I had the TV repaired about 5 years ago, but had the set in storage for the past year and now after having it on a few minutes, the screen went dark and the rectifier tube has glowing plates and the set starts to smoke. I assume since none of the tubes are shorted after testing, a cap went bad. Any ideas on what capacitors might have gone bad? Dave

If the low voltage rectifier plates are glowing, then you must check your electrolytic filter condensers associated with this circuit. This is the circuit that generates the 300 or so volts so common with AC operated radio tubes. All of the tubes that control the video and audio circuits (RF as well) receive power from this circuit. Ordinary radio type rectifier tubes, such as the 5U4, are used in this circuit. You should also check the set for shorted or leaky paper condensers, though electroltyics are likely the main trouble. In order for your set to give reliable and accurate service in the future, however, I recommend that you replace all condensers. Paper condensers, even if they do not short out, often develop leakage. Often enough this leakage is only a small trace--in the millions of ohms. However, this leakage is enough to throw off the extremely sensitive tube circuitry (tubes are more sensitive than transistors and IC chips, contrary to popular myth).

If the high voltage rectifier plate is glowing, then you should check for a short in the high voltage section. The high voltage rectifier is often a filamentary tube with a terminal on top of the tube for the plate. Common numbers are 1B3 or 1G3, 1J3, 1K3, etc. There are other types as well, even some with indirectly heated cathodes or higher filament voltages. The high voltage section in most modern sets (post WWII) is derived from the horizontal oscillator output. This frequency is used to operate the flyback coil, which generates the thousands of volts used for painting the screen. The high voltage rectifier rectifies the output of the flyback coil. After the rectifier is sometimes a very small value condenser for filtering purposes. Sometimes this condenser will look like a bakelite knob of sorts with a screw shaft out each end for terminals. Sometimes, too, there can be regulators in this circuit of various types. Usually there will only be this small condenser or nothing at all. The outer aquadag coating of the picture tube is connected to the chassis (which is also the negative side of the high voltage). The inner aquadag coating is connected to the positive side of the high voltage supply. The glass between the two forms an insulator. The two act as a sort of condenser, which is why the small "knob" filter condenser may or may not be present. Often the filter condenser built right into the picture tube is enough to filter the high voltage.

Since the horizontal oscillator is supplied with current by the low voltage rectifier system (300 volts), and since the horizontal oscillator circuit is what feeds the flyback and high voltage circuit, it is easy to see why the picture would go dark if the low voltage rectification system was failing. If the entire set goes dead (sound and all), then the low voltage rectifier circuit is definitely failing (shorted electrolytic or other device). If, however, you still have sound but just no picture, then it is definitely the high voltage rectifier circuit which is failing.

If you find that the low voltage circuit is what is failing (which is most likely), it is still a good idea to clean up the high voltage area (after thoroughly discharging the picture tube by shorting between the inner and outer aquadags). Dust collects in this area, and can cause spurratic arcing, especially on humid days. Also, if you want to improve your picture brightness and stability, check the 1 MEG (or there-abouts) resistor that connects to the high voltage rectifier. If it has drifted, replace it.

