Clare-Pendar Series S840

Clare-Pendar Series S840
Manufacturer	Clare-Pendar, Pollak, Electro-Mech
Product code	S840nn …
Switch type	Linear
Sense method	Metal contact
Switch mount	Plate mount

This article requires additional photographic illustration

Clare-Pendar Series S840 is a metal contact keyboard switch series with support for illumination at at least two pairs of contacts.

Description

Per the illuminated version, the shell is 16.2 mm tall including standoffs, and around 14.3 mm wide by 14.2 mm deep. The lid is around 18.9 mm square and 1.4 mm tall. The switch travel seems to be somewhere in the region of 4.5 mm.

The switch uses pairs of identical contacts that face each other, similar to the PED keyswitch. A large block on the slider holds the contacts apart at rest, and when the slider is lowered, the contacts closed. The design is similar to Hi-Tek High Profile, but the contacts are in bays at the sides of the switch, allowing for more than one pair of contacts per switch, something not possible with the Hi-Tek design.

The base is marked with six positions, numbered (when seen from below) anti-clockwise from 2 to 7, two per side. Positions 6 and 7 are the terminals of an SPST switch, and a DPST switch has a second pair of terminals on the opposite side in the 2 and 3 positions. No switch has been seen with terminals in positions 4 and 5, and the slider in the illuminated version only accepts up to two pairs of terminals, one pair per side (these being the only two sides with the separator block moulded in). The empty terminal position can have a rubber O-ring placed around it for damping.

In the two instances of these switches being found in keyboards, they have crosspoint contacts,^[1]^[2] while the "ASM MEXICO" illuminated version (found only as unidentified surplus stock) is not crosspoint.

Centre illumination is supported. A small plug is inserted into a chamber in the bottom of the switch, containing two terminals and two lamp terminal receptacles. The lamp can then be inserted into the centre of the switch within the slider.

No alternate action version has been sighted, but a small peg on one of the slider types found in the illuminated version may be there to support a latching arm.

Disassembly

The switch body comprises a shell and a lid. Four tabs, one per side, hold the lid in place. Each tab should be gently pried outwards using a sharp knife, releasing one side of the lid; as each tab is levered open, that side of the lid can be released.

It is possible to pull the slider out past the contacts, but afterwards they are likely not to close together (having being forced apart) and will need bending back to the correct angle. Trying to insert the slider past the contacts is likely to crushing them and should never be attempted. To insert the slider, first remove the contacts, by pushing carefully on the terminals and then pulling the contacts out using tweezers. Then, insert the slider (and the return spring if necessary), and push down hard on the slider so that it snaps back into the shell (this can require considerable force). Finally, slide each contact back down into the shell. The switch contacts look sturdy but, at least with the non-prism version, are are fairly delicate and can even snap when trying to restore their shape after damage has occurred.

Variants

No documentation has been recovered for Series S840 beyond details of modification codes. No switches have been found for sale to the public with a known part number, and switches for sale business to business do not include illustration.

A specific variant was previously sold on eBay with NSN 5930-01-089-6772; this NSN indicates S84010, but the images of it (below) show an adapted switch. Clare-Pendar documentation indicates that modification K2 is the "Castillated [sic] S840 support lid", as shown in the photos. Sadly the documentation that accompanied those switches is now lost, and the specific part number cannot be recovered.

Per Clare-Pendar practice, the following codes are appended to the part numbers to customise the switch.

Mod.	Description
E9	11° angle plunger on S820, S830, S840, S860 or S830 11° angle adapter.
H3	Lighted S840 switch or keytop.
J6	Bezel on switch case to fit KQ keytop (S840).
K2	Castillated [sic] S840 support lid 301-136
K5	S840 blocking ring for castillated cover (309087).

Known variants include:

	Part number	Type
	S84010 (unconfirmed)	Standard SPST
	S84020 E9 (unconfirmed)	DPST with angled keystem
	S84010 K2 (unconfirmed)	Castellated top SPST
	S84010 H3 (unconfirmed)	Illuminated SPST

Keyboards

Uncertain Clare-Pendar keyboard (SPST)^[1]
NASA control panel with Bendix keyboard (DPST angled)^[2]

Gallery

S84010 K2

Based on the NSN code, these should be S84010, but the design is clearly K2 modification.

S84010 K2 front view
S84010 K2 side view

S84010 H3

The depicted switches were obtained NOS from Electronic Surplus, with no known part number or manufacturer. Based on the design, these are taken to be S84010 H3. Within this set of switches, two different slider designs were found; the sliders differ in the shape of the parts on side 2; one design features a small peg, which may be used for the latching arm, similar to how it functions in Clare-Pendar Series S880.

A small plug fits into the bottom of the switch; below it are two additional terminals, for the lamp, and it provides two sprung receptacles for lamp terminals. As with many other switches, this allows for incandescent lamps to be removed and replaced without needing to desolder and remove the switch.