Valve - o - Tron

Some pictures of the Valve - O - Tron being built

Looking through the garage at the various bits and bobs, I've chosen this old Wheatstone box to turn into a clock. Ideally suited as it has a nice wooden casing, and 5 big well proportioned knobs that could fit a clock layout quite nicely.

Obviously old and a bit grubby, also noted that the casing has had some woodworm at one point - now long since dead.

The main Chassis is made out of some old Bakelite material, and there are lots of contacts arranged in a circular pattern around the central spindle that the knobs sit on. At the rear are all the resistance coils that make the unit function

In order to fit a Nixie tube, I've had to remove the central spindle and drill out a central hole - 30mm in diameter that will accommodate a socket for a GN-4 type Nixie tube. The challenge is to get the holes central.

At the rear I have now fitted some sockets, and also in the middle is an A101 Dekatron tube, just placed there at the moment to check for fit.

Again another check from the front, making sure I've not put any of the sockets 180 degrees out, and that it generally looks the way I want it. I decided to keep the little round contacts in place as it looks quite interesting once the front cover is back on.

With the cover placed back on, I think I was right in leaving the little silver contact blocks in place. The first slot does not have a full 360 degree compliment of silver contacts, but I don't think it is much of a problem.

The next part is the wiring, fortunately I can multiplex the tubes so each cathode is wired to the next giving a total of 10 cathode wires and then 4 individual anode wires. Even so there is quite a lot of individual wires that have to be cut / prepared and then soldered. I also choose to then heatshrink every connection for neatness and reliability.

I've also used some 2 part epoxy adhesive on the rear of the sockets. As the tubes push in from the front, it could be possible to push the socket from the retaining ring, so extra strenght here does not go amiss.. I also do tend to over engineer things!

The next thing to consider is the casing, this one is made out of ply and is really a bit sorry for itself. I've marked out and drilled the mounting holes for all the valves to sit, along with the controls for the clock and dekatron on the LHS. It is just on the way to the garage to get sanded back to bare wood and then I think I put 5 coats of clear varnish all over.

I mentioned earlier that there was a bit of woodworm, they certainly got their fill out of this! No evidence of recent worm, and will be completely varnished over - it does however give the piece a bit of character.

The wood is now looking a lot better, and I have fitted some of the valves and sockets in order to try and get the right level of lighting. At the request of the client I have gone for a subtle effect to try and mimic, rather than have a huge blue LED that lights it up like a Christmass tree. The valve brightness level can be programmed in the clock parameters. I did consider using the actual valve heater but would then require a transformer / mains connection etc and I erred on the side of safety and stuck with a very safe 12v

Tubes fitted, I've used the red coated GN-4's here and the clock is in test mode - you would never normally see 4 eights displayed. It cycles through all the digits to allow me to check if there are any defects with the tubes. Left to do now is fit the controls, quite a lot of soak testing and then populate the rest of the casing.


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