Date   : Fri, 16 Oct 2009 18:13:19 +0100
From   : muzerakascooby@... (Muzer)
Subject: Dual drive power supply

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Mick Champion wrote:
> Mark Usher wrote:
>> Hi all,
>>
>> I've noticed that the power supply on my dual drives is making a bit of a
>> "noise" - audible, not electrical. Best described as an oscillating hum.
>>
>> With the previous discussions on the Beeb Power Supplies, I wondered if this
>> was a sign the capacitors on this psu were also starting to show their age
>> and should be replaced. Or was it just a bad design in the first place.
>>
>> -Mark
>>   
> In my opinion (and that's all  this is), this sounds more like the 
> windings of a switch mode transformer rattling (at whatever frequency 
> mains is being pulsed to it) rather than a capacitor problem. Capacitors 
> tend to be silent, until they are ready to blow. On the other hand, 
> switch mode power supplies are not unknown to make a whine / whistle 
> sound.  Could this be what you are hearing? The audible pitch can vary 
> as the switching transistors adjust the frequency of rectified mains 
> input to the primary transformer windings, this keep up with the load 
> (output) requirements.  Does the pitch change when you start the disc 
> motors?
> 
> 
> Cheers,
> 
> Mick.
> 
> 
> 
> 
> 
> 
> 
> 
> _______________________________________________
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> http://lists.cloud9.co.uk/mailman/listinfo/bbc-micro
> 
Is it a buzzing sort of sound? A few of my supplies do that, I think I
heard it was where the transformer had come loose and started to
vibrate. Nothing to worry about unless it starts rattling if you shake it :p

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