07-25-2019, 07:05 PM
Ed,
Me thinks that it's using the 2nd harmonic from band 4 osc to operate the mixer on band 5. This is why the two share the same adjustment and the frequency is double. Bare in mind that this set was produced at the height of the depression and perhaps the Philco engineers got creative to cut costs. Would require a trimmer and a place to put it along w/a contact on the bandswitch.
The saga continues. Found that the lo isn't running at the low end of band 4 and 5 (abt the first 1/3) or my counter can't make sense of it. Checked the cap plates and all looks good sez Homer the ohm meter. With the dial drive stuck in low gear I almost need a drill to get from one end to the other. Checked the 76 again and was still ok. Swap it out again just to be sure. Need to do a little more investigating to see if my counter is making a red herring for me to chase. Did find the the 25K plate resistor was 46K. After replacing it plate voltage went from 39v to 70v.
Revisited what I did last time played w/the dial and alignment and ended up keeping it abt the same as last time. Now the SW bands are within 100kc or better. BC band is within 5kc.
Steve,
I'm going to sort the band switch, coils, and tuning cap sections and see if I can figure out what's what. Philco decided not to list those trimmers on the tuning cap w/the same # on the schematic vs the alignment instructions. Anyway I'm going to give it a go.
Me thinks that it's using the 2nd harmonic from band 4 osc to operate the mixer on band 5. This is why the two share the same adjustment and the frequency is double. Bare in mind that this set was produced at the height of the depression and perhaps the Philco engineers got creative to cut costs. Would require a trimmer and a place to put it along w/a contact on the bandswitch.
The saga continues. Found that the lo isn't running at the low end of band 4 and 5 (abt the first 1/3) or my counter can't make sense of it. Checked the cap plates and all looks good sez Homer the ohm meter. With the dial drive stuck in low gear I almost need a drill to get from one end to the other. Checked the 76 again and was still ok. Swap it out again just to be sure. Need to do a little more investigating to see if my counter is making a red herring for me to chase. Did find the the 25K plate resistor was 46K. After replacing it plate voltage went from 39v to 70v.
Revisited what I did last time played w/the dial and alignment and ended up keeping it abt the same as last time. Now the SW bands are within 100kc or better. BC band is within 5kc.
Steve,
I'm going to sort the band switch, coils, and tuning cap sections and see if I can figure out what's what. Philco decided not to list those trimmers on the tuning cap w/the same # on the schematic vs the alignment instructions. Anyway I'm going to give it a go.
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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