Another question: Why did Grigsby-Grunow use that silly ballast resistor in their power supplies? Could you change the resistor so that the set could be used at different voltages? It is otherwise pointless.
I wish that there was a chat site for 1937-1952 Chevrolets. Then I could ask all sorts of questions like why on earth did Chevrolet use splash lubrication on the 216.5 engine. Seems pointless and over complicated putting all those dippers, troughs, and sprayers in there when they could have simply drilled passages through the crank shaft like everyone else was doing. I see no benefits to splash lubrication, where the oil pressure is 15 p.s.i. at best, and when the oil is sluggish, it never even makes it to the rods.
Lots of pointless things are baffling me right now. The 6B5 tube sounds like a good idea, though. Another kind of pointless thing is using a triode as a detector when many radios had dual-diode-triode tubes running right along with these triode detector tubes (or using both a 6H6 and a 6Q7 in the same radio...pointless). Strange how some radio manufacturers were trying to increase tube count and others were trying to decrease it. A triode sort-of makes a better detector than a diode, I guess. I have noticed miniscual (spelling?) increases in sensitivity when a triode is used instead of a diode, with the plate and grid tied together. I suppose whenever the plate goes positive, so does the grid, which encourages current flow. I'd like to know why my Crosley 1117 has separate triode detector and triode AVC tubes along with a 6K5 triode amplifier, which could have easily been a 6Q7, which would serve all three purposes. The radio also has a separate oscillator tube. Still, with all of these unnecessary extras, it takes the phase inversion for the second output tube (push-pull) off of the screen grid of the first output tube. Why not just add a phase inverter tube and make it a 12 tube set? Is there any benefit to having a separate oscillator tube?
Thomas
It's particularly hard for me to understand the rationale behind the resistance line cord. OK, if there wasn't an available tube line-up that added up to a 115-V filament voltage, why not stick in a ballast tube?
To replace those curtain burners, I've had good luck putting in a series non-polarized cap to drop the voltage. But, in any case, I think all resistance line cords should be replaced before they cause a house fire.
Thomas,
Perhaps the manufacturers thought the buying public would think that a radio with more tubes would be a better radio. During the CB radio craze, guess which CB radio (from my experience)would sell better, one with two knobs on the front or one with six knobs on the front? I sold more of the six knob radios. Go figure.
Radiodoc
You hit the nail on the head with resistance line cords. In their day, it was a cheap and easy fix for inexpensive compact sets like the 1939 4 tube TRF RCA catalins. There wasn't any room left for a ballast tube. Another big danger in those cords is not only the heat but the asbestos that covers the nichrome wire. If you try to replace a line plug, you have to trim the cord back which releases asbestos dust right at you.
As far as tube count with some uses of triodes hooked up as diodes, a lot of that was marketing and bulk availability of tubes at that time. For 1937 and 1938, Philco marked both the 37-116 and 38-116 as 15 tube models. I have the 38-116 and it could have easily used less tubes. They use a 6R7G for the first audio only with it's two diodes grounded. They then use a 6J5G diode connected for the second detector. It gets stranger. The 38-116 also has automatic frequency control for pulling it into resonance to make up for inacuracies in the automatic dial. The previous model 37-116 uses a 6H6G for the discrimnator. To bring the tube count back up to 15, the 38-116 uses a pair of 6J5G's both diode connected as the discriminator. A waste of several tubes but they were able to market a fifteen tube console.
Fred WA3KIO
::Thomas, you raise so many great questions. I'm struggling for answers, and coming up short!
::
::It's particularly hard for me to understand the rationale behind the resistance line cord. OK, if there wasn't an available tube line-up that added up to a 115-V filament voltage, why not stick in a ballast tube?
::
::To replace those curtain burners, I've had good luck putting in a series non-polarized cap to drop the voltage. But, in any case, I think all resistance line cords should be replaced before they cause a house fire.
:
:Thomas,
:
:Perhaps the manufacturers thought the buying public would think that a radio with more tubes would be a better radio. During the CB radio craze, guess which CB radio (from my experience)would sell better, one with two knobs on the front or one with six knobs on the front? I sold more of the six knob radios. Go figure.
:
:Radiodoc
:
Interesting questions..
The line cord resistor did spead out heat. Some sort of resistor was needed in series with filaments. A resistor inside a small cabinet would get too hot. No one expected these radios to be around for 70 years.. The line cord resistors worked as long as someone didn't coil them up.. Discuss before using a cap in place of resistor line cord. It does stay cool but has other problems.
