Quote:
Originally Posted by AC/HL
Looking at the photo in post 1, those capacitors look suspiciously like early low voltage electrolytics, possibly only 1uf?
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Yes, I'd agree with that Bill. There are no polarity markings, but one end is 'crimped' to seemingly differentiate it from the other. I've tried a couple of 1uF caps out of curiosity, (with the same resistors) and the frequency of oscillation is only 140Hz, so they must be a good bit lower in capacity than that. As I said earlier, the originals actually measure 8nF and 20nF respectively, so doubtless they'll have changed over time. Remarkable that this little injector still performs excellently despite it being maybe 50 years old or more. The cardboard box is marked '15 shillings'. If that was circa 1960, it equates to £16.00 today when adjusted for inflation.
(Incidentally, the scope traces I posted are 'upside down', in that the delay in the rise time represents the caps charging up on each cycle).
Thanks to everyone who has posted to the thread.