Bad Cap
I dug out the Morsemaster II, last mentioned here: https://wb9kzy.blogspot.com/2023/11/morsemaster-switches-part-ii.html I tried it out but it didn't seem to be working. After fiddling with it a little I could hear a really faint stream of Morse code. After opening it up I decided that the earphone jack might be bad so I took it out - WRONG. The sidetone uses a 555 timer circuit, some variation of which has been used by many hams for a CPO. I finally realized it was the 220 uF output cap. So I replaced it with a 100 uF cap (all I had at hand) and bingo, it worked, very loud and thumpy ! I had to turn down the volume. it wasn't born bad - it became bad :) I decided to check the cap value, the AADE LC Meter manual cautions against polarized caps so I dug out the B&K 810C cap meter. Here is the reading: So sometime along the line that cap lost almost all of the original value. And since capacitive reactance is inversely related to capacit...