800 Stackpole KB, loads of sticking keys, fix?

[Mclaneinc]

 

Just took down my beloved 800 off the wardrobe and gave it a nice clear up but spotted that most of the keys  stick down when pressed. I gave the kb mech a clean and noticed that the yellow plungers for the most part move freely up and down but its when the key cap is put on it sticks..

 

Is this serviceable?

 

I've no problem with desoldering the main PCB but can anything actually be worked on if I do that?

 

I read some posts about cracked plungers but the machine was full of dust and I washed the keyboard to see if that helped but to no effect..

 

Is there a fix, I saw the B&C NOS keyboards but that gets real expensive to the UK and I saw that someone said there's a note that the old plungers could be brittle after all these years so it makes it a big risk.

 

Help / answers would be appreciated...

[Faicuai]

Could you please, (slowly / carefully) pull out one or two of those "sticky" keys and do the following:

 

1. Check color of plunger (white, yellow or green)
2. Verify that NO foreign residues appear around the outer edges / walls of the plungers.
3. Manually and gently PUSH in the offending socket/plunger and verify that it returns freely and essily back to its extended / protruding position.

 

I find it suspicious that these plungers are getting stuck. 

Edited March 29, 2021 by Faicuai

[Mclaneinc]

Hi there,

 

The colour is yellow, there appears to be no residue on the outside of the plunger and the kb unit was given a warm soapy bath incase there was something I could not see (was already sticking before the wash). As said, if I push the plunger on 99% of the keys it springs back up, a few seem to have something near the bottom of the push and don't fully return but most do, its purely when the key is fitted that they mostly stick..

 

If I desolder the main board of the keyboard will I be able to access the plungers directly and be manually able to check for grime. I think for a while it had something on top of the keyboard as I remember having to remove some gear that had slipped and fallen on the keys (books). I'm wondering if the spring have lost most of their elastic strength from having a weight on them for a prolonged time.

 

Apart from a LOT of dust and hair there was no residue off a spill to be found and to be honest I don't drink things like coke that would go syrapy or keep cups on my desk (one of the many rules of IT I do follow)

 

I don't mind taking it fully apart to check for any crap in there but I have no clue if I can get to the plungers to replace / clean them properly.

 

Thanks for the reply..

 

Paul..

Edited March 29, 2021 by Mclaneinc

[Faicuai]

1 hour ago, Mclaneinc said:

a few seem to have something near the bottom of the push and don't fully return

 

That's quite intriguing. That's the part I am having a hard time visualizing.

 

Do they come back up if partially pressed in? Or do they get stuck no matter what the inward travel-length during push?

 

FYI, on both YELLOW and GREEN plungers, when you press in the plunger into its socket, they will NOT go in fully (about a 1mm "neck" will remain above the edges of the square-socket itself). This will NOT happen with white-plungers keyboards. Could you verify that such is the case on the sticky-ones as well? Or are they going even below the socket-edge?

 

I would suggest before dismantling anything to closely look with strong source of light, and magnifying glass, right at the plunger socket. Just to make sure the inner L+R contacts "tongues" close-in to each other slowly, as you press inward, and eventually make full contact without getting tangled with each other. Besides this, try looking deeper down, for ANY signs of foreign residue or substances that may have found its way in... Or simply excess dirt / dust combined with humidity collected throughout years.

 

You may consider disassembling as much of the keyboard TOP-SIDE as possible, but I would honestly advise against de-soldering ANYTHING at this initial stage. It is possible that a permanent excess of vertical-pressure applied on some particular keys, may have physically damaged the plunger socket or the actual elements that provide back-pressure.

Edited March 29, 2021 by Faicuai

[Sugarland]

One of the main problems with the yellow plungers is they crack and keycaps will fall off/out very, very easily.  However that the keys do not return when pressed seems to me to be a springs issue. Are the lesser used keys behaving the same as the heavily used keys? Inverse for example...

[Sugarland]

14 hours ago, Mclaneinc said:

 

Is there a fix, I saw the B&C NOS keyboards but that gets real expensive to the UK and I saw that someone said there's a note that the old plungers could be brittle after all these years so it makes it a big risk.

 

Help / answers would be appreciated...

 

Oh his NOS 800 keyboard auction shows a yellow plunger variant, which seems to be the worst keyboard made for the 800.  He may have other variants and he just uses the yellow plunger keyboard as a stock photo.  I would ask him first with the ebay 'contact seller' feature so the conversation is documented in ebay.

 

[Mclaneinc]

Thanks for the responses guys, some of the lesser used keys suffer no issue, the contacts inside the plungers seem to meet happily to activate the key, if I can I'll make a video showing the issue.

[Mclaneinc]

Sorry for no video, been really busy but I just found out you can pull the plungers out, I thought the bottom PCB needed to come off..

 

When I got a couple off I found they were gunky so I'm going to remove them all, make sure they get a good but gentle wash and get some cotton buds and gently clean inside the plunger hole around the leafs, I think Isoprp should be ok but I'll await a nod from the pro's before I use it..

 

Oh and when I cleaned the two that were sticking that I pulled out, after a clean they seemed ok...Here's hoping.....Thankfully the leafs close up giving you a little more cleaning room...

 

EDIT: Hmmm...some room but it seems no where near enough to put a qtip down there without damaging the leafs..Obviously if there's gunk on the plunger that did not get washed off when I gave the whole keyboard a dunk then there's got to be some gunk in the recess for the plunger. Any thoughts on how I could clean that without a full removal of the PCB. I guess just spraying a little isop (if its ok to use) down the hole the plunger fits in would do little.

 

If I have to remove the bottom board so I can wash the unit more thoroughly then so be it, I'd just be mega careful of not bashing the leafs..

 

Again, any thoughts appreciated..

 

Would that Deoxit do anything?  (or similar?)

Edited March 30, 2021 by Mclaneinc

[Mclaneinc]

Think I've found the cause, managed to get all but 11 keys non sticking, no matter how much I cleaned they just kept sticking and then  I spotted a thread that says the plungers can split and sure enough, all 11 plungers had splits down the side. I presume that the weight of the stuff that was on top of the keyboard for so long had as adverse reaction with the plungers and split them...

 

Also not the best time to see a post saying Brad was out of them a while back...Looks like I'm stuck...