Alps SKCL: LED and non-LED
After purchasing a bag of used Alps SKCLAR (and one green linear), I noticed something interesting: SKCLAR has no holes in the base for the legs of the LED, and neither does SKCL Green. I was aware that the LED versions of SKCL Yellow have separate part numbers (so far, SKCLFM and SKCLFQ, for green and red LEDs respectively, vs SKCLAR for no LED), but I did not realise that the LED versions were constructed differently.
Having also acquired a bag of NOS SKCLFQ, I have been able to examine the differences in detail.
From the top, the LED and non-LED switches appear to be the same. Both have a rectangular slot for an LED:
In fact, the upper shell is the same between the two designs. However, when you invert the switch, it becomes clear that the switches are different. The pattern of recesses in the base of the switch (the purpose of which remains a mystery) is very different between LED and non-LED switches. LED holes take the place of the Alps logo, which is moved to one side.
Since SKCL/SKCM is presently believed to have started with SKCL Green, this does seem strange: why would such a difference exist? This is not the only switch with such a difference: Omron B3G-S also gained such a difference, although it was not present in the “flat” switches.
There is one more difference, which is more subtle. To provide clearance for the LED, a recess is cut into the front retaining flap. Once you discover this difference, you realise that many photographs of these switches do show this recess, but it is subtle enough as to be overlooked.
Looking at photos of green Alps switches within keyboards, I have confirmed that this clearance recess is also present in green Alps switches. I have not seen the base of a green with-LED switch. In the case of E3E’s 60% project, he created all the missing LED leg holes with a hand drill! He also mentions that his LEDs had flanges, which had to be removed before insertion; this is likely because of the missing LED clearance in the bases of non-LED switches.
In fact, there is also a downward-facing step within the upper shell of the switch, to hold the LED in place (present in both LED and non-LED switches, since they share the same upper shell):
To remove the LED, first open the switch. Then, angle the LED forwards and slide it out. If you try pulling the LED out vertically, it will appear to be wedged solid, as the rear flange of the LED is being blocked by this step; the LED cannot be removed while the switch is closed.
In the case of my switches, there is also a small difference with the length of the return spring:
In the case of my examples (SKCLAR from an unknown keyboard, and SKCLFQ from an unknown source), the SKCLAR return spring is around 1 mm longer than that of SKCLFQ. As a note, the part numbers used in this article are not official: I am simply matching the characteristics up to the 1994 Alps catalogue.