough pressure on the board to hold it in place, and put a little cap of glue on the stake.

Interesting idea.

I use the hot glue gun to fix wiring n the walls from time to time.
I was not sure if the hot glue would really stick strongly enough to the calculator PCB in order to resist the continued key pressings, so I never tried.
I will test it on one of my next repairs and see how it goes.

I have been using stronger adhesives on these keyboards, like Araldite fast cure variant. It takes more time to cure than just a few seconds on hot glue, and of course it will be much harder to undo the rivets later on if we need to do another repair.

Dave Britten · 01-26-2018, 05:32 PM

(01-26-2018 04:08 PM)jebem Wrote: Interesting idea.

I use the hot glue gun to fix wiring n the walls from time to time.
I was not sure if the hot glue would really stick strongly enough to the calculator PCB in order to resist the continued key pressings, so I never tried.
I will test it on one of my next repairs and see how it goes.

I have been using stronger adhesives on these keyboards, like Araldite fast cure variant. It takes more time to cure than just a few seconds on hot glue, and of course it will be much harder to undo the rivets later on if we need to do another repair.

Once you've removed the mushroom tops of the heat stakes, the hot glue makes an excellent replacement. It doesn't have to bond with the PCB, rather it has to bond with the tip of the plastic stake, and spread out a bit over the PCB to hold it in once it hardens. Make sure you use a generous enough blob, and if you can get the glue down around the stake itself (i.e. inside the hole through the PCB), it should have a really good grip. The fact that the load is being shared by multiple glue stakes also helps.

The only annoying part is cleaning up all the little wispy strings of hot glue that you'll undoubtedly trail everywhere.