The Philco does not use cathode resistors on this set, but they could be added if the tubes are hot enough to cook the paint. (about 27 ohms, 2watts- This only after everything else has been addressed to correct the problem.
I would check the resistor that is between the second grid (pin 4) between the two tubes. If there is a problem with the condenser that ties to pin 3 of one of the tubes, it will also cause limited volume, and some excessive heating of one tube, and the output trasnformer/field winding of the speaker. It is supposed to be a .003 mfd, and it would be prudent to remove it from the bakelite block, and slip a new replacement inside, or remove any connection made to that terminal to isolate it. Replace the one soldered outside too, or get rid of it if you put a replacement inside of the bakelite block.
I am aking an assumption that you have a Philco based on the reference to a bakelite block; Chuck Scwark has good Philco references on his site:
http://members.aol.com/caschwark
The schematic for a Philco 38-4 is here on Nostalgia Air:
http://ww3.nostalgiaair.org/schematics/PHL/PHL_8-61.gif
:hello, I have a 38-c4 radio that has average volume output at best. The 6f6 tubes get VERY HOT (HOT ENOUGH THAT WHEN LICK MY FINGER AND TOUCH ONE, IT SIZZLES!) With the speaker unplugged the tubes seem to be the normal tube temperature. does this mean the speaker or output trans is shorted? I did notice that external capacitors were soldered onto some of the bakelite cap blocks.(they didnt remove the caps inside the blocks) I cant seem to find the values for the block that has the number 8378 SU
That particular cap, you should be able to remove from the circuit without a problem for purposes of testing that section. You might try isolating troubles in that way.
The resistance you measured on the field coil should be about right if it were about 700 ohms. If it is almost 700 thousand ohms, then there is an issue with the field coil.
If you have a pair of 6F6's, and only one is getting very hot, that .003 cap may be shorting out at the higher plate voltage potential, and only one tube is then driving the speaker, or there may be a shorted lead, or wire, and these are not always that noticable.
If you only have one 6F6 as a single ended driver, the tube will get hot, 150 degrees C is not out of expectation.
It is possible that the output transformer is shorted on one side (if two tube push-pull), or if it had been replaced, it may not be the correct one for the plate impedance.
:::Hello, I checked and it is only one tube that sizzles when I touch it(6f6). The field coil measures 655k ohms. The caps measure .003 from the plate to ground, but I havn't removed the original cap in the block yet. If these caps were shorting or failing in some other way, wouldn't it show up on the multimeter cap test?
::Hi,
::The 6F6's do tend to operate rather warm, but you may be seeing other issues in the radio. If the speaker is unplugged, no current is flowing through the tube.
::
::The Philco does not use cathode resistors on this set, but they could be added if the tubes are hot enough to cook the paint. (about 27 ohms, 2watts- This only after everything else has been addressed to correct the problem.
::I would check the resistor that is between the second grid (pin 4) between the two tubes. If there is a problem with the condenser that ties to pin 3 of one of the tubes, it will also cause limited volume, and some excessive heating of one tube, and the output trasnformer/field winding of the speaker. It is supposed to be a .003 mfd, and it would be prudent to remove it from the bakelite block, and slip a new replacement inside, or remove any connection made to that terminal to isolate it. Replace the one soldered outside too, or get rid of it if you put a replacement inside of the bakelite block.
::
::I am aking an assumption that you have a Philco based on the reference to a bakelite block; Chuck Scwark has good Philco references on his site:
::http://members.aol.com/caschwark
::
::The schematic for a Philco 38-4 is here on Nostalgia Air:
::http://ww3.nostalgiaair.org/schematics/PHL/PHL_8-61.gif
::
::
:::hello, I have a 38-c4 radio that has average volume output at best. The 6f6 tubes get VERY HOT (HOT ENOUGH THAT WHEN LICK MY FINGER AND TOUCH ONE, IT SIZZLES!) With the speaker unplugged the tubes seem to be the normal tube temperature. does this mean the speaker or output trans is shorted? I did notice that external capacitors were soldered onto some of the bakelite cap blocks.(they didnt remove the caps inside the blocks) I cant seem to find the values for the block that has the number 8378 SU
Looking at the bottom of a tube, with keyway toward you, pin #1 is first one on the left. Pin #3 is plate, #4 screen. These will be positive. Pin #5 is grid and should be negative 20 volts in relation to pin #8, cathode. Think you have the right voltages just numbering doesn't seem right.
If grid 1, pin #5, isn't negative enough a tube will operate too hot. Metal 6F6 tubes run very hot, hotter than 6F6G's. They will burn your hand.
Since your schematic calls out 6F6G does pin #1 of your tube sockets connect to chassis? This pin isn't used on a 6F6G but is connected to the shield on 6F6 tubes. Without pin #1 being grounded your radio could go into oscillation.
Output tubes should be fairly well matched. Either one pulled should drop volume a similar amount.
If you don't have other 6F6 tubes to exchange try a pair of 6K6GT or 6V6GT tubes.
Norm
::I have now tried to see which tube is working. The 6f6 at the end of the chassis can be taken out with little drop in volume, the one to the right of it is giving most of the output. Is this where matching of the tubes comes into play since they are different brands? I have replaced the plate .003 caps. Both tubes still get sizzling hot.
:::Hello, I found out that the bakelite block has the number 8318 dg on it which according to philco cap info, pins 1 and 3 contain a .03 cap. This is the 1st audio tube coupler cap to the 6f6's I removed the .03 cap someone soldered on the outside to pins 1 and 2, and put it inside soldered to pins 1 and 3. Now both tubes get sizzling hot, however I have louder volume with a constant whistle when the volume is a quarter up. I did notice that the schematic showes the tube numbers as 6f6G, which I think means glass type. I have 6f6 in the metal can type. I am not sure if this makes a difference or not. the tube voltages are pin 1 and 2=0v. pin 3=292/300 pin 4=0v pin 5=303v/306v. pin 6=275v/295v and pin 7=-21v/-21v
:::Hi,
:::The tester applies only a low voltage, And right off of the plate, you should be seeing a significant voltage.
