Any advice please
Frank.
Hi Frank. With the radio inside the bakelite case and the knobs attached, there should be no shock hazard. You can make sure that the B(-) is connected to the neutral side of the AC line (the wide prong of the ac socket)with a polarized plug. This will keep the chaasis at low potential. To be extra safe, use an isolation transformer.
R102 is probably the culprit. Remove it, or a little rewiring of the power cord and a polarized (wide prong to neutral) plug should make the radio safer. Rewire the power cord so the on/off switch is in series with the narrow pin of the AC plug, so the AC hot is never connected to the chassis side of the radio, either directly or through the filaments. Some people (like me) solder a piece of solid #18 ga. wire to the plug so it can only be inserted one way. It's amazing that the AA5 wasn't nicknamed "The Widder Maker" as some of the designs can be deadly for the inexperienced to work on.
Lewis
Many thanks to you both for your advice. I plan to put your ideas to work over the next couple of nights
Frank
Even using a polarized plug won't help. The chassis will be hot one way off, the other way on. You need to wire the switch in hot side of the line.
R102 is giving the hot chassis but there is a reason for this resistor. It prevents the chassis from building up a charge that could give you a larger shock.
Norm
::::I have just repaired a Philco 49-900. Is there a cure for the 50 volts to ground via the chassis that is present. The finger touch tingle voltage must be?- capacitive/inductive but would prefer it was not present.
::::
::::Any advice please
::::
::::
::::Frank.
:::
:::
:::
:::Hi Frank. With the radio inside the bakelite case and the knobs attached, there should be no shock hazard. You can make sure that the B(-) is connected to the neutral side of the AC line (the wide prong of the ac socket)with a polarized plug. This will keep the chaasis at low potential. To be extra safe, use an isolation transformer.
::
::R102 is probably the culprit. Remove it, or a little rewiring of the power cord and a polarized (wide prong to neutral) plug should make the radio safer. Rewire the power cord so the on/off switch is in series with the narrow pin of the AC plug, so the AC hot is never connected to the chassis side of the radio, either directly or through the filaments. Some people (like me) solder a piece of solid #18 ga. wire to the plug so it can only be inserted one way. It's amazing that the AA5 wasn't nicknamed "The Widder Maker" as some of the designs can be deadly for the inexperienced to work on.
::
::Lewis
: ----------------------------
:
:
:Many thanks to you both for your advice. I plan to put your ideas to work over the next couple of nights
:
:
:Frank
I am using a dropper capacitor ( I am in the UK) and it works fine. But as you mention - the isolation switch really needs to be in the live side of the supply.
Thanks Frank
:Frank
:
: Even using a polarized plug won't help. The chassis will be hot one way off, the other way on. You need to wire the switch in hot side of the line.
:
: R102 is giving the hot chassis but there is a reason for this resistor. It prevents the chassis from building up a charge that could give you a larger shock.
:
:Norm
:
:::::I have just repaired a Philco 49-900. Is there a cure for the 50 volts to ground via the chassis that is present. The finger touch tingle voltage must be?- capacitive/inductive but would prefer it was not present.
:::::
:::::Any advice please
:::::
:::::
:::::Frank.
::::
::::
::::
::::Hi Frank. With the radio inside the bakelite case and the knobs attached, there should be no shock hazard. You can make sure that the B(-) is connected to the neutral side of the AC line (the wide prong of the ac socket)with a polarized plug. This will keep the chaasis at low potential. To be extra safe, use an isolation transformer.
:::
:::R102 is probably the culprit. Remove it, or a little rewiring of the power cord and a polarized (wide prong to neutral) plug should make the radio safer. Rewire the power cord so the on/off switch is in series with the narrow pin of the AC plug, so the AC hot is never connected to the chassis side of the radio, either directly or through the filaments. Some people (like me) solder a piece of solid #18 ga. wire to the plug so it can only be inserted one way. It's amazing that the AA5 wasn't nicknamed "The Widder Maker" as some of the designs can be deadly for the inexperienced to work on.
:::
:::Lewis
:: ----------------------------
::
::
::Many thanks to you both for your advice. I plan to put your ideas to work over the next couple of nights
::
::
::Frank