12-06-2019, 12:14 PM
Hi Forest and welcome,
It's not an unusual issue for the 1928-35 Philco sets to have open primaries on their ant, rf, and oscillator coils. By 1936 Philco changed the design of the coil so that the windings are not over top of each other and no celluloid strip. But there are a few exceptions and guess what the 84/37-84 is one. The good news is that the winding it self is pretty easy to rewind. It's on the outside and doesn't require a lot of surgery to get at it.
One important point is to note the direction that the winding is wound. The new coil must be wound in the same direction (the phasing is important). If it is wound in the reverse direction the oscillator will not oscillate.
Just did one a month of so ago. A 2nd gen 84 (1935 model). My best recollection is that was 17 turns for the feedback or tickler winding.
Something else to check is the primary of the antenna coil. This can de accomplished by unplugging the set, turning the volume full up, the then measuring the resistance from the ant to the gnd posts. If all is well you should see a very low resistance like <10 ohms. If more some investigation is in order.
With either of these coils open the set will not work worth a tinkers darn. A bad osc coil will give you very poor sensitivity, stations won't track on the dial and tuning will be very broad. Bad antenna coil will give you poor sensitivity .
One last thing must use a signal generator to align the IF stage. Without it's difficult to get good performance from this little set.
GL.
It's not an unusual issue for the 1928-35 Philco sets to have open primaries on their ant, rf, and oscillator coils. By 1936 Philco changed the design of the coil so that the windings are not over top of each other and no celluloid strip. But there are a few exceptions and guess what the 84/37-84 is one. The good news is that the winding it self is pretty easy to rewind. It's on the outside and doesn't require a lot of surgery to get at it.
One important point is to note the direction that the winding is wound. The new coil must be wound in the same direction (the phasing is important). If it is wound in the reverse direction the oscillator will not oscillate.
Just did one a month of so ago. A 2nd gen 84 (1935 model). My best recollection is that was 17 turns for the feedback or tickler winding.
Something else to check is the primary of the antenna coil. This can de accomplished by unplugging the set, turning the volume full up, the then measuring the resistance from the ant to the gnd posts. If all is well you should see a very low resistance like <10 ohms. If more some investigation is in order.
With either of these coils open the set will not work worth a tinkers darn. A bad osc coil will give you very poor sensitivity, stations won't track on the dial and tuning will be very broad. Bad antenna coil will give you poor sensitivity .
One last thing must use a signal generator to align the IF stage. Without it's difficult to get good performance from this little set.
GL.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got it!
Terry
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