Hello Everyone,
I just bought a beautiful, looks fully restored Philco Model 48-482 Radio. This thing works great on all the bands. SW picks up stations from all over the globe. Problem is after about an hour there is no sound, the dial light is on but you cannot hear anything. The radio will work again after it cools off. I am a newbe and would appreciate any help offered. I have the trouble shooting guide and the schematics but I don't have a clue on where to start.
Thanks for any input.
Terry N.

Hi, Terry. Here's your schematic: http://www.nostalgiaair.org/PagesByModel/637/M0013637.pdf This is an AM/FM set and not a good one to tear into if it's your first.

A bad tube might do this, but it shouldn't take an hour for all the tubes to reach their maximum temperature. So, I'm suspecting that something else may be the problem.

If all the AM and FM bands go dead at once, then I would suspect something in the audio circuit or power supply. The audio circuit is Section 2 on the schematic, and involves the 6SQ7 and the 6V6.

When the set goes silent, do all the tubes stay lighted? Pay particular attention to the 6SQ7 and the 6V6.

You can pull the tubes one at a time and reinsert them. That might clear up a bad connection in one of the tube sockets.

The next step would be to check the voltages in the audio section while the set is dead. This can be done from the top of the chassis, checking voltages in the audio tube sockets. If this seems too complicated, then you'll probably need some help.

I doubt there is anything seriously wrong with the set.
Doug

:Hello Everyone,
:I just bought a beautiful, looks fully restored Philco Model 48-482 Radio. This thing works great on all the bands. SW picks up stations from all over the globe. Problem is after about an hour there is no sound, the dial light is on but you cannot hear anything. The radio will work again after it cools off. I am a newbe and would appreciate any help offered. I have the trouble shooting guide and the schematics but I don't have a clue on where to start.
:Thanks for any input.
:Terry N.

:Hi, Terry. Here's your schematic: http://www.nostalgiaair.org/PagesByModel/637/M0013637.pdf This is an AM/FM set and not a good one to tear into if it's your first.
:
:A bad tube might do this, but it shouldn't take an hour for all the tubes to reach their maximum temperature. So, I'm suspecting that something else may be the problem.
:
:If all the AM and FM bands go dead at once, then I would suspect something in the audio circuit or power supply. The audio circuit is Section 2 on the schematic, and involves the 6SQ7 and the 6V6.
:
:When the set goes silent, do all the tubes stay lighted? Pay particular attention to the 6SQ7 and the 6V6.
:
:You can pull the tubes one at a time and reinsert them. That might clear up a bad connection in one of the tube sockets.
:
:The next step would be to check the voltages in the audio section while the set is dead. This can be done from the top of the chassis, checking voltages in the audio tube sockets. If this seems too complicated, then you'll probably need some help.
:
:I doubt there is anything seriously wrong with the set.
:Doug
:
::Hello Everyone,
::I just bought a beautiful, looks fully restored Philco Model 48-482 Radio. This thing works great on all the bands. SW picks up stations from all over the globe. Problem is after about an hour there is no sound, the dial light is on but you cannot hear anything. The radio will work again after it cools off. I am a newbe and would appreciate any help offered. I have the trouble shooting guide and the schematics but I don't have a clue on where to start.
::Thanks for any input.
::Terry N.

On the schematic, I see a J200, test point "D" that connects directly to the volume control. If this is a phono input, it is a good place to check the audio output section with a signal generator appliec to whatever "J200". If you don't have an audio generator, use the poor man's model, a battery operated transistor radio's earphone jack. If J200 is dead when the rest of the radio is, you have just placed the problem squarely in the audio section, the easiest of all to repair, IMHO.
Lewis

Hi

It could be caused by a tube but usually doesn't take an hour. As a tube heats metal inside expands. Does it pop and quit or slowly fade out? If you hear a pop cathode connection inside a tube probably opened. This is quite common. If the signal slowly fades out a filament opened.

Do you have a tube tester? If so test 6 volt tubes with 7.5 on the filament. This should make the problem show up sooner.

Testing, like other suggested, will help locate the stage. Just touching the phono input should cause hum if you don't have a signal generator.

