This is an All American-five AC set.
Well, two nights ago, I turned it on, and it was dead.
Not immediately, but the next day, I opened it up on my bench. I figured that one tube's filament had burned out, since nothing lighted.
Which tube to check first? I figured that either the audio output tube or the rectifier was most likely to be bad - they run the hottest. I made a big gamble, and pulled the 35L6 output tube. It's filament was, indeed, burned out.
I rummaged around - couldn't find a 35L6 (which is prescribed on the schematic), but came up with a 50L6. Same tube, but a 50-V rather than 35-V filament. Plugged it in, and it works fine. The extra voltage drop gets spread among all five tubes.
Probably, there is a little less sensitivity with the 50L6, but for my nearby stations it doesn't matter too much. Plus, the added resistance of the 50L6, compared to the 35L6, should prolong the life of all the tubes.
I can't wait to go to bed. zzzzzz
Richard
I usually look for burned out tubes in the low voltage section first, as these are the ones that usually take the most stress. When you turn on an AC-DC radio, usually these tubes come on really bright before the 35s and 50s start to warm up.
Still......you checked the high voltage tubes and found the burned out one on your first try. Looks like you're the winner here.
Thomas
Actually, your post raises some very interesting issues. We all know that audio and rectifier tubes run hotter - does that affect longevity? I've always assumed so.
But, then, there is the issue of turn-on current transients. For a particular surge current, it would seem that the low-voltage tubes would take a special beating.
What causes filaments to blow? Well, there are these scenarios:
1. At turn-on.
2. During steady-state operation.
3. At turn-off.
4. While the tube is not energized.
#3 and #4 are somewhat silly. I have not observed #2, even though that represents the largest time ON. That leaves #1.
Bill VA
:Thanks, Thomas. One out of five - if that makes me a winner, I'll accept it!
:
:Actually, your post raises some very interesting issues. We all know that audio and rectifier tubes run hotter - does that affect longevity? I've always assumed so.
:
:But, then, there is the issue of turn-on current transients. For a particular surge current, it would seem that the low-voltage tubes would take a special beating.
:
:What causes filaments to blow? Well, there are these scenarios:
:
:1. At turn-on.
:2. During steady-state operation.
:3. At turn-off.
:4. While the tube is not energized.
:
:#3 and #4 are somewhat silly. I have not observed #2, even though that represents the largest time ON. That leaves #1.
I believe that using a 50L6 for a 35L6 was a common practice. Several of the radios I have purchased in antique shops have come with a 50L6 where a 35L6 should be.
Now, if I could just figure out how to stop myself from hitting the submit button before I have typed my message.
:One other way to blow a tube...forget to reset the filament setting on a tube tester. Ouch! Yes I know it's not what you mean. I'm probably one of the few people who has done this.
:
:Bill VA
:
:
:
::Thanks, Thomas. One out of five - if that makes me a winner, I'll accept it!
::
::Actually, your post raises some very interesting issues. We all know that audio and rectifier tubes run hotter - does that affect longevity? I've always assumed so.
::
::But, then, there is the issue of turn-on current transients. For a particular surge current, it would seem that the low-voltage tubes would take a special beating.
::
::What causes filaments to blow? Well, there are these scenarios:
::
::1. At turn-on.
::2. During steady-state operation.
::3. At turn-off.
::4. While the tube is not energized.
::
::#3 and #4 are somewhat silly. I have not observed #2, even though that represents the largest time ON. That leaves #1.
Regarding #3 and #4, #3 is quite possible, and I've had it happen. As the filament cools, it contracts and moves, so it can crack during this time. Of course it is kind of difficult usually to tell whether the cool-down or start-up surge is what killed the filament. Usually the start-up surge will light the filament for a moment, though, and then it will go out. If the tube works one day and not the next, chances are it burned out during cool down. I'm not sure about #4, though it is possible, I guess, especially if a tube is bounced around. Filaments are always the most fragile when hot. This is why you can drop a light bulb that is off and still have it work. Drop one that is on, and it will most likely burn out, especially if it is one of those cheap modern bulbs that has the filament supported only at the ends. Tubes don't usually burn out from dropping (if you don't break them), but sometimes they do.
Thomas
:I've done that. And with a 1L6 no less.
:
:I believe that using a 50L6 for a 35L6 was a common practice. Several of the radios I have purchased in antique shops have come with a 50L6 where a 35L6 should be.
:
:Now, if I could just figure out how to stop myself from hitting the submit button before I have typed my message.
:
:
::One other way to blow a tube...forget to reset the filament setting on a tube tester. Ouch! Yes I know it's not what you mean. I'm probably one of the few people who has done this.