:::
:::That particular cap, you should be able to remove from the circuit without a problem for purposes of testing that section. You might try isolating troubles in that way.
:::
:::The resistance you measured on the field coil should be about right if it were about 700 ohms. If it is almost 700 thousand ohms, then there is an issue with the field coil.
:::
:::If you have a pair of 6F6's, and only one is getting very hot, that .003 cap may be shorting out at the higher plate voltage potential, and only one tube is then driving the speaker, or there may be a shorted lead, or wire, and these are not always that noticable.
:::
:::If you only have one 6F6 as a single ended driver, the tube will get hot, 150 degrees C is not out of expectation.
:::
:::It is possible that the output transformer is shorted on one side (if two tube push-pull), or if it had been replaced, it may not be the correct one for the plate impedance.
:::
:::
:::
:::
:::
:::
:::
::::::Hello, I checked and it is only one tube that sizzles when I touch it(6f6). The field coil measures 655k ohms. The caps measure .003 from the plate to ground, but I havn't removed the original cap in the block yet. If these caps were shorting or failing in some other way, wouldn't it show up on the multimeter cap test?
:::::Hi,
:::::The 6F6's do tend to operate rather warm, but you may be seeing other issues in the radio. If the speaker is unplugged, no current is flowing through the tube.
:::::
:::::The Philco does not use cathode resistors on this set, but they could be added if the tubes are hot enough to cook the paint. (about 27 ohms, 2watts- This only after everything else has been addressed to correct the problem.
:::::I would check the resistor that is between the second grid (pin 4) between the two tubes. If there is a problem with the condenser that ties to pin 3 of one of the tubes, it will also cause limited volume, and some excessive heating of one tube, and the output trasnformer/field winding of the speaker. It is supposed to be a .003 mfd, and it would be prudent to remove it from the bakelite block, and slip a new replacement inside, or remove any connection made to that terminal to isolate it. Replace the one soldered outside too, or get rid of it if you put a replacement inside of the bakelite block.
:::::
:::::I am aking an assumption that you have a Philco based on the reference to a bakelite block; Chuck Scwark has good Philco references on his site:
:::::http://members.aol.com/caschwark
:::::
:::::The schematic for a Philco 38-4 is here on Nostalgia Air:
:::::http://ww3.nostalgiaair.org/schematics/PHL/PHL_8-61.gif
:::::
:::::
::::::hello, I have a 38-c4 radio that has average volume output at best. The 6f6 tubes get VERY HOT (HOT ENOUGH THAT WHEN LICK MY FINGER AND TOUCH ONE, IT SIZZLES!) With the speaker unplugged the tubes seem to be the normal tube temperature. does this mean the speaker or output trans is shorted? I did notice that external capacitors were soldered onto some of the bakelite cap blocks.(they didnt remove the caps inside the blocks) I cant seem to find the values for the block that has the number 8378 SU
If there is plate voltage on one, and not the other (with the questionable cap out of the circuit, then the issue is in the audio output transformes- providing that there is nothing shorting to ground between that plate (pin 3), and the transformer portion of the speker itself. Look at the terminals on the speaker if the transformer is actually wound as part of the field coil assembly,or seperate, just to make sure that those connections are sound and not shorted.
::Hello, The tubes themselves drop about the same volume when used in the socket closer to the center of the chassis, but when either tube is used in the socket closer to the side of the chassis, there isnt much output.
::
::Hi Sean
::
:: Looking at the bottom of a tube, with keyway toward you, pin #1 is first one on the left. Pin #3 is plate, #4 screen. These will be positive. Pin #5 is grid and should be negative 20 volts in relation to pin #8, cathode. Think you have the right voltages just numbering doesn't seem right.
::
:: If grid 1, pin #5, isn't negative enough a tube will operate too hot. Metal 6F6 tubes run very hot, hotter than 6F6G's. They will burn your hand.
::
:: Since your schematic calls out 6F6G does pin #1 of your tube sockets connect to chassis? This pin isn't used on a 6F6G but is connected to the shield on 6F6 tubes. Without pin #1 being grounded your radio could go into oscillation.
::
:: Output tubes should be fairly well matched. Either one pulled should drop volume a similar amount.
::
:: If you don't have other 6F6 tubes to exchange try a pair of 6K6GT or 6V6GT tubes.
::
::Norm
::
::::I have now tried to see which tube is working. The 6f6 at the end of the chassis can be taken out with little drop in volume, the one to the right of it is giving most of the output. Is this where matching of the tubes comes into play since they are different brands? I have replaced the plate .003 caps. Both tubes still get sizzling hot.
:::::Hello, I found out that the bakelite block has the number 8318 dg on it which according to philco cap info, pins 1 and 3 contain a .03 cap. This is the 1st audio tube coupler cap to the 6f6's I removed the .03 cap someone soldered on the outside to pins 1 and 2, and put it inside soldered to pins 1 and 3. Now both tubes get sizzling hot, however I have louder volume with a constant whistle when the volume is a quarter up. I did notice that the schematic showes the tube numbers as 6f6G, which I think means glass type. I have 6f6 in the metal can type. I am not sure if this makes a difference or not. the tube voltages are pin 1 and 2=0v. pin 3=292/300 pin 4=0v pin 5=303v/306v. pin 6=275v/295v and pin 7=-21v/-21v
:::::Hi,
:::::The tester applies only a low voltage, And right off of the plate, you should be seeing a significant voltage.
:::::
:::::That particular cap, you should be able to remove from the circuit without a problem for purposes of testing that section. You might try isolating troubles in that way.
:::::
:::::The resistance you measured on the field coil should be about right if it were about 700 ohms. If it is almost 700 thousand ohms, then there is an issue with the field coil.
