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

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Old 25th Apr 2017, 4:11 pm   #1
Goldieoldie
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Default Murphy A100 microphony

Hi All,
I have a problem when any valve is slightly tapped except v1 there is microphony.
This can be heard even with v/c at zero
It gets worse when in its cabinet !
Anyone had this with this radio please ?
Cheers Pete
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Old 25th Apr 2017, 4:44 pm   #2
jonnybear
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Default Re: Murphy a100 microfony

So the problem would seem around 10LD11 & 10P13, firstly have you changed any capacitors such as C19 decoupling or C20 coupling capacitors ?.other than that you could short grid one to chassis on the 10P13, if it is still there probably a noisey 10P13 if not then 10LD11 could be the culprit .
John
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Old 25th Apr 2017, 6:41 pm   #3
Goldieoldie
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Default Re: Murphy A100 microphony

Hi John,
I have re cap the whole radio so I don't think it's decoupling
I'll try shorting the grids
The performance is not good at all but looking at threads I think it was this way unless it has a decent aerial .Def not one in the mains lead !
Cheers Pete
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Old 26th Apr 2017, 8:01 pm   #4
Goldieoldie
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Default Re: Murphy A100 microphony

Hi John,
It was v3 the det/amp valve causing the problem.
Cheers Pete
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