10-06-2021, 06:00 PM
Right, Chris. I do the same, makes the radio much safer, though in some cases it increases hum. Worst case, don't run anything to the volume control mounted power switch, and use a line cord switch (properly installed in the Hot Side) I probably exceeded the usual word count of experts so I did not add that mod to my original reply to Tonto, so here it is.
Hi Tonto,
One very bad habit of these "AA5" style radios and other radios that do not use a power transformer is that the chassis is either directly connected to one side of the AC Line or connected through a capacitor and resistor arrangement to the Common (B-) Bus which is connected to the AC Line. To make matters worse, the power switch is placed between this point and the power cord. Furthermore, the power cord is usually not "polarized". This is a loose - loose safety wise. If the chassis is connected to Neutral lead by the way the plug is inserted then with the switch on, the chassis and common bus is at neutral (ground) potential, lessening the chance of shock- until the power switch is turned off. With the switch off, the filament string ,which is at very low resistance when cold, connects the Chassis to the Hot lead. The shock can be lethal, especially to a geezer my age and condition.
A common safety mod made by many collectors and referenced in several websites is as follows:
1. Obtain a schematic of your radio. Confirm by schematic and inspection that the power switch connects the common bus to the power cord. Remove the power cord from the radio. Remove the connections to the power switch.
2. Obtain a line cord with a "polarized" plug. A common recently purchased extension cord with the "outlet" end cut off will do.
3. Connect the conductor that leads to the wider of the 2 prongs (the neutral conductor) to the common bus.
4. Connect the other conductor to one leg of the power switch. Connect the remaining connection removed from the power cord (usually the plate of the rectifier and rectifier filament to the power switch. Dress the power cord as far away from audio and RF Signals as possible and as close to the Chassis as possible to minimize hum.
Unfortunately, a picture is worth 1000 words (or 10,000 of mine). Maybe an expert has written an article that can be published in an appropriate section of of this Phorum.
Best Regards,
John "MrFixr" Stroh
Hi Tonto,
One very bad habit of these "AA5" style radios and other radios that do not use a power transformer is that the chassis is either directly connected to one side of the AC Line or connected through a capacitor and resistor arrangement to the Common (B-) Bus which is connected to the AC Line. To make matters worse, the power switch is placed between this point and the power cord. Furthermore, the power cord is usually not "polarized". This is a loose - loose safety wise. If the chassis is connected to Neutral lead by the way the plug is inserted then with the switch on, the chassis and common bus is at neutral (ground) potential, lessening the chance of shock- until the power switch is turned off. With the switch off, the filament string ,which is at very low resistance when cold, connects the Chassis to the Hot lead. The shock can be lethal, especially to a geezer my age and condition.
A common safety mod made by many collectors and referenced in several websites is as follows:
1. Obtain a schematic of your radio. Confirm by schematic and inspection that the power switch connects the common bus to the power cord. Remove the power cord from the radio. Remove the connections to the power switch.
2. Obtain a line cord with a "polarized" plug. A common recently purchased extension cord with the "outlet" end cut off will do.
3. Connect the conductor that leads to the wider of the 2 prongs (the neutral conductor) to the common bus.
4. Connect the other conductor to one leg of the power switch. Connect the remaining connection removed from the power cord (usually the plate of the rectifier and rectifier filament to the power switch. Dress the power cord as far away from audio and RF Signals as possible and as close to the Chassis as possible to minimize hum.
Unfortunately, a picture is worth 1000 words (or 10,000 of mine). Maybe an expert has written an article that can be published in an appropriate section of of this Phorum.
Best Regards,
John "MrFixr" Stroh
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
Best Regards,
MrFixr55