Grigsby-Grunow used ballasts to compensate for line voltage variation. Atwater Kent and others did the same. These line ballasts tend to drop more voltage with higher line. RCA used a giant UV876 tube.
Cheaper? and more engines to replace.
The 6B5 was used to save on components. It didn't require bias. You will find a 42 works just as well. In place of 6N6G a person can use 6F6 or 6V6. These substitutions require a cathode resistor to be added. Should also be bypassed with a cap.
As far as I can tell 6H6's were developed only to add to tube count. There are a few radios which used full wave detection. FM needs separate diodes but these radios were made before that time.
Never could understand why someone would use a 6K5 or 6F5 instead of 6Q7? Again maybe to add to tube count since you also needed a 6H6?
Shouldn't be any difference between a diode tube and triode with plate & grid connected. If there was we would have amplifier diodes.
A separate oscillator does have an advantage. It's more stable. Even using a 6K8 instead of 6A8 is supposed to have better stability.
Norm
:More questions: What on earth is the purpose of the line cord resistor? Why were they so popular during the mid-1930s? Is this a way to spread out the heat so that it doesn't get the radio really hot? It just sounds so pointless to put a resistor in a line cord and expect it to neither start a fire nor break. I guess when they were operated properly they didn't usually start fires. I don't know of any that get too hot.
:
:Another question: Why did Grigsby-Grunow use that silly ballast resistor in their power supplies? Could you change the resistor so that the set could be used at different voltages? It is otherwise pointless.
:
:I wish that there was a chat site for 1937-1952 Chevrolets. Then I could ask all sorts of questions like why on earth did Chevrolet use splash lubrication on the 216.5 engine. Seems pointless and over complicated putting all those dippers, troughs, and sprayers in there when they could have simply drilled passages through the crank shaft like everyone else was doing. I see no benefits to splash lubrication, where the oil pressure is 15 p.s.i. at best, and when the oil is sluggish, it never even makes it to the rods.
:
:Lots of pointless things are baffling me right now. The 6B5 tube sounds like a good idea, though. Another kind of pointless thing is using a triode as a detector when many radios had dual-diode-triode tubes running right along with these triode detector tubes (or using both a 6H6 and a 6Q7 in the same radio...pointless). Strange how some radio manufacturers were trying to increase tube count and others were trying to decrease it. A triode sort-of makes a better detector than a diode, I guess. I have noticed miniscual (spelling?) increases in sensitivity when a triode is used instead of a diode, with the plate and grid tied together. I suppose whenever the plate goes positive, so does the grid, which encourages current flow. I'd like to know why my Crosley 1117 has separate triode detector and triode AVC tubes along with a 6K5 triode amplifier, which could have easily been a 6Q7, which would serve all three purposes. The radio also has a separate oscillator tube. Still, with all of these unnecessary extras, it takes the phase inversion for the second output tube (push-pull) off of the screen grid of the first output tube. Why not just add a phase inverter tube and make it a 12 tube set? Is there any benefit to having a separate oscillator tube?
:
:Thomas
I've never tried that condenser idea with one of my line cord resistor radios. I've always stuck to resistors simply because I worry about the condenser shorting out and then frying the tubes.
Thomas
Bill VA
:Hi Thomas
:
: Interesting questions..
:
: The line cord resistor did spead out heat. Some sort of resistor was needed in series with filaments. A resistor inside a small cabinet would get too hot. No one expected these radios to be around for 70 years.. The line cord resistors worked as long as someone didn't coil them up.. Discuss before using a cap in place of resistor line cord. It does stay cool but has other problems.
:
: Grigsby-Grunow used ballasts to compensate for line voltage variation. Atwater Kent and others did the same. These line ballasts tend to drop more voltage with higher line. RCA used a giant UV876 tube.
:
: Cheaper? and more engines to replace.
:
: The 6B5 was used to save on components. It didn't require bias. You will find a 42 works just as well. In place of 6N6G a person can use 6F6 or 6V6. These substitutions require a cathode resistor to be added. Should also be bypassed with a cap.
:
: As far as I can tell 6H6's were developed only to add to tube count. There are a few radios which used full wave detection. FM needs separate diodes but these radios were made before that time.
:
: Never could understand why someone would use a 6K5 or 6F5 instead of 6Q7? Again maybe to add to tube count since you also needed a 6H6?
:
: Shouldn't be any difference between a diode tube and triode with plate & grid connected. If there was we would have amplifier diodes.
:
: A separate oscillator does have an advantage. It's more stable. Even using a 6K8 instead of 6A8 is supposed to have better stability.
