I'm not to sure about how these neutrdyne radios are suppose to operate, I had to replace the interstage transformer , and all the caps , well it plays OK but will only receive the upper portion of the AM band say from 1210 on up below that is dead, I think is the varible cap is shorting out after a certain point it has 3 gangs and the stationary plates are adjustable with screws, I adjusted to the point as to where I am now , but here's where I am stumped I checked the varible cap for shorting with my VOM, and even with the cap unmeshed it reads shorted? the only way the moveable portion is conected is though the coils and they read fine , this is suppose to have 3 neutralizing caps across the tuner per the schematic, but I don't see them anywhere on the radio, are these required to tune the whole AM band? IF so what value should they be , and what were there purpose?
Thanks
Elton

Hi Elton

Tuner plates shorting will stop reception from that point down. Some radios used pot metal tuners. This metal cracks and expends. You may need to bend plates to get tuners to operate properly?

There will be some difference in resistance when a tuner shorts. If it doesn't show on your meter unsolder coils across your tuners to get a meaningful reading.

A Neutrodyne is a TRF with neutralizing caps to eliminate unwanted oscillation. The caps cancel out tube capacity by adding a signal of the opposite phase. Neutralizing caps are not causing your problem.

Norm

:I'm not to sure about how these neutrdyne radios are suppose to operate, I had to replace the interstage transformer , and all the caps , well it plays OK but will only receive the upper portion of the AM band say from 1210 on up below that is dead, I think is the varible cap is shorting out after a certain point it has 3 gangs and the stationary plates are adjustable with screws, I adjusted to the point as to where I am now , but here's where I am stumped I checked the varible cap for shorting with my VOM, and even with the cap unmeshed it reads shorted? the only way the moveable portion is conected is though the coils and they read fine , this is suppose to have 3 neutralizing caps across the tuner per the schematic, but I don't see them anywhere on the radio, are these required to tune the whole AM band? IF so what value should they be , and what were there purpose?
:Thanks
:Elton

Thanks Norm, This is a old pot metal varible and the plates are nice and strait but it seems no matter which way you adjust the stationary plates they touch it apears like you say I think they have swollen or expanded to the point I probably wont get this any better, at least it works on part of the band
Thanks
Elton
:Hi Elton
:
: Tuner plates shorting will stop reception from that point down. Some radios used pot metal tuners. This metal cracks and expends. You may need to bend plates to get tuners to operate properly?
:
: There will be some difference in resistance when a tuner shorts. If it doesn't show on your meter unsolder coils across your tuners to get a meaningful reading.
:
: A Neutrodyne is a TRF with neutralizing caps to eliminate unwanted oscillation. The caps cancel out tube capacity by adding a signal of the opposite phase. Neutralizing caps are not causing your problem.
:
:Norm
:
::I'm not to sure about how these neutrdyne radios are suppose to operate, I had to replace the interstage transformer , and all the caps , well it plays OK but will only receive the upper portion of the AM band say from 1210 on up below that is dead, I think is the varible cap is shorting out after a certain point it has 3 gangs and the stationary plates are adjustable with screws, I adjusted to the point as to where I am now , but here's where I am stumped I checked the varible cap for shorting with my VOM, and even with the cap unmeshed it reads shorted? the only way the moveable portion is conected is though the coils and they read fine , this is suppose to have 3 neutralizing caps across the tuner per the schematic, but I don't see them anywhere on the radio, are these required to tune the whole AM band? IF so what value should they be , and what were there purpose?
::Thanks
::Elton

Oh I forgot to mention that when it stops reception it slowly fades to nothing , does not stop abrubly as you would think with shorted plates , it makes me think one of the coils could have a partial short killing the signal at the lower end of dial , but since I have no figures as to what the resistance is suppose to be there is no way to tell if one of the coils is suspect?
Elton
:Thanks Norm, This is a old pot metal varible and the plates are nice and strait but it seems no matter which way you adjust the stationary plates they touch it apears like you say I think they have swollen or expanded to the point I probably wont get this any better, at least it works on part of the band
:Thanks
:Elton
::Hi Elton
::
:: Tuner plates shorting will stop reception from that point down. Some radios used pot metal tuners. This metal cracks and expends. You may need to bend plates to get tuners to operate properly?
::
:: There will be some difference in resistance when a tuner shorts. If it doesn't show on your meter unsolder coils across your tuners to get a meaningful reading.
::
:: A Neutrodyne is a TRF with neutralizing caps to eliminate unwanted oscillation. The caps cancel out tube capacity by adding a signal of the opposite phase. Neutralizing caps are not causing your problem.
::
::Norm
::
:::I'm not to sure about how these neutrdyne radios are suppose to operate, I had to replace the interstage transformer , and all the caps , well it plays OK but will only receive the upper portion of the AM band say from 1210 on up below that is dead, I think is the varible cap is shorting out after a certain point it has 3 gangs and the stationary plates are adjustable with screws, I adjusted to the point as to where I am now , but here's where I am stumped I checked the varible cap for shorting with my VOM, and even with the cap unmeshed it reads shorted? the only way the moveable portion is conected is though the coils and they read fine , this is suppose to have 3 neutralizing caps across the tuner per the schematic, but I don't see them anywhere on the radio, are these required to tune the whole AM band? IF so what value should they be , and what were there purpose?
:::Thanks
:::Elton

Elton

Just a guess... When three tuners are ganged all must track properly. When one is 100 pf the others must be the same. Could the pot metal have caused differences between sections, having different capacities as you tune lower in frequency.

I usually don't find a coil problem.

Norm

:Oh I forgot to mention that when it stops reception it slowly fades to nothing , does not stop abrubly as you would think with shorted plates , it makes me think one of the coils could have a partial short killing the signal at the lower end of dial , but since I have no figures as to what the resistance is suppose to be there is no way to tell if one of the coils is suspect?
:Elton
::Thanks Norm, This is a old pot metal varible and the plates are nice and strait but it seems no matter which way you adjust the stationary plates they touch it apears like you say I think they have swollen or expanded to the point I probably wont get this any better, at least it works on part of the band
::Thanks
::Elton
:::Hi Elton
:::
::: Tuner plates shorting will stop reception from that point down. Some radios used pot metal tuners. This metal cracks and expends. You may need to bend plates to get tuners to operate properly?
:::
::: There will be some difference in resistance when a tuner shorts. If it doesn't show on your meter unsolder coils across your tuners to get a meaningful reading.
:::
::: A Neutrodyne is a TRF with neutralizing caps to eliminate unwanted oscillation. The caps cancel out tube capacity by adding a signal of the opposite phase. Neutralizing caps are not causing your problem.
:::
:::Norm
:::
::::I'm not to sure about how these neutrdyne radios are suppose to operate, I had to replace the interstage transformer , and all the caps , well it plays OK but will only receive the upper portion of the AM band say from 1210 on up below that is dead, I think is the varible cap is shorting out after a certain point it has 3 gangs and the stationary plates are adjustable with screws, I adjusted to the point as to where I am now , but here's where I am stumped I checked the varible cap for shorting with my VOM, and even with the cap unmeshed it reads shorted? the only way the moveable portion is conected is though the coils and they read fine , this is suppose to have 3 neutralizing caps across the tuner per the schematic, but I don't see them anywhere on the radio, are these required to tune the whole AM band? IF so what value should they be , and what were there purpose?
::::Thanks
::::Elton

Well 3 gangs conected to 3 coils, is there a way to check what the capacity is at certain points on the dial and compare to the other sections? or would I need a cap checker to do this?
Thanks
Elton
:Elton
:
: Just a guess... When three tuners are ganged all must track properly. When one is 100 pf the others must be the same. Could the pot metal have caused differences between sections, having different capacities as you tune lower in frequency.
:
: I usually don't find a coil problem.
:
:Norm
:
::Oh I forgot to mention that when it stops reception it slowly fades to nothing , does not stop abrubly as you would think with shorted plates , it makes me think one of the coils could have a partial short killing the signal at the lower end of dial , but since I have no figures as to what the resistance is suppose to be there is no way to tell if one of the coils is suspect?
::Elton
:::Thanks Norm, This is a old pot metal varible and the plates are nice and strait but it seems no matter which way you adjust the stationary plates they touch it apears like you say I think they have swollen or expanded to the point I probably wont get this any better, at least it works on part of the band
:::Thanks
:::Elton
::::Hi Elton
::::
:::: Tuner plates shorting will stop reception from that point down. Some radios used pot metal tuners. This metal cracks and expends. You may need to bend plates to get tuners to operate properly?
::::
:::: There will be some difference in resistance when a tuner shorts. If it doesn't show on your meter unsolder coils across your tuners to get a meaningful reading.
::::
:::: A Neutrodyne is a TRF with neutralizing caps to eliminate unwanted oscillation. The caps cancel out tube capacity by adding a signal of the opposite phase. Neutralizing caps are not causing your problem.
::::
::::Norm
::::
:::::I'm not to sure about how these neutrdyne radios are suppose to operate, I had to replace the interstage transformer , and all the caps , well it plays OK but will only receive the upper portion of the AM band say from 1210 on up below that is dead, I think is the varible cap is shorting out after a certain point it has 3 gangs and the stationary plates are adjustable with screws, I adjusted to the point as to where I am now , but here's where I am stumped I checked the varible cap for shorting with my VOM, and even with the cap unmeshed it reads shorted? the only way the moveable portion is conected is though the coils and they read fine , this is suppose to have 3 neutralizing caps across the tuner per the schematic, but I don't see them anywhere on the radio, are these required to tune the whole AM band? IF so what value should they be , and what were there purpose?
:::::Thanks
:::::Elton

If the neutralizing condensers are not adjusted properly, or you can't seem to locate them (they don't exist), won't the circuitry break into oscillation for certain parts of the dial (either the high end or the low end...I forgot)? I know that with a regenerative radio, regeneration is more "potent" on one end of the dial than on the other. Since your neutralizing condensers are neutralizing unwanted oscillation, this may be your trouble as well?

Neutralizing condensers won't always be in the form of screw type trimmers. Sometimes they are a porcelain tube with a wire which is moved into or out of the porcelain tube. This must be done with a wooden stick. Your fingers will throw things off. Neutralizing condensers are also not normally mounted to the tuning condensers. Look for these within the radio.

Thomas

Thomas, if the neutralizing condesers look as you describe they are not anywhere to be seen, I was told they could be mounted inside the coil towers but I have had the covers off of them and nothing in there except the coils , it would seem they would be obvious to locate if they were there....
Elton
:If the neutralizing condensers are not adjusted properly, or you can't seem to locate them (they don't exist), won't the circuitry break into oscillation for certain parts of the dial (either the high end or the low end...I forgot)? I know that with a regenerative radio, regeneration is more "potent" on one end of the dial than on the other. Since your neutralizing condensers are neutralizing unwanted oscillation, this may be your trouble as well?
:
:Neutralizing condensers won't always be in the form of screw type trimmers. Sometimes they are a porcelain tube with a wire which is moved into or out of the porcelain tube. This must be done with a wooden stick. Your fingers will throw things off. Neutralizing condensers are also not normally mounted to the tuning condensers. Look for these within the radio.
:
:Thomas

Well, examine all grid wiring and look for any wires other than coil wires going to the grids. As you can see in the schematic, the neutralizers go from one grid to the next and to the next. I think Norm knows a lot more about these radios, so he probably knows about all of the various types of neutralizers, and what you should look for. If they're missing, the radio might not work properly, though it may howl instead of go dead. Your going dead sounds like a different problem like Norm said.

Thomas

Well Guys I have looked all over for the netrulizing caps and they are not obvious and this radio has very little components as it is I think 4 paper caps total( all I replaced)2 mica caps and a few resistors, but nothing like thomas desribed, but on a brighter note I disassembled the tuner and washed it out and carfully adjusted the plates so now there is no shorting and it now recieves across the am band although the low end of the dial is very weak(low volume) compared to the high end and since there are no trimmers or a way to tweak this radio I guess this is good as it gets , I appreciate all the advice everyone gave, but I still would like to know what the neutrizing caps looked like and how if any they could improve the performace of the radio, and if it would do any good to try and install replacments just for kicks or just leave it go the way it is.
Thanks
Elton
:Well, examine all grid wiring and look for any wires other than coil wires going to the grids. As you can see in the schematic, the neutralizers go from one grid to the next and to the next. I think Norm knows a lot more about these radios, so he probably knows about all of the various types of neutralizers, and what you should look for. If they're missing, the radio might not work properly, though it may howl instead of go dead. Your going dead sounds like a different problem like Norm said.
:
:Thomas

If you want to install neutralizing condensers, you can simply purchase very low capacitance trimmers of the more conventional type. I'll see if I can get you a value from one of the TRF projects I have in a book. This might be a good approximation for you.

I don't know about everyone else's experience, but in mine, all TRFs that I've ever owned had lower sensitivity at the low end of the dial. It did not matter whether I readjusted the trimmers or not.

THomas