3 hours ago
Did an alignment today which was interesting. IF alignment went great, almost all was already spot-on. Adjusting on the tuning condenser itself was a bit more of a challenge. Once I figured out to switch to AF on the signal generator it started going better. 
Even so, I apparently at first aligned to a harmonic of 1400 kc instead of 1400 itself because when I disconnected the external antenna, it didn't pick up anymore except way far away. To get things back to where they should be, basically had to back out the oscillator and RF adjustments till they were loose, which I thought was weird.
Also took some voltages which I'm not going to post right now. Suffice it to say they were high though not like the craziness I ran into with the 37-620. I traced it back and the B+ coming out of the rectifier was 130V instead of 115V. Checked the AC coming in and it was getting 130 from the Isotap which was set for 115, so note to self, check AC voltage at the switch first before measuring the tubes. Dialed it down and the B+ coming off the rectifier similarly came down to where it was supposed to be. Still a little high (mid 80s) at the plate and screen grids of the 12SK7s and 12SA7 where the schematic say it should be 70.
This brings me to a riddle I was trying to figure out for a while. At least according to the schematic and this does match what I see in the radio, the two 12SK7s, the 12SA7, and the screen grid of the 35L6GT are all tied to the same section of B+, after the field coil and second filter cap (50 uF). There are no resistors anywhere along this string of connections, yet only the 35L6GT screen grid is marked at 85V while all the others are marked as 70V. They are all testing at approximately 85V-86V. Error in the schematic? Sorcery?
And lastly, just to confirm, since this radio has a floating B-, when I'm adding in the aux input, the ground connection coming off the isolation transformer, that should go to any B- point and not the chassis, correct?
Best wishes,
Roy
Even so, I apparently at first aligned to a harmonic of 1400 kc instead of 1400 itself because when I disconnected the external antenna, it didn't pick up anymore except way far away. To get things back to where they should be, basically had to back out the oscillator and RF adjustments till they were loose, which I thought was weird.Also took some voltages which I'm not going to post right now. Suffice it to say they were high though not like the craziness I ran into with the 37-620. I traced it back and the B+ coming out of the rectifier was 130V instead of 115V. Checked the AC coming in and it was getting 130 from the Isotap which was set for 115, so note to self, check AC voltage at the switch first before measuring the tubes. Dialed it down and the B+ coming off the rectifier similarly came down to where it was supposed to be. Still a little high (mid 80s) at the plate and screen grids of the 12SK7s and 12SA7 where the schematic say it should be 70.
This brings me to a riddle I was trying to figure out for a while. At least according to the schematic and this does match what I see in the radio, the two 12SK7s, the 12SA7, and the screen grid of the 35L6GT are all tied to the same section of B+, after the field coil and second filter cap (50 uF). There are no resistors anywhere along this string of connections, yet only the 35L6GT screen grid is marked at 85V while all the others are marked as 70V. They are all testing at approximately 85V-86V. Error in the schematic? Sorcery?
And lastly, just to confirm, since this radio has a floating B-, when I'm adding in the aux input, the ground connection coming off the isolation transformer, that should go to any B- point and not the chassis, correct?
Best wishes,
Roy
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