Norm

::Hi, Terry. Here's your schematic: http://www.nostalgiaair.org/PagesByModel/637/M0013637.pdf This is an AM/FM set and not a good one to tear into if it's your first.
::
::A bad tube might do this, but it shouldn't take an hour for all the tubes to reach their maximum temperature. So, I'm suspecting that something else may be the problem.
::
::If all the AM and FM bands go dead at once, then I would suspect something in the audio circuit or power supply. The audio circuit is Section 2 on the schematic, and involves the 6SQ7 and the 6V6.
::
::When the set goes silent, do all the tubes stay lighted? Pay particular attention to the 6SQ7 and the 6V6.
::
::You can pull the tubes one at a time and reinsert them. That might clear up a bad connection in one of the tube sockets.
::
::The next step would be to check the voltages in the audio section while the set is dead. This can be done from the top of the chassis, checking voltages in the audio tube sockets. If this seems too complicated, then you'll probably need some help.
::
::I doubt there is anything seriously wrong with the set.
::Doug
::
:::Hello Everyone,
:::I just bought a beautiful, looks fully restored Philco Model 48-482 Radio. This thing works great on all the bands. SW picks up stations from all over the globe. Problem is after about an hour there is no sound, the dial light is on but you cannot hear anything. The radio will work again after it cools off. I am a newbe and would appreciate any help offered. I have the trouble shooting guide and the schematics but I don't have a clue on where to start.
:::Thanks for any input.
:::Terry N.
:
:On the schematic, I see a J200, test point "D" that connects directly to the volume control. If this is a phono input, it is a good place to check the audio output section with a signal generator appliec to whatever "J200". If you don't have an audio generator, use the poor man's model, a battery operated transistor radio's earphone jack. If J200 is dead when the rest of the radio is, you have just placed the problem squarely in the audio section, the easiest of all to repair, IMHO.
:Lewis
:

Hi Terry,
I have been into a fair amount of AM/FM sets and tend to look for Silver Mica Disease often. Sets of this vintage are prone to it, although you set may be less so.
First, and I think I am repeating what was asked before, when it cuts out is it all bands or FM only.
You may try to isolate it with freeze mist, available from Radio shack. If it only happens on FM, direct your spay to the IF can that does the discrimination, the one that feeds the FM1000 tube. If cooling the IF can brings it back, this indicates that that is where the problem is. If the problem is on all bands, you will need to try spraying all IF cans. Do it in a ventalated space, too. Cooling the can that has the bad silver mica capacitor should cause reception to resume.
Once the bad can is found the first step would be to tighten the MECHANICAL adjustment (not the frequency adjustment). What is likely happening is that after the radio warms the capacitor inside is loosing conneciton with the rest of its circuit. Tightening sould re-establish the connection.
If htat doesn't do it you may need to rebuild the IF, something to be avoided if possible.

By the way, I had a cut out problem on an AM/SW set a while ago. That took 20 minutes and turned out to be a tube. As mentioned before, 1 hour is a little long for it to be a tube. That is one reason I am suspecting a poor connetion in an IF can.

Best Regards,

Bill Grimm

All bands are affected the same. Thanks for the replies.
Terry N.
:Hi Terry,
: I have been into a fair amount of AM/FM sets and tend to look for Silver Mica Disease often. Sets of this vintage are prone to it, although you set may be less so.
: First, and I think I am repeating what was asked before, when it cuts out is it all bands or FM only.
: You may try to isolate it with freeze mist, available from Radio shack. If it only happens on FM, direct your spay to the IF can that does the discrimination, the one that feeds the FM1000 tube. If cooling the IF can brings it back, this indicates that that is where the problem is. If the problem is on all bands, you will need to try spraying all IF cans. Do it in a ventalated space, too. Cooling the can that has the bad silver mica capacitor should cause reception to resume.
: Once the bad can is found the first step would be to tighten the MECHANICAL adjustment (not the frequency adjustment). What is likely happening is that after the radio warms the capacitor inside is loosing conneciton with the rest of its circuit. Tightening sould re-establish the connection.
: If htat doesn't do it you may need to rebuild the IF, something to be avoided if possible.
:
: By the way, I had a cut out problem on an AM/SW set a while ago. That took 20 minutes and turned out to be a tube. As mentioned before, 1 hour is a little long for it to be a tube. That is one reason I am suspecting a poor connetion in an IF can.
:
:Best Regards,
:
:Bill Grimm

:All bands are affected the same. Thanks for the replies.
:Terry N.
::Hi Terry,
:: I have been into a fair amount of AM/FM sets and tend to look for Silver Mica Disease often. Sets of this vintage are prone to it, although you set may be less so.
:: First, and I think I am repeating what was asked before, when it cuts out is it all bands or FM only.
:: You may try to isolate it with freeze mist, available from Radio shack. If it only happens on FM, direct your spay to the IF can that does the discrimination, the one that feeds the FM1000 tube. If cooling the IF can brings it back, this indicates that that is where the problem is. If the problem is on all bands, you will need to try spraying all IF cans. Do it in a ventalated space, too. Cooling the can that has the bad silver mica capacitor should cause reception to resume.
:: Once the bad can is found the first step would be to tighten the MECHANICAL adjustment (not the frequency adjustment). What is likely happening is that after the radio warms the capacitor inside is loosing conneciton with the rest of its circuit. Tightening sould re-establish the connection.
:: If htat doesn't do it you may need to rebuild the IF, something to be avoided if possible.
::
:: By the way, I had a cut out problem on an AM/SW set a while ago. That took 20 minutes and turned out to be a tube. As mentioned before, 1 hour is a little long for it to be a tube. That is one reason I am suspecting a poor connetion in an IF can.
::
::Best Regards,
::
::Bill Grimm

