If the tube is very dim, check voltages against the schematic, if voltages are listed on the schematic. The resistor in the base, if there is only one, and of 1 MEG in value, does not control brightness. It controls the plate of the control triode, which in turn controls how the tube responds. The control triode, underneath the target, is what sends the message to the deflector grid (little strip of metal) to widen or narrow the eye opening. Some eye tubes do not have this triode underneath. I am pretty sure your's has one. The triode section will look somewhat similar to that of a 6SQ7GT tube. If there are other resistors in the base, then you'd have to mention them to me as to how they're hooked up, because generally the eye tube sockets only have that one resistor. Other resistors to check are the ones that supply B+ current throughout the radio. The resistors, if any, which normally are found in the radio itself, that supply the target, should supply it with at least 200 volts unless the radio is an AC/DC set. In that case the voltage should be around 100 to 110 volts. AC/DC radios usually use a different eye tube than straight AC sets.
If the above requirements have been met, and the tube is still dim, then your eye tube is likely worn out. Sometimes eye tubes also become unresponsive with age, though if your tube performs well on AM, then something is likely amiss with the FM. The eye tube is fed AVC (automatic volume control) voltage from the AM circuit. If the resistors are off or the condensers are shorted in this circuit, the eye tube will be unresponsive. I forgot how the FM circuit operates the eye tube, because FM uses something slightly different from the AM AVC circuit, but if you follow how the grid of the control triode is hooked to your radio, you will discover the FM control circuit. If you mention your radio model number, and it's listed on this site, I'll find the circuit for you. Make sure that all components are in fine condition in this circuit. Condensers must have NO leakage.....not even several million ohms. If you take, for example, the AM AVC circuit, which often employs a 2.2 MEG resistor, you can easily see how a condenser with several million ohms leakage could throw off the AVC voltage sent through this resistor. For perfect performance you must have perfectly performing components. With condensers, I cannot emphasize this enough. With tubes and resistors, you can play around and be a bit more sloppy. If a trouble exists, though, don't be afraid to replace tubes and resistors, too, especially if replacing them corrects the problem. Be sure that the originals actually have a defect that calls for replacement....don't just replace things blindly. If the tube is dim, and you can't seem to find a problem with components, try replacing it to see if this also improves response. You probably want to replace the tube anyway, simply because it is dim.
Thomas
:I recently picked up a Grundig model 5077 AM/FM/SW radio. This is the first radio for me that has an eye tube. How bright should the tube be? Should it be easily visible in a lighted room? It seems rather dim and doesn't seem to move when on FM. The radio works fine otherwise. The only thing I've checked on the eye tube so far are the resistors at the base of the socket. They all read nearly dead on equal with their markings. Anything else I should check, or could the tube be weak and need replacement?
:The tube should be very bright (optimum situation). It should be perhaps half as bright as the white on your television screen, definitely as bright as the white or green on your computer screen. You will notice it across the room quite well. As the tube ages, it will get dimmer. Sadly they get somewhat dimmer with only a little time. They usually last quite a while, though. The same holds true for your television. If you're the average person, though, including me, you probably won't notice it. If you watch your television for several hours every day, it will be noticeably dimmer, when compared to a brand new one, after three years.
:
:If the tube is very dim, check voltages against the schematic, if voltages are listed on the schematic. The resistor in the base, if there is only one, and of 1 MEG in value, does not control brightness. It controls the plate of the control triode, which in turn controls how the tube responds. The control triode, underneath the target, is what sends the message to the deflector grid (little strip of metal) to widen or narrow the eye opening. Some eye tubes do not have this triode underneath. I am pretty sure your's has one. The triode section will look somewhat similar to that of a 6SQ7GT tube. If there are other resistors in the base, then you'd have to mention them to me as to how they're hooked up, because generally the eye tube sockets only have that one resistor. Other resistors to check are the ones that supply B+ current throughout the radio. The resistors, if any, which normally are found in the radio itself, that supply the target, should supply it with at least 200 volts unless the radio is an AC/DC set. In that case the voltage should be around 100 to 110 volts. AC/DC radios usually use a different eye tube than straight AC sets.
