(My news server hasn't shown any new posts, here, for about a fortnight, so to make sure there is still someone, apart from myself, here .... ;-P )
My bedside Clock-Radio is gaining time. Back when we dropped out of Daylight Saving at the beginning of April, I expect I adjusted it to be correct, but currently it is approx 70 mins fast, so gaining about two minutes a day. Gaining time is better than loosing time, as it means if I had to rely on it to wake me up for an early morning appointment, I'd be being woken earlier than required. Not that I have many early morning appointments to attend in any case!!
So I ask, "What might cause my 25-30 year old Clock-Radio to start gaining time??"
About eighteen months ago, I moved about 200km, so, it could be that the Mains supply frequency, here, was at a slightly higher frequency than my former location, but then why isn't everyone in this location complaining about their clocks gaining time?? And the clock on my PVR is keeping reasonable time!
So I'm guessing the Mains Supply Frequency is O.K.!!
That more or less points at the Phase Locked Loop in the Clock-Radio. From my having taught Electronics twenty or more years ago, I'd expect the PLL circuit to consist of a crystal controlled circuit with a trimmer capacitor ... and it's this "trimmer" that is my suspect!!
Back when I was teaching, we taught CB Radio circuits that included discrete physical trimmer capacitors, but, I would expect the circuitry of my Clock-Radio to use a reverse-biased PN junction with-in an IC as the "trimmer capacitor" of the PLL circuit.
If my Clock-Radio is gaining time (a minute or two each day), apart from the fact that the clock-radio is dying, does this mean that this PN junction is most likely the problem?? Or could there be another cause??