Hi Terry,
A slow fade out is consistant with silver mica and an intermittant filament in a tube.
Your radio has fewer silver mica capacitors in the IF transformers than Zeniths of the same vintage. I agree with the other postings to focus on the tubes now. Look at the IF tubes also in your search, as they seem to be used on AM, FM, and Short Wave. The 5Y3GT could be the problem, too. Of course that is one you will be able to see.
If you come up dry with tubes keep the IFs in mind as a fault source.

Best Regards,

Bill Grimm

Bill, this is a 1948 model, which probably wouldn't have those little 1"-square IF xfmrs? It seems like those were most prone to the silver mica disease? I'm not familiar with this set, though.

If both the AM and FM bands conk out, that would steer me away from suspecting IF xfmrs.
Doug

:Hi Terry,
: I have been into a fair amount of AM/FM sets and tend to look for Silver Mica Disease often. Sets of this vintage are prone to it, although you set may be less so.
: First, and I think I am repeating what was asked before, when it cuts out is it all bands or FM only.
: You may try to isolate it with freeze mist, available from Radio shack. If it only happens on FM, direct your spay to the IF can that does the discrimination, the one that feeds the FM1000 tube. If cooling the IF can brings it back, this indicates that that is where the problem is. If the problem is on all bands, you will need to try spraying all IF cans. Do it in a ventalated space, too. Cooling the can that has the bad silver mica capacitor should cause reception to resume.
: Once the bad can is found the first step would be to tighten the MECHANICAL adjustment (not the frequency adjustment). What is likely happening is that after the radio warms the capacitor inside is loosing conneciton with the rest of its circuit. Tightening sould re-establish the connection.
: If htat doesn't do it you may need to rebuild the IF, something to be avoided if possible.
:
: By the way, I had a cut out problem on an AM/SW set a while ago. That took 20 minutes and turned out to be a tube. As mentioned before, 1 hour is a little long for it to be a tube. That is one reason I am suspecting a poor connetion in an IF can.
:
:Best Regards,
:
:Bill Grimm

The radio fades out slowly thank for the replies.
Terry N.
:Hi
:
: It could be caused by a tube but usually doesn't take an hour. As a tube heats metal inside expands. Does it pop and quit or slowly fade out? If you hear a pop cathode connection inside a tube probably opened. This is quite common. If the signal slowly fades out a filament opened.
:
: Do you have a tube tester? If so test 6 volt tubes with 7.5 on the filament. This should make the problem show up sooner.
:
: Testing, like other suggested, will help locate the stage. Just touching the phono input should cause hum if you don't have a signal generator.
:
:Norm
:
:
:::Hi, Terry. Here's your schematic: http://www.nostalgiaair.org/PagesByModel/637/M0013637.pdf This is an AM/FM set and not a good one to tear into if it's your first.
:::
:::A bad tube might do this, but it shouldn't take an hour for all the tubes to reach their maximum temperature. So, I'm suspecting that something else may be the problem.
:::
:::If all the AM and FM bands go dead at once, then I would suspect something in the audio circuit or power supply. The audio circuit is Section 2 on the schematic, and involves the 6SQ7 and the 6V6.
:::
:::When the set goes silent, do all the tubes stay lighted? Pay particular attention to the 6SQ7 and the 6V6.
:::
:::You can pull the tubes one at a time and reinsert them. That might clear up a bad connection in one of the tube sockets.
:::
:::The next step would be to check the voltages in the audio section while the set is dead. This can be done from the top of the chassis, checking voltages in the audio tube sockets. If this seems too complicated, then you'll probably need some help.
:::
:::I doubt there is anything seriously wrong with the set.
:::Doug
:::
::::Hello Everyone,
::::I just bought a beautiful, looks fully restored Philco Model 48-482 Radio. This thing works great on all the bands. SW picks up stations from all over the globe. Problem is after about an hour there is no sound, the dial light is on but you cannot hear anything. The radio will work again after it cools off. I am a newbe and would appreciate any help offered. I have the trouble shooting guide and the schematics but I don't have a clue on where to start.
::::Thanks for any input.
::::Terry N.
::
::On the schematic, I see a J200, test point "D" that connects directly to the volume control. If this is a phono input, it is a good place to check the audio output section with a signal generator appliec to whatever "J200". If you don't have an audio generator, use the poor man's model, a battery operated transistor radio's earphone jack. If J200 is dead when the rest of the radio is, you have just placed the problem squarely in the audio section, the easiest of all to repair, IMHO.
::Lewis
::

Terry: OK, now look to see if one tube becomes unlit when the radio conks out. Before it conks out, look at the tubes and see how they look, filament-glow-wise.