:
:If the above requirements have been met, and the tube is still dim, then your eye tube is likely worn out. Sometimes eye tubes also become unresponsive with age, though if your tube performs well on AM, then something is likely amiss with the FM. The eye tube is fed AVC (automatic volume control) voltage from the AM circuit. If the resistors are off or the condensers are shorted in this circuit, the eye tube will be unresponsive. I forgot how the FM circuit operates the eye tube, because FM uses something slightly different from the AM AVC circuit, but if you follow how the grid of the control triode is hooked to your radio, you will discover the FM control circuit. If you mention your radio model number, and it's listed on this site, I'll find the circuit for you. Make sure that all components are in fine condition in this circuit. Condensers must have NO leakage.....not even several million ohms. If you take, for example, the AM AVC circuit, which often employs a 2.2 MEG resistor, you can easily see how a condenser with several million ohms leakage could throw off the AVC voltage sent through this resistor. For perfect performance you must have perfectly performing components. With condensers, I cannot emphasize this enough. With tubes and resistors, you can play around and be a bit more sloppy. If a trouble exists, though, don't be afraid to replace tubes and resistors, too, especially if replacing them corrects the problem. Be sure that the originals actually have a defect that calls for replacement....don't just replace things blindly. If the tube is dim, and you can't seem to find a problem with components, try replacing it to see if this also improves response. You probably want to replace the tube anyway, simply because it is dim.
:
:Thomas
:
::I recently picked up a Grundig model 5077 AM/FM/SW radio. This is the first radio for me that has an eye tube. How bright should the tube be? Should it be easily visible in a lighted room? It seems rather dim and doesn't seem to move when on FM. The radio works fine otherwise. The only thing I've checked on the eye tube so far are the resistors at the base of the socket. They all read nearly dead on equal with their markings. Anything else I should check, or could the tube be weak and need replacement?
:I will have to check the things you mentioned. The radio is a Grundig type 5077 WE. I looked for a schematic on this site when I first got the radio, but I couldn't find a section for Grundig.
:
:
:
::The tube should be very bright (optimum situation). It should be perhaps half as bright as the white on your television screen, definitely as bright as the white or green on your computer screen. You will notice it across the room quite well. As the tube ages, it will get dimmer. Sadly they get somewhat dimmer with only a little time. They usually last quite a while, though. The same holds true for your television. If you're the average person, though, including me, you probably won't notice it. If you watch your television for several hours every day, it will be noticeably dimmer, when compared to a brand new one, after three years.
::
::If the tube is very dim, check voltages against the schematic, if voltages are listed on the schematic. The resistor in the base, if there is only one, and of 1 MEG in value, does not control brightness. It controls the plate of the control triode, which in turn controls how the tube responds. The control triode, underneath the target, is what sends the message to the deflector grid (little strip of metal) to widen or narrow the eye opening. Some eye tubes do not have this triode underneath. I am pretty sure your's has one. The triode section will look somewhat similar to that of a 6SQ7GT tube. If there are other resistors in the base, then you'd have to mention them to me as to how they're hooked up, because generally the eye tube sockets only have that one resistor. Other resistors to check are the ones that supply B+ current throughout the radio. The resistors, if any, which normally are found in the radio itself, that supply the target, should supply it with at least 200 volts unless the radio is an AC/DC set. In that case the voltage should be around 100 to 110 volts. AC/DC radios usually use a different eye tube than straight AC sets.
::
::If the above requirements have been met, and the tube is still dim, then your eye tube is likely worn out. Sometimes eye tubes also become unresponsive with age, though if your tube performs well on AM, then something is likely amiss with the FM. The eye tube is fed AVC (automatic volume control) voltage from the AM circuit. If the resistors are off or the condensers are shorted in this circuit, the eye tube will be unresponsive. I forgot how the FM circuit operates the eye tube, because FM uses something slightly different from the AM AVC circuit, but if you follow how the grid of the control triode is hooked to your radio, you will discover the FM control circuit. If you mention your radio model number, and it's listed on this site, I'll find the circuit for you. Make sure that all components are in fine condition in this circuit. Condensers must have NO leakage.....not even several million ohms. If you take, for example, the AM AVC circuit, which often employs a 2.2 MEG resistor, you can easily see how a condenser with several million ohms leakage could throw off the AVC voltage sent through this resistor. For perfect performance you must have perfectly performing components. With condensers, I cannot emphasize this enough. With tubes and resistors, you can play around and be a bit more sloppy. If a trouble exists, though, don't be afraid to replace tubes and resistors, too, especially if replacing them corrects the problem. Be sure that the originals actually have a defect that calls for replacement....don't just replace things blindly. If the tube is dim, and you can't seem to find a problem with components, try replacing it to see if this also improves response. You probably want to replace the tube anyway, simply because it is dim.
::
::Thomas
::
:::I recently picked up a Grundig model 5077 AM/FM/SW radio. This is the first radio for me that has an eye tube. How bright should the tube be? Should it be easily visible in a lighted room? It seems rather dim and doesn't seem to move when on FM. The radio works fine otherwise. The only thing I've checked on the eye tube so far are the resistors at the base of the socket. They all read nearly dead on equal with their markings. Anything else I should check, or could the tube be weak and need replacement?