:::::
:::::If you have a pair of 6F6's, and only one is getting very hot, that .003 cap may be shorting out at the higher plate voltage potential, and only one tube is then driving the speaker, or there may be a shorted lead, or wire, and these are not always that noticable.
:::::
:::::If you only have one 6F6 as a single ended driver, the tube will get hot, 150 degrees C is not out of expectation.
:::::
:::::It is possible that the output transformer is shorted on one side (if two tube push-pull), or if it had been replaced, it may not be the correct one for the plate impedance.
:::::
:::::
:::::
:::::
:::::
:::::
:::::
::::::::Hello, I checked and it is only one tube that sizzles when I touch it(6f6). The field coil measures 655k ohms. The caps measure .003 from the plate to ground, but I havn't removed the original cap in the block yet. If these caps were shorting or failing in some other way, wouldn't it show up on the multimeter cap test?
:::::::Hi,
:::::::The 6F6's do tend to operate rather warm, but you may be seeing other issues in the radio. If the speaker is unplugged, no current is flowing through the tube.
:::::::
:::::::The Philco does not use cathode resistors on this set, but they could be added if the tubes are hot enough to cook the paint. (about 27 ohms, 2watts- This only after everything else has been addressed to correct the problem.
:::::::I would check the resistor that is between the second grid (pin 4) between the two tubes. If there is a problem with the condenser that ties to pin 3 of one of the tubes, it will also cause limited volume, and some excessive heating of one tube, and the output trasnformer/field winding of the speaker. It is supposed to be a .003 mfd, and it would be prudent to remove it from the bakelite block, and slip a new replacement inside, or remove any connection made to that terminal to isolate it. Replace the one soldered outside too, or get rid of it if you put a replacement inside of the bakelite block.
:::::::
:::::::I am aking an assumption that you have a Philco based on the reference to a bakelite block; Chuck Scwark has good Philco references on his site:
:::::::http://members.aol.com/caschwark
:::::::
:::::::The schematic for a Philco 38-4 is here on Nostalgia Air:
:::::::http://ww3.nostalgiaair.org/schematics/PHL/PHL_8-61.gif
:::::::
:::::::
::::::::hello, I have a 38-c4 radio that has average volume output at best. The 6f6 tubes get VERY HOT (HOT ENOUGH THAT WHEN LICK MY FINGER AND TOUCH ONE, IT SIZZLES!) With the speaker unplugged the tubes seem to be the normal tube temperature. does this mean the speaker or output trans is shorted? I did notice that external capacitors were soldered onto some of the bakelite cap blocks.(they didnt remove the caps inside the blocks) I cant seem to find the values for the block that has the number 8378 SU
Just looked at the circuit. You won't have equal volume pulling one output tube at a time. This is one of those Philco circuits where a signal is taken off the screen of one tube to feed input of the second.
If you have proper voltages on 6F6's they will be very hot but this is expected.
Do you hear a loud hum touching the top cap of your 6K5?
Try peaking up IF transformer adjustments.
Norm
::Hello, The tubes themselves drop about the same volume when used in the socket closer to the center of the chassis, but when either tube is used in the socket closer to the side of the chassis, there isnt much output.
::
::Hi Sean
::
:: Looking at the bottom of a tube, with keyway toward you, pin #1 is first one on the left. Pin #3 is plate, #4 screen. These will be positive. Pin #5 is grid and should be negative 20 volts in relation to pin #8, cathode. Think you have the right voltages just numbering doesn't seem right.
::
:: If grid 1, pin #5, isn't negative enough a tube will operate too hot. Metal 6F6 tubes run very hot, hotter than 6F6G's. They will burn your hand.
::
:: Since your schematic calls out 6F6G does pin #1 of your tube sockets connect to chassis? This pin isn't used on a 6F6G but is connected to the shield on 6F6 tubes. Without pin #1 being grounded your radio could go into oscillation.
::
:: Output tubes should be fairly well matched. Either one pulled should drop volume a similar amount.
::
:: If you don't have other 6F6 tubes to exchange try a pair of 6K6GT or 6V6GT tubes.
::
::Norm
::
::::I have now tried to see which tube is working. The 6f6 at the end of the chassis can be taken out with little drop in volume, the one to the right of it is giving most of the output. Is this where matching of the tubes comes into play since they are different brands? I have replaced the plate .003 caps. Both tubes still get sizzling hot.
:::::Hello, I found out that the bakelite block has the number 8318 dg on it which according to philco cap info, pins 1 and 3 contain a .03 cap. This is the 1st audio tube coupler cap to the 6f6's I removed the .03 cap someone soldered on the outside to pins 1 and 2, and put it inside soldered to pins 1 and 3. Now both tubes get sizzling hot, however I have louder volume with a constant whistle when the volume is a quarter up. I did notice that the schematic showes the tube numbers as 6f6G, which I think means glass type. I have 6f6 in the metal can type. I am not sure if this makes a difference or not. the tube voltages are pin 1 and 2=0v. pin 3=292/300 pin 4=0v pin 5=303v/306v. pin 6=275v/295v and pin 7=-21v/-21v
:::::Hi,
:::::The tester applies only a low voltage, And right off of the plate, you should be seeing a significant voltage.
:::::
:::::That particular cap, you should be able to remove from the circuit without a problem for purposes of testing that section. You might try isolating troubles in that way.
:::::
:::::The resistance you measured on the field coil should be about right if it were about 700 ohms. If it is almost 700 thousand ohms, then there is an issue with the field coil.
:::::
:::::If you have a pair of 6F6's, and only one is getting very hot, that .003 cap may be shorting out at the higher plate voltage potential, and only one tube is then driving the speaker, or there may be a shorted lead, or wire, and these are not always that noticable.
:::::
:::::If you only have one 6F6 as a single ended driver, the tube will get hot, 150 degrees C is not out of expectation.
:::::
:::::It is possible that the output transformer is shorted on one side (if two tube push-pull), or if it had been replaced, it may not be the correct one for the plate impedance.
