This radio uses a different type volume control circuit. Instead of a signal divider it adjusts cathode voltage on your 6A8 & 6K7 tubes. It really should be a 2 watt control.
http://www.nostalgiaair.org/PagesByModel/749/M0007749.pdf
If something causes either 6A8 or 6K7 to draw too much current this control will burn.
Norm
:What would cause the volume control of an electronically restored GE A-53 to fail suddenly? While playing it recently the speaker began to make a loud buzzing and humming sounds with the loss of all other audio. I immediately turned it off and unplugged the cord. There was also the smell of burning electronics in the air. I pulled the chassis and after some investigating I narrowed down the damaged component to the volume control based on the fact that the control shaft now rotates with excessive stiffness, parts of the plastic portion of the control unit show signs of excessive heat damage (welts) and it smells strongly of having been fried. None of the other components under or on top of the chassis have any apparent damage (no fried resistors or exploded capacitors). I have checked the values of some of the capacitors and the speaker and they are all within the correct ranges. Prior to this incident it has played fine for 30 minutes to an hour or so at a time without any problems.
Both the chassis wiring diagram and the parts list show the value for the volume control as 5250 ohms while the schematic shows a value of 5000 ohms with a separate 250 ohm resistor. Neither the diagram or the parts list reference this resistor. My radio has the separate resistor installed. Is it safe to install a 5000 ohm control unit rated at less than 2 watts and a separate 250 ohm resistor rated for at least 2 watts?
:Hi Tony
:
: This radio uses a different type volume control circuit. Instead of a signal divider it adjusts cathode voltage on your 6A8 & 6K7 tubes. It really should be a 2 watt control.
:
: http://www.nostalgiaair.org/PagesByModel/749/M0007749.pdf
:
: If something causes either 6A8 or 6K7 to draw too much current this control will burn.
:
:Norm
:
::What would cause the volume control of an electronically restored GE A-53 to fail suddenly? While playing it recently the speaker began to make a loud buzzing and humming sounds with the loss of all other audio. I immediately turned it off and unplugged the cord. There was also the smell of burning electronics in the air. I pulled the chassis and after some investigating I narrowed down the damaged component to the volume control based on the fact that the control shaft now rotates with excessive stiffness, parts of the plastic portion of the control unit show signs of excessive heat damage (welts) and it smells strongly of having been fried. None of the other components under or on top of the chassis have any apparent damage (no fried resistors or exploded capacitors). I have checked the values of some of the capacitors and the speaker and they are all within the correct ranges. Prior to this incident it has played fine for 30 minutes to an hour or so at a time without any problems.
The problem is that I don't find a 5K linear pot at either RadioDaze or AES. You could use a dual section 10K audio pot such as RadioDaze part no. R-DPA-10K, and wire the two sections in parallel. That would give you 0.5W.
Most variable resistors that are rated, say, 2W generally fall under the rheostat classification. You can surely find such a beast at Mouser, and that would be your best option. Check the dimensions to make sure it will fit. Mouser organizes its catalog and website by manufacturer - try Ohmite.
The wattage of the 250-ohm series resistor really won't keep the pot from getting warm. The 250-ohm resistor can be 1W.
:Norm,
:
:Both the chassis wiring diagram and the parts list show the value for the volume control as 5250 ohms while the schematic shows a value of 5000 ohms with a separate 250 ohm resistor. Neither the diagram or the parts list reference this resistor. My radio has the separate resistor installed. Is it safe to install a 5000 ohm control unit rated at less than 2 watts and a separate 250 ohm resistor rated for at least 2 watts?
:
::Hi Tony
::
:: This radio uses a different type volume control circuit. Instead of a signal divider it adjusts cathode voltage on your 6A8 & 6K7 tubes. It really should be a 2 watt control.
::
:: http://www.nostalgiaair.org/PagesByModel/749/M0007749.pdf
::
:: If something causes either 6A8 or 6K7 to draw too much current this control will burn.
::
::Norm
::
:::What would cause the volume control of an electronically restored GE A-53 to fail suddenly? While playing it recently the speaker began to make a loud buzzing and humming sounds with the loss of all other audio. I immediately turned it off and unplugged the cord. There was also the smell of burning electronics in the air. I pulled the chassis and after some investigating I narrowed down the damaged component to the volume control based on the fact that the control shaft now rotates with excessive stiffness, parts of the plastic portion of the control unit show signs of excessive heat damage (welts) and it smells strongly of having been fried. None of the other components under or on top of the chassis have any apparent damage (no fried resistors or exploded capacitors). I have checked the values of some of the capacitors and the speaker and they are all within the correct ranges. Prior to this incident it has played fine for 30 minutes to an hour or so at a time without any problems.
This is going to be hard to explain but here goes.
A 250 ohm resistor which dissipates 20 ma drops 5 volts. That would only be .1 watts. 250 x .02 = 5 volts. 5 volts x .02 amps = .1 watts
Now if a 5000 ohm control was to handle 20 ma it would need to be 2 watts. 5000 x .02 = 100 volts. 100 volts x .02 amps = 2 watts.
No part of a 5000 ohm 2 watt control should handle more than 20 ma. The same current which flows through the 250 ohm resistor goes through the control. When a low wattage carbon control is turned nearly all the way up it can cause an small area to burn.
Norm
:Tony, I've done a little figuring in my head and I think you can get by with a 5K linear taper pot, but it will get warm. Based on what I'm reading, garden-variety linear pots are typically rated at 0.5W whereas audio taper pots are rated at 0.25W.
:
:The problem is that I don't find a 5K linear pot at either RadioDaze or AES. You could use a dual section 10K audio pot such as RadioDaze part no. R-DPA-10K, and wire the two sections in parallel. That would give you 0.5W.
:
:Most variable resistors that are rated, say, 2W generally fall under the rheostat classification. You can surely find such a beast at Mouser, and that would be your best option. Check the dimensions to make sure it will fit. Mouser organizes its catalog and website by manufacturer - try Ohmite.
:
:The wattage of the 250-ohm series resistor really won't keep the pot from getting warm. The 250-ohm resistor can be 1W.
:
::Norm,
::
::Both the chassis wiring diagram and the parts list show the value for the volume control as 5250 ohms while the schematic shows a value of 5000 ohms with a separate 250 ohm resistor. Neither the diagram or the parts list reference this resistor. My radio has the separate resistor installed. Is it safe to install a 5000 ohm control unit rated at less than 2 watts and a separate 250 ohm resistor rated for at least 2 watts?
::
:::Hi Tony
:::
::: This radio uses a different type volume control circuit. Instead of a signal divider it adjusts cathode voltage on your 6A8 & 6K7 tubes. It really should be a 2 watt control.
:::
::: http://www.nostalgiaair.org/PagesByModel/749/M0007749.pdf
:::
::: If something causes either 6A8 or 6K7 to draw too much current this control will burn.
:::
:::Norm
:::
::::What would cause the volume control of an electronically restored GE A-53 to fail suddenly? While playing it recently the speaker began to make a loud buzzing and humming sounds with the loss of all other audio. I immediately turned it off and unplugged the cord. There was also the smell of burning electronics in the air. I pulled the chassis and after some investigating I narrowed down the damaged component to the volume control based on the fact that the control shaft now rotates with excessive stiffness, parts of the plastic portion of the control unit show signs of excessive heat damage (welts) and it smells strongly of having been fried. None of the other components under or on top of the chassis have any apparent damage (no fried resistors or exploded capacitors). I have checked the values of some of the capacitors and the speaker and they are all within the correct ranges. Prior to this incident it has played fine for 30 minutes to an hour or so at a time without any problems.
Now, with the pot at it's maximum resistance, surely the plate current would be less, right?
If I ignore the plate current and just look at the string of resistances between the two plates and ground, I get 40,250 ohms. The plate voltage is 275V. Current thru the resistor string from this source = 275/40K = 6ma.
Help me understand your reasoning here.
By the way, I do agree a 2W pot would be idea.
:Hi
:
: This is going to be hard to explain but here goes.
:
: A 250 ohm resistor which dissipates 20 ma drops 5 volts. That would only be .1 watts. 250 x .02 = 5 volts. 5 volts x .02 amps = .1 watts
:
: Now if a 5000 ohm control was to handle 20 ma it would need to be 2 watts. 5000 x .02 = 100 volts. 100 volts x .02 amps = 2 watts.
:
: No part of a 5000 ohm 2 watt control should handle more than 20 ma. The same current which flows through the 250 ohm resistor goes through the control. When a low wattage carbon control is turned nearly all the way up it can cause an small area to burn.
:
:Norm
:
::Tony, I've done a little figuring in my head and I think you can get by with a 5K linear taper pot, but it will get warm. Based on what I'm reading, garden-variety linear pots are typically rated at 0.5W whereas audio taper pots are rated at 0.25W.