Well, if you need help finding the FM control circuit for the eye tube, let me know what the model number is for your radio (and the make). Sounds like you have a European radio since you have a European eye tube. The schematic may not be on this site then. If you have a schematic yourself, though, and can photograph it and e-mail it to me, I'll look it over and let you know what's up.
Good luck,
Thomas
:I replaced the eye tube today and the new tube is much, much brighter compared to the original tube. It still doesn't deflect on FM so I'll just have to identify and check the FM control circuit that you mentioned.
:
:
::I will have to check the things you mentioned. The radio is a Grundig type 5077 WE. I looked for a schematic on this site when I first got the radio, but I couldn't find a section for Grundig.
::
::
::
:::The tube should be very bright (optimum situation). It should be perhaps half as bright as the white on your television screen, definitely as bright as the white or green on your computer screen. You will notice it across the room quite well. As the tube ages, it will get dimmer. Sadly they get somewhat dimmer with only a little time. They usually last quite a while, though. The same holds true for your television. If you're the average person, though, including me, you probably won't notice it. If you watch your television for several hours every day, it will be noticeably dimmer, when compared to a brand new one, after three years.
:::
:::If the tube is very dim, check voltages against the schematic, if voltages are listed on the schematic. The resistor in the base, if there is only one, and of 1 MEG in value, does not control brightness. It controls the plate of the control triode, which in turn controls how the tube responds. The control triode, underneath the target, is what sends the message to the deflector grid (little strip of metal) to widen or narrow the eye opening. Some eye tubes do not have this triode underneath. I am pretty sure your's has one. The triode section will look somewhat similar to that of a 6SQ7GT tube. If there are other resistors in the base, then you'd have to mention them to me as to how they're hooked up, because generally the eye tube sockets only have that one resistor. Other resistors to check are the ones that supply B+ current throughout the radio. The resistors, if any, which normally are found in the radio itself, that supply the target, should supply it with at least 200 volts unless the radio is an AC/DC set. In that case the voltage should be around 100 to 110 volts. AC/DC radios usually use a different eye tube than straight AC sets.
:::
:::If the above requirements have been met, and the tube is still dim, then your eye tube is likely worn out. Sometimes eye tubes also become unresponsive with age, though if your tube performs well on AM, then something is likely amiss with the FM. The eye tube is fed AVC (automatic volume control) voltage from the AM circuit. If the resistors are off or the condensers are shorted in this circuit, the eye tube will be unresponsive. I forgot how the FM circuit operates the eye tube, because FM uses something slightly different from the AM AVC circuit, but if you follow how the grid of the control triode is hooked to your radio, you will discover the FM control circuit. If you mention your radio model number, and it's listed on this site, I'll find the circuit for you. Make sure that all components are in fine condition in this circuit. Condensers must have NO leakage.....not even several million ohms. If you take, for example, the AM AVC circuit, which often employs a 2.2 MEG resistor, you can easily see how a condenser with several million ohms leakage could throw off the AVC voltage sent through this resistor. For perfect performance you must have perfectly performing components. With condensers, I cannot emphasize this enough. With tubes and resistors, you can play around and be a bit more sloppy. If a trouble exists, though, don't be afraid to replace tubes and resistors, too, especially if replacing them corrects the problem. Be sure that the originals actually have a defect that calls for replacement....don't just replace things blindly. If the tube is dim, and you can't seem to find a problem with components, try replacing it to see if this also improves response. You probably want to replace the tube anyway, simply because it is dim.
:::
:::Thomas
:::
::::I recently picked up a Grundig model 5077 AM/FM/SW radio. This is the first radio for me that has an eye tube. How bright should the tube be? Should it be easily visible in a lighted room? It seems rather dim and doesn't seem to move when on FM. The radio works fine otherwise. The only thing I've checked on the eye tube so far are the resistors at the base of the socket. They all read nearly dead on equal with their markings. Anything else I should check, or could the tube be weak and need replacement?
:Isn't that great? It's pretty cool putting a brand new eye tube in a radio. They're REALLY bright!
:
:Well, if you need help finding the FM control circuit for the eye tube, let me know what the model number is for your radio (and the make). Sounds like you have a European radio since you have a European eye tube. The schematic may not be on this site then. If you have a schematic yourself, though, and can photograph it and e-mail it to me, I'll look it over and let you know what's up.
:
:Good luck,
:
:Thomas
:
::I replaced the eye tube today and the new tube is much, much brighter compared to the original tube. It still doesn't deflect on FM so I'll just have to identify and check the FM control circuit that you mentioned.
