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

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Old 22nd May 2006, 8:28 pm   #1
PaulR
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Default Murphy coupling capacitor values.

A friend has asked me to have a look at a Murphy A262 which is working but somewhat distorted.

I haven't actually got it yet, but an obvious starting place is the final AF coupling capacitor. I have got part of the Trader sheet from this site (Paul - have you seen my emails about the apparently missing bits of the sheet?) and the value is shown as .005 uf. This seems a bit on the low side. Is it likely to be correct, or possibly a mis-print?

The nearest I have to hand is 0.047 - would the 10x over value make any difference?

Thanks

Paul
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Old 22nd May 2006, 8:39 pm   #2
paulsherwin
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Default Re: "That" capacitor on a Murphy A262

Hi Paul. Full circuit here: http://www.******************************/A262.jpg

Murphy did tend to use a low value capacitor at this point. I found that increasing the value in my A684 actually helped remove some troublesome hum. An 0.047uF should be fine in this position.

Here's the A684 so you can compare it: http://www.******************************/A674.jpg

Best regards, Paul

Last edited by Darren-UK; 20th Jul 2007 at 2:50 pm. Reason: Removed reference to another, now deleted, thread.
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Old 23rd May 2006, 9:11 pm   #3
PaulR
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Default Re: "That" capacitor on a Murphy A262

Well, I have replaced the capacitor and shivered at the sight of all the Hunts over the rest of the set!

The performance is astounding. Even on the internal aerial VHF is very powerful and clear. Murphy certainly knew how to make them!

Paul
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