:::::
:::::
:::::
:::::
:::::
:::::
:::::
::::::::Hello, I checked and it is only one tube that sizzles when I touch it(6f6). The field coil measures 655k ohms. The caps measure .003 from the plate to ground, but I havn't removed the original cap in the block yet. If these caps were shorting or failing in some other way, wouldn't it show up on the multimeter cap test?
:::::::Hi,
:::::::The 6F6's do tend to operate rather warm, but you may be seeing other issues in the radio. If the speaker is unplugged, no current is flowing through the tube.
:::::::
:::::::The Philco does not use cathode resistors on this set, but they could be added if the tubes are hot enough to cook the paint. (about 27 ohms, 2watts- This only after everything else has been addressed to correct the problem.
:::::::I would check the resistor that is between the second grid (pin 4) between the two tubes. If there is a problem with the condenser that ties to pin 3 of one of the tubes, it will also cause limited volume, and some excessive heating of one tube, and the output trasnformer/field winding of the speaker. It is supposed to be a .003 mfd, and it would be prudent to remove it from the bakelite block, and slip a new replacement inside, or remove any connection made to that terminal to isolate it. Replace the one soldered outside too, or get rid of it if you put a replacement inside of the bakelite block.
:::::::
:::::::I am aking an assumption that you have a Philco based on the reference to a bakelite block; Chuck Scwark has good Philco references on his site:
:::::::http://members.aol.com/caschwark
:::::::
:::::::The schematic for a Philco 38-4 is here on Nostalgia Air:
:::::::http://ww3.nostalgiaair.org/schematics/PHL/PHL_8-61.gif
:::::::
:::::::
::::::::hello, I have a 38-c4 radio that has average volume output at best. The 6f6 tubes get VERY HOT (HOT ENOUGH THAT WHEN LICK MY FINGER AND TOUCH ONE, IT SIZZLES!) With the speaker unplugged the tubes seem to be the normal tube temperature. does this mean the speaker or output trans is shorted? I did notice that external capacitors were soldered onto some of the bakelite cap blocks.(they didnt remove the caps inside the blocks) I cant seem to find the values for the block that has the number 8378 SU
Pin #1 needs to be grounded on a metal tube. That voltage may be stray or oscillation at a high frequency. Whatever it is can cause problems.
The second output tube gets it's signal from the first one. Both are working. When you pull one tube most of the signal is lost going to the second one. Think only Philco used this circuit.
Norm
::Hello, If I ground pin 1, would that create maximimum smoke since pin 1 has 295 volts on it or is that just stray voltage because the shield isnt grounded?
::
:::Hello, I touched the grid cap on the 6k5 tube and you do get a hum, not real loud more like average. Here are the proper pin voltages..1=294v, 2=0v, 3=302v, 4=294, 5=-21v 6=not used, 7=0v, and 8=0v
:::
:::Hi Sean
:::
::: Just looked at the circuit. You won't have equal volume pulling one output tube at a time. This is one of those Philco circuits where a signal is taken off the screen of one tube to feed input of the second.
:::
::: If you have proper voltages on 6F6's they will be very hot but this is expected.
:::
::: Do you hear a loud hum touching the top cap of your 6K5?
:::
::: Try peaking up IF transformer adjustments.
:::
:::Norm
:::
:::
:::
:::::Hello, The tubes themselves drop about the same volume when used in the socket closer to the center of the chassis, but when either tube is used in the socket closer to the side of the chassis, there isnt much output.
:::::
:::::Hi Sean
:::::
::::: Looking at the bottom of a tube, with keyway toward you, pin #1 is first one on the left. Pin #3 is plate, #4 screen. These will be positive. Pin #5 is grid and should be negative 20 volts in relation to pin #8, cathode. Think you have the right voltages just numbering doesn't seem right.
:::::
::::: If grid 1, pin #5, isn't negative enough a tube will operate too hot. Metal 6F6 tubes run very hot, hotter than 6F6G's. They will burn your hand.
:::::
::::: Since your schematic calls out 6F6G does pin #1 of your tube sockets connect to chassis? This pin isn't used on a 6F6G but is connected to the shield on 6F6 tubes. Without pin #1 being grounded your radio could go into oscillation.
:::::
::::: Output tubes should be fairly well matched. Either one pulled should drop volume a similar amount.
:::::
::::: If you don't have other 6F6 tubes to exchange try a pair of 6K6GT or 6V6GT tubes.
:::::
:::::Norm
:::::
:::::::I have now tried to see which tube is working. The 6f6 at the end of the chassis can be taken out with little drop in volume, the one to the right of it is giving most of the output. Is this where matching of the tubes comes into play since they are different brands? I have replaced the plate .003 caps. Both tubes still get sizzling hot.
::::::::Hello, I found out that the bakelite block has the number 8318 dg on it which according to philco cap info, pins 1 and 3 contain a .03 cap. This is the 1st audio tube coupler cap to the 6f6's I removed the .03 cap someone soldered on the outside to pins 1 and 2, and put it inside soldered to pins 1 and 3. Now both tubes get sizzling hot, however I have louder volume with a constant whistle when the volume is a quarter up. I did notice that the schematic showes the tube numbers as 6f6G, which I think means glass type. I have 6f6 in the metal can type. I am not sure if this makes a difference or not. the tube voltages are pin 1 and 2=0v. pin 3=292/300 pin 4=0v pin 5=303v/306v. pin 6=275v/295v and pin 7=-21v/-21v
::::::::Hi,
::::::::The tester applies only a low voltage, And right off of the plate, you should be seeing a significant voltage.
::::::::
::::::::That particular cap, you should be able to remove from the circuit without a problem for purposes of testing that section. You might try isolating troubles in that way.
::::::::
::::::::The resistance you measured on the field coil should be about right if it were about 700 ohms. If it is almost 700 thousand ohms, then there is an issue with the field coil.