Try to inspect all the tubes, but with particular attention to the two audio tubes, 6SQ7 and 6V6.

Since all bands, AM and FM, are affected I would bet that the problem is in the audio section. Maybe in the power supply, but seems less probable to me.
Doug

:The radio fades out slowly thank for the replies.
:Terry N.

::Hi
:: It could be caused by a tube but usually doesn't take an hour. As a tube heats metal inside expands. Does it pop and quit or slowly fade out? If you hear a pop cathode connection inside a tube probably opened. This is quite common. If the signal slowly fades out a filament opened.
::

Figures like a watched pot never boils the radio has been working great tonight for 4 hours straight. Sounds better than ever also the signal does not fade which it was doing before but I will keep playing it and check the tubes if she stops playing!!!!
Thanks again,
Terry N.
:Terry: OK, now look to see if one tube becomes unlit when the radio conks out. Before it conks out, look at the tubes and see how they look, filament-glow-wise.
:
:Try to inspect all the tubes, but with particular attention to the two audio tubes, 6SQ7 and 6V6.
:
:Since all bands, AM and FM, are affected I would bet that the problem is in the audio section. Maybe in the power supply, but seems less probable to me.
:Doug
:
::The radio fades out slowly thank for the replies.
::Terry N.
:
:::Hi
::: It could be caused by a tube but usually doesn't take an hour. As a tube heats metal inside expands. Does it pop and quit or slowly fade out? If you hear a pop cathode connection inside a tube probably opened. This is quite common. If the signal slowly fades out a filament opened.
:::
:

Terry,
Sounds almost like my Philco 48-460 Bakelite table model. Didn't do a complete restoration, just a couple power supply caps. Intermittent operation, then wiggle a couple tubes and it comes back on. Cleaned sockets and tube pins, and seems problem disappeared.

marv

:Figures like a watched pot never boils the radio has been working great tonight for 4 hours straight. Sounds better than ever also the signal does not fade which it was doing before but I will keep playing it and check the tubes if she stops playing!!!!
:Thanks again,
:Terry N.
::Terry: OK, now look to see if one tube becomes unlit when the radio conks out. Before it conks out, look at the tubes and see how they look, filament-glow-wise.
::
::Try to inspect all the tubes, but with particular attention to the two audio tubes, 6SQ7 and 6V6.
::
::Since all bands, AM and FM, are affected I would bet that the problem is in the audio section. Maybe in the power supply, but seems less probable to me.
::Doug
::
:::The radio fades out slowly thank for the replies.
:::Terry N.
::
::::Hi
:::: It could be caused by a tube but usually doesn't take an hour. As a tube heats metal inside expands. Does it pop and quit or slowly fade out? If you hear a pop cathode connection inside a tube probably opened. This is quite common. If the signal slowly fades out a filament opened.
::::
::

Slowly dying out sounds like a tube filament. If it fades out, leave the radio on and see if it'll come alive again. If some of your tubes are metal ones, it might be hard to find the tube that's turning off. If the radio goes dead, and none of the glass tubes are dark, you might try replacing each metal tube until the set comes alive again (be sure to wait 15 seconds for each replacement tube to light). As you are replacing tubes, the set might come back to life even if the dud tube hasn't been replaced yet, so if you only get so far and the set comes back to life, and then later it dies again, the bad tube might still be in the set. Once you locate the bad tube, you may put back all of the other original tubes.

T.

If the radio fades out and doesn't come back until it's turned off touch each tube. One might have cooled off?

Norm

:Slowly dying out sounds like a tube filament. If it fades out, leave the radio on and see if it'll come alive again. If some of your tubes are metal ones, it might be hard to find the tube that's turning off. If the radio goes dead, and none of the glass tubes are dark, you might try replacing each metal tube until the set comes alive again (be sure to wait 15 seconds for each replacement tube to light). As you are replacing tubes, the set might come back to life even if the dud tube hasn't been replaced yet, so if you only get so far and the set comes back to life, and then later it dies again, the bad tube might still be in the set. Once you locate the bad tube, you may put back all of the other original tubes.
:
:T.