Repair of Digital Clock Radio that time drifts. (Sanyo RM-6018)

[crunch]

I have a Digital Clock Radio (Sanyo Model RM-6018) that is about 10 years old and that recently began to time drift quite drastically, Up to 10 minutes a week compared to my wifes one (completely different make and model) on the other side of the bed.

I was wondering if anybody had suggestions on what could have gone wrong within it that might make it drift like this.

I don't think its the mains frequency because the other clock, which still maintains accurate time, is on the same power circuit as the time drifting clock

We do have solar power in our how which appears to maintain a reasonably consistent frequency, but again, I would have expected if that was the cause it would cause the working clock to drift as well.

Are there standard components which fail which could easily be replaced to see if it fixed the problem? if so how easy are they to identify and replace?

Hopefully I have given enough information for somebody to make repair suggestions etc.

Regards,
David

[fzabkar]

Disconnect it from the mains and connect a DC power supply to the battery terminals. Monitor the time over 7 days. This will isolate your AC supply and solar inverter.

If the problem turns out be related to the AC frequency sensing, there will usually be an optocoupler which squares up the rectified AC pulses and feeds them to the uC. You might like to compare the circuits in the two clocks to see how they do this.

BTW, does the clock run slow? If so, then it must be dropping pulses.

[xavier60]

I have seen the odd clock radio advance in time. It was because spikes on the mains were reaching the reference input on the clock IC and being counted. Putting an appropriate sized capacitor between the   input pin and ground cured the problem.

[fzabkar]

Maybe this (Zellweger Off-Peak Signalling)?

https://goughlui.com/2014/02/02/project-analyze-mains-power-flicker-issue-ripple-signalling/

[Haenk]

Maybe check your mains frequency.
Most cheap radios use 50Hz or 60Hz mains frequency as a base for the timing.
This has been quite an issue in Europe about two years ago.

In German: https://www.heise.de/newsticker/meldung/Zeit-Synchronisation-per-Stromnetz-Energieknappheit-laesst-Uhren-nachgehen-3984126.html

10 Minutes a week seem to be a lot though, might be something completely different...