::
::Bill VA
::
::
::
:::Thanks, Thomas. One out of five - if that makes me a winner, I'll accept it!
:::
:::Actually, your post raises some very interesting issues. We all know that audio and rectifier tubes run hotter - does that affect longevity? I've always assumed so.
:::
:::But, then, there is the issue of turn-on current transients. For a particular surge current, it would seem that the low-voltage tubes would take a special beating.
:::
:::What causes filaments to blow? Well, there are these scenarios:
:::
:::1. At turn-on.
:::2. During steady-state operation.
:::3. At turn-off.
:::4. While the tube is not energized.
:::
:::#3 and #4 are somewhat silly. I have not observed #2, even though that represents the largest time ON. That leaves #1.
Bill VA
:Once I put in a 35L6 after testing a 117Z6, and I forgot to reset the filament setting. The tube didn't burn out, but it glowed brightly for a moment. I caught it right away.
:
:Regarding #3 and #4, #3 is quite possible, and I've had it happen. As the filament cools, it contracts and moves, so it can crack during this time. Of course it is kind of difficult usually to tell whether the cool-down or start-up surge is what killed the filament. Usually the start-up surge will light the filament for a moment, though, and then it will go out. If the tube works one day and not the next, chances are it burned out during cool down. I'm not sure about #4, though it is possible, I guess, especially if a tube is bounced around. Filaments are always the most fragile when hot. This is why you can drop a light bulb that is off and still have it work. Drop one that is on, and it will most likely burn out, especially if it is one of those cheap modern bulbs that has the filament supported only at the ends. Tubes don't usually burn out from dropping (if you don't break them), but sometimes they do.
:
:Thomas
:
::I've done that. And with a 1L6 no less.
::
::I believe that using a 50L6 for a 35L6 was a common practice. Several of the radios I have purchased in antique shops have come with a 50L6 where a 35L6 should be.
::
::Now, if I could just figure out how to stop myself from hitting the submit button before I have typed my message.
::
::
:::One other way to blow a tube...forget to reset the filament setting on a tube tester. Ouch! Yes I know it's not what you mean. I'm probably one of the few people who has done this.
:::
:::Bill VA
:::
:::
:::
::::Thanks, Thomas. One out of five - if that makes me a winner, I'll accept it!
::::
::::Actually, your post raises some very interesting issues. We all know that audio and rectifier tubes run hotter - does that affect longevity? I've always assumed so.
::::
::::But, then, there is the issue of turn-on current transients. For a particular surge current, it would seem that the low-voltage tubes would take a special beating.
::::
::::What causes filaments to blow? Well, there are these scenarios:
::::
::::1. At turn-on.
::::2. During steady-state operation.
::::3. At turn-off.
::::4. While the tube is not energized.
::::
::::#3 and #4 are somewhat silly. I have not observed #2, even though that represents the largest time ON. That leaves #1.
Along the same lines, I was trying to track done some hum in one of my TOs and I had a 50 uf cap that I touched to the 100 volt line. Didn't help so I moved down to the filament string without discharging the cap. No current limiting there. The 3V4 blew but the 1 volt tubes were OK. I guess the 3V4 took more of the load because the filament resistance is higher.
I'm not proud of that move either.
Tony
:And Thomas that's part of the answer about tubes blowing. The filament of some tubes will handle an increase much greater than others. They have a higher tolerance. How much tolerance do you think a 1L6 has Tony? On the very early tubes warnings abounded about not exceeding the voltage.
:
:Bill VA
:
::Once I put in a 35L6 after testing a 117Z6, and I forgot to reset the filament setting. The tube didn't burn out, but it glowed brightly for a moment. I caught it right away.
::
::Regarding #3 and #4, #3 is quite possible, and I've had it happen. As the filament cools, it contracts and moves, so it can crack during this time. Of course it is kind of difficult usually to tell whether the cool-down or start-up surge is what killed the filament. Usually the start-up surge will light the filament for a moment, though, and then it will go out. If the tube works one day and not the next, chances are it burned out during cool down. I'm not sure about #4, though it is possible, I guess, especially if a tube is bounced around. Filaments are always the most fragile when hot. This is why you can drop a light bulb that is off and still have it work. Drop one that is on, and it will most likely burn out, especially if it is one of those cheap modern bulbs that has the filament supported only at the ends. Tubes don't usually burn out from dropping (if you don't break them), but sometimes they do.
::
::Thomas
::
:::I've done that. And with a 1L6 no less.
