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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

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Old 16th Oct 2021, 5:09 pm   #1
sparkymike
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Default Murphy A 252

I thought it was high time I switched on my late father's Murphy table radio Model A 252 as it had been neglected for a while. Now when I switched it on, the volume control seems to have lost the first part of its track, as the sound bursts in after control has rotated a small amount. Sound is fine with no hint of distortion, so it this just a simple pot change or could there be something else here?
Mike.
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Old 16th Oct 2021, 5:48 pm   #2
paulsherwin
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Default Re: Murphy A 252

Try a squirt of Servisol before doing anything more drastic.
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Old 17th Oct 2021, 7:21 am   #3
sparkymike
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Default Re: Murphy A 252

I have switch cleaner, probably RS, not sure. If that fails I could bridge out the pot with a known good pot and see what happens.
These old Murphy sets give out a good tone. Nor sure if they are push pull without looking at the circuit.
Mike.
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Old 17th Oct 2021, 9:20 am   #4
paulsherwin
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Default Re: Murphy A 252

Remember that it will have dodgy capacitors by now if unrestored, even though it's a family heirloom.

Not push pull, but a good quality set. I think it was Murphy's first model with VHF.
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Old 17th Oct 2021, 10:05 am   #5
dazzlevision
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Default Re: Murphy A 252

Quote:
Originally Posted by paulsherwin View Post
Remember that it will have dodgy capacitors by now if unrestored, even though it's a family heirloom.

Not push pull, but a good quality set. I think it was Murphy's first model with VHF.
Yes, a good AM/FM radio, but Murphy's first was the very similarly styled A242.

As Paul says, there will be quite a few paper dielectric capacitors to replace, especially the "infamous" one that couples the audio signal to the control grid of the audio output valve (Mazda 6P1 in the case of the A252).

Its circuit reference is C76 in the official Murphy circuit diagram (10nF = 0.01uF). If it's leaky, it can damage the 6P1 and/or the audio output transformer. So, it should be replaced before the set is run for an extended period of time.
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Old 18th Oct 2021, 4:06 pm   #6
sparkymike
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Default Re: Murphy A 252

Thanks for info, will check that cap out.
Mike.
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