It seems like most Atwater Kent model 20C's were only marked 20. I've only seen 1 model 20C marked that way and believe the "C" may have been added later.
It's easy to tell the models apart by size. The Model 20 is around 26" wide while 20C, 21". I'll send you pictures of both.
You don't need the ground connected to have all tubes lit. Either a wire is disconnected or the left rheostat isn't turned up high enough.
If you are using a power supply the ground terminal doesn't need a connection. Use a water pipe when connecting the radio to batteries.
To tune in a station all three knobs need to be set the same. Start with the filaments turned up to 5 volts and adjust the 3 knobs. After finding a station the rheostats can be set to the proper volume.
Norm
: I have a model 20 that I'd like to know how to tune in stations with. Just a brief description should do (I hope)
: Second question: the ground connection next to the antenna terminal--to what do I connect it? I've found that if I don't connect it to the A- lead two tubes/valves won't light up, but I'm not sure if I'm doing the right thing. A schematic I saw was inconclusive about what connects to the ground lug. I don't have an earth ground nearby and I don't suppose a water pipe will do ??
: Finally, how does one tell a Model 20 from a 20C? The nameplate on mine says only that it's a model 20, then gives a serial #. Is there information stamped or marked on the chassis that would tell me this?
: Thanks!
Hi Lee
: It seems like most Atwater Kent model 20C's were only marked 20. I've only seen 1 model 20C marked that way and believe the "C" may have been added later.
: It's easy to tell the models apart by size. The Model 20 is around 26" wide while 20C, 21". I'll send you pictures of both.
: You don't need the ground connected to have all tubes lit. Either a wire is disconnected or the left rheostat isn't turned up high enough.
: If you are using a power supply the ground terminal doesn't need a connection. Use a water pipe when connecting the radio to batteries.
: To tune in a station all three knobs need to be set the same. Start with the filaments turned up to 5 volts and adjust the 3 knobs. After finding a station the rheostats can be set to the proper volume.
: Norm
:
:
: : I have a model 20 that I'd like to know how to tune in stations with. Just a brief description should do (I hope)
: : Second question: the ground connection next to the antenna terminal--to what do I connect it? I've found that if I don't connect it to the A- lead two tubes/valves won't light up, but I'm not sure if I'm doing the right thing. A schematic I saw was inconclusive about what connects to the ground lug. I don't have an earth ground nearby and I don't suppose a water pipe will do ??
: : Finally, how does one tell a Model 20 from a 20C? The nameplate on mine says only that it's a model 20, then gives a serial #. Is there information stamped or marked on the chassis that would tell me this?
: : Thanks!
You can use a meter to measure voltage on two large pins or just be sure rheostats are turned up with 5 volts on the "A" wires. Tubes filaments can look bright in 01A's but be well under 5 volts with little emission.
Yes, rheostats increase filament voltage and are volume controls in these battery radios. You will notice when the volume is below the point of being heard tubes may still be lit.
Norm
: Hey Norm,
: I'm glad Lee ask this question because I am just starting to collect battery radios as you know. You said to turn up the filiment voltage to 5 volts. How does a person know when they have five volts? You have to use a volt meter everytime you turn one of these things on?
: Secondly, what does the rheostats do, increase voltage to the tubes for more volume?
: Thanks as always for all your help.
: Bud
: Hi Lee
: : It seems like most Atwater Kent model 20C's were only marked 20. I've only seen 1 model 20C marked that way and believe the "C" may have been added later.
: : It's easy to tell the models apart by size. The Model 20 is around 26" wide while 20C, 21". I'll send you pictures of both.
: : You don't need the ground connected to have all tubes lit. Either a wire is disconnected or the left rheostat isn't turned up high enough.
: : If you are using a power supply the ground terminal doesn't need a connection. Use a water pipe when connecting the radio to batteries.
: : To tune in a station all three knobs need to be set the same. Start with the filaments turned up to 5 volts and adjust the 3 knobs. After finding a station the rheostats can be set to the proper volume.
: : Norm
: :
: :
: : : I have a model 20 that I'd like to know how to tune in stations with. Just a brief description should do (I hope)
: : : Second question: the ground connection next to the antenna terminal--to what do I connect it? I've found that if I don't connect it to the A- lead two tubes/valves won't light up, but I'm not sure if I'm doing the right thing. A schematic I saw was inconclusive about what connects to the ground lug. I don't have an earth ground nearby and I don't suppose a water pipe will do ??
: : : Finally, how does one tell a Model 20 from a 20C? The nameplate on mine says only that it's a model 20, then gives a serial #. Is there information stamped or marked on the chassis that would tell me this?
: : : Thanks!
Another point to consider is to make sure the knobs are all aligned with the Capacitors in the same way. I often find AK20's with wildly differing alignments.
I guess 0 should be plates fully out and 100 fully in?
or Vice Versa? Norm would know. just set them all the same way whichever. the later belt driven sets like the AK 55 are misaligned intentionally to compenstate for tuning variations.