::::::::
::::::::If you have a pair of 6F6's, and only one is getting very hot, that .003 cap may be shorting out at the higher plate voltage potential, and only one tube is then driving the speaker, or there may be a shorted lead, or wire, and these are not always that noticable.
::::::::
::::::::If you only have one 6F6 as a single ended driver, the tube will get hot, 150 degrees C is not out of expectation.
::::::::
::::::::It is possible that the output transformer is shorted on one side (if two tube push-pull), or if it had been replaced, it may not be the correct one for the plate impedance.
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
:::::::::::Hello, I checked and it is only one tube that sizzles when I touch it(6f6). The field coil measures 655k ohms. The caps measure .003 from the plate to ground, but I havn't removed the original cap in the block yet. If these caps were shorting or failing in some other way, wouldn't it show up on the multimeter cap test?
::::::::::Hi,
::::::::::The 6F6's do tend to operate rather warm, but you may be seeing other issues in the radio. If the speaker is unplugged, no current is flowing through the tube.
::::::::::
::::::::::The Philco does not use cathode resistors on this set, but they could be added if the tubes are hot enough to cook the paint. (about 27 ohms, 2watts- This only after everything else has been addressed to correct the problem.
::::::::::I would check the resistor that is between the second grid (pin 4) between the two tubes. If there is a problem with the condenser that ties to pin 3 of one of the tubes, it will also cause limited volume, and some excessive heating of one tube, and the output trasnformer/field winding of the speaker. It is supposed to be a .003 mfd, and it would be prudent to remove it from the bakelite block, and slip a new replacement inside, or remove any connection made to that terminal to isolate it. Replace the one soldered outside too, or get rid of it if you put a replacement inside of the bakelite block.
::::::::::
::::::::::I am aking an assumption that you have a Philco based on the reference to a bakelite block; Chuck Scwark has good Philco references on his site:
::::::::::http://members.aol.com/caschwark
::::::::::
::::::::::The schematic for a Philco 38-4 is here on Nostalgia Air:
::::::::::http://ww3.nostalgiaair.org/schematics/PHL/PHL_8-61.gif
::::::::::
::::::::::
:::::::::::hello, I have a 38-c4 radio that has average volume output at best. The 6f6 tubes get VERY HOT (HOT ENOUGH THAT WHEN LICK MY FINGER AND TOUCH ONE, IT SIZZLES!) With the speaker unplugged the tubes seem to be the normal tube temperature. does this mean the speaker or output trans is shorted? I did notice that external capacitors were soldered onto some of the bakelite cap blocks.(they didnt remove the caps inside the blocks) I cant seem to find the values for the block that has the number 8378 SU
Looking at the schematic again, I would look at the caps that are #58 and #59 on the schematic, both are .003mfd. A bad solder joint, or a failing cap itself could contribute to the difficulties if alignment of the IF's does not eliminate the noise, and if there is one that is excessively leaky it will also reduce output signal.
One thing though, Tube circuits do pick up stray RF signals very well, so check to see if the noise is external to the Philco first So if you are close to a flourescent light fixture, computer, monitor, or a TV(Philips/Magnavox radiate well beyond 6 feet), variable speed ceiling fans, Sodium vapor/mercury outdoor lamp, all of these can create interference noise. Sometimes an AM radio (the cheaper the better) can pick the interference up and you just go through and eliminate them one at a time.
::Hello, If the 6f6 tube near the edge or side of the chassis doesnt hardly output anything, what good is it to have this tube installed in the radio? 95% of the output is coming from the 6f6 that has the coupling cap from the 6k5 tube going to its control grid or grid closest to the heater
::
::Hi Sean
::
:: Just looked at the circuit. You won't have equal volume pulling one output tube at a time. This is one of those Philco circuits where a signal is taken off the screen of one tube to feed input of the second.
::
:: If you have proper voltages on 6F6's they will be very hot but this is expected.
::
:: Do you hear a loud hum touching the top cap of your 6K5?
::
:: Try peaking up IF transformer adjustments.
::
::Norm
::
::
::
::::Hello, The tubes themselves drop about the same volume when used in the socket closer to the center of the chassis, but when either tube is used in the socket closer to the side of the chassis, there isnt much output.
::::
::::Hi Sean
::::
:::: Looking at the bottom of a tube, with keyway toward you, pin #1 is first one on the left. Pin #3 is plate, #4 screen. These will be positive. Pin #5 is grid and should be negative 20 volts in relation to pin #8, cathode. Think you have the right voltages just numbering doesn't seem right.
::::
:::: If grid 1, pin #5, isn't negative enough a tube will operate too hot. Metal 6F6 tubes run very hot, hotter than 6F6G's. They will burn your hand.
::::
:::: Since your schematic calls out 6F6G does pin #1 of your tube sockets connect to chassis? This pin isn't used on a 6F6G but is connected to the shield on 6F6 tubes. Without pin #1 being grounded your radio could go into oscillation.
::::
:::: Output tubes should be fairly well matched. Either one pulled should drop volume a similar amount.
::::
:::: If you don't have other 6F6 tubes to exchange try a pair of 6K6GT or 6V6GT tubes.
::::
::::Norm
::::
::::::I have now tried to see which tube is working. The 6f6 at the end of the chassis can be taken out with little drop in volume, the one to the right of it is giving most of the output. Is this where matching of the tubes comes into play since they are different brands? I have replaced the plate .003 caps. Both tubes still get sizzling hot.
:::::::Hello, I found out that the bakelite block has the number 8318 dg on it which according to philco cap info, pins 1 and 3 contain a .03 cap. This is the 1st audio tube coupler cap to the 6f6's I removed the .03 cap someone soldered on the outside to pins 1 and 2, and put it inside soldered to pins 1 and 3. Now both tubes get sizzling hot, however I have louder volume with a constant whistle when the volume is a quarter up. I did notice that the schematic showes the tube numbers as 6f6G, which I think means glass type. I have 6f6 in the metal can type. I am not sure if this makes a difference or not. the tube voltages are pin 1 and 2=0v. pin 3=292/300 pin 4=0v pin 5=303v/306v. pin 6=275v/295v and pin 7=-21v/-21v
:::::::Hi,
:::::::The tester applies only a low voltage, And right off of the plate, you should be seeing a significant voltage.
