Kalibr Tube tester L3-3. Some improvements

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Replace calibration switches by push buttons.

There is not so much to say about this project. I am not so unexperienced with the L3-3, but I made the mistake actually a few times myself. If the Calibration switch is not in the "Measurement" position, the whole tester is not working, and there is no clue what you are doing wrong. The switches were only a few Euro one, and what made me very happy is, the 12mm thread is exactly the same as the Russian.

So I could use this nice crome plated ring, which was originally used to attach the switch. Like this, I do not change the optics of the tester. The hole in the switch has to be increased to 10.6mm. This material of the ring, it looks to me like a brass alloy, but it must be somethig else. It is very hard, it got hot when drilling a hole in it. When filing the hole, it feels like filing on a very hard material. So be carefull not to break it. In order to get it off undamaged, a wrapped a thick cloth around it. Well but using the original ring looks a lot better than just a nuts. The "feel" of the switch is not very good, but after using it a while it becomes normal. It looks a bit to me like those foot switches for electric guitar accesories.

By mistake, I bought the Version with PCB pins, but there is also one with solder lugs. In case you take another one, you don't need a regular "switch", you need a "push button". So it always comes back to the original position.

Take a good brand, and make sure you buy no factory rejects from online sellers. Just google for: CLIFF FC7105.

Such a nice result :)