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

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Old 18th Sep 2020, 3:20 pm   #1
Northyorks1
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Default Defiant A5 Resistor function

Just bought this Defiant A5 in great all round condition, Can anyone please tell me the function of this resistor shown in pic.

Thanks Ian
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Old 18th Sep 2020, 3:31 pm   #2
ms660
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Default Re: Defiant A5 Resistor function

Looks like a damper.

Lawrence.
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Old 18th Sep 2020, 3:37 pm   #3
G6Tanuki
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Default Re: Defiant A5 Resistor function

Yes - on LW a nicely-peaked, efficient ferrite-cored coil can have such a high Q and so narrow bandwidth that it limits the audio response (causing loss of treble). The resistor across the coil reduces the Q so broadening the bandwidth and avoiding treble-cut.

(not that there was generally much treble on LW broadcasts anyway!)
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Old 18th Sep 2020, 4:20 pm   #4
Northyorks1
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Default Re: Defiant A5 Resistor function

Thanks for replies, I have managed to power it up and volume on LW is very good but on MW volume has to be turned up fully to hear stations, and then radio has to be constantly moved to improve reception on each individual station, never had one this sensitive regarding reception. The Resistor in question is 220k but is reading 6.5ohms ? Have added a few more pics just to show condition of radio.

Ian
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Old 18th Sep 2020, 4:23 pm   #5
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Default Re: Defiant A5 Resistor function

The resistor is in parallel with the low resistance coil, your 6.5 ohms is the coil resistance.
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Old 18th Sep 2020, 4:28 pm   #6
G6Tanuki
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Default Re: Defiant A5 Resistor function

I always loved those Ediswan "top hat" transistors!

I see it's got a couple of the Plessey electrolytics with the red/black ends and yellow label. These are known to be a problem.
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Old 18th Sep 2020, 4:39 pm   #7
Northyorks1
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Default Re: Defiant A5 Resistor function

Thanks for putting me right Frank.
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