:
:Norm
:
::More questions: What on earth is the purpose of the line cord resistor? Why were they so popular during the mid-1930s? Is this a way to spread out the heat so that it doesn't get the radio really hot? It just sounds so pointless to put a resistor in a line cord and expect it to neither start a fire nor break. I guess when they were operated properly they didn't usually start fires. I don't know of any that get too hot.
::
::Another question: Why did Grigsby-Grunow use that silly ballast resistor in their power supplies? Could you change the resistor so that the set could be used at different voltages? It is otherwise pointless.
::
::I wish that there was a chat site for 1937-1952 Chevrolets. Then I could ask all sorts of questions like why on earth did Chevrolet use splash lubrication on the 216.5 engine. Seems pointless and over complicated putting all those dippers, troughs, and sprayers in there when they could have simply drilled passages through the crank shaft like everyone else was doing. I see no benefits to splash lubrication, where the oil pressure is 15 p.s.i. at best, and when the oil is sluggish, it never even makes it to the rods.
::
::Lots of pointless things are baffling me right now. The 6B5 tube sounds like a good idea, though. Another kind of pointless thing is using a triode as a detector when many radios had dual-diode-triode tubes running right along with these triode detector tubes (or using both a 6H6 and a 6Q7 in the same radio...pointless). Strange how some radio manufacturers were trying to increase tube count and others were trying to decrease it. A triode sort-of makes a better detector than a diode, I guess. I have noticed miniscual (spelling?) increases in sensitivity when a triode is used instead of a diode, with the plate and grid tied together. I suppose whenever the plate goes positive, so does the grid, which encourages current flow. I'd like to know why my Crosley 1117 has separate triode detector and triode AVC tubes along with a 6K5 triode amplifier, which could have easily been a 6Q7, which would serve all three purposes. The radio also has a separate oscillator tube. Still, with all of these unnecessary extras, it takes the phase inversion for the second output tube (push-pull) off of the screen grid of the first output tube. Why not just add a phase inverter tube and make it a 12 tube set? Is there any benefit to having a separate oscillator tube?
::
::Thomas
A 6K8 is often a direct replacement for 6A8 although it's not shown that way in substitution guides. Notice a 6K8 has a separate triode for oscillator but basing is the same as 6A8.
Norm
:Norm, is the 6K8 in place of 6A8 a direct replacement?
:
:Bill VA
:
:
::Hi Thomas
::
:: Interesting questions..
::
:: The line cord resistor did spead out heat. Some sort of resistor was needed in series with filaments. A resistor inside a small cabinet would get too hot. No one expected these radios to be around for 70 years.. The line cord resistors worked as long as someone didn't coil them up.. Discuss before using a cap in place of resistor line cord. It does stay cool but has other problems.
::
:: Grigsby-Grunow used ballasts to compensate for line voltage variation. Atwater Kent and others did the same. These line ballasts tend to drop more voltage with higher line. RCA used a giant UV876 tube.
::
:: Cheaper? and more engines to replace.
::
:: The 6B5 was used to save on components. It didn't require bias. You will find a 42 works just as well. In place of 6N6G a person can use 6F6 or 6V6. These substitutions require a cathode resistor to be added. Should also be bypassed with a cap.
::
:: As far as I can tell 6H6's were developed only to add to tube count. There are a few radios which used full wave detection. FM needs separate diodes but these radios were made before that time.
::
:: Never could understand why someone would use a 6K5 or 6F5 instead of 6Q7? Again maybe to add to tube count since you also needed a 6H6?
::
:: Shouldn't be any difference between a diode tube and triode with plate & grid connected. If there was we would have amplifier diodes.
::
:: A separate oscillator does have an advantage. It's more stable. Even using a 6K8 instead of 6A8 is supposed to have better stability.
::
::Norm
::
:::More questions: What on earth is the purpose of the line cord resistor? Why were they so popular during the mid-1930s? Is this a way to spread out the heat so that it doesn't get the radio really hot? It just sounds so pointless to put a resistor in a line cord and expect it to neither start a fire nor break. I guess when they were operated properly they didn't usually start fires. I don't know of any that get too hot.
:::
:::Another question: Why did Grigsby-Grunow use that silly ballast resistor in their power supplies? Could you change the resistor so that the set could be used at different voltages? It is otherwise pointless.
:::
:::I wish that there was a chat site for 1937-1952 Chevrolets. Then I could ask all sorts of questions like why on earth did Chevrolet use splash lubrication on the 216.5 engine. Seems pointless and over complicated putting all those dippers, troughs, and sprayers in there when they could have simply drilled passages through the crank shaft like everyone else was doing. I see no benefits to splash lubrication, where the oil pressure is 15 p.s.i. at best, and when the oil is sluggish, it never even makes it to the rods.
