Vintage Cherry Solid-State Capacitive keyboard – KFN3-8358

snuci · 16 Mar 2016, 00:13

This keyboard was purchased at the same time as a Cherry model KFN3-8351 keyboard that looks almost exactly like this Cherry Solid State capacitive keyboard except for the model number. Once the key caps are removed and the internal keyboard mechanism is examined, that’s where things change.

: Cherry KFN3-8358 - keyboard profile; Cherry KFN3-8358 - keyboard profile.JPG (139.49 KiB) Viewed 3106 times

This model has a different capacitive circuit board design that is visible from the pictures below. However, the main difference is the key switches.

: Cherry difference; Cherry Shamrock.jpg (189.11 KiB) Viewed 3106 times

This keyboard on the left is different in that it has a slim plastic bar across the key cap hole. This may be have been put in place to stabilize the key cap mounting hole but it’s a guess at this point. Also of note is that Enter key for the normal key region and the Enter key for the numeric key pad are adorned with white key stems. I can’t find any difference between the white and black stems. Since they use a foam and foil technology and the foam has long degraded, I can’t tell if the foam was any different. The external springs on the key switches are the same as all other keys except for the space bar. That spring is stiffer but the space bar has a black key stem like all other keys. That’s a bit of a mystery.

Of note on these Cherry keyboards is the case. It it not plastic but is made out of molded structured foam, the same material used on Apple II cases, making the case top very light. This, however, is evened out with the case bottom being black painted metal.

Below are some pics:

: Cherry KFN3-8358 - keyboard top; Cherry KFN3-8358 - keyboard top.JPG (184.77 KiB) Viewed 3106 times

: Cherry KFN3-8358 - keyboard bottom; Cherry KFN3-8358 - keyboard bottom.JPG (200 KiB) Viewed 3106 times

: Cherry KFN3-8358 - no key caps; Cherry KFN3-8358 - no key caps.JPG (223.21 KiB) Viewed 3106 times

: Cherry KFN3-8358 - keyboard mechanism top; Cherry KFN3-8358 - keyboard mechanism top.JPG (250.6 KiB) Viewed 3106 times

: Cherry KFN3-8358 - case top removed; Cherry KFN3-8358 - case top removed.JPG (287.02 KiB) Viewed 3106 times

: Cherry KFN3-8358 - PCB front; Cherry KFN3-8358 - PCB front.JPG (342.91 KiB) Viewed 3106 times

: Cherry KFN3-8358 - PCB back; Cherry KFN3-8358 - PCB back.JPG (320.8 KiB) Viewed 3106 times

: Cherry KFN3-8358 - PCB keyboard controller; Cherry KFN3-8358 - PCB keyboard controller.JPG (253.04 KiB) Viewed 3106 times

: Cherry KFN3-8358 - PCB logic chips with dates; Cherry KFN3-8358 - PCB logic chips with dates.JPG (296.7 KiB) Viewed 3106 times

snuci · 16 Mar 2016, 00:14

More pics:

: Cherry KFN3-8358 - key switch tops 1; Cherry KFN3-8358 - key switch tops 1.JPG (347.94 KiB) Viewed 3093 times

: Cherry KFN3-8358 - key switch tops 2; Cherry KFN3-8358 - key switch tops 2.JPG (336.58 KiB) Viewed 3093 times

: Cherry KFN3-8358 - key switch pic 1; Cherry KFN3-8358 - key switch pic 1.JPG (413.42 KiB) Viewed 3093 times

: Cherry KFN3-8358 - key switch pic 2; Cherry KFN3-8358 - key switch pic 2.JPG (297.94 KiB) Viewed 3093 times

: Cherry KFN3-8358 - key switch pic 3; Cherry KFN3-8358 - key switch pic 3.JPG (348.81 KiB) Viewed 3093 times

: Cherry KFN3-8358 - key switch pic 4; Cherry KFN3-8358 - key switch pic 4.JPG (384.01 KiB) Viewed 3093 times

: Cherry KFN3-8358 - key switches with springs close-up; Cherry KFN3-8358 - key switchew with springs close-up.JPG (431.13 KiB) Viewed 3093 times

: Cherry KFN3-8358 - keyboard case top exterior; Cherry KFN3-8358 - keyboard case top exterior.JPG (118.49 KiB) Viewed 3093 times

: Cherry KFN3-8358 - keyboard case top interior; Cherry KFN3-8358 - keyboard case top interior.JPG (172.14 KiB) Viewed 3093 times

: Cherry KFN3-8358 - keyboard case bottom interior; Cherry KFN3-8358 - keyboard case bottom interior.JPG (168.78 KiB) Viewed 3093 times

: Cherry KFN3-8358 - keyboard case bottom exterior; Cherry KFN3-8358 - keyboard case bottom exterior.JPG (202.31 KiB) Viewed 3093 times

seebart · 16 Mar 2016, 00:19

Very good information snuci, pretty rare item I guess. Looks to be in very good condidtion. Do the switches feel like other foam and foil switches?

snuci · 16 Mar 2016, 00:30

seebart wrote: Very good information snuci, pretty rare item I guess. Looks to be in very good condidtion. Do the switches feel like other foam and foil switches?

\

Unfortunately, this foam is shot and would take quite a bit of work to recreate because of the shape. The foam has the foil side that you see as well as a hard plastic side. The hard plastic side clicks into the key switches so they are stuck in place. Most other foam and foil key pads are round so they are easy to recreate (I sometimes use overhead projector sheets) but with this shape, they are not easily produced to fit.

What is odd is that the foam is actually very thin on these. I can't be sure of the thickness because the foam has collapsed but it is at least half the thickness of normal foam and foil pads.

These will never be used again but they are cool. This particular keyboard does not have an FCC ID so it may be possible that it's a prototype with a slightly different key switch for testing. It makes no sense to have two key switches that are almost alike with no difference in feel.

bocahgundul · 17 Mar 2016, 01:48

Very good information bro!

can you make a typing demonstration on this keyboard? I really want to hear the sound that this one makes

Engicoder · 17 Mar 2016, 23:30

Its interesting that the raised area of the case above the keys is similar to that used by Keytronic and 725 series Hi-Tek keyboards of that era. I wonder where this design originated.

Keytronic

Hi-Tek

Cherry

snuci · 17 Mar 2016, 23:47

Here's another 84 key Cherry that Compgeke pointed out to me that I acquired from eBay (still waiting for it to come) that would have also fit the same case. This one is wireless.

: Cherry KXN3-8451 keyboard; KXN3-8451.JPG (294.26 KiB) Viewed 3007 times

bocahgundul,

I don't have any video equipment. I suppose I can do something with my phone but it will be underwhelming because of the lack of foam to cushion the keys. Let's see if this one is any different once it arrives.