07-13-2019, 05:13 PM
Hold the presses!
Yesterday morning I was all set the check the LO frequency w/ my little counter. Flipped the set on and was greeted w/a big cloud of smoke. This isn't good! It looked liked it was coming from the 7K bleeder resistor (it's the big one along the back edge of the chassis). What was worrying me was that right above it is the power transformer (that would suck if that was bad!!). Pulled the 80 out and checked the hv at the plates and it was good (yay!!). Measure the output @ the 80 tube and it was down from 300v to 296 so that's good. Left it on for few more seconds to find the resistor used to replaced the shadow meter (1500 ohms) was the smoker. The 200v rail (fed by that resistor) that feeds the IF amps and mixer was at abt 10v (not so good), Did some resistance checks to find that the 2nd IF transformer was shorted. After doing a few more tests the short disappeared. Turn it back on and play fine. Wiggled the hv terminals on the IF can and seem to be ok. Wiring is good between the hv, IF can. and the other connections to the tubes. So it's up for further investigation. Maybe a scrape piece of wire got in between the trimmer and can. It will give me something to think about in my spare time.
Started to look at the LO frequency to find that is pretty good but it seems that the tuning runs out of capacitance near the high end of the dial. I'm thinking I need to move the dial a little off center to give a little more capacitance. I have a local station @ 1440kc if the set the osc so that is in it's proper place and tune up yo 1500kc I'm @ 1460kc. Both trimmers work fine just not enough capacitance in the tuning cap.
More Later...
Yesterday morning I was all set the check the LO frequency w/ my little counter. Flipped the set on and was greeted w/a big cloud of smoke. This isn't good! It looked liked it was coming from the 7K bleeder resistor (it's the big one along the back edge of the chassis). What was worrying me was that right above it is the power transformer (that would suck if that was bad!!). Pulled the 80 out and checked the hv at the plates and it was good (yay!!). Measure the output @ the 80 tube and it was down from 300v to 296 so that's good. Left it on for few more seconds to find the resistor used to replaced the shadow meter (1500 ohms) was the smoker. The 200v rail (fed by that resistor) that feeds the IF amps and mixer was at abt 10v (not so good), Did some resistance checks to find that the 2nd IF transformer was shorted. After doing a few more tests the short disappeared. Turn it back on and play fine. Wiggled the hv terminals on the IF can and seem to be ok. Wiring is good between the hv, IF can. and the other connections to the tubes. So it's up for further investigation. Maybe a scrape piece of wire got in between the trimmer and can. It will give me something to think about in my spare time.
Started to look at the LO frequency to find that is pretty good but it seems that the tuning runs out of capacitance near the high end of the dial. I'm thinking I need to move the dial a little off center to give a little more capacitance. I have a local station @ 1440kc if the set the osc so that is in it's proper place and tune up yo 1500kc I'm @ 1460kc. Both trimmers work fine just not enough capacitance in the tuning cap.
More Later...
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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