::
::The problem is that I don't find a 5K linear pot at either RadioDaze or AES. You could use a dual section 10K audio pot such as RadioDaze part no. R-DPA-10K, and wire the two sections in parallel. That would give you 0.5W.
::
::Most variable resistors that are rated, say, 2W generally fall under the rheostat classification. You can surely find such a beast at Mouser, and that would be your best option. Check the dimensions to make sure it will fit. Mouser organizes its catalog and website by manufacturer - try Ohmite.
::
::The wattage of the 250-ohm series resistor really won't keep the pot from getting warm. The 250-ohm resistor can be 1W.
::
:::Norm,
:::
:::Both the chassis wiring diagram and the parts list show the value for the volume control as 5250 ohms while the schematic shows a value of 5000 ohms with a separate 250 ohm resistor. Neither the diagram or the parts list reference this resistor. My radio has the separate resistor installed. Is it safe to install a 5000 ohm control unit rated at less than 2 watts and a separate 250 ohm resistor rated for at least 2 watts?
:::
::::Hi Tony
::::
:::: This radio uses a different type volume control circuit. Instead of a signal divider it adjusts cathode voltage on your 6A8 & 6K7 tubes. It really should be a 2 watt control.
::::
:::: http://www.nostalgiaair.org/PagesByModel/749/M0007749.pdf
::::
:::: If something causes either 6A8 or 6K7 to draw too much current this control will burn.
::::
::::Norm
::::
:::::What would cause the volume control of an electronically restored GE A-53 to fail suddenly? While playing it recently the speaker began to make a loud buzzing and humming sounds with the loss of all other audio. I immediately turned it off and unplugged the cord. There was also the smell of burning electronics in the air. I pulled the chassis and after some investigating I narrowed down the damaged component to the volume control based on the fact that the control shaft now rotates with excessive stiffness, parts of the plastic portion of the control unit show signs of excessive heat damage (welts) and it smells strongly of having been fried. None of the other components under or on top of the chassis have any apparent damage (no fried resistors or exploded capacitors). I have checked the values of some of the capacitors and the speaker and they are all within the correct ranges. Prior to this incident it has played fine for 30 minutes to an hour or so at a time without any problems.
Plate current & screen current for both tubes flows through this control. In addition some current is drawn through R5 & R6 resistors.
The cathode current can be 10 ma (osc & mixer sections) for 6A8 and 14 ma for 6K7. Current may actually be more as plate voltage is 275 in Rider data. Tube data book shows plate at 250 volts. In addition we still have R5 & R6 to B+.
You are right at max resistance current will be much less. The problem comes at near min resistance. If tubes draw 24 ma this current has to flow through a very small portion of the control. Just because a control is rated .5 watts doesn't mean it can handle higher current over a small portion. At near min resistance the control has to handle 24 ma current burning a hole in the carbon element. A 5000 ohm control can only handle 10 ma current through any portion of the resistor. 5000 ohms x .01 amps = 50 volts. 50 volts x .01 amps = 10 ma. ( There is an easier way but this should be more understandable.)
Norm
:OK, Norm, but what I'm looking at is the highest current that could go through the pot and the 250-ohm resistor. The plate current for the two tubes in question, combined, is 7.2ma, per the set's data sheet. Correct?
:
:Now, with the pot at it's maximum resistance, surely the plate current would be less, right?
:
:If I ignore the plate current and just look at the string of resistances between the two plates and ground, I get 40,250 ohms. The plate voltage is 275V. Current thru the resistor string from this source = 275/40K = 6ma.
:
:Help me understand your reasoning here.
:
:By the way, I do agree a 2W pot would be idea.
:
:
:
::Hi
::
:: This is going to be hard to explain but here goes.
::
:: A 250 ohm resistor which dissipates 20 ma drops 5 volts. That would only be .1 watts. 250 x .02 = 5 volts. 5 volts x .02 amps = .1 watts
::
:: Now if a 5000 ohm control was to handle 20 ma it would need to be 2 watts. 5000 x .02 = 100 volts. 100 volts x .02 amps = 2 watts.
::
:: No part of a 5000 ohm 2 watt control should handle more than 20 ma. The same current which flows through the 250 ohm resistor goes through the control. When a low wattage carbon control is turned nearly all the way up it can cause an small area to burn.
::
::Norm
::
:::Tony, I've done a little figuring in my head and I think you can get by with a 5K linear taper pot, but it will get warm. Based on what I'm reading, garden-variety linear pots are typically rated at 0.5W whereas audio taper pots are rated at 0.25W.