:::
:::I believe that using a 50L6 for a 35L6 was a common practice. Several of the radios I have purchased in antique shops have come with a 50L6 where a 35L6 should be.
:::
:::Now, if I could just figure out how to stop myself from hitting the submit button before I have typed my message.
:::
:::
::::One other way to blow a tube...forget to reset the filament setting on a tube tester. Ouch! Yes I know it's not what you mean. I'm probably one of the few people who has done this.
::::
::::Bill VA
::::
::::
::::
:::::Thanks, Thomas. One out of five - if that makes me a winner, I'll accept it!
:::::
:::::Actually, your post raises some very interesting issues. We all know that audio and rectifier tubes run hotter - does that affect longevity? I've always assumed so.
:::::
:::::But, then, there is the issue of turn-on current transients. For a particular surge current, it would seem that the low-voltage tubes would take a special beating.
:::::
:::::What causes filaments to blow? Well, there are these scenarios:
:::::
:::::1. At turn-on.
:::::2. During steady-state operation.
:::::3. At turn-off.
:::::4. While the tube is not energized.
:::::
:::::#3 and #4 are somewhat silly. I have not observed #2, even though that represents the largest time ON. That leaves #1.
Also, I know you were doing something with a condenser, but there is another warning I should tell about that is similar to this. Never pull tubes out of a 3-way portable while the radio is running and then plug them back in. Never pull tubes out of a radio that is running and then plug them back in after turning off the radio. In either case, current is stored up in electrolytics that is greater than normal filament voltage. The load of the filaments on the ballast resistor normally limits the amount of voltage to the maximum filament voltage (that of the entire string). As we know, though, resistors limit current, not voltage. Because of this, with one of the tubes removed from the string, the resistor will pass whatever it can pass and the electrolytic will hold whatever it will hold (often electrolytics at the end of the line are rated at 25 WVDC or higher, and a 25 WVDC condenser can be momentarily charged up to a much higher voltage, say 90 to 100 volts). This voltage will blow out one or more of the tubes when the removed tube is plugged back in. I've done it many times, and I thought I had learned my lesson each time. Makes me so angry! Oh well.
Thomas
I actually don't recall if the voltage was 25 or not. It might have been 12. In either case, I really stressed that filament and it held. With that particular tube, when I am measuring Gm on my Hickok tester, I press the test button and the needle moves way up above the value on the roll chart, but then it quickly decays down to a very low value. I think this corresponds to the few seconds of oscillation I get out of it.
Thomas
:You make a good point about removing a tube from a running set. The same thing will happen if you power the set up without the tube, turn the set off, and stick the tube back in. The "fix" for this is to add a bleeder resistor of some kind, big enoough so that it doesn't present much of a load, but small enough to discharge the cap to a safe level in a second or two.
:
:I actually don't recall if the voltage was 25 or not. It might have been 12. In either case, I really stressed that filament and it held. With that particular tube, when I am measuring Gm on my Hickok tester, I press the test button and the needle moves way up above the value on the roll chart, but then it quickly decays down to a very low value. I think this corresponds to the few seconds of oscillation I get out of it.
:
Bill VA
:You make a good point about removing a tube from a running set. The same thing will happen if you power the set up without the tube, turn the set off, and stick the tube back in. The "fix" for this is to add a bleeder resistor of some kind, big enoough so that it doesn't present much of a load, but small enough to discharge the cap to a safe level in a second or two.
:
:I actually don't recall if the voltage was 25 or not. It might have been 12. In either case, I really stressed that filament and it held. With that particular tube, when I am measuring Gm on my Hickok tester, I press the test button and the needle moves way up above the value on the roll chart, but then it quickly decays down to a very low value. I think this corresponds to the few seconds of oscillation I get out of it.
:
Back in the 40’s and 50’s, TV sets were fairly unreliable, and at least one tube would usually burn out by the time it was a few months old. I bought a new Motorola way back when and left it turned on all the time. The only time it was turned off was when the electricity went off or when we moved to another house. The last move was when it was moved to the bedroom as a second TV. After about 15 years, the picture tube was getting a short, so I shot it. As far as I know, that was the only thing that was ever done to it. I was divorced after that, so don’t know what the ex finally did with it. Also, the mechanical tuners of these old sets usually needed to be cleaned periodically, but this one was never cleaned.
Along about that time, I built a high powered stereo amplifier. I installed a switch for the B+ and never turned the filaments off. Didn’t keep track of the number of years, but never changed a tube.
