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When you have limited time, de-solder components from a printed circuit board. Collect components and put them in trays. Remember them when you have a ‘project’ and some ‘spare time’!
Aha! On reading through an old Elektor issue, I came across a ‘grid dip oscillator’. It no longer uses valves as the detection method. But the combined current of the two transistors to vary a multivibrator frequency.
It runs from a 1.5 Volt AA battery. And uses a small loudspeaker as the indicator. First off I wondered where to get a battery holder for the battery. Then I remembered the insect spray that we bought some time ago. This was always on special to get you to buy the refills at a large markup. So we ended up with spare units – in fact quite a few!
So battery holder – sorted!
Four NPN transistors needed. No problem. C945 transistors in plenty salvaged from several blown ATX power supplies. Quite a few modern meters come with the transistor testing built in. So all were checked before placing in ‘bin’ for later use.
Well that was easy! I assembled the oscillator on a piece of Vero type board. And proceeded to test. It all worked! Now to document it…