14

On the one hand it was clearly down to cost - being very much cheaper than a conventional keyboard. However, remember that the Spectrum was the replacement for the ZX81 and ZX80. These had absolutely no tactile feedback in their capacitive keyboards and so the Spectrum could be marketed as a great leap forward in quality and user experience. Although that ...


14

In the end, I decided that it had to be easier to take the keyboard apart than to de-solder the 4051's and so I carefully removed the 18 tiny screws from the back of the keyboard. It wasn't nearly as bad as I expected (I was concerned that I was going to have springs everywhere). After disassembly I fired up the Atari to try and see if I could get the A ...


12

As simple as that: because it is the cheapest solution. Mechanical keys, separate circuit boards to hold the switches, etc, add costs to the final product. The ZX Spectrum case is slighly bigger than the circuit board itself, and thick enough to accomodate chips with sockets (there is no room even for a heatsinked socketed ULA). In addition to manufacturing ...


11

For the keyboard itself: Undo the screws from the bottom of the case. Lift the top of the case gently off. Disconnect the ribbon cables from the keyboard (CAREFUL fragile) Slide out the keyboard. Insert the new one and attach the ribbon cables. Clip the case back together and do up the screws For the membrane: Prise the top off the case - early models ...


8

It depends on a number of factors, a major one being the material that the membrane is made from. Various types of plastics can be used, with different properties. Some will age and become brittle, or otherwise degrade over time. The contact mechanism for each switch also varies. Some use metal domes that buckle for a somewhat tactile feel, and the metal ...


8

I've found that the old Atari keyboards can lose conductivity and that pressing they key repeatedly, not necessarily with a lot of pressure, can revive them. I've had Apple II keys start working again after pressing them a hundred or two times. Assuming the above isn't the issue, if the rest of the keys, particularly in the same row and column work (not ...


6

Chip checking time! Pull, inspect, and re-seat the 4051s (two of em, the small chips near the center of the board) and the POKEY chip on the motherboard. Hopefully they are socketed and not soldered, I'm not sure how consistent Atari was with those. If that doesn't resolve anything, and since some of the keys do work, try swapping the two 4051s and see if a ...


5

According to jdv's answer to another question, cotton swabs and isopropyl (rubbing) alcohol will do the trick. Try to keep the alcohol away from plastics, use it sparingly and be gentle when you rub the dirt. His answer also says that "fancy contact cleaner" will work: For example, "CRC QD Contact Cleaner". Make sure you don't get the type used for ...


5

A pink pencil eraser is a reasonable contact cleaner for this sort of thing. Just scrub the black dots a bit and see if they will respond to softer pressure.


4

Some early computers used a membrane keyboard (ZX80, ZX81, Atari 400), or semi-membrane with minimal keys (ZX Spectrum). Not just early ones. Membrane keyboards are still made and used today, usually for industrial use, as they have inherent advantages - like every design. This is because it was cheaper than a mechanical keyboard. That's right, at least ...


4

As is usually the case with manufacturing, the selection of a component/construction type (the keyboard, in this case) is not so simple as just knowing the cost per manufactured unit. This is because the cost per manufactured unit is impacted by the scale of production. Generally speaking, larger volume production leads to lower per unit cost. A corollary ...


2

Intuitively, I would be inclined to think either the keyboard matters more to your target market than cost or it doesn't, and in the latter case you might as well use a membrane keyboard, being the cheapest option, but empirically, chiclet keyboards were more common. Target market is cost. When targeting for example text entry as a business case, the ...


2

Yes it is pretty easy. Dataserve is a great site, devoted to retro computing. And if you want a video showing you how, to minimise getting it wrong, here is one from Mark Fixes Stuff on YouTube https://m.youtube.com/watch?v=O61Yy00GHEc And if you are buying, SellMyRetro is a good site. Make sure you buy the right membrane. For example, the Spectrum + ...


2

After finding this community just in the last couple days, some of these questions bring back great memories from my younger days. I used to repair the ATARI computers and did modifications to bump up the RAM in the ATARI computers. I remember opening the keyboards to do cleaning on the membrane. Just don't rub too hard or use any heavy cleaners on them as ...


1

I have an 800XL that does this once in a while though the keyboard in my rig seems 100% mechanical. Others seem to be less so with a sheet of mylar in there. Anywho - in my case I'll simply pop the keycap and use compressed air to clean out the switch. I do this a few times and magically the key starts working again.


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