:::
:::Lots of pointless things are baffling me right now. The 6B5 tube sounds like a good idea, though. Another kind of pointless thing is using a triode as a detector when many radios had dual-diode-triode tubes running right along with these triode detector tubes (or using both a 6H6 and a 6Q7 in the same radio...pointless). Strange how some radio manufacturers were trying to increase tube count and others were trying to decrease it. A triode sort-of makes a better detector than a diode, I guess. I have noticed miniscual (spelling?) increases in sensitivity when a triode is used instead of a diode, with the plate and grid tied together. I suppose whenever the plate goes positive, so does the grid, which encourages current flow. I'd like to know why my Crosley 1117 has separate triode detector and triode AVC tubes along with a 6K5 triode amplifier, which could have easily been a 6Q7, which would serve all three purposes. The radio also has a separate oscillator tube. Still, with all of these unnecessary extras, it takes the phase inversion for the second output tube (push-pull) off of the screen grid of the first output tube. Why not just add a phase inverter tube and make it a 12 tube set? Is there any benefit to having a separate oscillator tube?
:::
:::Thomas
Bill VA
:Hi Bill
:
: A 6K8 is often a direct replacement for 6A8 although it's not shown that way in substitution guides. Notice a 6K8 has a separate triode for oscillator but basing is the same as 6A8.
:
:Norm
:
::Norm, is the 6K8 in place of 6A8 a direct replacement?
::
::Bill VA
::
::
:::Hi Thomas
:::
::: Interesting questions..
:::
::: The line cord resistor did spead out heat. Some sort of resistor was needed in series with filaments. A resistor inside a small cabinet would get too hot. No one expected these radios to be around for 70 years.. The line cord resistors worked as long as someone didn't coil them up.. Discuss before using a cap in place of resistor line cord. It does stay cool but has other problems.
:::
::: Grigsby-Grunow used ballasts to compensate for line voltage variation. Atwater Kent and others did the same. These line ballasts tend to drop more voltage with higher line. RCA used a giant UV876 tube.
:::
::: Cheaper? and more engines to replace.
:::
::: The 6B5 was used to save on components. It didn't require bias. You will find a 42 works just as well. In place of 6N6G a person can use 6F6 or 6V6. These substitutions require a cathode resistor to be added. Should also be bypassed with a cap.
:::
::: As far as I can tell 6H6's were developed only to add to tube count. There are a few radios which used full wave detection. FM needs separate diodes but these radios were made before that time.
:::
::: Never could understand why someone would use a 6K5 or 6F5 instead of 6Q7? Again maybe to add to tube count since you also needed a 6H6?
:::
::: Shouldn't be any difference between a diode tube and triode with plate & grid connected. If there was we would have amplifier diodes.
:::
::: A separate oscillator does have an advantage. It's more stable. Even using a 6K8 instead of 6A8 is supposed to have better stability.
:::
:::Norm
:::
::::More questions: What on earth is the purpose of the line cord resistor? Why were they so popular during the mid-1930s? Is this a way to spread out the heat so that it doesn't get the radio really hot? It just sounds so pointless to put a resistor in a line cord and expect it to neither start a fire nor break. I guess when they were operated properly they didn't usually start fires. I don't know of any that get too hot.
::::
::::Another question: Why did Grigsby-Grunow use that silly ballast resistor in their power supplies? Could you change the resistor so that the set could be used at different voltages? It is otherwise pointless.
::::
::::I wish that there was a chat site for 1937-1952 Chevrolets. Then I could ask all sorts of questions like why on earth did Chevrolet use splash lubrication on the 216.5 engine. Seems pointless and over complicated putting all those dippers, troughs, and sprayers in there when they could have simply drilled passages through the crank shaft like everyone else was doing. I see no benefits to splash lubrication, where the oil pressure is 15 p.s.i. at best, and when the oil is sluggish, it never even makes it to the rods.
