Sparton I.F coil replacement

7/16/2008 7:28:12 PMIan

Hi every one. I have been repairing a Sparton 1268. It has been entirely recapped and tubes replaced, but the 3rd IF coil was open. This coil is NOT a standard coil. This coil has 3 windings, 2 working as a standard IF coil and the 3rd for pushbutton use. Unfourtunatly the primary is open and repair is not really an option. The secondary was wrapped around the primary and the break was in the begining of the primary within the first 10 wraps of the form. the tertiary winding is lower on the form and center tapped. I Have a sparton model 1091 which I can use for parts. The 1091 has a 3 winding if coil but does not have a center tap like the 1268, the 1268 also has alot of parts mounted directly to the coil. Can these coils be switched? Or do I need an Original coil?

If anyone has a spare 1068, 1268, 1568 radio chassis or If coil Please tell me, I am willing to pay for it with shipping.

Here are the schematics.

1091
http://www.nostalgiaair.org/PagesByModel/638/M0018638.pdf

1268
http://www.nostalgiaair.org/PagesByModel/656/M0018656.pdf

Thank You

7/16/2008 10:50:29 PMEdd

That is one special little unit that you have yourself there.
Full RF front end and then not one, but mind you, two IF stages and then there
are the separately supported functions of the left diode of the 6R7 providing
the AVC for the set and then the right diode supplying the audio detection
funstion and then the final embellisment of the unit is having a 6H6 used
in a 456 kc freequency discriminator to then take its developed +- Dc then be
fed down to a 6J7 control tube which then squeggs the local oscillator in order
to correctively maintain a precisely tuned in frequency compliance.

I think that the other IF coils set, that you have available to play with, can be
used in your situation. In the 1268 sets situation the diode detector is using an
untuned winding, but it seems that that a tuning of that winding would certainly
be permissible in using that 1091 transformer in the 1268 set.

Why dont you sub in that available unit and take care of the problem of not having
a centertap unit by the phantom aliasing of one by the placement of two series connected
4.7 k resistors from the top of the secondary discriminator winding to the bottom winding
and then the center tap of the resistors then becomes the point where you connect on:

1. . .C35. . .the 50 mmfd plate Rf coupling capacitor and. . .

2.. . The junction of resistors R14-R15

See if that won't get you in business again. . . . . .BUT. . . .maybe that unit has not
been in its AFC tuned aspect. . . .possibly for decades, by virtue of that exact problem
that you have discovered.

REFERENCING:

73's de Edd

7/16/2008 11:55:29 PMIan(64093:64088)

Thanks I will get to work on it possibly tomorrow, and I was just wondering what exactly is the 3rd coil on the 1091 doing? And would it work with out it?

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:That is one special little unit that you have yourself there.
:Full RF front end and then not one, but mind you, two IF stages and then there
:are the separately supported functions of the left diode of the 6R7 providing
:the AVC for the set and then the right diode supplying the audio detection
:funstion and then the final embellisment of the unit is having a 6H6 used
:in a 456 kc freequency discriminator to then take its developed +- Dc then be
:fed down to a 6J7 control tube which then squeggs the local oscillator in order
:to correctively maintain a precisely tuned in frequency compliance.
:
:
:
:I think that the other IF coils set, that you have available to play with, can be
:used in your situation. In the 1268 sets situation the diode detector is using an
:untuned winding, but it seems that that a tuning of that winding would certainly
:be permissible in using that 1091 transformer in the 1268 set.
:
:
:
:Why dont you sub in that available unit and take care of the problem of not having
:a centertap unit by the phantom aliasing of one by the placement of two series connected
:4.7 k resistors from the top of the secondary discriminator winding to the bottom winding
:and then the center tap of the resistors then becomes the point where you connect on:
:
:
:1. . .C35. . .the 50 mmfd plate Rf coupling capacitor and. . .
:
:2.. . The junction of resistors R14-R15
:
:
:See if that won't get you in business again. . . . . .BUT. . . .maybe that unit has not
:been in its AFC tuned aspect. . . .possibly for decades, by virtue of that exact problem
:that you have discovered.
:
:
:
:REFERENCING:
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:
:
:
:
:
:
:
:73's de Edd
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7/17/2008 4:18:40 PMEdd(64119:64093)

:Thanks I will get to work on it possibly tomorrow, and I was just wondering what exactly is the 3rd coil on the 1091 doing? And would it work with out it?
:
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Sharper tuning and greater gain

::
::
::That is one special little unit that you have yourself there.
::Full RF front end and then not one, but mind you, two IF stages and then there
::are the separately supported functions of the left diode of the 6R7 providing
::the AVC for the set and then the right diode supplying the audio detection
::funstion and then the final embellisment of the unit is having a 6H6 used
::in a 456 kc freequency discriminator to then take its developed +- Dc then be
::fed down to a 6J7 control tube which then squeggs the local oscillator in order
::to correctively maintain a precisely tuned in frequency compliance.
::
::
::
::I think that the other IF coils set, that you have available to play with, can be
::used in your situation. In the 1268 sets situation the diode detector is using an
::untuned winding, but it seems that that a tuning of that winding would certainly
::be permissible in using that 1091 transformer in the 1268 set.
::
::
::
::Why dont you sub in that available unit and take care of the problem of not having
::a centertap unit by the phantom aliasing of one by the placement of two series connected
::4.7 k resistors from the top of the secondary discriminator winding to the bottom winding
::and then the center tap of the resistors then becomes the point where you connect on:
::
::
::1. . .C35. . .the 50 mmfd plate Rf coupling capacitor and. . .
::
::2.. . The junction of resistors R14-R15
::
::
::See if that won't get you in business again. . . . . .BUT. . . .maybe that unit has not
::been in its AFC tuned aspect. . . .possibly for decades, by virtue of that exact problem
::that you have discovered.
::
::
::
::REFERENCING:
::
::
::
::
::
::
::
::
::73's de Edd
::
::
::
::
::
::
::
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::