03-14-2006, 12:22 PM
40-155 unusual buzzing
First, as a first time correspondent with this forum, let me introduce myself. My name is Mike and I have been interested in radio since my Ground Radio Repair days in the USAF during the 50's.
I recently recapped and aligned both my 40-180 and 40-155, which are nearly the same radio electrically. Both have VG sensitivity, selectivity and volume. However, with the -155, when the volume control is set for low volume, there is a distictive 60cy buzz--not hum. As the volume is increased to a more moderate level the buzz disappears--not masked. Looking at the schematic, this seems to coincide when the slider is about at the area of the tap. In both sets the 7C6 1st audio grid wire is positioned the same so I doubt that though it is unshielded it is the cause. There is likely a simple explanation for this but it eludes me. Any help given is appreciated. Thanks, Mike
First, as a first time correspondent with this forum, let me introduce myself. My name is Mike and I have been interested in radio since my Ground Radio Repair days in the USAF during the 50's.
I recently recapped and aligned both my 40-180 and 40-155, which are nearly the same radio electrically. Both have VG sensitivity, selectivity and volume. However, with the -155, when the volume control is set for low volume, there is a distictive 60cy buzz--not hum. As the volume is increased to a more moderate level the buzz disappears--not masked. Looking at the schematic, this seems to coincide when the slider is about at the area of the tap. In both sets the 7C6 1st audio grid wire is positioned the same so I doubt that though it is unshielded it is the cause. There is likely a simple explanation for this but it eludes me. Any help given is appreciated. Thanks, Mike
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