::::
::::Lots of pointless things are baffling me right now. The 6B5 tube sounds like a good idea, though. Another kind of pointless thing is using a triode as a detector when many radios had dual-diode-triode tubes running right along with these triode detector tubes (or using both a 6H6 and a 6Q7 in the same radio...pointless). Strange how some radio manufacturers were trying to increase tube count and others were trying to decrease it. A triode sort-of makes a better detector than a diode, I guess. I have noticed miniscual (spelling?) increases in sensitivity when a triode is used instead of a diode, with the plate and grid tied together. I suppose whenever the plate goes positive, so does the grid, which encourages current flow. I'd like to know why my Crosley 1117 has separate triode detector and triode AVC tubes along with a 6K5 triode amplifier, which could have easily been a 6Q7, which would serve all three purposes. The radio also has a separate oscillator tube. Still, with all of these unnecessary extras, it takes the phase inversion for the second output tube (push-pull) off of the screen grid of the first output tube. Why not just add a phase inverter tube and make it a 12 tube set? Is there any benefit to having a separate oscillator tube?
::::
::::Thomas
Actually I have no clue, but these seem like reasonable thoughts.
Tony
:More questions: What on earth is the purpose of the line cord resistor? Why were they so popular during the mid-1930s? Is this a way to spread out the heat so that it doesn't get the radio really hot? It just sounds so pointless to put a resistor in a line cord and expect it to neither start a fire nor break. I guess when they were operated properly they didn't usually start fires. I don't know of any that get too hot.
:
:Another question: Why did Grigsby-Grunow use that silly ballast resistor in their power supplies? Could you change the resistor so that the set could be used at different voltages? It is otherwise pointless.
:
:I wish that there was a chat site for 1937-1952 Chevrolets. Then I could ask all sorts of questions like why on earth did Chevrolet use splash lubrication on the 216.5 engine. Seems pointless and over complicated putting all those dippers, troughs, and sprayers in there when they could have simply drilled passages through the crank shaft like everyone else was doing. I see no benefits to splash lubrication, where the oil pressure is 15 p.s.i. at best, and when the oil is sluggish, it never even makes it to the rods.
:
:Lots of pointless things are baffling me right now. The 6B5 tube sounds like a good idea, though. Another kind of pointless thing is using a triode as a detector when many radios had dual-diode-triode tubes running right along with these triode detector tubes (or using both a 6H6 and a 6Q7 in the same radio...pointless). Strange how some radio manufacturers were trying to increase tube count and others were trying to decrease it. A triode sort-of makes a better detector than a diode, I guess. I have noticed miniscual (spelling?) increases in sensitivity when a triode is used instead of a diode, with the plate and grid tied together. I suppose whenever the plate goes positive, so does the grid, which encourages current flow. I'd like to know why my Crosley 1117 has separate triode detector and triode AVC tubes along with a 6K5 triode amplifier, which could have easily been a 6Q7, which would serve all three purposes. The radio also has a separate oscillator tube. Still, with all of these unnecessary extras, it takes the phase inversion for the second output tube (push-pull) off of the screen grid of the first output tube. Why not just add a phase inverter tube and make it a 12 tube set? Is there any benefit to having a separate oscillator tube?
:
:Thomas
I suppose line cord resistors were a pretty good thing for their day in time. As has already been discussed, they got the heat away from the small cheap sets, but even then, that was not always enough. For instance, the cabinets of some catalins have hot spots that ruined the color. I have a few resistance power cords that are NOS in the box and tried one of them years ago just to see how well it worked. The rubber is so stiff in these things that they cannot be unfolded, but even in that position, the one I tried only got slightly warm.
Back during the time that I was tinkering with sets of this vintage, I did not know about using a condenser to reduce the filament line voltage. I got away with using large power resistors a time or two, but was uncomfortable about the amount of heat. I finally got the bright idea of using the reactance of a small iron core choke, which worked very well and did not even get warm. The difficulty of using a choke was getting the reactance exactly right, which turned out to be a long drawn out trial and error ordeal. To do this, I adjusted the air gap of the iron with paper shims. This method has been used for many years to adjust an air gap, so I thought it would be fairly simple. Wrong. A very small change in the air gap caused a large difference in the current, so I spent a lot of time getting the voltage exactly right. Dumb old me could have probably used a small condenser in conjunction with the choke to fine tune it.
Norm is right about using a ballast resistor for voltage regulation. The wire used for them is a blend that makes them more sensitive to heat changes. This is not desirable for other type resistors, so a different blend was used for them. One of the early uses for this type of wire is the Amperite resistor. These resistor cartridges were used instead of rheostats on battery sets to regulate the tube filaments. I don’t recall a manufactured set that used them, but they were popular with the home builders. A fully charged “A” battery increased the heat and reduced the filament voltage. As the battery discharged, the heat became less and reduced the resistance. They had different values, depending on what type of tube was used and how many were used with a single cartridge. I don’t especially care to use them because most of these early tubes work just as well, and in some cases even better with less than the recommended filament voltage. However, they reduced the number of controls, and this became a very important part of radio development. Ballast resistors were also used to regulate “B” batteries, but this use was fairly rare. My Leutz Pliodyne 9 has a ballast tube to regulate the RF plate voltage as the battery is drained. This ballast is installed in series with the 90 volt supply, which reduces the number of battery taps, making hookup less complicated.