Thomas

:If the low voltage recifier plates are glowing, then you must check your electrolytic filter condensers associated with this circuit. This is the circuit that generates the 300 or so volts so common with AC operated radio tubes. All of the tubes that control the video and audio circuits (RF as well) receive power from this circuit. Ordinary radio type rectifier tubes, such as the 5U4, are used in this circuit. You should also check the set for shorted or leaky paper condensers, though electroltyics are likely the main trouble. In order for your set to give reliable and accurate service in the future, however, I recommend that you replace all condensers. Paper condensers, even if they do not short out, often develop leakage. Often enough this leakage is only a small trace--in the millions of ohms. However, this leakage is enough to throw off the extremely sensitive tube circuitry (tubes are more sensitive than transistors and IC chips, contrary to popular myth).
:
:If the high voltage rectifier plate is glowing, then you should check for a short in the high voltage section. The high voltage rectifier is often a filamentary tube with a terminal on top of the tube for the plate. Common numbers are 1B3 or 1G3, 1J3, 1K3, etc. There are other types as well, even some with indirectly heated cathodes or higher filament voltages. The high voltage section in most modern sets (post WWII) is derived from the horizontal oscillator output. This frequency is used to operate the flyback coil, which generates the thousands of volts used for painting the screen. The high voltage rectifier rectifies the output of the flyback coil. After the rectifier is sometimes a very small value condenser for filtering purposes. Sometimes this condenser will look like a bakelite knob of sorts with a screw shaft out each end for terminals. Sometimes, too, there can be regulators in this circuit of various types. Usually there will only be this small condenser or nothing at all. The outer aquadag coating of the picture tube is connected to the chassis (which is also the negative side of the high voltage). The inner aquadag coating is connected to the positive side of the high voltage supply. The glass between the two forms an insulator. The two act as a sort of condenser, which is why the small "knob" filter condenser may or may not be present. Often the filter condenser built right into the picture tube is enough to filter the high voltage.
:
:Since the horizontal oscillator is supplied with current by the low voltage rectifier system (300 volts), and since the horizontal oscillator circuit is what feeds the flyback and high voltage circuit, it is easy to see why the picture would go dark if the low voltage rectification system was failing. If the entire set goes dead (sound and all), then the low voltage rectifier circuit is definitely failing (shorted electrolytic or other device). If, however, you still have sound but just no picture, then it is definitely the high voltage rectifier circuit which is failing.
:
:If you find that the low voltage circuit is what is failing (which is most likely), it is still a good idea to clean up the high voltage area (after thoroughly discharging the picture tube by shorting between the inner and outer aquadags). Dust collects in this area, and can cause spurratic arcing, especially on humid days. Also, if you want to improve your picture brightness and stability, check the 1 MEG (or there-abouts) resistor that connects to the high voltage rectifier. If it has drifted, replace it.
:
:Thomas

Tom, I did have some sound, but the 5U4 was definitely glowing red, I did see some smoke come up out of the high voltage cage the first time the set powered up and the screen went black, perhaps more than one cap went short. I will check and replace the electrolytic can and look for a melted or cracked paper cap in the high voltage area?
Dave

You won't find paper caps on the secondary side of the high voltage section, but it is possible that something is shorting out in the primary of the high voltage section which is causing a large draw on the low voltage rectifier. It is also possible that something else is shorting out in the secondary of the high voltage section. It could be an arc forming on dirt, the little knob condenser (if one is used), or maybe a bad wire. Before you go any further, though, replace all of the condensers.

It is a wise idea, especially when dealing with televisions, which have critical circuits and high voltages, to replace all condensers before you fire up the set or attempt to get it working. Antique Electronic Supply sells multi-section electrolytics, and the small yellow metalized film condensers they sell fit neatly inside of the paper tubes of the original condensers in your set. If you're looking for originality, you can keep the original look while still replacing all of the condensers.

Televisions are such complicated devices that the amount of condensers that can fail is sometimes baffling. There are so many different circuits that troubleshooting can be very difficult. They are not computers, but they are on par to a hi-fi set or a modern stereo, with the amount of components and sections they have. When I started working on my DeWald BT-100 (RCA 630-TS chassis), I found all of the electrolytics and many of the paper condensers to either be leaky or shorted. After I replaced all of the electrolytics and many of the paper condensers, I still had much difficulty with the remaining paper condensers (along with some mica condensers in the little bakelite shells that turned out to be paper condensers). The remaining condensers would eventually short out or cause momentary shorts which were hard to locate due to their intermittant nature. Many of the resistors were drifted, too.

Your television is very old, and not many critical parts are sold for it, so it is wise to replace the parts that fail the most and are easiest to replace so that you don't destroy the hard to replace parts (flyback, various other transformers and coils, etc.).