::
::
:::I will have to check the things you mentioned. The radio is a Grundig type 5077 WE. I looked for a schematic on this site when I first got the radio, but I couldn't find a section for Grundig.
:::
:::
:::
::::The tube should be very bright (optimum situation). It should be perhaps half as bright as the white on your television screen, definitely as bright as the white or green on your computer screen. You will notice it across the room quite well. As the tube ages, it will get dimmer. Sadly they get somewhat dimmer with only a little time. They usually last quite a while, though. The same holds true for your television. If you're the average person, though, including me, you probably won't notice it. If you watch your television for several hours every day, it will be noticeably dimmer, when compared to a brand new one, after three years.
::::
::::If the tube is very dim, check voltages against the schematic, if voltages are listed on the schematic. The resistor in the base, if there is only one, and of 1 MEG in value, does not control brightness. It controls the plate of the control triode, which in turn controls how the tube responds. The control triode, underneath the target, is what sends the message to the deflector grid (little strip of metal) to widen or narrow the eye opening. Some eye tubes do not have this triode underneath. I am pretty sure your's has one. The triode section will look somewhat similar to that of a 6SQ7GT tube. If there are other resistors in the base, then you'd have to mention them to me as to how they're hooked up, because generally the eye tube sockets only have that one resistor. Other resistors to check are the ones that supply B+ current throughout the radio. The resistors, if any, which normally are found in the radio itself, that supply the target, should supply it with at least 200 volts unless the radio is an AC/DC set. In that case the voltage should be around 100 to 110 volts. AC/DC radios usually use a different eye tube than straight AC sets.
::::
::::If the above requirements have been met, and the tube is still dim, then your eye tube is likely worn out. Sometimes eye tubes also become unresponsive with age, though if your tube performs well on AM, then something is likely amiss with the FM. The eye tube is fed AVC (automatic volume control) voltage from the AM circuit. If the resistors are off or the condensers are shorted in this circuit, the eye tube will be unresponsive. I forgot how the FM circuit operates the eye tube, because FM uses something slightly different from the AM AVC circuit, but if you follow how the grid of the control triode is hooked to your radio, you will discover the FM control circuit. If you mention your radio model number, and it's listed on this site, I'll find the circuit for you. Make sure that all components are in fine condition in this circuit. Condensers must have NO leakage.....not even several million ohms. If you take, for example, the AM AVC circuit, which often employs a 2.2 MEG resistor, you can easily see how a condenser with several million ohms leakage could throw off the AVC voltage sent through this resistor. For perfect performance you must have perfectly performing components. With condensers, I cannot emphasize this enough. With tubes and resistors, you can play around and be a bit more sloppy. If a trouble exists, though, don't be afraid to replace tubes and resistors, too, especially if replacing them corrects the problem. Be sure that the originals actually have a defect that calls for replacement....don't just replace things blindly. If the tube is dim, and you can't seem to find a problem with components, try replacing it to see if this also improves response. You probably want to replace the tube anyway, simply because it is dim.
::::
::::Thomas
::::
:::::I recently picked up a Grundig model 5077 AM/FM/SW radio. This is the first radio for me that has an eye tube. How bright should the tube be? Should it be easily visible in a lighted room? It seems rather dim and doesn't seem to move when on FM. The radio works fine otherwise. The only thing I've checked on the eye tube so far are the resistors at the base of the socket. They all read nearly dead on equal with their markings. Anything else I should check, or could the tube be weak and need replacement?
Obtaining working Grundig radios is fairly common, though. U.S. manufacturers stuck with oil soaked paper insulated condensers for quite some time. Electrolytics improved by the 1950s and 1960s, so quite often they lasted for some time. Some U.S. manufacturers went with ceramic disc condensers, which certainly improves your chances of having a working set. The paper insulated condensers short quite often, though, or at very least they leak.
Many German companies started using revolutionary vacuum deposited metalized film condensers way back then. You will see these as condensers that look plastic in nature, almost like a miniature roll of tightly wound plastic film (which is what they actually are). The leads are drawn out through a couple of layers of the plastic roll. The metal film is clearly visible when looking into the condenser through the clear plastic film. As most of us know, these condensers tend to be self healing as any shorts happening between the two metal electrodes vaporizes that portion of each thin film of metal, and eliminates the short. Furthermore, the use of plastic greatly improves the dielectric strength. Paper is porous, and can absorb moisture. Though paper condensers are usually sealed when new, the wax or tar used to seal them usually cracks and allows moisture into the condenser. This small amount of moisture is enough to cause leakage between the electrodes, especially if aluminum oxides mix with the water moisture. Also, invariably aluminum oxides work their way into the oil, which also makes a fine path for leakage, which will eventually develop into a short.