All you radio guys can skip this next part. Me and Thomas are gonna talk Chevrolet. I was cutting my eye teeth while working on the 216 Chevrolet engine, and still remember a little bit about it. My parents had a 1939 model and later on a 1941 model, and this is the one I began working on. My first car was a 1946 model, and the last one I had with this engine was a 1953 model. Seems to me like I remember the standard shift for that year had the old engine with the splash system and babbitt rods, while the Power Glide had the new engine with a pressurized oil system and rod inserts. Maybe I’m wrong about that, but I know for certain that both engines were different. I have never given much thought as to why they stayed with the splash system for so long, but can look back and guess.
I imagine the number one reason was because it worked all those years, and held up just as well as other engines in the low price range. Quite a few of the older engines used the splash system because they did not require an oil pump, but when Chevrolet went to overhead valves, one was required. Even at 15 pounds (30 cold), the small oil line going to the rocker arm shaft was too much and the system had to be further restricted to reduce the flow. Actually, the splash system may have done more than you have imagined. It creates a very violent action inside the crankcase, and breaks up a lot of oil into a fine mist. Don’t forget that the under side of the pistons are air compressors working both ways, so the mist goes everywhere. I have removed many a rod cap to tighten the bearings and have never seen one that was starving for oil.
My question back then was not why the splash system was used, but why the other manufacturers did not go to overhead valves. I said back then that General Motors could develop an overhead valve V8 that would be the hottest thing on the road. The 1949 Oldsmobile Rocket 88 proved that prediction to be true and the small block Chevy engine drove it home. I got tickled when Ford came out with their first OHV engine. This was a 6 cylinder engine in 1953 that replaced their flathead 6. It was better in every way when compared with their flathead V8. More power, faster acceleration, higher top speed, better fuel economy and less initial cost. However, most people thought a Ford had to be a V8, so they kept on buying the flathead. Maybe some radio manufacturers had the same mentality.
That gets us back to pointless baffling radio things such as, “a triode sort-of makes a better detector than a diode.” Well yeah, it sort of does in some ways, but a diode produces less distortion and permits the use of a simple avc circuit, so this method was most widely used in broadcast receivers. But then, it draws current from the input circuit and reduces the selectivity, so that certainly does not make it better. Other than linear distortion, a triode can make a better detector mainly because it can amplify while it is detecting, but it can do more than that. Most RF and IF circuits are designed to perform just below the point of becoming unstable. This is why some sets squeal if you remove just one tube shield. What this means is that the detector circuit is using regeneration to increase the signal strength and selectivity, which decreases the number of tubes required. This method was not just used for vacuum tube circuits, but also transistor radios. I had the privilege of talking with one of the designers of the Regency TR-1 transistor radio circuit. He said that the IF amplifier was designed with a certain amount of regeneration to reduce the number of transistors. Seems like I remember him saying that they burned the midnight oil and had the prototype ready in just a few days after the orders to design a shirt pocket radio.
As for why some manufacturers used certain tubes, we can only guess in some situations. Things were happening so fast during these years that no one person could keep up with everything. Before a manufacturer learned to make the best use of a tube, a new one came out. By that time, the manufacturer may have had a large number of the earlier tubes and may have designed a circuit with a weird tube combination to get rid of them. Then too, the newer type tubes were not all introduced at the same time, and some of them came out as radio progressed. For instance, the first radio with automatic volume control did not have a special triode with diodes, but they were available later on. Perhaps a 6H6 is a good way of getting rid of a boxcar load of surplus triodes, I don’t know. I once had a radio with 2 digit tubes that came out a couple years after octal base tubes were introduced. Probably designed with surplus tubes and parts, and maybe worked just as well with these tubes, since some of them had the same characteristics as the octal based tubes.
Yep. Some manufacturers sold radios with only a few tubes for common folk who could hardly afford them, and some sold more elaborate sets to people who could afford the best, or at least what they thought was the best. Midwest is most noted today for using too many tubes just for the sake of tube count, but I have owned a few of them and most of the tubes were put to fairly good use. I had a 20 tube chair side that actually had a well designed circuit, but they put it in a cheap chassis along with flashy cheap everything else, including a flimsy cabinet that would have came to pieces if the main speaker would have done anything. It would have been just as well off with a single output tube instead of the four in parallel push pull.
