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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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9th Feb 2020, 1:14 am | #1 |
Diode
Join Date: Dec 2019
Location: Porto, Portugal.
Posts: 8
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National Panasonic 702 B AM/FM clock radio static when off
Hi.
I've just bought an old National Panasonic clock radio. It was not working at all. After a quick cleaning with contact cleaner spray (except for the flip clock) everything started functioning but with a strange issue. When i put the volume down you can hear a weak and permanent static white noise sound coming from the speaker. When you turn the radio off that noise continues. It seems that this a permanent noise in the background. When you tune it to a radio station with the volume up you cant hear but i think its there. Ive looked carefully inside but everything seems to be ok. Can anyone help me or give some clues to repair this? |
9th Feb 2020, 2:07 am | #2 |
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,723
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Re: National Panasonic 702 B AM/FM clock radio static when off
Hi correiadesa and welcome.
Have you got a cordless telephone close to the radio?
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9th Feb 2020, 4:49 am | #3 |
Diode
Join Date: Dec 2019
Location: Porto, Portugal.
Posts: 8
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Re: National Panasonic 702 B AM/FM clock radio static when off
Thank you Graham.
I've tried in diferent places and nothing changes. The static noise doesnt seem to be an external interference and is a very stable noise and not scrachy. |
9th Feb 2020, 10:34 am | #4 |
Rest in Peace
Join Date: Sep 2010
Location: Ripley, Derbyshire, UK.
Posts: 785
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Re: National Panasonic 702 B AM/FM clock radio static when off
Hi correiadesa, are you certain the sound is coming from the speaker, and not from the clock mechanism? Just a thought, as the clock will continued to be powered when the radio is off. Tony.
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9th Feb 2020, 1:53 pm | #5 |
Diode
Join Date: Dec 2019
Location: Porto, Portugal.
Posts: 8
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Re: National Panasonic 702 B AM/FM clock radio static when off
Thank you Tony.
It's definitely coming from the speaker and its loud enough to ear it clearly trough a silent room. I wonder if it could be a faulty on off switch. Best regards. |
10th Feb 2020, 10:43 am | #6 |
Nonode
Join Date: Jan 2004
Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area.
Posts: 2,967
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Re: National Panasonic 702 B AM/FM clock radio static when off
When the radio is turned on and with the volume control at minimum do you still hear the noise?
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Simon BVWS member |
10th Feb 2020, 11:08 am | #7 |
Nonode
Join Date: Jan 2008
Location: Milton Keynes, Bucks. UK.
Posts: 2,552
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Re: National Panasonic 702 B AM/FM clock radio static when off
Correiadesa
What type of display does the clock have? If it's LCD, that can produce the problem.
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10th Feb 2020, 11:39 am | #8 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,535
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Re: National Panasonic 702 B AM/FM clock radio static when off
Chances are when the radio is "off" it isn't OFF. Just muted. The noise could just be residual hiss from noisy transistors/resistors etc. It's easier for the radio/alarm design if the alarm doesn't have to physically turn on the radio power, just unmute the sound.
Does it sound the same with the radio on and volume turned right down?
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10th Feb 2020, 1:43 pm | #9 |
Diode
Join Date: Dec 2019
Location: Porto, Portugal.
Posts: 8
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Re: National Panasonic 702 B AM/FM clock radio static when off
Thank you Simon.
Yes, when the radio is turned with the volume at minimum level you can ear the same background noise. Best regards. |
10th Feb 2020, 1:48 pm | #10 |
Diode
Join Date: Dec 2019
Location: Porto, Portugal.
Posts: 8
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Re: National Panasonic 702 B AM/FM clock radio static when off
Thank you "camtechman".
This is a little1971 flip clock transistor radio. Best regards. |
10th Feb 2020, 2:10 pm | #11 |
Diode
Join Date: Dec 2019
Location: Porto, Portugal.
Posts: 8
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Re: National Panasonic 702 B AM/FM clock radio static when off
Thank you Herald.
I hope that is not the case because in a silent room that sound get's too loud. You couldnt use it in a bedroom at night That sound( no hum noise, just a "shhhh" sound) is present when the volume is down. If you turn off the sound continues. Best regards. |
16th Feb 2020, 6:12 pm | #12 |
Diode
Join Date: Dec 2019
Location: Porto, Portugal.
Posts: 8
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Re: National Panasonic 702 B AM/FM clock radio static when off
I found out that if you unplug the radio from ac current for some hours, when you plug it again to ac current, there is no noise. After 20 or 30 minute the noise returns even with the radio in "off" position. I 've tried to see if any of components were warmer than normal but didnt find any. There is one 1uf capacitor that when you touch makes a loud "hum" noise but i dont know if thats normal.
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