:::
:::The problem is that I don't find a 5K linear pot at either RadioDaze or AES. You could use a dual section 10K audio pot such as RadioDaze part no. R-DPA-10K, and wire the two sections in parallel. That would give you 0.5W.
:::
:::Most variable resistors that are rated, say, 2W generally fall under the rheostat classification. You can surely find such a beast at Mouser, and that would be your best option. Check the dimensions to make sure it will fit. Mouser organizes its catalog and website by manufacturer - try Ohmite.
:::
:::The wattage of the 250-ohm series resistor really won't keep the pot from getting warm. The 250-ohm resistor can be 1W.
:::
::::Norm,
::::
::::Both the chassis wiring diagram and the parts list show the value for the volume control as 5250 ohms while the schematic shows a value of 5000 ohms with a separate 250 ohm resistor. Neither the diagram or the parts list reference this resistor. My radio has the separate resistor installed. Is it safe to install a 5000 ohm control unit rated at less than 2 watts and a separate 250 ohm resistor rated for at least 2 watts?
::::
:::::Hi Tony
:::::
::::: This radio uses a different type volume control circuit. Instead of a signal divider it adjusts cathode voltage on your 6A8 & 6K7 tubes. It really should be a 2 watt control.
:::::
::::: http://www.nostalgiaair.org/PagesByModel/749/M0007749.pdf
:::::
::::: If something causes either 6A8 or 6K7 to draw too much current this control will burn.
:::::
:::::Norm
:::::
::::::What would cause the volume control of an electronically restored GE A-53 to fail suddenly? While playing it recently the speaker began to make a loud buzzing and humming sounds with the loss of all other audio. I immediately turned it off and unplugged the cord. There was also the smell of burning electronics in the air. I pulled the chassis and after some investigating I narrowed down the damaged component to the volume control based on the fact that the control shaft now rotates with excessive stiffness, parts of the plastic portion of the control unit show signs of excessive heat damage (welts) and it smells strongly of having been fried. None of the other components under or on top of the chassis have any apparent damage (no fried resistors or exploded capacitors). I have checked the values of some of the capacitors and the speaker and they are all within the correct ranges. Prior to this incident it has played fine for 30 minutes to an hour or so at a time without any problems.
Thank you for the information and your help. I will be on the lookout for a 5000 ohm 2 watt unit.
By the way; The volume control/on-off switch installed in my radio appears to be an older replacement unit. I am unable to perform an accurate reading of this unit's value due to to the damage it has sustained. In addition, there are no markings stamped on it showing the wattage specs. Before it became completely fried, it performed poorly with the audio coming on only after it was rotated about 3/4 of the way through it's range.
The resistor that is connected in series with the control is 100 ohms (color coded brown-black-brown and testing at 118.8 ohms on my multimeter). It also appears to be at least a 2 watt unit.
Once last question: Will a bad 6A8 and/or 6K7 cause a good volume control in this radio to overheat and eventually burn-up?
:Hi Doug
:
: Plate current & screen current for both tubes flows through this control. In addition some current is drawn through R5 & R6 resistors.
:
: The cathode current can be 10 ma (osc & mixer sections) for 6A8 and 14 ma for 6K7. Current may actually be more as plate voltage is 275 in Rider data. Tube data book shows plate at 250 volts. In addition we still have R5 & R6 to B+.
:
: You are right at max resistance current will be much less. The problem comes at near min resistance. If tubes draw 24 ma this current has to flow through a very small portion of the control. Just because a control is rated .5 watts doesn't mean it can handle higher current over a small portion. At near min resistance the control has to handle 24 ma current burning a hole in the carbon element. A 5000 ohm control can only handle 10 ma current through any portion of the resistor. 5000 ohms x .01 amps = 50 volts. 50 volts x .01 amps = 10 ma. ( There is an easier way but this should be more understandable.)
:
:Norm
:
:
:
::OK, Norm, but what I'm looking at is the highest current that could go through the pot and the 250-ohm resistor. The plate current for the two tubes in question, combined, is 7.2ma, per the set's data sheet. Correct?
::
::Now, with the pot at it's maximum resistance, surely the plate current would be less, right?
::
::If I ignore the plate current and just look at the string of resistances between the two plates and ground, I get 40,250 ohms. The plate voltage is 275V. Current thru the resistor string from this source = 275/40K = 6ma.
::
::Help me understand your reasoning here.
::
::By the way, I do agree a 2W pot would be idea.
