Now we are dating ourselves mate remember the wiring and how the colours were always faded and testing them with a meter (if you had one) for polarity and stuff?? Mind you all I had was an analogue one that was way too sensitive and the readout so tiny in increments
Plus I remember spending many hours trying to get rid of the AC hum in stereos - never had a Heathkit and I can't remember the brand we used in the UK back then but in any case it was terribly expensive back then and took a lot of saving to get the darn things.
My whipping boy was designing frequency circuits for audio use to love doing that and still have my old notes and schematics!!