This next one is not really normal, but nevertheless it is true. We bought a house more than 30 years ago, which was a few years old at the time. It had a 2 foot fluorescent light above the kitchen sink, which has never been changed. Because of the way it is situated, it makes an ideal night light for that part of the house, and we never turn it off. It doesn’t burn quite as bright as a new one, but still provides plenty of light for normal use.
Hey Doug. Are you still there? You’re bad, man. Really bad. 8^)
However, the typical life of incandescent lamps is so much shorter than fluorescents, any reduced life may not be all that noticable. Typical incandescent lamps have lifetimes less than 1000 hours, while fluorescent lamps are often quoted with a 20,000 hour life - and fluorescents are much more energy efficient.
Regarding fluorescents, my grandmother had one over her sink, one of those 2 foot units. She said she had the tube in there for over 35 years, too. I think that the gas bulb starters are easier on tubes, though. She turned hers on and off all the time, but the thing never burned out. When she got sick, though, we moved her to a nursing home for a short while before she passed away. We left that fluorescent on 24 hours a day just for a light so that people would think someone was home. Well, on one of those days the ballast decided to blow a tar hole out the side of the fluorescent. It burned up and smoked up the entire kitchen. Luckily no damage was done, but it made a small tar mess in the area around the fluorescent. Now we have those dimmable halogen lamps in place--the ones that cause all the AM static.
Regarding long lasting incandescent bulbs, General Electric makes lousy bulbs. The life expectancy of their bulbs is inexcusable. If you ever look inside of one of their bulbs, you'll see that even with the long 100 watt filaments, the filaments are supported only by the very very THIN lead-in wires. Nothing is done to support the filament in the middle. The first thing you want to do if you want longer life is to purchase bulbs with support wires on the filaments. Those so-called "heavy-duty" bulbs are a scam. They do last longer and you can drop them, but that is how every bulb should be made. They charge you an extra 3 dollars for something that doesn't cost them more than 5 cents to change.
The second thing you can do is avoid General Electric at all costs. They make wonderful headlamps. They do a lot of other wonderful things. However, when you consider how they make home light bulbs, they are a terrible company that I wish would go out of business. There is no excuse for how poorly their light bulbs are made. If you go with other companies, some of them much cheaper, you will find that their light bulbs last longer than the 3 months you get out of a General Electric bulb. You can also purchase 130 volt bulbs. These bulbs last forever. Interestingly enough, though, is that there still is a bulb in my closet at my parents' home that is from before I was born (1979), and it still gets used every day by my brother. I moved out of that room years ago, but my brother still lives in it. I moved into the other room upstairs, and went through about 3 General Electric bulbs in the time I lived there (since about 1993 until last June). Still, that Westinghouse bulb in my brother's closet, which is a 120 volt bulb, keeps burning day after day. Westinghouse used to make superb fluorescent tubes, too, but then, so did everyone. Old General Electric and Sylvania fluorescents last a long time, too. The few that I have remaining from years ago still light up well.
I found recently that the voltage in my home and in all of the homes in my city is about 124, which is unacceptable when using 120 volt bulbs. I suppose the next thing you should do is avoid Wisconsin Electric. Everyone knows they're a scam anyway. When a public utility runs million dollar ads on how they're trying to save you money, you know they need to be shut down. What other choice do we have? Do they think we're going to switch to another electric company if they don't save us money? I suppose I could get myself a small generator. That isn't economical, though. Maybe they think we'll move to a different state! I should.
Thomas
Just a quick comment about a 35L6 with 117 on the filaments. Probably didn't blow due to limited tube tester current. If you tried it directly on the 117 volt line don't think you could pull the plug fast enough?
Norm
:Once I put in a 35L6 after testing a 117Z6, and I forgot to reset the filament setting. The tube didn't burn out, but it glowed brightly for a moment. I caught it right away.
:
:Regarding #3 and #4, #3 is quite possible, and I've had it happen. As the filament cools, it contracts and moves, so it can crack during this time. Of course it is kind of difficult usually to tell whether the cool-down or start-up surge is what killed the filament. Usually the start-up surge will light the filament for a moment, though, and then it will go out. If the tube works one day and not the next, chances are it burned out during cool down. I'm not sure about #4, though it is possible, I guess, especially if a tube is bounced around. Filaments are always the most fragile when hot. This is why you can drop a light bulb that is off and still have it work. Drop one that is on, and it will most likely burn out, especially if it is one of those cheap modern bulbs that has the filament supported only at the ends. Tubes don't usually burn out from dropping (if you don't break them), but sometimes they do.
:
:Thomas
:
::I've done that. And with a 1L6 no less.
