Faulty dk'tronics KEYBOARD

[fordp2002]

I have some faulty keys on my keyboard does anyone know of a source of spare key switches?

Also I could not see any other keyboards just like this on the web (repeat key and no numeric keypad) does anyone have information about this model. (I was given it by a friend).

[Moggy]

That switch looks identical to the ones used in Memotech and DK's next door Yarmouth neighbour KayDee, keyboards.

These switches work by having copper strips slide over each other to make contact which can verdigris over when not used for a while and if you feel confident they can taken apart to be cleaned up.

You will notice they are made in two sections held together with with a clip over lip affair on two sides.
Carefully prise these two clips open just enough to free the two halves but be wary of the two tiny springs inside.

The copper strips are very delicate so require some care when cleaning which I use a small fibreglass stick for and reassembly is just a reverse of what you have done up to press.

All this is assuming the switches are at fault. Have you tried a multimeter on them to check for continuity?

If you are convinced it is the switches and don't feel confident in repairing them yourself then please take a decent picture of the cruciform peg the key cap fits on,also a picture of the switch side on and I'll compare it to the spare switches I posses for Memotech,KayDee and Maplin keyboards and if suitable we can arrange between us to have some posted to you as I don't know of any supplier of new stock.

I would also add that those key-caps look like the type used on Maplin and Crofton keyboards, DK's and KayDees had solid grey key-caps with stuck on transfers whereas those pictured have a removable cap with a paper graphic underneath. Dk's also have a keypad using red/orange key caps as per the picture so this looks like a home-brew affair from an original cased keyboard or something DK made for another company.

LATE EDIT.

The second picture shows the switches for the DK keyboard and they do look somewhat different to yours.

[Moggy]

This image I found however does look like yours so looks like a very early DK effort made perhaps before they made the cased version.

[roganjosh]

I can't improve on Moggy's excellent reply, just relate my experience The switches are easy to clean. I ended up dismantling and cleaning all 50 or so switches on a Dk'tronics keyboard I bought off ebay a couple of years ago. Approximately three had failed and most of them were showing a higher resistance than I was comfortable with. After cleaning all 50 showed negligible resistance. Though a session of repeatedly pressing the 47 keys that initially worked might have helped to improve/retain their conductivity, given the state of the 3 failed keys I felt like I was just storing up future problems by not doing a thorough job.

Alan

[Moggy]

As well as thanking Alan for his kind words could I also add to his post by saying that for a year or so I put my Memotech keyboard to one side in favour of a Fuller keyboard(much nicer action) and when I eventually went back to the Memotech I found more than a few switches non operative at first until after much key bashing they finally started working.

[fordp2002]

Thanks for the replies. The switch on top was the P key and I did try contact cleaner and much bashing. I did take it apart but the bit of metal inside was not in a good way and I gave up trying to make it work again.

[XavSnap]

Moggy,
Your keys are named "Cherry MX".





Kicad 3D models

[Moggy]

Being old and decrepit I have to keep notes of things these days and looking back through some old scribblings I re-discovered that with the Memotech style switches that..

1) Trying to clean the copper strip inside is next to impossible as it's made of cucumber.

2) That it's not usually the strip that actually tarnishes rather it's the two fixed pins which seems bares the brunt of the tarnishing and the obvious tarnishing on the contact side of the pin only,bares this out.

3) To clean these pins the switch does not have to be dismantled only the pins, which are a friction fit, need be pulled out of the base and cleaned then pressed back in and according to my scribbles A switch showing high resistance went down to 0.9 ohms after cleaning.

The method I adopted looking back is to pull the pins clean them up then indeed just press them back in. it goes without saying that this method wont last forever as the friction fit may wear after many pulls and pushes but according to my notes I last did this about seven years ago and everything is still working ok and it's not something that needs doing every five minutes.

[Moggy]

@Fordp2002

If you are still needing switches then as I said earlier take a shot of the cruciform stem that the key fits onto and if it matches my Memotech ones then I can get them off to you.