Electron Keyboard - Key Switches and the Aluminium Plate ?

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BeebMan2018
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Electron Keyboard - Key Switches and the Aluminium Plate ?

Post by BeebMan2018 » Sat Nov 10, 2018 11:14 pm

Alright Guys.

Ive been trying to get this sick Electron back to health but shes proving to be stubborn. THe problem is someone has i think spilt a cup of coffee or coco over the keyboard. Ive stripped her and cleaned everything. the keys, the plate around the switches and the motherboard and the power supply. She boots to her basic os fine but the keyboard is very tempremental. Ive checked the ribbon and it seems ok. I get a continuity signal on each trace. Likewise i checked the cpu, ula rom and ram for ground and 5 v and they seem ok.

Initilly it was only the delete key but since rubbing all the coffee of with isopropanol alcohol now a whole heap of keys dont operate. I think the coffe/alcohol solution is now gumming up the contacts inside the keyboard.

So i can try to clean them with contact spray which will be hap hazard at best or i strip the keyboard totally and manyally clen it !

What I am after is how to remove the key switches ? They have a black surrond with what seems like little depressable plastic clips. on on each side and on to the top but i cant seem to get them out. Are they glued in or are they all hard soldered to the pcb first then the plate pushed down into place ? If its the latter im going to have to desolder each switch before i can remove the plate and then strip the switches !

Has anyone done this before ?

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1024MAK
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Re: Electron Keyboard - Key Switches and the Aluminium Plate ?

Post by 1024MAK » Sat Nov 10, 2018 11:40 pm

Yes!

This site may help ;-)

See also this thread ;-)

Mark
Last edited by 1024MAK on Sat Nov 10, 2018 11:44 pm, edited 1 time in total.

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rmbrowngr
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Re: Electron Keyboard - Key Switches and the Aluminium Plate ?

Post by rmbrowngr » Sun Nov 11, 2018 8:29 am

I had problems with keys on my Electron. All I did to fix them is first desolder them from the board, then removed them from there fitting using two thin, flat screwdrivers either side. Once out I then unscrewed this legs and cleaned them. You can also buy from RetroClinic replacement keys. I did this to have a few spares.
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Re: Electron Keyboard - Key Switches and the Aluminium Plate ?

Post by BeebMan2018 » Sun Nov 11, 2018 12:30 pm

I've stumbled upon this solution already. I am curious about a number of things though ! Why does simply de soldering and re soldering the switch repair it ? Does the heat anneal the copper contact inside the switch perhaps ? Causing it to bend back to a more positive position ? Also it doesn't work for all switches so how do you split an individual switch ? Finally how did you clean the pins ? The ends that make contact inside the switch have a helical form type thread and as i have no spares currently i wouldn't wish to damage them.

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1024MAK
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Re: Electron Keyboard - Key Switches and the Aluminium Plate ?

Post by 1024MAK » Sun Nov 11, 2018 12:53 pm

Desoldering and resoldering only works if the problem was a dry solder joint on the PCB.

The main problem with the contacts is that with little or no use, the surface of the contacts gets dirty with slight oxidation of the contacts. Pressing and releasing each switch (about 50 times typically) can get most keys working again.

If this does not work, you do have to desolder it and either remove one pin at a time, or completely disassemble the key switch. Ultrasonic cleaners can also clean contacts.

For keys that are just sticky, wash the keys with a mild detergent.

Mark
Last edited by 1024MAK on Sun Nov 11, 2018 12:54 pm, edited 1 time in total.

BeebMan2018
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Re: Electron Keyboard - Key Switches and the Aluminium Plate ?

Post by BeebMan2018 » Sun Nov 11, 2018 10:47 pm

Thanks Mark,

OK So I am making progress, I've de-soldered all the offending keys and have discovered the two pin holes above the pins which makes testing with a fluke a LOT easier rather than trying to hold the probes on the soldered joints on the pcb base ! :) Duh. I read the websites linked to earlier and have unscrewed the pins and lightly scrubbed them with fine Emery. Scotch brite didn't cut it ! On reassembly of the key switches they tested good. I only did the ones that my check list showed as being a problem ! I suspect more will fail over time but i will fix those when needed now i know how.

How do you split the top and bottom halves of the plastic body anyway ? They seem stuck together !

So Ive put it all back together and tested the keyboard and it works ! KINDA !!

Now all the keys on the top row apart from the Esc and Break dont work correctly. I can display all the Upper Case Charachters but none of the lower case on that row. So 1234567890-CursorLeft and CursorRight are all out but !"#$%&'()@=~\ all work !!!

Worryingly when i first boot to basic the Screen displays

Acorn Electron

Searching
FileNotFound

BASIC

>

Also the screen begins to wobble slightly then flicker and finally thick banding appears and misc corruption being displayed. I suspect failing capacitors on the RF Modulator but am only guessing at this point. m very much an amateur at this sort of thing.

So other gremlins are lurking within.

Any advice or help is always appreciated.

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leenew
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Re: Electron Keyboard - Key Switches and the Aluminium Plate ?

Post by leenew » Mon Nov 12, 2018 12:18 am

Is a 'shift' key stuck on?

Lee

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Re: Electron Keyboard - Key Switches and the Aluminium Plate ?

Post by BeebMan2018 » Mon Nov 12, 2018 12:23 am

I've just looked and they don't appear to be ! I gently prise'd the keys of and used a continuity tester on the pins. No continuity. Press the Cross into the switch body and a continuity tone is output ! They feel OK as well not sticky at all so I'm guessing there fine.

Whats my next most likely fault ?
Last edited by BeebMan2018 on Mon Nov 12, 2018 3:22 pm, edited 1 time in total.

elkrepair
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Re: Electron Keyboard - Key Switches and the Aluminium Plate ?

Post by elkrepair » Tue Nov 13, 2018 3:12 pm

This link might help with the key switches:

https://deskthority.net/wiki/Futaba_ML_series

Pictures show the internals of the switches.

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Re: Electron Keyboard - Key Switches and the Aluminium Plate ?

Post by Kazzie » Tue Nov 13, 2018 4:27 pm

From all you've done, it seems as though the key switches are operating fine. Is the fault be elsewhere, perhaps?

In the lower left corner of the keyboard (under the plastic case), there are four resistors (as well as eleven diodes). These "pull-up" resistors should ensure that the electron reads a clear 5V when scanning the keyboard, unless a key is pressed.

Could you measure the voltage across these diodes, when no keys are pressed? They should all have a low/no voltage drop if everything's working fine. You should also find that the resistors are all connected together on either the left or right-hand side: a continuity test with a voltmeter will make sure.
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