I could keep on rambling, but since a good bit of what I have said is pure speculation and part of that is probably wrong, I reckon I better quit. However, before I do, I have a question of my own that I would like to ask. Why does Microsoft Word recognize the spelling of the word flathead and not the word babbitt?
It's so great to hear all about this stuff. I wish I could pick the brains of all the designers of all the radios and cars produced back then. I guess they're mostly dead now, though. I always wanted to meet Helen Forrest, but she died a couple of years after I graduated from high school. Everything I like is kind of going away. Oh well.
Your knowledge is appreciated.
Thomas
:Hi Thomas,
:I read your questions when you first posted them, but was too busy with other things to reply. Now that I have the time, I see that several of them have been discussed fairly well and some have not. Therefore, I’ll ramble on a bit about my experiences concerning some of them, and either add to the confusion, or maybe take some of it away.
:
:I suppose line cord resistors were a pretty good thing for their day in time. As has already been discussed, they got the heat away from the small cheap sets, but even then, that was not always enough. For instance, the cabinets of some catalins have hot spots that ruined the color. I have a few resistance power cords that are NOS in the box and tried one of them years ago just to see how well it worked. The rubber is so stiff in these things that they cannot be unfolded, but even in that position, the one I tried only got slightly warm.
:
:Back during the time that I was tinkering with sets of this vintage, I did not know about using a condenser to reduce the filament line voltage. I got away with using large power resistors a time or two, but was uncomfortable about the amount of heat. I finally got the bright idea of using the reactance of a small iron core choke, which worked very well and did not even get warm. The difficulty of using a choke was getting the reactance exactly right, which turned out to be a long drawn out trial and error ordeal. To do this, I adjusted the air gap of the iron with paper shims. This method has been used for many years to adjust an air gap, so I thought it would be fairly simple. Wrong. A very small change in the air gap caused a large difference in the current, so I spent a lot of time getting the voltage exactly right. Dumb old me could have probably used a small condenser in conjunction with the choke to fine tune it.
:
:Norm is right about using a ballast resistor for voltage regulation. The wire used for them is a blend that makes them more sensitive to heat changes. This is not desirable for other type resistors, so a different blend was used for them. One of the early uses for this type of wire is the Amperite resistor. These resistor cartridges were used instead of rheostats on battery sets to regulate the tube filaments. I don’t recall a manufactured set that used them, but they were popular with the home builders. A fully charged “A” battery increased the heat and reduced the filament voltage. As the battery discharged, the heat became less and reduced the resistance. They had different values, depending on what type of tube was used and how many were used with a single cartridge. I don’t especially care to use them because most of these early tubes work just as well, and in some cases even better with less than the recommended filament voltage. However, they reduced the number of controls, and this became a very important part of radio development. Ballast resistors were also used to regulate “B” batteries, but this use was fairly rare. My Leutz Pliodyne 9 has a ballast tube to regulate the RF plate voltage as the battery is drained. This ballast is installed in series with the 90 volt supply, which reduces the number of battery taps, making hookup less complicated.
:
:All you radio guys can skip this next part. Me and Thomas are gonna talk Chevrolet. I was cutting my eye teeth while working on the 216 Chevrolet engine, and still remember a little bit about it. My parents had a 1939 model and later on a 1941 model, and this is the one I began working on. My first car was a 1946 model, and the last one I had with this engine was a 1953 model. Seems to me like I remember the standard shift for that year had the old engine with the splash system and babbitt rods, while the Power Glide had the new engine with a pressurized oil system and rod inserts. Maybe I’m wrong about that, but I know for certain that both engines were different. I have never given much thought as to why they stayed with the splash system for so long, but can look back and guess.
:
:I imagine the number one reason was because it worked all those years, and held up just as well as other engines in the low price range. Quite a few of the older engines used the splash system because they did not require an oil pump, but when Chevrolet went to overhead valves, one was required. Even at 15 pounds (30 cold), the small oil line going to the rocker arm shaft was too much and the system had to be further restricted to reduce the flow. Actually, the splash system may have done more than you have imagined. It creates a very violent action inside the crankcase, and breaks up a lot of oil into a fine mist. Don’t forget that the under side of the pistons are air compressors working both ways, so the mist goes everywhere. I have removed many a rod cap to tighten the bearings and have never seen one that was starving for oil.