Thomas

:You Twon't find paper caps on the secondary side of the high voltage section, but it is possible that something is shorting out in the primary of the high voltage section which is causing a large draw on the low voltage rectifier. It is also possible that something else is shorting out in the secondary of the high voltage section. It could be an arc forming on dirt, the little knob condenser (if one is used), or maybe a bad wire. Before you go any further, though, replace all of the condensers.
:
:It is a wise idea, especially when dealing with televisions, which have critical circuits and high voltages, to replace all condensers before you fire up the set or attempt to get it working. Antique Electronic Supply sells multi-section electrolytics, and the small yellow metalized film condensers they sell fit neatly inside of the paper tubes of the original condensers in your set. If you're looking for originality, you can keep the original look while still replacing all of the condensers.
:
:Televisions are such complicated devices that the amount of condensers that can fail is sometimes baffling. There are so many different circuits that troubleshooting can be very difficult. They are not computers, but they are on par to a hi-fi set or a modern stereo, with the amount of components and sections they have. When I started working on my DeWald BT-100 (RCA 630-TS chassis), I found all of the electrolytics and many of the paper condensers to either be leaky or shorted. After I replaced all of the electrolytics and many of the paper condensers, I still had much difficulty with the remaining paper condensers (along with some mica condensers in the little bakelite shells that turned out to be paper condensers). The remaining condensers would eventually short out or cause momentary shorts which were hard to locate due to their intermittant nature. Many of the resistors were drifted, too.
:
:Your television is very old, and not many critical parts are sold for it, so it is wise to replace the parts that fail the most and are easiest to replace so that you don't destroy the hard to replace parts (flyback, various other transformers and coils, etc.).
:
:Thomas
Thomas, I replaced many paper caps that may have been shorted out, as long as they aren't electrolytic, do I have to worry about polarity? I have many of those yellow plastic caps that do not have any polarity on them to use. Also, the low voltage rectifier plates heat up and smoke comes from the high voltage cage area when the TV is plugged into the other chassis that is for the radio and phono, in other words, the TV does not smoke when it is outside of the console and plugged in on its own. Any ideas? David

As for electrolytics and other condensers, only electrolytics are polarity sensitive. You may see on old condensers the notation "outside foil". This is simply so that if the condenser is used in a circuit in which one side is more sensitive than the other (if this is at all possible), the outside foil is connected to the less sensitive portion of the circuit. This way the outside foil, which is most exposed to interference, is connected to the less sensitive item. Such a place would be in an audio circuit as a tone condenser. The inside foil would be connected to the grid circuit and the outside foil would be connected to the chassis, which would tend to reduce any tendency for hum to get into this circuit.

Other than that, do not worry about polarity with non-electrolytic condensers. Also, those nifty little yellow caps can fit nicely inside the old condensers' paper tubes, which can keep the set looking more original.

Regarding your smoke problem, if there is only smoke when the radio-phono is plugged into the television, then you need to look for things like whether the radio-phono uses power from the television's rectifier or not. Examine the circuit closely.

Also, unless your original electrolytics test out well, it is not wise to keep using them. Occasionally you can get sets from the 1940s and 1950s in which the electrolytics all function perfectly (not dried up or leaky in any way). If so, I have had much success with such sets. I have at least 5 sets that are this way, and I continue to use them almost daily. However, if the electrolytics are at all questionable, it is wise to replace them. An accumulative leakage problem could cause a heavy drain on the rectifier even if each condenser is not terribly leaky (generally any resistance lower than 10 meg is unfavorable).

Examine the power supply and how it is related to the radio-phono set-up. Your trouble then probably lies in the radio-phono set-up. The phonograph does not likely have any relation to the problem if both use the television's amplifier and power supply or just the television's power supply if the amplifier happens to lie in the radio. The radio, whether it is simply a tuner or a tuner with audio amplifier, is probably your problem. Replace all faulty condensers in the radio. Remember that any leakage in paper and mica condensers is unacceptable, and remember that anything lower than 10 meg in electrolytics is undesirable, if not unacceptable.