::
::I believe that using a 50L6 for a 35L6 was a common practice. Several of the radios I have purchased in antique shops have come with a 50L6 where a 35L6 should be.
::
::Now, if I could just figure out how to stop myself from hitting the submit button before I have typed my message.
::
::
:::One other way to blow a tube...forget to reset the filament setting on a tube tester. Ouch! Yes I know it's not what you mean. I'm probably one of the few people who has done this.
:::
:::Bill VA
:::
:::
:::
::::Thanks, Thomas. One out of five - if that makes me a winner, I'll accept it!
::::
::::Actually, your post raises some very interesting issues. We all know that audio and rectifier tubes run hotter - does that affect longevity? I've always assumed so.
::::
::::But, then, there is the issue of turn-on current transients. For a particular surge current, it would seem that the low-voltage tubes would take a special beating.
::::
::::What causes filaments to blow? Well, there are these scenarios:
::::
::::1. At turn-on.
::::2. During steady-state operation.
::::3. At turn-off.
::::4. While the tube is not energized.
::::
::::#3 and #4 are somewhat silly. I have not observed #2, even though that represents the largest time ON. That leaves #1.
T.
:Hi Thomas
:
: Just a quick comment about a 35L6 with 117 on the filaments. Probably didn't blow due to limited tube tester current. If you tried it directly on the 117 volt line don't think you could pull the plug fast enough?
:
:Norm
:
::Once I put in a 35L6 after testing a 117Z6, and I forgot to reset the filament setting. The tube didn't burn out, but it glowed brightly for a moment. I caught it right away.
::
::Regarding #3 and #4, #3 is quite possible, and I've had it happen. As the filament cools, it contracts and moves, so it can crack during this time. Of course it is kind of difficult usually to tell whether the cool-down or start-up surge is what killed the filament. Usually the start-up surge will light the filament for a moment, though, and then it will go out. If the tube works one day and not the next, chances are it burned out during cool down. I'm not sure about #4, though it is possible, I guess, especially if a tube is bounced around. Filaments are always the most fragile when hot. This is why you can drop a light bulb that is off and still have it work. Drop one that is on, and it will most likely burn out, especially if it is one of those cheap modern bulbs that has the filament supported only at the ends. Tubes don't usually burn out from dropping (if you don't break them), but sometimes they do.
::
::Thomas
::
:::I've done that. And with a 1L6 no less.
:::
:::I believe that using a 50L6 for a 35L6 was a common practice. Several of the radios I have purchased in antique shops have come with a 50L6 where a 35L6 should be.
:::
:::Now, if I could just figure out how to stop myself from hitting the submit button before I have typed my message.
:::
:::
::::One other way to blow a tube...forget to reset the filament setting on a tube tester. Ouch! Yes I know it's not what you mean. I'm probably one of the few people who has done this.
::::
::::Bill VA
::::
::::
::::
:::::Thanks, Thomas. One out of five - if that makes me a winner, I'll accept it!
:::::
:::::Actually, your post raises some very interesting issues. We all know that audio and rectifier tubes run hotter - does that affect longevity? I've always assumed so.
:::::
:::::But, then, there is the issue of turn-on current transients. For a particular surge current, it would seem that the low-voltage tubes would take a special beating.
:::::
:::::What causes filaments to blow? Well, there are these scenarios:
:::::
:::::1. At turn-on.
:::::2. During steady-state operation.
:::::3. At turn-off.
:::::4. While the tube is not energized.
:::::
:::::#3 and #4 are somewhat silly. I have not observed #2, even though that represents the largest time ON. That leaves #1.
I play my Sonora bedstead radio every night. Here it is, if you're interested: http://www.enginova.com/sonora_wcu.htm
:
:This is an All American-five AC set.
:
:Well, two nights ago, I turned it on, and it was dead.
:
:Not immediately, but the next day, I opened it up on my bench. I figured that one tube's filament had burned out, since nothing lighted.
:
:Which tube to check first? I figured that either the audio output tube or the rectifier was most likely to be bad - they run the hottest. I made a big gamble, and pulled the 35L6 output tube. It's filament was, indeed, burned out.
:
:I rummaged around - couldn't find a 35L6 (which is prescribed on the schematic), but came up with a 50L6. Same tube, but a 50-V rather than 35-V filament. Plugged it in, and it works fine. The extra voltage drop gets spread among all five tubes.
:
:Probably, there is a little less sensitivity with the 50L6, but for my nearby stations it doesn't matter too much. Plus, the added resistance of the 50L6, compared to the 35L6, should prolong the life of all the tubes.
:
:I can't wait to go to bed. zzzzzz
: