I need more help! My Zenith 4B131 seems to be working except for one thing, I get no stations between 600 and 1100. Nothing, zip, nada, not even a blip or squawk as you spin past a station on the dial. I can get 580 from Topeka, but here in Kansas City there are several powerhouses much stronger than 580 in Topeka, they are 610, 710, 760, 810, 980, 1090 and 1140, but the next station I get is 1250. I can get stations between 1250 and 1660 at the top of the dial. I'm stumped! Can anyone point me in the right direction?

Dave, see if one or more of the leaves of the variable capacitors is somehow warped, and shorting out over the frequencies that are silent. Use a flashlight or an ohmmeter to check.

Dave,
Assume you've re-capped everything? I've had similar experiences with mis-aligned plates on the variable tuning condenser touching the grounded plates during a part of its rotation. Some units have their plates slotted in such a way that a smaller segment of the half moon grounded plates can be bent toward the stationary plates. A malfunction in the AVC circuit on strong local stations only, but Thomas is the Guru on AVC.
marv

:I need more help! My Zenith 4B131 seems to be working except for one thing, I get no stations between 600 and 1100. Nothing, zip, nada, not even a blip or squawk as you spin past a station on the dial. I can get 580 from Topeka, but here in Kansas City there are several powerhouses much stronger than 580 in Topeka, they are 610, 710, 760, 810, 980, 1090 and 1140, but the next station I get is 1250. I can get stations between 1250 and 1660 at the top of the dial. I'm stumped! Can anyone point me in the right direction?

I have recapped everything and also replaced every resistor. I took the tuning cap out of the set last night, hooked my ohmmeter to both sets of plates and found no problems. I'm beginning to think my "fix" for the oscillator coil did not work and it starts oscillating around 1200KHz. I get great reception above 1200KHz, but below that nothing. The oscillator tickler coil was broken on both ends, I soldered some scrap wire of the same size from a slavaged oscillator coil to both ends and got voltage to the plate of the first tube. I beginning to think I threw off the oacillator frequency with my fix. I didn't run any "extra" wire just enough to reconnect it to the solder lugs. Could this be a problem? How sensitive are these coils? Help... Dave
:Dave,
:Assume you've re-capped everything? I've had similar experiences with mis-aligned plates on the variable tuning condenser touching the grounded plates during a part of its rotation. Some units have their plates slotted in such a way that a smaller segment of the half moon grounded plates can be bent toward the stationary plates. A malfunction in the AVC circuit on strong local stations only, but Thomas is the Guru on AVC.
:marv
:
::I need more help! My Zenith 4B131 seems to be working except for one thing, I get no stations between 600 and 1100. Nothing, zip, nada, not even a blip or squawk as you spin past a station on the dial. I can get 580 from Topeka, but here in Kansas City there are several powerhouses much stronger than 580 in Topeka, they are 610, 710, 760, 810, 980, 1090 and 1140, but the next station I get is 1250. I can get stations between 1250 and 1660 at the top of the dial. I'm stumped! Can anyone point me in the right direction?

They are not that sensitive. If you reconnected the coil properly, and didn't accidently connect to another possible break, then it should work well. I have rewound a few oscillator coils, and even though I did not wind them exactly like original, they work quite well. The worst that usually happens is that station spacing is a bit off. Most likely your set needs a good alignment with a good signal generator. If the IF transformers are off, you may have adjusted your oscillator trimmer and padder to points that bring in stations at the high end, but cause the oscillator to malfunction at the low end. Could also be a weak tube. It could possibly be that you reconnected one of the oscillator coils in reverse, but normally this causes the oscillator to simply not function. Be sure that the variable condenser has NO leakage. If it is dirty or coated with a yellow film, this can set up leakage. Check the condenser with your most sensitive meter setting (capable of checking in the millions of ohms). Check both the oscillator and antenna sections.

Thomas

Dave, first you said that you got stations in the middle of the band, but not at the top or the bottom. Now, you get everything above 1200Hz?

Sometimes, a weak oscillator tube will poop out below a particular freq, but work OK above that freq. When that's the problem, the oscillator will start at, say, cutoff+ when tuning from below, and stop at cutoff- when tuning from above.

Hi Dave,
Doug is right about the osc. tube being weak. If you don't have another tube to try in it's place, try swapping the osc. and IF tubes.
Another thing you can do is replace R2 (the 9Kohm resistor) with a lower value. R2 is the cathode self-bias resistor. Lowering its value will result in stronger electron flow in the tube.
BR,
Dave

:Hi Dave,
:Doug is right about the osc. tube being weak. If you don't have another tube to try in it's place, try swapping the osc. and IF tubes.
:Another thing you can do is replace R2 (the 9Kohm resistor) with a lower value. R2 is the cathode self-bias resistor. Lowering its value will result in stronger electron flow in the tube.
:BR,
:Dave

Thomas, Doug & Dave,

I'll swap tubes first. I have an extra new Philco 15 somewhere so I'll put it on the tester and see if it is still good before installing it in the radio. If that doesn't improve things I may try Doug's trick and replace R2 with a smaller value. I seems to me that a 9K ohm resistor was hard to find and I used a 10K ohm, so maybe that is my problem. Instead od using a larger value, I should have used a smaller one. Thanks for the tips guys, I'll have something to work on this weekend!

Try making the resistor right on value by using two resistors in series. Though this circuit is not that sensitive, too little resistance may diminish sensitivity, where-as too much resistance may make the circuit too "loose," which causes it to be unstable.

A note on the tube: Usually an oscillator tube that works irratically does show up as weak. Sometimes, however, it will not, especially if there are traces of gas in the tube which are causing the problem, or if the cathode coating is working intermittently. I had a couple of 1LA6 tubes act like this. Sometimes they would test good and sometimes bad. Sometimes the set would work and sometimes not. Feeding a high cathode to plate current through each of them on my tube tester usually "rejuvenated" them for about a week. Still, if the tube in question tests good, do not assume that it is bad yet until you have tried out several other good tubes in the circuit. If, then, only the original tube causes the trouble, you can assume that it is faulty in some way. Still, you may want to try the tube in some other circuit to see if it causes other troubles or if it is still usable. Usually, however, when a tube is bad, it tests bad.

Thomas

Dave I had the same problem with a RCA and it was that my osc coil was not repaired correctly mine was as thomas said earlier , that there was a additional break on it and was not found, I had to remove the coil and un wind it until I found all the breaks then reconnected it all back together and the whole band came back to life if all else fails check your coil again.
Elton
:Try making the resistor right on value by using two resistors in series. Though this circuit is not that sensitive, too little resistance may diminish sensitivity, where-as too much resistance may make the circuit too "loose," which causes it to be unstable.
:
:A note on the tube: Usually an oscillator tube that works irratically does show up as weak. Sometimes, however, it will not, especially if there are traces of gas in the tube which are causing the problem, or if the cathode coating is working intermittently. I had a couple of 1LA6 tubes act like this. Sometimes they would test good and sometimes bad. Sometimes the set would work and sometimes not. Feeding a high cathode to plate current through each of them on my tube tester usually "rejuvenated" them for about a week. Still, if the tube in question tests good, do not assume that it is bad yet until you have tried out several other good tubes in the circuit. If, then, only the original tube causes the trouble, you can assume that it is faulty in some way. Still, you may want to try the tube in some other circuit to see if it causes other troubles or if it is still usable. Usually, however, when a tube is bad, it tests bad.
:
:Thomas

Elton,

I have repaired this coil a couple of times and tried it in the radio with no luck. I get voltage to the tube plate and it has to go through the coil to get there, so it doesn't seem likely to me that there is another break in the wire. However, at this point I'm willing to try anything. So with that in mind, how do I find out what size of wire is used and where do i purchase wire that small. It is tiny!!

Dave

:Dave I had the same problem with a RCA and it was that my osc coil was not repaired correctly mine was as thomas said earlier , that there was a additional break on it and was not found, I had to remove the coil and un wind it until I found all the breaks then reconnected it all back together and the whole band came back to life if all else fails check your coil again.
:Elton
::Try making the resistor right on value by using two resistors in series. Though this circuit is not that sensitive, too little resistance may diminish sensitivity, where-as too much resistance may make the circuit too "loose," which causes it to be unstable.
::
::A note on the tube: Usually an oscillator tube that works irratically does show up as weak. Sometimes, however, it will not, especially if there are traces of gas in the tube which are causing the problem, or if the cathode coating is working intermittently. I had a couple of 1LA6 tubes act like this. Sometimes they would test good and sometimes bad. Sometimes the set would work and sometimes not. Feeding a high cathode to plate current through each of them on my tube tester usually "rejuvenated" them for about a week. Still, if the tube in question tests good, do not assume that it is bad yet until you have tried out several other good tubes in the circuit. If, then, only the original tube causes the trouble, you can assume that it is faulty in some way. Still, you may want to try the tube in some other circuit to see if it causes other troubles or if it is still usable. Usually, however, when a tube is bad, it tests bad.
::
::Thomas

You say that there were only two breaks in the coil which you repaired. You must be sure that where you made your repair, you soldered only one wire to one wire. If by chance you accidentally soldered to more than one wire, you could have caused a short. If you made more than two repairs, and accidently soldered the coil so that current goes through part of the coil one way and then part of the coil the other way, you will also have trouble. A both situations make the coil extremely inefficient. A short also changes the frequency response of the coil. Retuning trimmers may fix the problem, but with a lack of power due to the mismatch of the circuit. Both problems will create generation of random unwanted frequencies, which may or may not affect tuning.

Thomas

You say that there were only two breaks in the coil which you repaired. You must be sure that where you made your repair, you soldered only one wire to one wire. If by chance you accidentally soldered to more than one wire, you could have caused a short. If you made more than two repairs, and accidently soldered the coil so that current goes through part of the coil one way and then part of the coil the other way, you will also have trouble. Both situations make the coil extremely inefficient. A short also changes the frequency response of the coil. Retuning trimmers may fix the problem, but with a lack of power due to the mismatch of the circuit. Both problems will create generation of random unwanted frequencies, which may or may not affect tuning.
:
:Thomas

Dave ,
You stated that you had repaired a part of the oscillator coil in order to obtain B+ at the first detector/osc, but thats only part of the entire assembly. It has 2 windings, and the part you fixed looks like a choke at the RF frequency and an untuned coupling winding to the tuned section of this assembly. There are 3 other terminals that are the actual tuned/tuning portion of this circuit to C2 (the padder) and C14 the actual tuning condenser. Hopefully you were able to isolate the 2 windings when the fix was made, and assure that you havent erroneously interconnected the 2 windings. Locate the other 3 terminals, and verify their continuity and connections.
marv

:Elton,
:
:I have repaired this coil a couple of times and tried it in the radio with no luck. I get voltage to the tube plate and it has to go through the coil to get there, so it doesn't seem likely to me that there is another break in the wire. However, at this point I'm willing to try anything. So with that in mind, how do I find out what size of wire is used and where do i purchase wire that small. It is tiny!!
:
:Dave
:
::Dave I had the same problem with a RCA and it was that my osc coil was not repaired correctly mine was as thomas said earlier , that there was a additional break on it and was not found, I had to remove the coil and un wind it until I found all the breaks then reconnected it all back together and the whole band came back to life if all else fails check your coil again.
::Elton
:::Try making the resistor right on value by using two resistors in series. Though this circuit is not that sensitive, too little resistance may diminish sensitivity, where-as too much resistance may make the circuit too "loose," which causes it to be unstable.
:::
:::A note on the tube: Usually an oscillator tube that works irratically does show up as weak. Sometimes, however, it will not, especially if there are traces of gas in the tube which are causing the problem, or if the cathode coating is working intermittently. I had a couple of 1LA6 tubes act like this. Sometimes they would test good and sometimes bad. Sometimes the set would work and sometimes not. Feeding a high cathode to plate current through each of them on my tube tester usually "rejuvenated" them for about a week. Still, if the tube in question tests good, do not assume that it is bad yet until you have tried out several other good tubes in the circuit. If, then, only the original tube causes the trouble, you can assume that it is faulty in some way. Still, you may want to try the tube in some other circuit to see if it causes other troubles or if it is still usable. Usually, however, when a tube is bad, it tests bad.
:::
:::Thomas

Marv & Thomas,

The tickler part of the coil was the only part open. An ohmmeter on the antenna part of the coil shows continuity between terminals and between each terminal and ground so I'm certain this part of the coil is OK. Also, this coil is double wound, with the oscillator winding being placed on another cardboard form and slipped over the antenna part of the coil. The outer winding actually protects the inner winding and while I haven't melted the wax to pull them apart, I figured as long as they tested good and are still sealed in wax, I'll leave that part alone. The problem exists in the outer winding which is shown on the schematic as a tickler that supplies B+ to the plate of the oscillator/mixer. I'm getting voltage with the radio powered up, it just doesn't pick up any stations from 550KHz to 1200KHz. Above 1200KHZ everything is loud, clear and very sensitive. I don't have my signal generator back from my friend, so I haven't done a proper alignment. If there are shorted oscillator windings then with a shorter coil the oscillator is operating out of spec too high, I need the extra turns of wire to bring the oscillator back down to the range of 1005KHz to 2165KHz in order to receive stations on the lower part of the band. My thinking at this point is the windings are shorted and with the smaller inductance the oscillator cannot operate at a frequency below 1655KHz and gives me my lowest tuned frequency of 1200KHz (1655-1200=455). Sound reasonable?

:Dave ,
:You stated that you had repaired a part of the oscillator coil in order to obtain B+ at the first detector/osc, but thats only part of the entire assembly. It has 2 windings, and the part you fixed looks like a choke at the RF frequency and an untuned coupling winding to the tuned section of this assembly. There are 3 other terminals that are the actual tuned/tuning portion of this circuit to C2 (the padder) and C14 the actual tuning condenser. Hopefully you were able to isolate the 2 windings when the fix was made, and assure that you havent erroneously interconnected the 2 windings. Locate the other 3 terminals, and verify their continuity and connections.
:marv
:
::Elton,
::
::I have repaired this coil a couple of times and tried it in the radio with no luck. I get voltage to the tube plate and it has to go through the coil to get there, so it doesn't seem likely to me that there is another break in the wire. However, at this point I'm willing to try anything. So with that in mind, how do I find out what size of wire is used and where do i purchase wire that small. It is tiny!!
::
::Dave
::
:::Dave I had the same problem with a RCA and it was that my osc coil was not repaired correctly mine was as thomas said earlier , that there was a additional break on it and was not found, I had to remove the coil and un wind it until I found all the breaks then reconnected it all back together and the whole band came back to life if all else fails check your coil again.
:::Elton
::::Try making the resistor right on value by using two resistors in series. Though this circuit is not that sensitive, too little resistance may diminish sensitivity, where-as too much resistance may make the circuit too "loose," which causes it to be unstable.
::::
::::A note on the tube: Usually an oscillator tube that works irratically does show up as weak. Sometimes, however, it will not, especially if there are traces of gas in the tube which are causing the problem, or if the cathode coating is working intermittently. I had a couple of 1LA6 tubes act like this. Sometimes they would test good and sometimes bad. Sometimes the set would work and sometimes not. Feeding a high cathode to plate current through each of them on my tube tester usually "rejuvenated" them for about a week. Still, if the tube in question tests good, do not assume that it is bad yet until you have tried out several other good tubes in the circuit. If, then, only the original tube causes the trouble, you can assume that it is faulty in some way. Still, you may want to try the tube in some other circuit to see if it causes other troubles or if it is still usable. Usually, however, when a tube is bad, it tests bad.
::::
::::Thomas

Dave,
I'm not sure I understand your response in refering to the other half as the antenna part. Item 3 on the schematic is strictly a tunable oscillator inductor w/tickler, to form a feedback path, and sustain oscillations. Item 2 on the other hand is the antenna tuning element. Is there any evidence that the tickler has missing turns, other than the simple break you repaired? Is there any evidence that the outer form was moved enough to cause the broken wire, or its position over the oscillator coil? If its position over the oscillator coil has been altered appreciably, coupled energy may be insufficient to sustain oscillations. By your description, it appears that the oscillator function ceases below 1.65 mHz (1.2 mHz + 0.456mHz/high side injection), but if the dial pointer is remotely accurate, shorted turns in the oscillator coil would have the pointer far removed from the stations you found, unless a radio technician of yesteryear severely mis-adjusted C2 to compensate for unknown problems, but managed to find an area on the upper end of the dial that was accurate.
marv

:Marv & Thomas,
:
:The tickler part of the coil was the only part open. An ohmmeter on the antenna part of the coil shows continuity between terminals and between each terminal and ground so I'm certain this part of the coil is OK. Also, this coil is double wound, with the oscillator winding being placed on another cardboard form and slipped over the antenna part of the coil. The outer winding actually protects the inner winding and while I haven't melted the wax to pull them apart, I figured as long as they tested good and are still sealed in wax, I'll leave that part alone. The problem exists in the outer winding which is shown on the schematic as a tickler that supplies B+ to the plate of the oscillator/mixer. I'm getting voltage with the radio powered up, it just doesn't pick up any stations from 550KHz to 1200KHz. Above 1200KHZ everything is loud, clear and very sensitive. I don't have my signal generator back from my friend, so I haven't done a proper alignment. If there are shorted oscillator windings then with a shorter coil the oscillator is operating out of spec too high, I need the extra turns of wire to bring the oscillator back down to the range of 1005KHz to 2165KHz in order to receive stations on the lower part of the band. My thinking at this point is the windings are shorted and with the smaller inductance the oscillator cannot operate at a frequency below 1655KHz and gives me my lowest tuned frequency of 1200KHz (1655-1200=455). Sound reasonable?
:
::Dave ,
::You stated that you had repaired a part of the oscillator coil in order to obtain B+ at the first detector/osc, but thats only part of the entire assembly. It has 2 windings, and the part you fixed looks like a choke at the RF frequency and an untuned coupling winding to the tuned section of this assembly. There are 3 other terminals that are the actual tuned/tuning portion of this circuit to C2 (the padder) and C14 the actual tuning condenser. Hopefully you were able to isolate the 2 windings when the fix was made, and assure that you havent erroneously interconnected the 2 windings. Locate the other 3 terminals, and verify their continuity and connections.
::marv
::
:::Elton,
:::
:::I have repaired this coil a couple of times and tried it in the radio with no luck. I get voltage to the tube plate and it has to go through the coil to get there, so it doesn't seem likely to me that there is another break in the wire. However, at this point I'm willing to try anything. So with that in mind, how do I find out what size of wire is used and where do i purchase wire that small. It is tiny!!
:::
:::Dave
:::
::::Dave I had the same problem with a RCA and it was that my osc coil was not repaired correctly mine was as thomas said earlier , that there was a additional break on it and was not found, I had to remove the coil and un wind it until I found all the breaks then reconnected it all back together and the whole band came back to life if all else fails check your coil again.
::::Elton
:::::Try making the resistor right on value by using two resistors in series. Though this circuit is not that sensitive, too little resistance may diminish sensitivity, where-as too much resistance may make the circuit too "loose," which causes it to be unstable.
:::::
:::::A note on the tube: Usually an oscillator tube that works irratically does show up as weak. Sometimes, however, it will not, especially if there are traces of gas in the tube which are causing the problem, or if the cathode coating is working intermittently. I had a couple of 1LA6 tubes act like this. Sometimes they would test good and sometimes bad. Sometimes the set would work and sometimes not. Feeding a high cathode to plate current through each of them on my tube tester usually "rejuvenated" them for about a week. Still, if the tube in question tests good, do not assume that it is bad yet until you have tried out several other good tubes in the circuit. If, then, only the original tube causes the trouble, you can assume that it is faulty in some way. Still, you may want to try the tube in some other circuit to see if it causes other troubles or if it is still usable. Usually, however, when a tube is bad, it tests bad.
:::::
:::::Thomas

Marv,

By antenna part, I meant the larger part of the coil or in other words the coil on the oscillator with the greater number of turns. The tickler part only has (I'm guessing) maybe 50 turns of wire on it and is wound on a larger form that slips over the part with the larger numer of turns.

I'll probably try and rewind the outer coil and see if that gets my oscillator frequency back down where it needs to be.

Dave

:Dave,
:I'm not sure I understand your response in refering to the other half as the antenna part. Item 3 on the schematic is strictly a tunable oscillator inductor w/tickler, to form a feedback path, and sustain oscillations. Item 2 on the other hand is the antenna tuning element. Is there any evidence that the tickler has missing turns, other than the simple break you repaired? Is there any evidence that the outer form was moved enough to cause the broken wire, or its position over the oscillator coil? If its position over the oscillator coil has been altered appreciably, coupled energy may be insufficient to sustain oscillations. By your description, it appears that the oscillator function ceases below 1.65 mHz (1.2 mHz + 0.456mHz/high side injection), but if the dial pointer is remotely accurate, shorted turns in the oscillator coil would have the pointer far removed from the stations you found, unless a radio technician of yesteryear severely mis-adjusted C2 to compensate for unknown problems, but managed to find an area on the upper end of the dial that was accurate.
:marv
:
::Marv & Thomas,
::
::The tickler part of the coil was the only part open. An ohmmeter on the antenna part of the coil shows continuity between terminals and between each terminal and ground so I'm certain this part of the coil is OK. Also, this coil is double wound, with the oscillator winding being placed on another cardboard form and slipped over the antenna part of the coil. The outer winding actually protects the inner winding and while I haven't melted the wax to pull them apart, I figured as long as they tested good and are still sealed in wax, I'll leave that part alone. The problem exists in the outer winding which is shown on the schematic as a tickler that supplies B+ to the plate of the oscillator/mixer. I'm getting voltage with the radio powered up, it just doesn't pick up any stations from 550KHz to 1200KHz. Above 1200KHZ everything is loud, clear and very sensitive. I don't have my signal generator back from my friend, so I haven't done a proper alignment. If there are shorted oscillator windings then with a shorter coil the oscillator is operating out of spec too high, I need the extra turns of wire to bring the oscillator back down to the range of 1005KHz to 2165KHz in order to receive stations on the lower part of the band. My thinking at this point is the windings are shorted and with the smaller inductance the oscillator cannot operate at a frequency below 1655KHz and gives me my lowest tuned frequency of 1200KHz (1655-1200=455). Sound reasonable?
::
:::Dave ,
:::You stated that you had repaired a part of the oscillator coil in order to obtain B+ at the first detector/osc, but thats only part of the entire assembly. It has 2 windings, and the part you fixed looks like a choke at the RF frequency and an untuned coupling winding to the tuned section of this assembly. There are 3 other terminals that are the actual tuned/tuning portion of this circuit to C2 (the padder) and C14 the actual tuning condenser. Hopefully you were able to isolate the 2 windings when the fix was made, and assure that you havent erroneously interconnected the 2 windings. Locate the other 3 terminals, and verify their continuity and connections.
:::marv
:::
::::Elton,
::::
::::I have repaired this coil a couple of times and tried it in the radio with no luck. I get voltage to the tube plate and it has to go through the coil to get there, so it doesn't seem likely to me that there is another break in the wire. However, at this point I'm willing to try anything. So with that in mind, how do I find out what size of wire is used and where do i purchase wire that small. It is tiny!!
::::
::::Dave
::::
:::::Dave I had the same problem with a RCA and it was that my osc coil was not repaired correctly mine was as thomas said earlier , that there was a additional break on it and was not found, I had to remove the coil and un wind it until I found all the breaks then reconnected it all back together and the whole band came back to life if all else fails check your coil again.
:::::Elton
::::::Try making the resistor right on value by using two resistors in series. Though this circuit is not that sensitive, too little resistance may diminish sensitivity, where-as too much resistance may make the circuit too "loose," which causes it to be unstable.
::::::
::::::A note on the tube: Usually an oscillator tube that works irratically does show up as weak. Sometimes, however, it will not, especially if there are traces of gas in the tube which are causing the problem, or if the cathode coating is working intermittently. I had a couple of 1LA6 tubes act like this. Sometimes they would test good and sometimes bad. Sometimes the set would work and sometimes not. Feeding a high cathode to plate current through each of them on my tube tester usually "rejuvenated" them for about a week. Still, if the tube in question tests good, do not assume that it is bad yet until you have tried out several other good tubes in the circuit. If, then, only the original tube causes the trouble, you can assume that it is faulty in some way. Still, you may want to try the tube in some other circuit to see if it causes other troubles or if it is still usable. Usually, however, when a tube is bad, it tests bad.
::::::
::::::Thomas

Dave,
Assuming the winding is of Litz wire, count the turns as you remove them. Depending on the number of turns, it may have a special winding technique resembling a wax impregnated honeycomb. This winding technique will affect the ultimate inductance, parallel capacitance and performance of the coil in its circuit. Take note of the position of the tickler coil, over the oscillator coil as well. As you may have already noted, melted wax is good at stabilizing the winding as you progress, and can be the final solution to holding the
entire assembly in place. Good luck.
marv

:Marv,
:
:By antenna part, I meant the larger part of the coil or in other words the coil on the oscillator with the greater number of turns. The tickler part only has (I'm guessing) maybe 50 turns of wire on it and is wound on a larger form that slips over the part with the larger numer of turns.
:
:I'll probably try and rewind the outer coil and see if that gets my oscillator frequency back down where it needs to be.
:
:Dave
:
::Dave,
::I'm not sure I understand your response in refering to the other half as the antenna part. Item 3 on the schematic is strictly a tunable oscillator inductor w/tickler, to form a feedback path, and sustain oscillations. Item 2 on the other hand is the antenna tuning element. Is there any evidence that the tickler has missing turns, other than the simple break you repaired? Is there any evidence that the outer form was moved enough to cause the broken wire, or its position over the oscillator coil? If its position over the oscillator coil has been altered appreciably, coupled energy may be insufficient to sustain oscillations. By your description, it appears that the oscillator function ceases below 1.65 mHz (1.2 mHz + 0.456mHz/high side injection), but if the dial pointer is remotely accurate, shorted turns in the oscillator coil would have the pointer far removed from the stations you found, unless a radio technician of yesteryear severely mis-adjusted C2 to compensate for unknown problems, but managed to find an area on the upper end of the dial that was accurate.
::marv
::
:::Marv & Thomas,
:::
:::The tickler part of the coil was the only part open. An ohmmeter on the antenna part of the coil shows continuity between terminals and between each terminal and ground so I'm certain this part of the coil is OK. Also, this coil is double wound, with the oscillator winding being placed on another cardboard form and slipped over the antenna part of the coil. The outer winding actually protects the inner winding and while I haven't melted the wax to pull them apart, I figured as long as they tested good and are still sealed in wax, I'll leave that part alone. The problem exists in the outer winding which is shown on the schematic as a tickler that supplies B+ to the plate of the oscillator/mixer. I'm getting voltage with the radio powered up, it just doesn't pick up any stations from 550KHz to 1200KHz. Above 1200KHZ everything is loud, clear and very sensitive. I don't have my signal generator back from my friend, so I haven't done a proper alignment. If there are shorted oscillator windings then with a shorter coil the oscillator is operating out of spec too high, I need the extra turns of wire to bring the oscillator back down to the range of 1005KHz to 2165KHz in order to receive stations on the lower part of the band. My thinking at this point is the windings are shorted and with the smaller inductance the oscillator cannot operate at a frequency below 1655KHz and gives me my lowest tuned frequency of 1200KHz (1655-1200=455). Sound reasonable?
:::
::::Dave ,
::::You stated that you had repaired a part of the oscillator coil in order to obtain B+ at the first detector/osc, but thats only part of the entire assembly. It has 2 windings, and the part you fixed looks like a choke at the RF frequency and an untuned coupling winding to the tuned section of this assembly. There are 3 other terminals that are the actual tuned/tuning portion of this circuit to C2 (the padder) and C14 the actual tuning condenser. Hopefully you were able to isolate the 2 windings when the fix was made, and assure that you havent erroneously interconnected the 2 windings. Locate the other 3 terminals, and verify their continuity and connections.
::::marv
::::
:::::Elton,
:::::
:::::I have repaired this coil a couple of times and tried it in the radio with no luck. I get voltage to the tube plate and it has to go through the coil to get there, so it doesn't seem likely to me that there is another break in the wire. However, at this point I'm willing to try anything. So with that in mind, how do I find out what size of wire is used and where do i purchase wire that small. It is tiny!!
:::::
:::::Dave
:::::
::::::Dave I had the same problem with a RCA and it was that my osc coil was not repaired correctly mine was as thomas said earlier , that there was a additional break on it and was not found, I had to remove the coil and un wind it until I found all the breaks then reconnected it all back together and the whole band came back to life if all else fails check your coil again.
::::::Elton
:::::::Try making the resistor right on value by using two resistors in series. Though this circuit is not that sensitive, too little resistance may diminish sensitivity, where-as too much resistance may make the circuit too "loose," which causes it to be unstable.
:::::::
:::::::A note on the tube: Usually an oscillator tube that works irratically does show up as weak. Sometimes, however, it will not, especially if there are traces of gas in the tube which are causing the problem, or if the cathode coating is working intermittently. I had a couple of 1LA6 tubes act like this. Sometimes they would test good and sometimes bad. Sometimes the set would work and sometimes not. Feeding a high cathode to plate current through each of them on my tube tester usually "rejuvenated" them for about a week. Still, if the tube in question tests good, do not assume that it is bad yet until you have tried out several other good tubes in the circuit. If, then, only the original tube causes the trouble, you can assume that it is faulty in some way. Still, you may want to try the tube in some other circuit to see if it causes other troubles or if it is still usable. Usually, however, when a tube is bad, it tests bad.
:::::::
:::::::Thomas

:I need more help! My Zenith 4B131 seems to be working except for one thing, I get no stations between 600 and 1100. Nothing, zip, nada, not even a blip or squawk as you spin past a station on the dial. I can get 580 from Topeka, but here in Kansas City there are several powerhouses much stronger than 580 in Topeka, they are 610, 710, 760, 810, 980, 1090 and 1140, but the next station I get is 1250. I can get stations between 1250 and 1660 at the top of the dial. I'm stumped! Can anyone point me in the right direction?

sounds like you need to give an if alignment. start on front end and slowly work to the audio. missaligned var caps will do it sometimes,check all caps,etc.

Hello Everyone,

I wanted to write back on this topic I originally started several weeks ago. I now have the radio working and I'd like to share with the group what I finally did. I don't like those posts that get abandoned once a solution is found, so hopefully my explaination will help someone else. I'm especially thankful to Marv, Thomas, Dave, Doug, kg9rb and Elton for responding to my posts and pointing me in the right direction.

The problem turned out to be actually two different problems. I got my signal generator out and did an alignment of the set. The IF I was using turned out to be about 670KHz which limited the oscillator's ability to pull in stations in the higher part of the band. Once the IF was set correctly at 456KHz the upper stations appeared back on the dial.

The lower stations were a little more difficult to restore. Even though the oscillator coil tested good with my ohmmeter, there was very little resistance in the windings, about 1 or 2 ohms. I didn't initially think this was a problem, being a newbie I didn't know what it should be, I was just testing for continuity. However, after talking with several of the gentlemen on this forum and other postings, I decided this might be the problem. I had never rewound a coil before but decided it was time to learn. I carefully unwound the oscillator section of the coil counting the turns and found no breaks. Incidentially if anyone is doing this there are 45 turns of wire on the oscillator.

I matched the wire to samples at the local electronics store and found #36 wire was the closest match to what I had. I bought a 1/2 pound spool (not cheap) and wound 60 turns of wire on the oscillator.

The results were super! I got all the lower stations again but a few of them were gone at the top of the scale. However, I got some interesting whistles, squeals and other assorted sounds out of the speaker at the upper end of the dial. I decided that 60 turns (up from 45) was too many and took them off one at a time, resoldering each time I removed a coil, installing the coil and testing it. I wound up with about 54 turns of wire on the oscillator.

The radio now works perfectly and the resistance across the oscillator coil is about 15 ohms. In addition, another alignment brought the set back to perfect working order and all stations are right on the money across the dial.

I want to tank everyone again on this forum who offered me advice. It is nice to know help is available anytime I need it and it was a very satisfying experience to take advice from the mentors on this site and use my ability to apply it and solve this problem. Thanks again to everyone who helped me!!

Dave

Dave,
Nice work! A stellar example of patience and determination. You are an inspiration!
Jim

Dave,
Good job!! Hopefully you fully documented your steps to success for the next user of your expertise and patience. In my years in the electronics industry, I found good documentation (facts) to be of the utmost importance. I keep large 3 ring binders, and insert my thoughts, experiments, sketches and pertinent data (all dated) inside clear plastic protectors.
marv

:Hello Everyone,
:
:I wanted to write back on this topic I originally started several weeks ago. I now have the radio working and I'd like to share with the group what I finally did. I don't like those posts that get abandoned once a solution is found, so hopefully my explaination will help someone else. I'm especially thankful to Marv, Thomas, Dave, Doug, kg9rb and Elton for responding to my posts and pointing me in the right direction.
:
:The problem turned out to be actually two different problems. I got my signal generator out and did an alignment of the set. The IF I was using turned out to be about 670KHz which limited the oscillator's ability to pull in stations in the higher part of the band. Once the IF was set correctly at 456KHz the upper stations appeared back on the dial.
:
:The lower stations were a little more difficult to restore. Even though the oscillator coil tested good with my ohmmeter, there was very little resistance in the windings, about 1 or 2 ohms. I didn't initially think this was a problem, being a newbie I didn't know what it should be, I was just testing for continuity. However, after talking with several of the gentlemen on this forum and other postings, I decided this might be the problem. I had never rewound a coil before but decided it was time to learn. I carefully unwound the oscillator section of the coil counting the turns and found no breaks. Incidentially if anyone is doing this there are 45 turns of wire on the oscillator.
:
:I matched the wire to samples at the local electronics store and found #36 wire was the closest match to what I had. I bought a 1/2 pound spool (not cheap) and wound 60 turns of wire on the oscillator.
:
:The results were super! I got all the lower stations again but a few of them were gone at the top of the scale. However, I got some interesting whistles, squeals and other assorted sounds out of the speaker at the upper end of the dial. I decided that 60 turns (up from 45) was too many and took them off one at a time, resoldering each time I removed a coil, installing the coil and testing it. I wound up with about 54 turns of wire on the oscillator.
:
:The radio now works perfectly and the resistance across the oscillator coil is about 15 ohms. In addition, another alignment brought the set back to perfect working order and all stations are right on the money across the dial.
:
:I want to tank everyone again on this forum who offered me advice. It is nice to know help is available anytime I need it and it was a very satisfying experience to take advice from the mentors on this site and use my ability to apply it and solve this problem. Thanks again to everyone who helped me!!
:
:Dave

:Dave,
:Good job!! Hopefully you fully documented your steps to success for the next user of your expertise and patience. In my years in the electronics industry, I found good documentation (facts) to be of the utmost importance. I keep large 3 ring binders, and insert my thoughts, experiments, sketches and pertinent data (all dated) inside clear plastic protectors.
:marv
:
Man oh man !! Did I get an education by following this exchange of thoughts and ideas or WHAT !!
Thanks to all of you guys that participated.
DennisWess
::Hello Everyone,
::
::I wanted to write back on this topic I originally started several weeks ago. I now have the radio working and I'd like to share with the group what I finally did. I don't like those posts that get abandoned once a solution is found, so hopefully my explaination will help someone else. I'm especially thankful to Marv, Thomas, Dave, Doug, kg9rb and Elton for responding to my posts and pointing me in the right direction.
::
::The problem turned out to be actually two different problems. I got my signal generator out and did an alignment of the set. The IF I was using turned out to be about 670KHz which limited the oscillator's ability to pull in stations in the higher part of the band. Once the IF was set correctly at 456KHz the upper stations appeared back on the dial.
::
::The lower stations were a little more difficult to restore. Even though the oscillator coil tested good with my ohmmeter, there was very little resistance in the windings, about 1 or 2 ohms. I didn't initially think this was a problem, being a newbie I didn't know what it should be, I was just testing for continuity. However, after talking with several of the gentlemen on this forum and other postings, I decided this might be the problem. I had never rewound a coil before but decided it was time to learn. I carefully unwound the oscillator section of the coil counting the turns and found no breaks. Incidentially if anyone is doing this there are 45 turns of wire on the oscillator.
::
::I matched the wire to samples at the local electronics store and found #36 wire was the closest match to what I had. I bought a 1/2 pound spool (not cheap) and wound 60 turns of wire on the oscillator.
::
::The results were super! I got all the lower stations again but a few of them were gone at the top of the scale. However, I got some interesting whistles, squeals and other assorted sounds out of the speaker at the upper end of the dial. I decided that 60 turns (up from 45) was too many and took them off one at a time, resoldering each time I removed a coil, installing the coil and testing it. I wound up with about 54 turns of wire on the oscillator.
::
::The radio now works perfectly and the resistance across the oscillator coil is about 15 ohms. In addition, another alignment brought the set back to perfect working order and all stations are right on the money across the dial.
::
::I want to tank everyone again on this forum who offered me advice. It is nice to know help is available anytime I need it and it was a very satisfying experience to take advice from the mentors on this site and use my ability to apply it and solve this problem. Thanks again to everyone who helped me!!
::
::Dave

Bravo! Lots of work. That's the kind of work that fries the brains and eyeballs. I, too, hate it when people abandon their posts. It would be nice if everyone would tell of their final successful results.

Thomas

Thomas,
Some of us, including myself have not accomplished anything especially noteworthy, although others have.
Consequently we fumble around in a dimly lit shop or spend hours in front of our PC screen searching for answers. The magic solution that will "Make our Day"
If Google, Yahoo or MS would only archive, edit and annotate all the information on this site, our answers would be a mouse click away. When do we start?????
marv

:Bravo! Lots of work. That's the kind of work that fries the brains and eyeballs. I, too, hate it when people abandon their posts. It would be nice if everyone would tell of their final successful results.
:
:Thomas

True that. Perhaps some that abandon their posts get discouraged. There have been many times, however, when I have made suggestions to someone that would likely be the cause....something rather simple, for instance. After I gave the advice, the post stopped. No biggie, really, but yeah, it's very nice to hear when someone successfully repairs their radio, especially after a long time of fooling around with it.

T.