:
:My question back then was not why the splash system was used, but why the other manufacturers did not go to overhead valves. I said back then that General Motors could develop an overhead valve V8 that would be the hottest thing on the road. The 1949 Oldsmobile Rocket 88 proved that prediction to be true and the small block Chevy engine drove it home. I got tickled when Ford came out with their first OHV engine. This was a 6 cylinder engine in 1953 that replaced their flathead 6. It was better in every way when compared with their flathead V8. More power, faster acceleration, higher top speed, better fuel economy and less initial cost. However, most people thought a Ford had to be a V8, so they kept on buying the flathead. Maybe some radio manufacturers had the same mentality.
:
:That gets us back to pointless baffling radio things such as, “a triode sort-of makes a better detector than a diode.” Well yeah, it sort of does in some ways, but a diode produces less distortion and permits the use of a simple avc circuit, so this method was most widely used in broadcast receivers. But then, it draws current from the input circuit and reduces the selectivity, so that certainly does not make it better. Other than linear distortion, a triode can make a better detector mainly because it can amplify while it is detecting, but it can do more than that. Most RF and IF circuits are designed to perform just below the point of becoming unstable. This is why some sets squeal if you remove just one tube shield. What this means is that the detector circuit is using regeneration to increase the signal strength and selectivity, which decreases the number of tubes required. This method was not just used for vacuum tube circuits, but also transistor radios. I had the privilege of talking with one of the designers of the Regency TR-1 transistor radio circuit. He said that the IF amplifier was designed with a certain amount of regeneration to reduce the number of transistors. Seems like I remember him saying that they burned the midnight oil and had the prototype ready in just a few days after the orders to design a shirt pocket radio.
:
:As for why some manufacturers used certain tubes, we can only guess in some situations. Things were happening so fast during these years that no one person could keep up with everything. Before a manufacturer learned to make the best use of a tube, a new one came out. By that time, the manufacturer may have had a large number of the earlier tubes and may have designed a circuit with a weird tube combination to get rid of them. Then too, the newer type tubes were not all introduced at the same time, and some of them came out as radio progressed. For instance, the first radio with automatic volume control did not have a special triode with diodes, but they were available later on. Perhaps a 6H6 is a good way of getting rid of a boxcar load of surplus triodes, I don’t know. I once had a radio with 2 digit tubes that came out a couple years after octal base tubes were introduced. Probably designed with surplus tubes and parts, and maybe worked just as well with these tubes, since some of them had the same characteristics as the octal based tubes.
:
:Yep. Some manufacturers sold radios with only a few tubes for common folk who could hardly afford them, and some sold more elaborate sets to people who could afford the best, or at least what they thought was the best. Midwest is most noted today for using too many tubes just for the sake of tube count, but I have owned a few of them and most of the tubes were put to fairly good use. I had a 20 tube chair side that actually had a well designed circuit, but they put it in a cheap chassis along with flashy cheap everything else, including a flimsy cabinet that would have came to pieces if the main speaker would have done anything. It would have been just as well off with a single output tube instead of the four in parallel push pull.
:
:I could keep on rambling, but since a good bit of what I have said is pure speculation and part of that is probably wrong, I reckon I better quit. However, before I do, I have a question of my own that I would like to ask. Why does Microsoft Word recognize the spelling of the word flathead and not the word babbitt?
:
A little off the subject of this exceptional forum regarding babbitt and flathead engines. I remember pouring babbitt bearings in place in a very old steam driven product pump in the cannery I worked in high school. It was explaned to me that these large pieces of equipment could be kept running much longer after the replacement parts stopped being produced. All you did was set up the portable forge and pot, then build the "dams", melt and pour. This was only in 1976, but I rarely meet anyone today that has ever heard of it. As for the flathead engines I never liked rebuilding them as getting the valve lash right on those solid lifters was a royal pain-or I just was not very good at it. Thanks for bringing back these memories. Jon.
I find it hillarious how I got a thread going on old engines in a radio forum. Somehow I have to switch the subject back to radios before someone gets angry.
T.
:A little off the subject of this exceptional forum regarding babbitt and flathead engines. I remember pouring babbitt bearings in place in a very old steam driven product pump in the cannery I worked in high school. It was explaned to me that these large pieces of equipment could be kept running much longer after the replacement parts stopped being produced. All you did was set up the portable forge and pot, then build the "dams", melt and pour. This was only in 1976, but I rarely meet anyone today that has ever heard of it. As for the flathead engines I never liked rebuilding them as getting the valve lash right on those solid lifters was a royal pain-or I just was not very good at it. Thanks for bringing back these memories. Jon.