::
::
::
:::Hi
:::
::: This is going to be hard to explain but here goes.
:::
::: A 250 ohm resistor which dissipates 20 ma drops 5 volts. That would only be .1 watts. 250 x .02 = 5 volts. 5 volts x .02 amps = .1 watts
:::
::: Now if a 5000 ohm control was to handle 20 ma it would need to be 2 watts. 5000 x .02 = 100 volts. 100 volts x .02 amps = 2 watts.
:::
::: No part of a 5000 ohm 2 watt control should handle more than 20 ma. The same current which flows through the 250 ohm resistor goes through the control. When a low wattage carbon control is turned nearly all the way up it can cause an small area to burn.
:::
:::Norm
:::
::::Tony, I've done a little figuring in my head and I think you can get by with a 5K linear taper pot, but it will get warm. Based on what I'm reading, garden-variety linear pots are typically rated at 0.5W whereas audio taper pots are rated at 0.25W.
::::
::::The problem is that I don't find a 5K linear pot at either RadioDaze or AES. You could use a dual section 10K audio pot such as RadioDaze part no. R-DPA-10K, and wire the two sections in parallel. That would give you 0.5W.
::::
::::Most variable resistors that are rated, say, 2W generally fall under the rheostat classification. You can surely find such a beast at Mouser, and that would be your best option. Check the dimensions to make sure it will fit. Mouser organizes its catalog and website by manufacturer - try Ohmite.
::::
::::The wattage of the 250-ohm series resistor really won't keep the pot from getting warm. The 250-ohm resistor can be 1W.
::::
:::::Norm,
:::::
:::::Both the chassis wiring diagram and the parts list show the value for the volume control as 5250 ohms while the schematic shows a value of 5000 ohms with a separate 250 ohm resistor. Neither the diagram or the parts list reference this resistor. My radio has the separate resistor installed. Is it safe to install a 5000 ohm control unit rated at less than 2 watts and a separate 250 ohm resistor rated for at least 2 watts?
:::::
::::::Hi Tony
::::::
:::::: This radio uses a different type volume control circuit. Instead of a signal divider it adjusts cathode voltage on your 6A8 & 6K7 tubes. It really should be a 2 watt control.
::::::
:::::: http://www.nostalgiaair.org/PagesByModel/749/M0007749.pdf
::::::
:::::: If something causes either 6A8 or 6K7 to draw too much current this control will burn.
::::::
::::::Norm
::::::
:::::::What would cause the volume control of an electronically restored GE A-53 to fail suddenly? While playing it recently the speaker began to make a loud buzzing and humming sounds with the loss of all other audio. I immediately turned it off and unplugged the cord. There was also the smell of burning electronics in the air. I pulled the chassis and after some investigating I narrowed down the damaged component to the volume control based on the fact that the control shaft now rotates with excessive stiffness, parts of the plastic portion of the control unit show signs of excessive heat damage (welts) and it smells strongly of having been fried. None of the other components under or on top of the chassis have any apparent damage (no fried resistors or exploded capacitors). I have checked the values of some of the capacitors and the speaker and they are all within the correct ranges. Prior to this incident it has played fine for 30 minutes to an hour or so at a time without any problems.
Yes, a bad (shorted or gassy) tube can draw too much current and burn up the control. Using a lower value resistor such as 100 ohms will also put more current through the control when it's turned up. Turned up high is where a control carries the most current.
Norm
:Norm and Doug,
:
:Thank you for the information and your help. I will be on the lookout for a 5000 ohm 2 watt unit.
:
:By the way; The volume control/on-off switch installed in my radio appears to be an older replacement unit. I am unable to perform an accurate reading of this unit's value due to to the damage it has sustained. In addition, there are no markings stamped on it showing the wattage specs. Before it became completely fried, it performed poorly with the audio coming on only after it was rotated about 3/4 of the way through it's range.
:
:The resistor that is connected in series with the control is 100 ohms (color coded brown-black-brown and testing at 118.8 ohms on my multimeter). It also appears to be at least a 2 watt unit.
:
:Once last question: Will a bad 6A8 and/or 6K7 cause a good volume control in this radio to overheat and eventually burn-up?
:
:
::Hi Doug
::
:: Plate current & screen current for both tubes flows through this control. In addition some current is drawn through R5 & R6 resistors.
::
:: The cathode current can be 10 ma (osc & mixer sections) for 6A8 and 14 ma for 6K7. Current may actually be more as plate voltage is 275 in Rider data. Tube data book shows plate at 250 volts. In addition we still have R5 & R6 to B+.