What I said does not guarantee that your radio has metalized film condensers, but it is highly likely. Sometimes these condensers will not be metalized film, either, but actual metal foil insulated by the plastic film. Still the plastic improves the quality of the condenser over paper. Your radio may contain paper condensers, though, or a mixture of several types.
I've seen several small Grundig radios with only 5 or 6 tubes, which is a very low tube count for an AM/FM radio, and yet amazing results were achieved in both performance and sound quality. I do not know how they managed to get such a radio with so few tubes. Yes, some were multi-purpose tubes, but still, there weren't that many sections of circuitry.
I own a Blaupunkt auto radio from an early 1950s Mercedes. The unit is amazingly small in size, comparable to a modern auto radio. It has 5 tubes, no rectifier (has synchronous vibrator), printed circuits!, and metalized film condensers. The radio also has a special power transformer that allows it to work on both 6 and 12 volts. It's a wonder in both engineering and performance.
Good luck, and if you can copy a diagram to this forum, I'll look it over.
T.
:Well, unfortunately Grundig is not listed on this site, so you will have to obtain a diagram and scan it so that you can list it here. If there is none on the radio, you may try www.samsphotofact.com.
:
:Obtaining working Grundig radios is fairly common, though. U.S. manufacturers stuck with oil soaked paper insulated condensers for quite some time. Electrolytics improved by the 1950s and 1960s, so quite often they lasted for some time. Some U.S. manufacturers went with ceramic disc condensers, which certainly improves your chances of having a working set. The paper insulated condensers short quite often, though, or at very least they leak.
:
:Many German companies started using revolutionary vacuum deposited metalized film condensers way back then. You will see these as condensers that look plastic in nature, almost like a miniature roll of tightly wound plastic film (which is what they actually are). The leads are drawn out through a couple of layers of the plastic roll. The metal film is clearly visible when looking into the condenser through the clear plastic film. As most of us know, these condensers tend to be self healing as any shorts happening between the two metal electrodes vaporizes that portion of each thin film of metal, and eliminates the short. Furthermore, the use of plastic greatly improves the dielectric strength. Paper is porous, and can absorb moisture. Though paper condensers are usually sealed when new, the wax or tar used to seal them usually cracks and allows moisture into the condenser. This small amount of moisture is enough to cause leakage between the electrodes, especially if aluminum oxides mix with the water moisture. Also, invariably aluminum oxides work their way into the oil, which also makes a fine path for leakage, which will eventually develop into a short.
:
:What I said does not guarantee that your radio has metalized film condensers, but it is highly likely. Sometimes these condensers will not be metalized film, either, but actual metal foil insulated by the plastic film. Still the plastic improves the quality of the condenser over paper. Your radio may contain paper condensers, though, or a mixture of several types.
:
:I've seen several small Grundig radios with only 5 or 6 tubes, which is a very low tube count for an AM/FM radio, and yet amazing results were achieved in both performance and sound quality. I do not know how they managed to get such a radio with so few tubes. Yes, some were multi-purpose tubes, but still, there weren't that many sections of circuitry.
:
:I own a Blaupunkt auto radio from an early 1950s Mercedes. The unit is amazingly small in size, comparable to a modern auto radio. It has 5 tubes, no rectifier (has synchronous vibrator), printed circuits!, and metalized film condensers. The radio also has a special power transformer that allows it to work on both 6 and 12 volts. It's a wonder in both engineering and performance.
:
:Good luck, and if you can copy a diagram to this forum, I'll look it over.
:
:T.
With your speaker count, I can imagine it would sound good. With the design I saw go into those little table model radios, I can imagine that the cross-over networks for your speakers are well done. You probably have push-pull, too.
Tube audio is marvelous. It really is. Of course poor design can always make someone root for the transistor, but if designed properly, it does sound far better. I must admit, though, that Pioneer put out a fine line of stereos in the early 1970s using transistors, and these sound as good as their tube counterparts. My dad owns an SX-440 (20 watts per channel). The speakers were very well designed. They are not extremely expensive models. The tweeters are paper as well as all the others, and the woofers are all paper (no leather or cloth or rubber surrounds). Still these speakers sound more beautiful than many other expensive makes I've seen produced recently. These speakers are also built in very thick wood cabinets, and insulated well with fiber glass. There are very few flaws to the sound. Not only are they beauties for sound, but the oiled mahogany veneers with lattice work in front something like mahogany at least in color. You do not find speakers like these anymore. They are show pieces. To-day everything is painted black or silver and a cheap foam or cloth cover is thrown over the front. It's supposed to look high tech, but lacks lasting beauty both acoustically and visually.
