Thursday, 3 December 2015

Day 3 - Sinclair QL USB keyboard

This is day 3 of the Advent Calendar of USB keyboards. Today, a new one, a Sinclair QL USB keyboard.
This is one requested by a number of members on the QL Forum, I will be supplying conversion kits to them. The keyboard is very similar to the Sinclair ZX Spectrum+ keyboard, only a little larger. The keys and stems are actually interchangeable between the two.
They also suffer from the same issues as the Spectrums, failing membranes. This QL has an intermittent keyboard, I had already shortened it to cut out some cracked sections, but still a few keys are failing to respond. The same procedure applies as my previous post on repairing Spectrum membranes.
It seems like a good time to replace it with one of RWAP's excellent replacement membranes. The process is fairly simple, with a good hint from the instructions that came with the membrane is to mark the screws that are fitted, as there are several unused holes.
The metal backplate is screwed back on and new membrane slots back into the connectors on the board.
I tested that with the QL main board, and it is working nicely. I'm borrowing the keyboard section of this to test the USB keyboard controller, but it will be going back afterwards.
I'm using my standard USB keyboard controller, with the appropriate connectors for the QL membrane.
The LEDs on the QL are wired unusually, six wires from the top of the case have bare tinned ends and are individually plugged into a socket on the board which clips down to hold them in place. Was a two part connector so expensive?
The membrane tails plug into the USB keyboard controller. There is a 2 pin socket for the red and black wires for the power LED.
The USB cable runs out the side and plugs into the PC. The other two LEDs are for the microdrives, these are left unconnected, and can be taped down out of the way.
The keyboard mapping is pretty straightforward, other than the lack of delete or backspace keys. On the QL you would use CTRL+left arrow to delete to the left of the cursor (backspace) and CTRL+right arrow to delete to the right of the cursor (delete). I've used the same key combinations for the PC mapping.

I'm now using slightly different membrane connectors from those shown above, the new ones slide in from the side.
If you already have a QL case and a working membrane, you can order a QL USB keyboard kit from my Tindie store.

Tune in tomorrow to open another window on the Advent Calendar of USB keyboards.