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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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Curious buzzing sound on AM car radio
Hi All,
I have a Motorola push-button AM car radio which is plagued with a buzzing sound on its audio. It is present at the low end of the medium wave band and it is right across the long wave band too. At first, I thought it was noise coming through the DC power adaptor I was using, but it was still there when I ran it in my car from a DC outlet. The buzz is only present with an antenna is connected and it almost disappears when you place a hand on the top of the radio chassis. I can't pick up this interference on any other radio and my ground connections to the chassis seem fine. I'm at a loss as to where to start fixing this! Any suggestions will be gratefully received. Regards, Gary |
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Curious buzzing sound on AM car radio
Your antenna lead may have a break in it or something loose at the
antenna end. Check the routing of the cable under the dash. |
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Curious buzzing sound on AM car radio
In article .com,
Spooky wrote: I have a Motorola push-button AM car radio which is plagued with a buzzing sound on its audio. It is present at the low end of the medium wave band and it is right across the long wave band too. At first, I thought it was noise coming through the DC power adaptor I was using, but it was still there when I ran it in my car from a DC outlet. The buzz is only present with an antenna is connected and it almost disappears when you place a hand on the top of the radio chassis. I can't pick up this interference on any other radio and my ground connections to the chassis seem fine. I'm at a loss as to where to start fixing this! Any suggestions will be gratefully received. In the AM only days, it used to be the practice to use a thick braided earth strap from the radio chassis to a nearby body ground, even if it had a ground power wire. There was usually a captive 1/4" bolt on the back for this purpose. Think the theory was that RF needs a lower impedance ground than the power lead which may well be grounded someway off at a central point, and pick up interference. -- *Why is the man who invests all your money called a broker? Dave Plowman London SW To e-mail, change noise into sound. |
#4
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Curious buzzing sound on AM car radio
is it really old i.e. does it have a vibrator type power supply? does
it have tubes? or is it all solid state? how about if you drive your car to a field away from power lines and houses? Mark |
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