Once you get the feel for how your
set tracks, tweak the capacitor positions to aproximate the same number. It is possible for the
knobs to read one way at the high end and the other way at the low end. Modern sets have split vanes & trimmers to compensate for non linear tracking. 20's dont.One of my 20's is dead linear, others not.
Tune with the first knob & set the other two to match.
then fine tune each knob. Set the rehostats initaly at 3/4 untill you start to hear airwave background static. Too low and you hear nothing. Adjust final volume to suit. fidelity & noise change with different rehostat positions so try different combinations to find the best sound.
My Horn speaker can sound better than I expected
with a little fiddling. P.S. The antenna tap select is the most sensitive at the far right .
A close inspection showed that a wire-wound resistor underneath the far left capacitor/coil assembly had broken wires. Since an identical-looking resistor is on the next assembly over, I measured its resistance (@500 ohms) and found a half-watt resistor of a near value. I soldered it in place and powered up. It worked! I felt SO smart.
I guess I'm bragging now, but that evening I listened to a station in Denver, 700 miles west of me, and another in Chicago, almost 400 miles east. I also heard what I thought was a Louisville station. The fidelity is awful, but the thrill is full stereo!
Thanks again!
Lee
PS. I too would like to know whether 0 is supposed to be fully meshed or if it should be 100. If these old radios tune like more recent ones, the extreme low end of the band is where the plates are fully meshed. It may not be the same for these TRF radios as for the superhets.
: 20C are the size of a loaf of white bread. 20's are as big as a breadbox. 20's have four round trim spots on the front panel. 20 delux are gold plated with feet. 20's have internal rear brackets to hold log cards.
: c's do not.20c have attached battery wires, 20's have
: individual wire holes and thumb nuts for the wires.
: Another point to consider is to make sure the knobs are all aligned with the Capacitors in the same way. I often find AK20's with wildly differing alignments.
: I guess 0 should be plates fully out and 100 fully in?
: or Vice Versa? Norm would know. just set them all the same way whichever. the later belt driven sets like the AK 55 are misaligned intentionally to compenstate for tuning variations.
: Once you get the feel for how your
: set tracks, tweak the capacitor positions to aproximate the same number. It is possible for the
: knobs to read one way at the high end and the other way at the low end. Modern sets have split vanes & trimmers to compensate for non linear tracking. 20's dont.One of my 20's is dead linear, others not.
: Tune with the first knob & set the other two to match.
: then fine tune each knob. Set the rehostats initaly at 3/4 untill you start to hear airwave background static. Too low and you hear nothing. Adjust final volume to suit. fidelity & noise change with different rehostat positions so try different combinations to find the best sound.
: My Horn speaker can sound better than I expected
: with a little fiddling. P.S. The antenna tap select is the most sensitive at the far right .
A close inspection showed that a wire-wound resistor underneath the far left capacitor/coil assembly had broken wires. Since an identical-looking resistor is on the next assembly over, I measured its resistance (@500 ohms) and found a half-watt resistor of a near value. I soldered it in place and powered up. It worked! I felt SO smart.
I guess I'm bragging now, but that evening I listened to a station in Denver, 700 miles west of me, and another in Chicago, almost 400 miles east. I also heard what I thought was a Louisville station. The fidelity is awful, but the thrill is full stereo!
Thanks again!
Lee
PS. I too would like to know whether 0 is supposed to be fully meshed or if it should be 100. If these old radios tune like more recent ones, the extreme low end of the band is where the plates are fully meshed. It may not be the same for these TRF radios as for the superhets.
: 20C are the size of a loaf of white bread. 20's are as big as a breadbox. 20's have four round trim spots on the front panel. 20 delux are gold plated with feet. 20's have internal rear brackets to hold log cards.
: c's do not.20c have attached battery wires, 20's have
: individual wire holes and thumb nuts for the wires.
: Another point to consider is to make sure the knobs are all aligned with the Capacitors in the same way. I often find AK20's with wildly differing alignments.
: I guess 0 should be plates fully out and 100 fully in?
: or Vice Versa? Norm would know. just set them all the same way whichever. the later belt driven sets like the AK 55 are misaligned intentionally to compenstate for tuning variations.
: Once you get the feel for how your
: set tracks, tweak the capacitor positions to aproximate the same number. It is possible for the
: knobs to read one way at the high end and the other way at the low end. Modern sets have split vanes & trimmers to compensate for non linear tracking. 20's dont.One of my 20's is dead linear, others not.
: Tune with the first knob & set the other two to match.
: then fine tune each knob. Set the rehostats initaly at 3/4 untill you start to hear airwave background static. Too low and you hear nothing. Adjust final volume to suit. fidelity & noise change with different rehostat positions so try different combinations to find the best sound.
: My Horn speaker can sound better than I expected
: with a little fiddling. P.S. The antenna tap select is the most sensitive at the far right .