Clock-Radio gaining time

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(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??

--  
Daniel

Re: Clock-Radio gaining time
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PVR will be using a crystal as the frequency reference. Your clock radio
(if mains powered) will probably be using the mains frequency. Other
people may use battery powered clocks, or don't think the deficiencies
in their clock radio is a worthy topic of conversation.

Otherwise it could be some locally induced noise on the mains supply.
Sillicon Chip published a circuit to monitor mains frequency in the
reader submissions section many years ago. I've long been meaning to
build something based on it.

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No PLL, just digital logic counting mains cycles. Look up the datasheet
for the LM8363 which was one of the LSI chips custom designed for use
in mains powered clock radios. It so happens I've got a couple of them
sitting next to me - I still haven't figured out where to file them in
my IC stockpile.

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I guess it's possible that the mains transition detector is dying and
causing the logic to mis-count intermittantly. Though it could also be
your mains power frequency or maybe local noise along the power line
running to it.

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Re: Clock-Radio gaining time


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Does your region have anything like MSF/DCF time signals?

Alarm clocks are easy to find - I'm finding the ones with ceiling display  
projection a bit more scarce.  


Re: Clock-Radio gaining time
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Nothing in Australia.

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Re: Clock-Radio gaining time
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yeah, nothing except for satellite time signals (GPS etc).
also GSM if you count that.

I once tuned to WWVH on 10MHz using an old shortwave set and a "random" wire
antenna but that was before computers went that fast, and the only
things with switched mode PSUs were TVs at ~16Khz. also that was not from  
Australia either that was from Christchurch NZ  

--  
     ?

Re: Clock-Radio gaining time


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EPE in the UK, which buys in most of its projects from SC has done at least  
one GPS and/or sat timepiece.

may be listed as a frequency standard, but pretty sure there was a display  
clock add on at some point.  


Clock-Radio with USB port
On Wed, 09 May 2018 22:12:21 +0100, Ian Field wrote:

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To ask about another feature, has anyone seen a clock "radio" with a usb  
port around the traps.

We have a clock radio as an morning alartm device, but I'm well over  
listening to the garbage that you get inflicted with by using the radio  
part. so I'm wondering if there is a modern version of the old clock-
radio with "Casette player", which we had a few years ago. It would be  
nice to wake up to some pleasant music instead of yesterdays stale "news".


Re: Clock-Radio gaining time
Daniel60 wrote on 08/05/18 19:51:
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Thanks for all the responses.

You know how "they" say you should quieten your mind as you try to go to  
sleep??

Well, last night, as I was trying to drift off to sleep, I was thinking  
about my bedside clock-radio and your responses, and I thought .....

Twenty months or so, I moved into this house and about fifteen months  
ago, I go twenty solar panels installed.

I expect solar panels produce DC volts which would then have to be  
converted to AC volts to power my house and get fed into the power system.

Does anyone, here, know the the frequency of this conversion process is  
controlled?? Does the switching circuitry sample the mains to determine  
the frequency, or something??

If this frequency is off, slightly, that could explain my clock-radio's  
problem. But wouldn't explain why the PVR keeps pretty good time ...  
maybe it's set to the T.V. signal, somehow!!

--  
Daniel

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