I've also heard the SX-660 (60 watts total), and I really enjoyed the sound. If I ever purchase a transistorized set, I will always look to eBay for these sets. They still sell for a bit of money even to this day (up to a hundred dollars or more).
Well, enjoy the radio. It is a well made set that you can likely be proud of for a long time. In the meantime, before you find a schematic, what you can do to try to find the circuit that operates the eye tube on FM is look at the end of the last FM IF transformer. Sometimes the signal is taken elsewhere, but usually it is taken here. The secondary of the IF transformer will go to the discriminator tube (two diodes) or possibly solid state diodes (germanium). More likely it will be a set of tube diodes possibly all in one glass shell (multi-section tube). The various parts in this circuit work to find the audio in the FM signal. There will be other various parts, perhaps a resistor of several million ohms somewhat like the AM AVC circuit. This resistor or some other parts will carry the signal to the eye tube grid (grid on the control triode--pin 4). Trouble comes in if these parts wander over to the selector switch. A careful eye and patience will show which parts are used for FM. Actually, if you trace backwards from pin 4 on the eye tube, you may be able to see what part of the selector it connects to, if in fact it does, and this will tell what the selector switches between when going from AM to FM. Resistors should be close to value, drifted no more than 20%. Usually a drift as high as 20% does not affect the eye tube, but it can. If you feel that this is excessive, go as low as 15 or 10%. As for condensers, they must have ABSOLUTELY NO leakage. When you test them on your multi-meter at its most sensitive resistance setting, the needle, if it jumps up at all, must fall all the way back to infinity. Nothing less, even a hare's breath. There may be a condenser or two in the circuit that goes on its way to the eye tube control triode grid, that connects between the circuit and ground (chassis, B-, etc.) This condenser must have no leakage. To test a resistor or condenser accurately, remove one of the two wires, and do not hold both leads of your meter at the same time, or the resistance in your hands will throw things off. If you really don't know what you're looking at when you're trying to find the eye tube circuit, you may merrily go through your entire set and test every component if you wish to kill some time. This will certainly turn up any faulty resistors and condensers in the eye tube circuit whether you know that this is the eye tube circuit or not, and it may turn up some faulty components in another circuit.
Have fun!
T.D.
:My radio does have the metalized film caps you mentioned. I didn't see any of the older paper caps The design reminds me of the orange drop caps that you see for radio restoration today, but they appear to be original. Mine also has a total of 8 tubes including the eye tube and 4 speakers, a woofer, tweeter, and two midrange. The mid range ones don't work. But hopefully I can find a schematic that I can scan in use to solve that problem
:I am amazed by the sound this radio has on FM. I think it rivals my modern stereo in performance. There's just something about hearing music out of a tube powered radio that a solid state radio can't compete with. If I find a schematic, I'll be sure to scan it in.
:
:
::Well, unfortunately Grundig is not listed on this site, so you will have to obtain a diagram and scan it so that you can list it here. If there is none on the radio, you may try www.samsphotofact.com.
::
::Obtaining working Grundig radios is fairly common, though. U.S. manufacturers stuck with oil soaked paper insulated condensers for quite some time. Electrolytics improved by the 1950s and 1960s, so quite often they lasted for some time. Some U.S. manufacturers went with ceramic disc condensers, which certainly improves your chances of having a working set. The paper insulated condensers short quite often, though, or at very least they leak.
::
::Many German companies started using revolutionary vacuum deposited metalized film condensers way back then. You will see these as condensers that look plastic in nature, almost like a miniature roll of tightly wound plastic film (which is what they actually are). The leads are drawn out through a couple of layers of the plastic roll. The metal film is clearly visible when looking into the condenser through the clear plastic film. As most of us know, these condensers tend to be self healing as any shorts happening between the two metal electrodes vaporizes that portion of each thin film of metal, and eliminates the short. Furthermore, the use of plastic greatly improves the dielectric strength. Paper is porous, and can absorb moisture. Though paper condensers are usually sealed when new, the wax or tar used to seal them usually cracks and allows moisture into the condenser. This small amount of moisture is enough to cause leakage between the electrodes, especially if aluminum oxides mix with the water moisture. Also, invariably aluminum oxides work their way into the oil, which also makes a fine path for leakage, which will eventually develop into a short.
::
::What I said does not guarantee that your radio has metalized film condensers, but it is highly likely. Sometimes these condensers will not be metalized film, either, but actual metal foil insulated by the plastic film. Still the plastic improves the quality of the condenser over paper. Your radio may contain paper condensers, though, or a mixture of several types.