:::::::
:::::::That particular cap, you should be able to remove from the circuit without a problem for purposes of testing that section. You might try isolating troubles in that way.
:::::::
:::::::The resistance you measured on the field coil should be about right if it were about 700 ohms. If it is almost 700 thousand ohms, then there is an issue with the field coil.
:::::::
:::::::If you have a pair of 6F6's, and only one is getting very hot, that .003 cap may be shorting out at the higher plate voltage potential, and only one tube is then driving the speaker, or there may be a shorted lead, or wire, and these are not always that noticable.
:::::::
:::::::If you only have one 6F6 as a single ended driver, the tube will get hot, 150 degrees C is not out of expectation.
:::::::
:::::::It is possible that the output transformer is shorted on one side (if two tube push-pull), or if it had been replaced, it may not be the correct one for the plate impedance.
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::
:::::::
::::::::::Hello, I checked and it is only one tube that sizzles when I touch it(6f6). The field coil measures 655k ohms. The caps measure .003 from the plate to ground, but I havn't removed the original cap in the block yet. If these caps were shorting or failing in some other way, wouldn't it show up on the multimeter cap test?
:::::::::Hi,
:::::::::The 6F6's do tend to operate rather warm, but you may be seeing other issues in the radio. If the speaker is unplugged, no current is flowing through the tube.
:::::::::
:::::::::The Philco does not use cathode resistors on this set, but they could be added if the tubes are hot enough to cook the paint. (about 27 ohms, 2watts- This only after everything else has been addressed to correct the problem.
:::::::::I would check the resistor that is between the second grid (pin 4) between the two tubes. If there is a problem with the condenser that ties to pin 3 of one of the tubes, it will also cause limited volume, and some excessive heating of one tube, and the output trasnformer/field winding of the speaker. It is supposed to be a .003 mfd, and it would be prudent to remove it from the bakelite block, and slip a new replacement inside, or remove any connection made to that terminal to isolate it. Replace the one soldered outside too, or get rid of it if you put a replacement inside of the bakelite block.
:::::::::
:::::::::I am aking an assumption that you have a Philco based on the reference to a bakelite block; Chuck Scwark has good Philco references on his site:
:::::::::http://members.aol.com/caschwark
:::::::::
:::::::::The schematic for a Philco 38-4 is here on Nostalgia Air:
:::::::::http://ww3.nostalgiaair.org/schematics/PHL/PHL_8-61.gif
:::::::::
:::::::::
::::::::::hello, I have a 38-c4 radio that has average volume output at best. The 6f6 tubes get VERY HOT (HOT ENOUGH THAT WHEN LICK MY FINGER AND TOUCH ONE, IT SIZZLES!) With the speaker unplugged the tubes seem to be the normal tube temperature. does this mean the speaker or output trans is shorted? I did notice that external capacitors were soldered onto some of the bakelite cap blocks.(they didnt remove the caps inside the blocks) I cant seem to find the values for the block that has the number 8378 SU
:The method that Philco used was a method to increase current flow in the circuit. TUbes were, and often are cheaper than transformers and related circuit components, and this was one method of increasing current without adding parts.
:
:Looking at the schematic again, I would look at the caps that are #58 and #59 on the schematic, both are .003mfd. A bad solder joint, or a failing cap itself could contribute to the difficulties if alignment of the IF's does not eliminate the noise, and if there is one that is excessively leaky it will also reduce output signal.
:
:One thing though, Tube circuits do pick up stray RF signals very well, so check to see if the noise is external to the Philco first So if you are close to a flourescent light fixture, computer, monitor, or a TV(Philips/Magnavox radiate well beyond 6 feet), variable speed ceiling fans, Sodium vapor/mercury outdoor lamp, all of these can create interference noise. Sometimes an AM radio (the cheaper the better) can pick the interference up and you just go through and eliminate them one at a time.
:
:
:
:::Hello, If the 6f6 tube near the edge or side of the chassis doesnt hardly output anything, what good is it to have this tube installed in the radio? 95% of the output is coming from the 6f6 that has the coupling cap from the 6k5 tube going to its control grid or grid closest to the heater
:::
:::Hi Sean
:::
::: Just looked at the circuit. You won't have equal volume pulling one output tube at a time. This is one of those Philco circuits where a signal is taken off the screen of one tube to feed input of the second.
:::
::: If you have proper voltages on 6F6's they will be very hot but this is expected.
:::
::: Do you hear a loud hum touching the top cap of your 6K5?
:::
::: Try peaking up IF transformer adjustments.
:::
:::Norm
:::
:::
:::
:::::Hello, The tubes themselves drop about the same volume when used in the socket closer to the center of the chassis, but when either tube is used in the socket closer to the side of the chassis, there isnt much output.
:::::
:::::Hi Sean
:::::
::::: Looking at the bottom of a tube, with keyway toward you, pin #1 is first one on the left. Pin #3 is plate, #4 screen. These will be positive. Pin #5 is grid and should be negative 20 volts in relation to pin #8, cathode. Think you have the right voltages just numbering doesn't seem right.
:::::
::::: If grid 1, pin #5, isn't negative enough a tube will operate too hot. Metal 6F6 tubes run very hot, hotter than 6F6G's. They will burn your hand.
:::::
::::: Since your schematic calls out 6F6G does pin #1 of your tube sockets connect to chassis? This pin isn't used on a 6F6G but is connected to the shield on 6F6 tubes. Without pin #1 being grounded your radio could go into oscillation.
:::::
::::: Output tubes should be fairly well matched. Either one pulled should drop volume a similar amount.