::
:: You are right at max resistance current will be much less. The problem comes at near min resistance. If tubes draw 24 ma this current has to flow through a very small portion of the control. Just because a control is rated .5 watts doesn't mean it can handle higher current over a small portion. At near min resistance the control has to handle 24 ma current burning a hole in the carbon element. A 5000 ohm control can only handle 10 ma current through any portion of the resistor. 5000 ohms x .01 amps = 50 volts. 50 volts x .01 amps = 10 ma. ( There is an easier way but this should be more understandable.)
::
::Norm
::
::
::
:::OK, Norm, but what I'm looking at is the highest current that could go through the pot and the 250-ohm resistor. The plate current for the two tubes in question, combined, is 7.2ma, per the set's data sheet. Correct?
:::
:::Now, with the pot at it's maximum resistance, surely the plate current would be less, right?
:::
:::If I ignore the plate current and just look at the string of resistances between the two plates and ground, I get 40,250 ohms. The plate voltage is 275V. Current thru the resistor string from this source = 275/40K = 6ma.
:::
:::Help me understand your reasoning here.
:::
:::By the way, I do agree a 2W pot would be idea.
:::
:::
:::
::::Hi
::::
:::: This is going to be hard to explain but here goes.
::::
:::: A 250 ohm resistor which dissipates 20 ma drops 5 volts. That would only be .1 watts. 250 x .02 = 5 volts. 5 volts x .02 amps = .1 watts
::::
:::: Now if a 5000 ohm control was to handle 20 ma it would need to be 2 watts. 5000 x .02 = 100 volts. 100 volts x .02 amps = 2 watts.
::::
:::: No part of a 5000 ohm 2 watt control should handle more than 20 ma. The same current which flows through the 250 ohm resistor goes through the control. When a low wattage carbon control is turned nearly all the way up it can cause an small area to burn.
::::
::::Norm
::::
:::::Tony, I've done a little figuring in my head and I think you can get by with a 5K linear taper pot, but it will get warm. Based on what I'm reading, garden-variety linear pots are typically rated at 0.5W whereas audio taper pots are rated at 0.25W.
:::::
:::::The problem is that I don't find a 5K linear pot at either RadioDaze or AES. You could use a dual section 10K audio pot such as RadioDaze part no. R-DPA-10K, and wire the two sections in parallel. That would give you 0.5W.
:::::
:::::Most variable resistors that are rated, say, 2W generally fall under the rheostat classification. You can surely find such a beast at Mouser, and that would be your best option. Check the dimensions to make sure it will fit. Mouser organizes its catalog and website by manufacturer - try Ohmite.
:::::
:::::The wattage of the 250-ohm series resistor really won't keep the pot from getting warm. The 250-ohm resistor can be 1W.
:::::
::::::Norm,
::::::
::::::Both the chassis wiring diagram and the parts list show the value for the volume control as 5250 ohms while the schematic shows a value of 5000 ohms with a separate 250 ohm resistor. Neither the diagram or the parts list reference this resistor. My radio has the separate resistor installed. Is it safe to install a 5000 ohm control unit rated at less than 2 watts and a separate 250 ohm resistor rated for at least 2 watts?
::::::
:::::::Hi Tony
:::::::
::::::: This radio uses a different type volume control circuit. Instead of a signal divider it adjusts cathode voltage on your 6A8 & 6K7 tubes. It really should be a 2 watt control.
:::::::
::::::: http://www.nostalgiaair.org/PagesByModel/749/M0007749.pdf
:::::::
::::::: If something causes either 6A8 or 6K7 to draw too much current this control will burn.
:::::::
:::::::Norm
:::::::
::::::::What would cause the volume control of an electronically restored GE A-53 to fail suddenly? While playing it recently the speaker began to make a loud buzzing and humming sounds with the loss of all other audio. I immediately turned it off and unplugged the cord. There was also the smell of burning electronics in the air. I pulled the chassis and after some investigating I narrowed down the damaged component to the volume control based on the fact that the control shaft now rotates with excessive stiffness, parts of the plastic portion of the control unit show signs of excessive heat damage (welts) and it smells strongly of having been fried. None of the other components under or on top of the chassis have any apparent damage (no fried resistors or exploded capacitors). I have checked the values of some of the capacitors and the speaker and they are all within the correct ranges. Prior to this incident it has played fine for 30 minutes to an hour or so at a time without any problems.
5000 ohms x 6ma x 6ma = 0.2W