Posts: 7,273
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City: Roslyn Pa
> it looks like the only way to adjust the 3 stages is to physically adjust the pulleys on each shaft for maximum signal.
That's it. A lot of the older trf set are set up that way. The ones that use #26 tubes or triodes may have a neutralization adjustment. Triode AK sets battery and early ac like the model 20 or 40 use a resistor in series w/the grid lead to prevent oscillation.
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!
Terry
Posts: 1,185
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Joined: Oct 2017
City: Allendale, MI
I was able to repair the RF transformer. The break was right next to the terminal so not much of a problem. That allowed a MUCH greater sensitivity. by increasing the spring tension on the tuning capacitor shafts, they settled into a more centered travel giving stations all accross the dial.
This is the first non AGC radio I've played with and can see/hear that AGC was a tremendous improvement in the day! The Philco 96 TRF performs so much better than the AK 55.
Voltages are indeed much higher than they should be. Interestingly, several resistors had been changed a long time ago to higher values, perhaps to compensate for 60 cycle rather than 25. Not sure what I'm going to do as it will take a pretty good resistor to drop the line voltage. Since I'm not too impressed with its performance, I may just leave it for an occasional demonstration and keep it for show.
(This post was last modified: 12-25-2017, 10:42 PM by rfeenstra.)
Posts: 1,185
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Joined: Oct 2017
City: Allendale, MI
Posts: 7,273
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Looking Great!!!!
I was never one for that strip down start from the ground up unless it was really really bad. When I was working it just took too much time and patience. Now that I'm retired it seems to be quite possible for me to do.
AVC is a big + on these older sets especially if you live in a city where there are some big guns transmitting. At night it's difficult to tune across the band without getting knocked off your chair by a powerful station.
I have a Philco 76 that I need to revisit. One of the 45 output tubes looses filament voltage (bad connection somewhere) but was toying with the idea of adding avc to it. Takes about 6 additional parts and have to reroute the volume control to the audio side of thing vs the ant.
One of these dayz...
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!
Terry
(This post was last modified: 12-26-2017, 03:03 PM by Radioroslyn.)
Posts: 1,185
Threads: 49
Joined: Oct 2017
City: Allendale, MI
Thanks! I don't think it's worth adding AVC to this. I'll keep it "somewhat" original. Not fully since some mods had been done in the past and in playing with it, I've done further changes in the resistors to get bias and plate voltages a bit closer to the specs that I have. It's playing pretty good, though it seems a bit more distorted than other radios I've worked on and tone quality is less than stellar! I don't know if the universal interstage audio driver transformer has anything to do with that, but at least it works. I did calculate a series resistor for the line voltage and it's not as bad as I thought it might be, so I ordered one that will get the line voltage down to 105 vac or so. That seems to bring things down to a reasonable value. This radio will spend virtually all of its time sitting an a shelf looking pretty, and, as I said before, will only be turned on for a quick demo.
(This post was last modified: 12-26-2017, 04:46 PM by rfeenstra.)
Posts: 1,185
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Joined: Oct 2017
City: Allendale, MI
(This post was last modified: 11-09-2020, 08:58 PM by rfeenstra.)
Posts: 1,185
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City: Bandon
State, Province, Country: OR
Beautiful job!
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