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Old 9th Jul 2018, 10:28 pm   #1
WayneL74
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Default Morphy Richards clock radio thinks it's a metronome

Hi all

The title says it all really.

Have had this digital alarm clock for some 30 years & it has behaved itself impeccably.

This other night I was woken by a rhythmic ticking.

The clock still displays the time & the alarm goes off as it should but there is a permanent 1Hz tick.

This has done this before. There are very little components beside the LM8363 IC & LED display, and as I had one the correct value I changed the smoothing capacitor. I plugged it in & it made no difference. I left is a while & then by itself the ticking stopped.

It was then put back into service & has been fine again until now.

Any thoughts anyone?

Thanks
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Old 9th Jul 2018, 10:41 pm   #2
michamoo
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Default Re: Morphy Richards clock radio thinks it's a metronome

Try replacing electrolytics in the audio output stage
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Old 10th Jul 2018, 8:51 am   #3
Rubberfingers
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Default Re: Morphy Richards clock radio thinks it's a metronome

I've had similar problems in the past with a clock radio, caused by leakage in the on/off/auto switch leaving the radio section partly powered when it should be off
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Old 10th Jul 2018, 10:38 am   #4
The Philpott
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Default Re: Morphy Richards clock radio thinks it's a metronome

Certain versions of Morphy Richards Clock Radios from this era did have problems.

Worth checking for dry solder joints.
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Old 20th Jul 2018, 9:06 pm   #5
WayneL74
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Default Re: Morphy Richards clock radio thinks it's a metronome

Hi all.

Firstly apologies for misleading you all with the title. I put the device was a clock radio when in fact it does not have a radio - it is just a digital alarm clock.

It seems to be sorted for now at least.

I re-soldered all the pins on the IC (all 42 of them) & no difference. I then tried the couple of resistors, ceramic caps, transistor & transformer that drive the output transducer. After re-soldering these and checking there were no tracking between tracks the issue seems to be resolved.

As I said I have been here before, but for the last few days it has been ok.

Thanks for all your suggestions.

Wayne
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Old 21st Jul 2018, 3:03 pm   #6
G6Tanuki
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Default Re: Morphy Richards clock radio thinks it's a metronome

I remember having a similar sort of "Micronta" [from Tandy] alarm-clock that started ticking.

Turned out the 'tick' was the alarm trying to sound, but the oscillator that drove one of those small circular piezo-sounders wasn't oscillating, so all that happened when the alarm sounded was the piezo got subjected to 15VDC every second, causing the 'tick'.

I hadn't associated the time of the ticking with the time the alarm had been set to in the past (when the sounder still actually sounded) and somehow I'd flicked the alarm switch to 'on'.
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