:::::
::::: If you don't have other 6F6 tubes to exchange try a pair of 6K6GT or 6V6GT tubes.
:::::
:::::Norm
:::::
:::::::I have now tried to see which tube is working. The 6f6 at the end of the chassis can be taken out with little drop in volume, the one to the right of it is giving most of the output. Is this where matching of the tubes comes into play since they are different brands? I have replaced the plate .003 caps. Both tubes still get sizzling hot.
::::::::Hello, I found out that the bakelite block has the number 8318 dg on it which according to philco cap info, pins 1 and 3 contain a .03 cap. This is the 1st audio tube coupler cap to the 6f6's I removed the .03 cap someone soldered on the outside to pins 1 and 2, and put it inside soldered to pins 1 and 3. Now both tubes get sizzling hot, however I have louder volume with a constant whistle when the volume is a quarter up. I did notice that the schematic showes the tube numbers as 6f6G, which I think means glass type. I have 6f6 in the metal can type. I am not sure if this makes a difference or not. the tube voltages are pin 1 and 2=0v. pin 3=292/300 pin 4=0v pin 5=303v/306v. pin 6=275v/295v and pin 7=-21v/-21v
::::::::Hi,
::::::::The tester applies only a low voltage, And right off of the plate, you should be seeing a significant voltage.
::::::::
::::::::That particular cap, you should be able to remove from the circuit without a problem for purposes of testing that section. You might try isolating troubles in that way.
::::::::
::::::::The resistance you measured on the field coil should be about right if it were about 700 ohms. If it is almost 700 thousand ohms, then there is an issue with the field coil.
::::::::
::::::::If you have a pair of 6F6's, and only one is getting very hot, that .003 cap may be shorting out at the higher plate voltage potential, and only one tube is then driving the speaker, or there may be a shorted lead, or wire, and these are not always that noticable.
::::::::
::::::::If you only have one 6F6 as a single ended driver, the tube will get hot, 150 degrees C is not out of expectation.
::::::::
::::::::It is possible that the output transformer is shorted on one side (if two tube push-pull), or if it had been replaced, it may not be the correct one for the plate impedance.
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::
:::::::::::Hello, I checked and it is only one tube that sizzles when I touch it(6f6). The field coil measures 655k ohms. The caps measure .003 from the plate to ground, but I havn't removed the original cap in the block yet. If these caps were shorting or failing in some other way, wouldn't it show up on the multimeter cap test?
::::::::::Hi,
::::::::::The 6F6's do tend to operate rather warm, but you may be seeing other issues in the radio. If the speaker is unplugged, no current is flowing through the tube.
::::::::::
::::::::::The Philco does not use cathode resistors on this set, but they could be added if the tubes are hot enough to cook the paint. (about 27 ohms, 2watts- This only after everything else has been addressed to correct the problem.
::::::::::I would check the resistor that is between the second grid (pin 4) between the two tubes. If there is a problem with the condenser that ties to pin 3 of one of the tubes, it will also cause limited volume, and some excessive heating of one tube, and the output trasnformer/field winding of the speaker. It is supposed to be a .003 mfd, and it would be prudent to remove it from the bakelite block, and slip a new replacement inside, or remove any connection made to that terminal to isolate it. Replace the one soldered outside too, or get rid of it if you put a replacement inside of the bakelite block.
::::::::::
::::::::::I am aking an assumption that you have a Philco based on the reference to a bakelite block; Chuck Scwark has good Philco references on his site:
::::::::::http://members.aol.com/caschwark
::::::::::
::::::::::The schematic for a Philco 38-4 is here on Nostalgia Air:
::::::::::http://ww3.nostalgiaair.org/schematics/PHL/PHL_8-61.gif
::::::::::
::::::::::
:::::::::::hello, I have a 38-c4 radio that has average volume output at best. The 6f6 tubes get VERY HOT (HOT ENOUGH THAT WHEN LICK MY FINGER AND TOUCH ONE, IT SIZZLES!) With the speaker unplugged the tubes seem to be the normal tube temperature. does this mean the speaker or output trans is shorted? I did notice that external capacitors were soldered onto some of the bakelite cap blocks.(they didnt remove the caps inside the blocks) I cant seem to find the values for the block that has the number 8378 SU
One thing to check before grounding that pin number 1, is to compare the schematic to what you have, and make sure that voltage you saw on that pin previously was not because pin1 on the socket was used as a circuit tie point- sometimes they are,which will explain the voltage you saw clearly. All of this discussion surrounding pin1 is academic if you have grounded those pins already with no adverse affects on performance.
:Hello, I see the first tube feeding the second 6f6, but then how would I determine if the second fed 6f6 tube circuit and tube is working properly? I know the tubes themselves work ok since I tried them both in the socket that gives 95% output.
::
:
::The method that Philco used was a method to increase current flow in the circuit. TUbes were, and often are cheaper than transformers and related circuit components, and this was one method of increasing current without adding parts.
::
::Looking at the schematic again, I would look at the caps that are #58 and #59 on the schematic, both are .003mfd. A bad solder joint, or a failing cap itself could contribute to the difficulties if alignment of the IF's does not eliminate the noise, and if there is one that is excessively leaky it will also reduce output signal.
::
::One thing though, Tube circuits do pick up stray RF signals very well, so check to see if the noise is external to the Philco first So if you are close to a flourescent light fixture, computer, monitor, or a TV(Philips/Magnavox radiate well beyond 6 feet), variable speed ceiling fans, Sodium vapor/mercury outdoor lamp, all of these can create interference noise. Sometimes an AM radio (the cheaper the better) can pick the interference up and you just go through and eliminate them one at a time.