::
::I've seen several small Grundig radios with only 5 or 6 tubes, which is a very low tube count for an AM/FM radio, and yet amazing results were achieved in both performance and sound quality. I do not know how they managed to get such a radio with so few tubes. Yes, some were multi-purpose tubes, but still, there weren't that many sections of circuitry.
::
::I own a Blaupunkt auto radio from an early 1950s Mercedes. The unit is amazingly small in size, comparable to a modern auto radio. It has 5 tubes, no rectifier (has synchronous vibrator), printed circuits!, and metalized film condensers. The radio also has a special power transformer that allows it to work on both 6 and 12 volts. It's a wonder in both engineering and performance.
::
::Good luck, and if you can copy a diagram to this forum, I'll look it over.
::
::T
:So you must have a consol of sorts. The Grundigs I saw were small table model radios. They had AM, FM, and short wave, and had amazingly small tube counts. Most U.S. radios would have 10 or so tubes, and these radios only had 5, 6, or 7. They sounded excellent, too, with only single ended output, which normally I am not a fan of. With the right impedances selected, though, and the proper negative feedback circuits used, a single ended amplifier can sound very good.
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:With your speaker count, I can imagine it would sound good. With the design I saw go into those little table model radios, I can imagine that the cross-over networks for your speakers are well done. You probably have push-pull, too.
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:Tube audio is marvelous. It really is. Of course poor design can always make someone root for the transistor, but if designed properly, it does sound far better. I must admit, though, that Pioneer put out a fine line of stereos in the early 1970s using transistors, and these sound as good as their tube counterparts. My dad owns an SX-440 (20 watts per channel). The speakers were very well designed. They are not extremely expensive models. The tweeters are paper as well as all the others, and the woofers are all paper (no leather or cloth or rubber surrounds). Still these speakers sound more beautiful than many other expensive makes I've seen produced recently. These speakers are also built in very thick wood cabinets, and insulated well with fiber glass. There are very few flaws to the sound. Not only are they beauties for sound, but the oiled mahogany veneers with lattice work in front something like mahogany at least in color. You do not find speakers like these anymore. They are show pieces. To-day everything is painted black or silver and a cheap foam or cloth cover is thrown over the front. It's supposed to look high tech, but lacks lasting beauty both acoustically and visually.
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:I've also heard the SX-660 (60 watts total), and I really enjoyed the sound. If I ever purchase a transistorized set, I will always look to eBay for these sets. They still sell for a bit of money even to this day (up to a hundred dollars or more).
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:Well, enjoy the radio. It is a well made set that you can likely be proud of for a long time. In the meantime, before you find a schematic, what you can do to try to find the circuit that operates the eye tube on FM is look at the end of the last FM IF transformer. Sometimes the signal is taken elsewhere, but usually it is taken here. The secondary of the IF transformer will go to the discriminator tube (two diodes) or possibly solid state diodes (germanium). More likely it will be a set of tube diodes possibly all in one glass shell (multi-section tube). The various parts in this circuit work to find the audio in the FM signal. There will be other various parts, perhaps a resistor of several million ohms somewhat like the AM AVC circuit. This resistor or some other parts will carry the signal to the eye tube grid (grid on the control triode--pin 4). Trouble comes in if these parts wander over to the selector switch. A careful eye and patience will show which parts are used for FM. Actually, if you trace backwards from pin 4 on the eye tube, you may be able to see what part of the selector it connects to, if in fact it does, and this will tell what the selector switches between when going from AM to FM. Resistors should be close to value, drifted no more than 20%. Usually a drift as high as 20% does not affect the eye tube, but it can. If you feel that this is excessive, go as low as 15 or 10%. As for condensers, they must have ABSOLUTELY NO leakage. When you test them on your multi-meter at its most sensitive resistance setting, the needle, if it jumps up at all, must fall all the way back to infinity. Nothing less, even a hare's breath. There may be a condenser or two in the circuit that goes on its way to the eye tube control triode grid, that connects between the circuit and ground (chassis, B-, etc.) This condenser must have no leakage. To test a resistor or condenser accurately, remove one of the two wires, and do not hold both leads of your meter at the same time, or the resistance in your hands will throw things off. If you really don't know what you're looking at when you're trying to find the eye tube circuit, you may merrily go through your entire set and test every component if you wish to kill some time. This will certainly turn up any faulty resistors and condensers in the eye tube circuit whether you know that this is the eye tube circuit or not, and it may turn up some faulty components in another circuit.
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:Have fun!
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:T.D.
