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Creating the finger plates
- Created: Friday, 04 February 2011 14:10
- Last Updated: Wednesday, 30 October 2013 11:53
- Written by Administrator
- Hits: 7364
making the fingerplates was a hell of a job. I bought a 2 square feet of brass sheet, 0,8mm thick. Cut some pieces and sprayed it with Positiv20 (the stuff that is used for making ordinary PCB light sensitive).
If you ever try this at home, make sure the XYL stays with her mother, or some place else anyway. It smells a lot...
I followed the instructions on the can and put it in the oven at 70oC. I put the brass on a piece of carton and that was not quite horizontally. So at the end all the lacqer was at one end of the brass. I removed the lacquer with aceton and tried it again, this time with the brass directly on the oven grid. And now the result looked a lot better. The lacqer tends to crawl to the edges, so make the piece of brass somewhat larger than the dimension you need.
I used those good old overhead-projector transparents to print the design. Then in the PCB UV exposure box for 5 minutes, and develope in NaOH for a minute or so. And then I put the developed piece of brass in the stuff that artists use to make copper black. Don't know the English name, but it's called koudpatina here, and this store sells it (516/3). Leave it there for a minute or so, until the brass turns black. Don't leave it there too long, otherwise the black comes off again. In the end, if you have all exposure and development times figured out, you get something like this:
soooo shiny, that you can see the camera reflection... After developing, grind the finger plates to the desired dimensions and paint them with a transparent paint to protect them. The final result of my B2 replica:
The B2 key is not yet fitted to the lid of the spares box. I obtained a real B2-key from Ebay and that is fitted to the lid right now. I've used the B2 replica on 80, 40, 30 and 20m now. Because I use modern xtals in FT243 housing, the xtals run too hot when fully loaded and I sound chirpy. The trick is to detune the grid so far that the output just starts to drop. Then it sounds a lot better. Hope to work you on the bands: I designed a special QSL card for QSO's with my B2. Mail me for a sked if you want. Xtals I have: 3560, 3575, 3579, 7006.667, 7012, 7020, 7030, 10106, 10116, 10120, 10125, 14020, 14042, 14060 and of course the double frequencies of the 40m xtals. Hpe cu sn!