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Humming from old alarm clock

Discussion in 'Electrics UK' started by cwhaley, 3 Jan 2019.

  1. cwhaley

    cwhaley

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    I have inherited a Wien Solid State Digital alarm clock; the digital type with flip numbers. I haven't dated it yet but I'm guessing it's from the era between the late 1960s and early 1970s.

    The unit works fine and is a pleasure to have. It also has a very loud alarm sound which is perfect for my partner who is a deep sleeper.

    The only problem I have with it is the hum/buzz it emits when plugged in. I can only liken it to the sound the large step-down transformers make near power stations -- all I know is that it constantly hums and pressing on the case changes the loudness of the hum.

    Should I open it up to take a look, what should I be looking for? What components within these alarm clocks would emit this sound?

    Capture.JPG
     
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  3. bernardgreen

    bernardgreen

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    There will be a transformer ( magnetic type ) to provide an Extra Low Voltage ( ELV ) to the electronics ( probably 12 volts or less ). This is the most likely source of the hum. There may also be a small synchronous motor and gearbox driving the display and with age and wear and tear this motor could also hum.

    Sometimes the transformer can be replaced by a similar one or it can be dipped in hot wax to "stick" the laminations and coils together which significantly reduces the amount of hum
     
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  4. cwhaley

    cwhaley

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    Thank you. When the digits flip down you can also hear a (quieter) whir of the gears driving the display mechanism.

    I think I'll grease these and figure out what I can do with the transformer. You mention wax -- I'm sure I remember opening old amplifiers and TVs to find wax-coated items.

    Can any wax be used. I only possess plain, un-scented candle wax and a bar of wax for the car. Presumably the melting point of the candle wax is higher than the temperature the transformer will reach?
     
  5. Tigercubrider

    Tigercubrider

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    I think that's more likely 1975 or so
     
  6. cwhaley

    cwhaley

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    Interesting -- what makes you think so? I can't find reference to Wien on the internet other than that Wien is the German word for Vienna. My guess at late '60s to early '70s was purely based on the design style in comparison to a 1969 clock I have.
     
  7. bernardgreen

    bernardgreen

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    https://www.vintage-radio.net/forum/showthread.php?t=64807 discusses the problem

    I have used candle wax with good results. The best candle type wax is the wax used for church candles as it has a higher melting point than "domestic" candles.

    The method is to warm the wax in a small pan until it is liquid and then submerge the transformer and leave it in the wax until the air bubbles from the transformer stop. This can be half an hour so be prepared to keep a close eye on the pan and the temperature of the wax. Then allow the wax to cool a bit before removing the transformer. Allow the tranformer to cool before removing excess wax ( as the wax cools and contracts some of the excess will be drawn into the transformer's voids ).
     
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  9. bernardgreen

    bernardgreen

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    Google for "wien solid state"

    Other search engines are available
     
  10. DetlefSchmitz

    DetlefSchmitz

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    I would be inclined to check the temperature the transformer reaches before doing this. I heard of a guy recently who followed similar advice and destroyed the equipment he was trying to quieten.
     
  11. cwhaley

    cwhaley

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    Oh I didn't think of that one... :rolleyes:

    Unfortunately even Google couldn't find anything relevant on this one.

    Thanks for the link and advice on using wax -- very useful I'll bear it in mind. I actually spent around half an hour reading other threads on the Vintage Radio forum out of pure interest. Will be taking the radio apart this weekend.
     
  12. conny

    conny

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    While the wax is melting warm the transformer in an oven, around 110-120 degrees c will suffice, this will help to expand any voids between the windings.
    After dipping in the hot wax let it begin to stiffen so it doesn't run out when you remove it from the wax. It won't matter if you get wax on the leads as it will easily scrape off. Let it go cold before refitting into the clock. Obviously liquid varnish which sets hard when warmed is better but not easy to come by.
     
  13. leezer3

    leezer3

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    Last similar 'repair' I did, I used half a rubber doorstop.
    You'll probably find the transformer is a standard metal framed wire wound thing attached to the baseplate and has a small gap at the top before the top casing.
    Chop a rubber doorstop in half (or thereabouts), and stuff this in the gap between the transformer and the casing.

    Screw the top back on, and the doorstop absorbs the vibration / hum nicely.
    Horribly low-tech, but doesn't require anything invasive.
     
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  14. Nige F

    Nige F

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    On a similar note:unsure: remove the rigid fixings and secure with heat resisting silicone. Trade mate Plumber flue for example
     
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