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::My radio does have the metalized film caps you mentioned. I didn't see any of the older paper caps The design reminds me of the orange drop caps that you see for radio restoration today, but they appear to be original. Mine also has a total of 8 tubes including the eye tube and 4 speakers, a woofer, tweeter, and two midrange. The mid range ones don't work. But hopefully I can find a schematic that I can scan in use to solve that problem
::I am amazed by the sound this radio has on FM. I think it rivals my modern stereo in performance. There's just something about hearing music out of a tube powered radio that a solid state radio can't compete with. If I find a schematic, I'll be sure to scan it in.
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:::Well, unfortunately Grundig is not listed on this site, so you will have to obtain a diagram and scan it so that you can list it here. If there is none on the radio, you may try www.samsphotofact.com.
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:::Obtaining working Grundig radios is fairly common, though. U.S. manufacturers stuck with oil soaked paper insulated condensers for quite some time. Electrolytics improved by the 1950s and 1960s, so quite often they lasted for some time. Some U.S. manufacturers went with ceramic disc condensers, which certainly improves your chances of having a working set. The paper insulated condensers short quite often, though, or at very least they leak.
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:::Many German companies started using revolutionary vacuum deposited metalized film condensers way back then. You will see these as condensers that look plastic in nature, almost like a miniature roll of tightly wound plastic film (which is what they actually are). The leads are drawn out through a couple of layers of the plastic roll. The metal film is clearly visible when looking into the condenser through the clear plastic film. As most of us know, these condensers tend to be self healing as any shorts happening between the two metal electrodes vaporizes that portion of each thin film of metal, and eliminates the short. Furthermore, the use of plastic greatly improves the dielectric strength. Paper is porous, and can absorb moisture. Though paper condensers are usually sealed when new, the wax or tar used to seal them usually cracks and allows moisture into the condenser. This small amount of moisture is enough to cause leakage between the electrodes, especially if aluminum oxides mix with the water moisture. Also, invariably aluminum oxides work their way into the oil, which also makes a fine path for leakage, which will eventually develop into a short.
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:::What I said does not guarantee that your radio has metalized film condensers, but it is highly likely. Sometimes these condensers will not be metalized film, either, but actual metal foil insulated by the plastic film. Still the plastic improves the quality of the condenser over paper. Your radio may contain paper condensers, though, or a mixture of several types.
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:::I've seen several small Grundig radios with only 5 or 6 tubes, which is a very low tube count for an AM/FM radio, and yet amazing results were achieved in both performance and sound quality. I do not know how they managed to get such a radio with so few tubes. Yes, some were multi-purpose tubes, but still, there weren't that many sections of circuitry.
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:::I own a Blaupunkt auto radio from an early 1950s Mercedes. The unit is amazingly small in size, comparable to a modern auto radio. It has 5 tubes, no rectifier (has synchronous vibrator), printed circuits!, and metalized film condensers. The radio also has a special power transformer that allows it to work on both 6 and 12 volts. It's a wonder in both engineering and performance.
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:::Good luck, and if you can copy a diagram to this forum, I'll look it over.
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:::T
I will check to see if I can locate a copy of the schematic - I have a left half and a right half of the schematic transliterated by our web site at radiomuseum.org
If you have an email listed here, I shall send a copy to you if you wish.
Respectfully,
Robert
:I recently picked up a Grundig model 5077 AM/FM/SW radio. This is the first radio for me that has an eye tube. How bright should the tube be? Should it be easily visible in a lighted room? It seems rather dim and doesn't seem to move when on FM. The radio works fine otherwise. The only thing I've checked on the eye tube so far are the resistors at the base of the socket. They all read nearly dead on equal with their markings. Anything else I should check, or could the tube be weak and need replacement?
:Brian,
:Your Grundig table model 5077 was made during the 1957/58 production season. It does use the EM34 eye tube, and YES to your question as to the brightness of the tube when NEW. . . it is very easily seen in a well lighted room. The 5077 had a pair of EL95 output tubes and was designed to use either the EM34 or the EM35 "magische auge" (magic eye tube).
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:I will check to see if I can locate a copy of the schematic - I have a left half and a right half of the schematic transliterated by our web site at radiomuseum.org
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:If you have an email listed here, I shall send a copy to you if you wish.
:Respectfully,
:Robert
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::I recently picked up a Grundig model 5077 AM/FM/SW radio. This is the first radio for me that has an eye tube. How bright should the tube be? Should it be easily visible in a lighted room? It seems rather dim and doesn't seem to move when on FM. The radio works fine otherwise. The only thing I've checked on the eye tube so far are the resistors at the base of the socket. They all read nearly dead on equal with their markings. Anything else I should check, or could the tube be weak and need replacement?