::
::
::
::::Hello, If the 6f6 tube near the edge or side of the chassis doesnt hardly output anything, what good is it to have this tube installed in the radio? 95% of the output is coming from the 6f6 that has the coupling cap from the 6k5 tube going to its control grid or grid closest to the heater
::::
::::Hi Sean
::::
:::: Just looked at the circuit. You won't have equal volume pulling one output tube at a time. This is one of those Philco circuits where a signal is taken off the screen of one tube to feed input of the second.
::::
:::: If you have proper voltages on 6F6's they will be very hot but this is expected.
::::
:::: Do you hear a loud hum touching the top cap of your 6K5?
::::
:::: Try peaking up IF transformer adjustments.
::::
::::Norm
::::
::::
::::
::::::Hello, The tubes themselves drop about the same volume when used in the socket closer to the center of the chassis, but when either tube is used in the socket closer to the side of the chassis, there isnt much output.
::::::
::::::Hi Sean
::::::
:::::: Looking at the bottom of a tube, with keyway toward you, pin #1 is first one on the left. Pin #3 is plate, #4 screen. These will be positive. Pin #5 is grid and should be negative 20 volts in relation to pin #8, cathode. Think you have the right voltages just numbering doesn't seem right.
::::::
:::::: If grid 1, pin #5, isn't negative enough a tube will operate too hot. Metal 6F6 tubes run very hot, hotter than 6F6G's. They will burn your hand.
::::::
:::::: Since your schematic calls out 6F6G does pin #1 of your tube sockets connect to chassis? This pin isn't used on a 6F6G but is connected to the shield on 6F6 tubes. Without pin #1 being grounded your radio could go into oscillation.
::::::
:::::: Output tubes should be fairly well matched. Either one pulled should drop volume a similar amount.
::::::
:::::: If you don't have other 6F6 tubes to exchange try a pair of 6K6GT or 6V6GT tubes.
::::::
::::::Norm
::::::
::::::::I have now tried to see which tube is working. The 6f6 at the end of the chassis can be taken out with little drop in volume, the one to the right of it is giving most of the output. Is this where matching of the tubes comes into play since they are different brands? I have replaced the plate .003 caps. Both tubes still get sizzling hot.
:::::::::Hello, I found out that the bakelite block has the number 8318 dg on it which according to philco cap info, pins 1 and 3 contain a .03 cap. This is the 1st audio tube coupler cap to the 6f6's I removed the .03 cap someone soldered on the outside to pins 1 and 2, and put it inside soldered to pins 1 and 3. Now both tubes get sizzling hot, however I have louder volume with a constant whistle when the volume is a quarter up. I did notice that the schematic showes the tube numbers as 6f6G, which I think means glass type. I have 6f6 in the metal can type. I am not sure if this makes a difference or not. the tube voltages are pin 1 and 2=0v. pin 3=292/300 pin 4=0v pin 5=303v/306v. pin 6=275v/295v and pin 7=-21v/-21v
:::::::::Hi,
:::::::::The tester applies only a low voltage, And right off of the plate, you should be seeing a significant voltage.
:::::::::
:::::::::That particular cap, you should be able to remove from the circuit without a problem for purposes of testing that section. You might try isolating troubles in that way.
:::::::::
:::::::::The resistance you measured on the field coil should be about right if it were about 700 ohms. If it is almost 700 thousand ohms, then there is an issue with the field coil.
:::::::::
:::::::::If you have a pair of 6F6's, and only one is getting very hot, that .003 cap may be shorting out at the higher plate voltage potential, and only one tube is then driving the speaker, or there may be a shorted lead, or wire, and these are not always that noticable.
:::::::::
:::::::::If you only have one 6F6 as a single ended driver, the tube will get hot, 150 degrees C is not out of expectation.
:::::::::
:::::::::It is possible that the output transformer is shorted on one side (if two tube push-pull), or if it had been replaced, it may not be the correct one for the plate impedance.
:::::::::
:::::::::
:::::::::
:::::::::
:::::::::
:::::::::
:::::::::
::::::::::::Hello, I checked and it is only one tube that sizzles when I touch it(6f6). The field coil measures 655k ohms. The caps measure .003 from the plate to ground, but I havn't removed the original cap in the block yet. If these caps were shorting or failing in some other way, wouldn't it show up on the multimeter cap test?
:::::::::::Hi,
:::::::::::The 6F6's do tend to operate rather warm, but you may be seeing other issues in the radio. If the speaker is unplugged, no current is flowing through the tube.
:::::::::::
:::::::::::The Philco does not use cathode resistors on this set, but they could be added if the tubes are hot enough to cook the paint. (about 27 ohms, 2watts- This only after everything else has been addressed to correct the problem.
:::::::::::I would check the resistor that is between the second grid (pin 4) between the two tubes. If there is a problem with the condenser that ties to pin 3 of one of the tubes, it will also cause limited volume, and some excessive heating of one tube, and the output trasnformer/field winding of the speaker. It is supposed to be a .003 mfd, and it would be prudent to remove it from the bakelite block, and slip a new replacement inside, or remove any connection made to that terminal to isolate it. Replace the one soldered outside too, or get rid of it if you put a replacement inside of the bakelite block.
:::::::::::
:::::::::::I am aking an assumption that you have a Philco based on the reference to a bakelite block; Chuck Scwark has good Philco references on his site:
:::::::::::http://members.aol.com/caschwark
:::::::::::
:::::::::::The schematic for a Philco 38-4 is here on Nostalgia Air:
:::::::::::http://ww3.nostalgiaair.org/schematics/PHL/PHL_8-61.gif
:::::::::::
:::::::::::
::::::::::::hello, I have a 38-c4 radio that has average volume output at best. The 6f6 tubes get VERY HOT (HOT ENOUGH THAT WHEN LICK MY FINGER AND TOUCH ONE, IT SIZZLES!) With the speaker unplugged the tubes seem to be the normal tube temperature. does this mean the speaker or output trans is shorted? I did notice that external capacitors were soldered onto some of the bakelite cap blocks.(they didnt remove the caps inside the blocks) I cant seem to find the values for the block that has the number 8378 SU