Of VFOs and Superglue.




5th January 2015. This is the second prototype for the VFO, based on a similar but rather more elaborate circuit gleaned from the ’net. Nothing would work without Superglue, of course. The prototype is ‘lashed up’ on a bit of (single-sided) copper coated fiberglass board. This is quite cheap. The construction method was developed many years ago (I think in the U.S.A.) whereby small squares or rectangles are cut from scrap bits of PCB. These little ‘islands’ are Superglued onto the main board, in convenient places. Components are soldered to the copper ‘islands’ – which are insulated from the copper ground of the board beneath, by the fiberglass. Other components – transistors, resistors, capacitors &c – are soldered to other islands, as required. Many of these resistors &c. have to be connected to ground potential (earth, or ‘deck’ it was often called) and the fact that there is a large expanse of copper ‘deck’ around the islands makes this extremely easy. You can tack things down to earth wherever is convenient. If you are old enough to remember how tedious and difficult it was trying to solder several resistors and capacitors to solder tags stuck deep in the corner of a chassis, being able to solder ’em down anywhere, is truly marvellous. The device above is working quite well now, so we can attempt a ‘proper’ build. This will involve exactly the same technique, but all the long leads will be cut down, the coil will be Superglued down to stop it wobbling about, all will be tidied up and so on. This should all get done tomorrow.


Now onto the really important bit. Superglue - where would we be without it? Of course it has its hazards, so we are very careful when we use it & we don’t let kids mess about with it. BUT –there comes that time, often all too soon, when our bright new tube of Superglue gets it top stuck on. Yes, even the ones which the packet tells us have cunningly designed patent ‘non-stick caps’. It used to be said that the Colman’s Mustard Co. made most of its money from the mustard we left on the side of our plate, rather than from the mustard we actually ate. Likewise, the Superglue manufacturers must make most of their money from the glue left in our tubes – the glue we can’t get at, because the top won’t come off, and we know better than to force it, in case the tube suddenly bursts & the Superglue fastens us together &c. In extremis, we might carefully snip off one corner of the tube, and get a little more out of it. Perhaps, even, the time after that when we need it, we can snip off the other corner, but that’s definitely the end of the line. The superglue left in our still well-filled tube, might as well be on the far side of the moon for all the use it is.


Now I’m sure you know this already, but ACETONE is the stuff. As Toad of Toad Hall might declaim it: ‘Acetone is THE ONLY THING!’ It is readily available, not terribly expensive, and most easily obtained by buying nail varnish remover. Quite often, pharmacies actually stock pure acetone, but if they haven’t got any, just get nail varnish remover, which is almost entirely acetone. Get a little acetone on a paper kitchen towel & wipe clean the pointy spout of the Superglue tube, before you put back on the patent non-stick cap. I assure you that then, it will not stick.


Mind you, this procedure requires a lot of will-power. Because if you are repeatedly using the Superglue, you will be tempted to leave it open & lying about AND NOT CLEAN IT AFTER EVERY SHORT PERIOD OF USE. It’s fine to stick down several pieces of circuit board, or stick back in place two or three shards of the Ming Pot you are restoring, as this will only take a few seconds. But then, clean the spout, replace the cap, and in addition, as a fail-safe, always keep the superglue tube vertically in any case. An anchovy jar, as employed above, or anything similar will do admirably.


By way of proof, the tube above has been opened, used, wiped & closed, probably about 30 or 40 times. There is no resistance whatever when I unscrew the cap – I’ve just tried it. Ta-raah!


Hazard warning: Acetone is highly volatile and flammable, so be careful. Apart from that, it is apparently not regarded as especially poisonous, or carcinogenic. That makes a change! Remember ‘Thawpit’? You don’t? Good! Many years ago it was commonly used domestically as a stain remover. ‘Thawpit’ was Carbon Tetrachloride, and is a very nasty substance with far too many hazards to list here, so it’s a good job it’s gone out of use.




Page re-formatted 19th December 2015.