KPT switch

KPT switch
Manufacturer	KPT
Discontinued	Unknown
Switch type	Clicky
Sense method	Metal leaf
Total travel	4.2 mm
Keycap mount	Alps mount
Switch mount	Plate mount

KPT switch refers to several related Alps mount switches manufactured by KPT.

Description

KPT switches borrow the click leaf from Alps SKCM series switches and the contact arrangement from SMK vintage linear switches. To aid with PCB routing, the switches have three legs instead of the usual two, with the two side legs connected together. The slider is asymmetric, with a ramp on one side that operates the contact mechanism. The contact plates are held apart by the ramp, and close together when the slider is depressed. Switch travel is comparatively long at around 4.2 mm; the slider can be pressed down until it is almost flush with, or completely flush with the top of the shell.

KPT switches are Alps mount, but the leg arrangement prevents them from being used in Alps keyboards.

KPT switches are taken to be those branded "KPT"; the letters are embossed on both the top and the bottom of the shell, in a fairly haphazard-looking way. These blue switches come in two varieties: a rectangular slider similar to SMK Alps mount, and an Alps-style slider.

All known KPT switches are clicky.

KPT switches appear to be designed in such a way that they cannot be opened while soldered in place. The lower plate mount lugs (that sit below the plate) are part of the upper shell, meaning that the PCB would have to be removed in order to release them.

Variants

Blue (rectangular slider)

Blue KPT switch with rectangular slider on a KPT-84 keyboard

This is the most common KPT switch. The slider is completely rectangular in cross section. There is one long lower plate mount securing lug per side.

The switch is confirmed to be not an Omron clone. The distance between the top of the PCB and the bottom of the plate should be 4.5 mm, but instead it is around 6.7 mm. Instead of 12.2 mm, the switch is 13.3 mm tall including stand-offs. With this deviation alone, replacement of all switches in a keyboard should be possible, as the PCB is not typically attached to the plate, and the leg spacing appears to be the same. However, the switch dimensions at the mounting plate are approximately 15.5 × 12.5 mm compared to the Omron expectation of 13.4 mm squared.

Blue (Alps-style slider)

The slider has an Alps-style cross section. There are two short lower plate mount securing lugs per side. The slider pigment is a darker, greenish shade of blue. The lower shell is effectively the same as that found in the rectangular slider version, so they should be fully interchangeable. In the KPT KPT-102, they have been found used for just the top two rows of keys, although more often the KPT-102 uses only the rectangular slider version. This version of the switch is described as "vaguely Alps-like feel", while the rectangular version is described as "closer to amber Omrons";^[1] the cause of this observation is a mystery as the internal parts appear to be the same.

Amber (Alps-style slider)

The lower shell of the amber version is distinctly different. The distance from the top of the PCB to the top of the plate is reduced to 5.2 mm, which in between that of blue KPT and Omron. At around 13.2 mm, the switch is marginally shorter. The tactile point seems to be higher than with blue KPT, and stronger, suggesting that this has the operational characteristics of the blue Alps-style switch.

No keyboards have yet been discovered using the Amber version of the switch.