Thomas

:As for electrolytics and other condensers, only electrolytics are polarity sensitive. You may see on old condensers the notation "outside foil". This is simply so that if the condenser is used in a circuit in which one side is more sensitive than the other (if this is at all possible), the outside foil is connected to the less sensitive portion of the circuit. This way the outside foil, which is most exposed to interference, is connected to the less sensitive item. Such a place would be in an audio circuit as a tone condenser. The inside foil would be connected to the grid circuit and the outside foil would be connected to the chassis, which would tend to reduce any tendency for hum to get into this circuit.
:
:Other than that, do not worry about polarity with non-electrolytic condensers. Also, those nifty little yellow caps can fit nicely inside the old condensers' paper tubes, which can keep the set looking more original.
:
:Regarding your smoke problem, if there is only smoke when the radio-phono is plugged into the television, then you need to look for things like whether the radio-phono uses power from the television's rectifier or not. Examine the circuit closely.
:
:Also, unless your original electrolytics test out well, it is not wise to keep using them. Occasionally you can get sets from the 1940s and 1950s in which the electrolytics all function perfectly (not dried up or leaky in any way). If so, I have had much success with such sets. I have at least 5 sets that are this way, and I continue to use them almost daily. However, if the electrolytics are at all questionable, it is wise to replace them. An accumulative leakage problem could cause a heavy drain on the rectifier even if each condenser is not terribly leaky (generally any resistance lower than 10 meg is unfavorable).
:
:Examine the power supply and how it is related to the radio-phono set-up. Your trouble then probably lies in the radio-phono set-up. The phonograph does not likely have any relation to the problem if both use the television's amplifier and power supply or just the television's power supply if the amplifier happens to lie in the radio. The radio, whether it is simply a tuner or a tuner with audio amplifier, is probably your problem. Replace all faulty condensers in the radio. Remember that any leakage in paper and mica condensers is unacceptable, and remember that anything lower than 10 meg in electrolytics is undesirable, if not unacceptable.
:
:Thomas
Thomas, The radio and phono work fine. Only the TV does not work and makes the low voltage rectifier glow and smoke out of the high voltage cage. There is a separate power supply for the radio/phono that plugs into the chassis on the TV set. I will remove the power supply and examine those caps. Dave

It is really odd that the television has its trouble with the rectifier when plugged into the radio chassis, even though the two have separate power supplies. Examine thoroughly. What exactly is being plugged into what? What flows through the connecting cables?

Thomas

I have this 12" Admiral tv radio phono and can add some input .

mike

Ok the tv has voltage that runs from or to the radio / phono chassis through the focus coil , i can't recall how this is done but when the chassis is not connected to the radio / phono part theres an incomplete circut ..... i sugesst take the tv chassis , replace the electrolytics as mentioned alread and check resistors in ans under the high voltage section , the shorted electrolytic could have a resistor or two overheating and smoking , if the paper caps are not replaced they must be , as long as the value and voltage are right on the new ones going in there should be no problem , since it was stored for a year it sounds like an electrolytic or two or so having no electric for a year were suddenly given electric and couldn't handle it anymore and shorted or started leaking too much , if you have to you can replace electrolytics and put them one by one under the chassis hooking the ground to the chassis ground and the plus to the wire / wires going to that value on the can .

Mike

Keep in mind that not all can electrolytics have their commons tied to the chassis. My 630TS, for instance (or is it TS630...I forgot) has a two part electrolytic can in the B+ section which is used in filtering the B+ which goes to the vertical and horizonatal circuits. The two sections of this can are extremely high in value. If I remember correctly, the common of the can is actually tied to some more negative portion of the B+ section, with the two positive leads tied elsewhere in this circuit. No part of the electrolytic is connected to the chassis in any way.

Thomas

I didn't think of mentioning that , thanks for pointing it out , i guess i should have said the replacement electrolytic the ground of it should go to where the ground is on the can your replacing , the 630 is simular to the 8-t-241 and theres a can on the bottom of the chassis that i think does what you are describing , just like in a motorola 7" set if i recall none of the cans are connected to the metal of the chassis but insulated from it .

mike

:Keep in mind that not all can electrolytics have their commons tied to the chassis. My 630TS, for instance (or is it TS630...I forgot) has a two part electrolytic can in the B+ section which is used in filtering the B+ which goes to the vertical and horizonatal circuits. The two sections of this can are extremely high in value. If I remember correctly, the common of the can is actually tied to some more negative portion of the B+ section, with the two positive leads tied elsewhere in this circuit. No part of the electrolytic is connected to the chassis in any way.
:
:Thomas