airline15
 

Hello all,
Last year I picked up a airline 15 and decided to see if the thing works or not.
Can't find a correct schematic on this set. Riders says it's a 120 volt set, but this is a battery set. The closest I found is a u-15.
On radiomuseum the pictures for the model 15 are the same thing I got, but the schematic shows the set is 120 ac with a transformer:scratch2: Again this is a battery set.
It has 5 201 tubes. Hookups are aerial, ground, speaker, a+, a-,B+, B-, B+ det,
B+ amp.
The u-15 has voltages listed as 90, 45, and 6.
I believe the 6 is the "A" voltage. Anyone know what the "B" voltages should be?

Is yours the table model shown on Radio Museum with the built in speaker? With 201A tubes, 6 volts for filaments would be correct, cut down to 5 volts by the filament rheostat. B voltages on sets like this would be usually 22-1/2 for the detector, 45 for other tubes, and 90 for the output tube. That's what I'd start with. Check the horn driver with an ohmmeter first: could be open, in which case you'd sub an ordinary output transformer primary there connected to a modern PM speaker. Could use any transformer in the junk box from an AA5. Put your voltmeter across the filament terminals of a tube, start with the rheostat off and don't go over 5 volts. 201A's could have a max of 135 on the output tube but would work better with C voltage of about 4.5V to bias the output tube. Does your set indicate connections for a C battery?

Nothing on the set about c voltage. So what voltage should I try for B+ det and B+ amp????
This does not have the stand with it, appears to be just a table top model.
I did hook up the A voltages and the tubes do light up.
I want to pull the chassis and make sure everything is intact.

B+ det try 22-1/2, "regular" B+ try 45, and amp try 90. Does it have the built-in horn?

Edit: this may have the grid leak resistor next to the detector tube open. It might be one of the ones that fits in like a cartridge fuse. It should read a couple of megohms. If open, tack in a resistor around 2 megs.

Resistor ok. No horn built in, takes a external one.
Hooked it up like you said, don't get any sound. There is a transformer underneath, checked the windings and they seem intact.
There is also a square can under the chassis with 4 wires going to it. Looking at the photo, lower right is marked "P", lower left "+", top left "F", top right "G"
Is this some kind of capacitor??
A schematic would make things so much easier........

That box is an interstage audio transformer. P goes to plate of the first audio, + to B+ for that tube. G goes to grid of the second audio, F to its filament. With power off, check the two windings with your ohmmeter: P to +, and then F to G. Neither winding should be open. Often they are. There are small modern replacements to hide under chassis if the transformer is open. There is also a work around to get it going temporarily if needed.

And I thought Cardwell just made variable capacitors.

http://antiqueradios.com/forums/viewtopic.php?t=30375

They are both open, both sides. Whats the work around, the .047 cap, 1meg and 100k resistor trick???? Where would I hook these up?

There's a picture of a similar Cardwell transformer in this thread:

http://antiqueradios.com/forums/view...?f=15&t=187051

The workaround is similar to what you stated: here's a good explanation of it:

http://www.antiqueradios.com/chrs/jo...nsformers.html

I'll try it this weekend...see what I can blow up:D

It would be a good exercise to trace out the wiring and make a schematic. These mid-twenties TRF sets were mostly similar.

what is the symbol for plate and grid?

Plate is either a heavy line, or a very narrow rectangle. Grid is either a zizag line like a resistor, or a dashed line.

Well I tried that work around, still no sound. I found what appears to be a capacitor, small square can painted green. One end was grounded, the other end connected to one of the round wound coils. It looks like the cap leaked.
There are no markings or stamping on the can:scratch2:
Also the volume control does not change the current to the tubes, although the control seems like it's working via a ohm meter. Tube brightness stays the same regardless where the control is.

The volume control isn't necessarily a filament voltage control. That was an early system that was quickly abandoned because it added distortion and was sluggish.

Where is that volume control wired in? If it operates filaments at all, sometimes it only adjusts those on an RF tube or two.

Hard to figure it out long distance without a schematic. Time to signal trace. Touch your plugged-in soldering iron to the grid terminal of the output tube. Should get speaker hum. If not, check everything from there to the speaker. Then touch grid of first audio tube and see if you get louder hum. Get the audio section working first.

This other transformer I found in here.....looks like it was replaced at one time...could it be for amplification? One lead does go to the B+ amp terminal.

Well I found one big problem.....seems like the speaker connection had only one wire going to it :scratch2: So I hooked a test clip up to the terminal that had the wire missing, and started poking around. I hit a spot and music came out of the speaker:music:!!!
Although the volume is not as loud as I would like it to be, it works. Tuned in different stations, volume control works. I still got that capacitor out of circuit, pic below.....not sure if it affects volume....it attached to one of the coils in the set. Any idea what value it should be????

Great! You got it going. The other transformer you mention is probably the other interstage audio transformer. You'll have one between the detector and first audio, and then another between first audio and output. One of these is the one you found open.

To figure out that capacitor, which I guess IS a capacitor, you could try clipping in some different ones. In those sets the caps tended to be large sometimes. I'd start with an .001, then an .01, then a 0.1 and see what happens. If it keeps getting stronger try a 1.0. On second thought is this in the grid leak circuit? If so the classic value is .00025 mfd which is 250pf. You could use a mica or ceramic cap close to this value if indeed this is connected to the grid of the detector. Although with it out of circuit and the radio working, it must not be?

If you know which of your '01A tubes had the strongest emission when tested, you could try that as the output tube.

There is something else you could try. The 01A tube as an amplifier would like some negative grid bias which some sets provide with connections for a C battery. You didn't mention any such connections on this set. The audio output tube on your set has its grid returned to ground, either through a transformer or through the work around you installed (wasn't clear which of the two audio transformers was open.) In any case you can connect a C battery to the output tube. Lift the grid's ground return. Connect a 4.5 volt battery with the + side to ground and the - side going back through the transformer (or work around) towards the grid. This will give a negative grid bias which will reduce distortion and help volume.

For the 4.5 volt C battery you can use three AAA or AA cells in series. You could use a holder from Radio Shack for them or just quickly solder them in series and tape them in a bundle as they will last shelf life; they are not called upon to provide any current.

The '01A tube can handle up to 135 volts B+ but I'd get the grid bias C battery going before trying anything over 90 volts on the output tube. Once the C is going, see how the volume is. Then you could try 100 volts, maybe 120. You are not going to get ear-splitting volume out of an '01A no matter what. It would take a different type of tube in the output section for that.

I tried a 0.1 and it kills the sound completely. Tested all the tubes, 2 are in the ? zone, all others are in the lower good range. So I shuffled some around. Sound got alot better, loud enough to hear across the room.
That capacitor is still unhooked. I measured the old capacitor and got a reading of 0.13 uf. If I hook it back in, it also kills the sound completely.

One other point: these TRF's like a ground connection and will pick up more and get louder with one.

There were 2 fiber board capacitors that I replaced. The can one I took apart. It had wax in it, most of it was laying on the bottom of the cabinet.
I replaced it with a 0.2 cap. That gave me the best results. Replaced the dial light ( it was missing ) So I consider it done:thmbsp: Just need to wipe down the cabinet with some howards.

We need a picture of the end product!

Here you go...

Came out nice looking!