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  #1  
Old 10-23-2004, 07:02 AM
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asynchronousman asynchronousman is offline
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My Airline is GROUNDED!

I have a ~1951 Airline 15WG-1813B that developed a problem with the volume. It started popping up and down at random to variable levels. At no time did the quality of reception on either band suffer, only the volume. While I have never done any real fixing (no tools for one), I think I have an idea about what is wrong.

The set is found in Beitman's 1951 volume, page 63.

Since the reception didn't change, I would have to narrow it down to maybe three tubes and unknown.

6AV6 is the tube that handles AVC.
6V6 is the output tube.
6X5 is the rectifier.

Another man who fixes and sells mostly 1930's radios looked it over a while back and didn't see anything that stuck out, so this came up quickly. He also said both the IFs were fine. He has suggested trying a 6AT6, although I don't have that either, unless it's in the Hoffman or untested in the Stromberg Carlson TV combo I can part out. I have a friend fixing a VTVM up for me and I'm trying to come up with tubes and equipment. At 38, I'm a newbie.

I assume this is a series circuit, so nothing's gonna light up either.

Thank you, Steven

Last edited by asynchronousman; 10-23-2004 at 07:04 AM. Reason: I can't type (I can dance to Soul Train though)
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  #2  
Old 10-23-2004, 07:08 AM
jstout66 jstout66 is offline
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Hi Steven, I'd test the tubes first. If you need any tubes you should try vacuumtubesinc.com Great prices and service. However.... I don't think the volume problem would be caused by a tube. Sounds more like a cap problem.
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  #3  
Old 10-23-2004, 07:25 AM
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Tom Bavis Tom Bavis is offline
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Sounds like a contact problem to me. Remove the tubes one at a time, clean the pins with a wire brush, apply a tiny dab of Deoxit (if you have it) with a Q-tip, and replace.

Unfortunately , there are plenty of other places for bad connections - but tube sockets seem most likely.
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Old 10-23-2004, 08:03 AM
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asynchronousman asynchronousman is offline
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Hmmmm...

I did have it turned on it's face. Maybe the "simple" fix will be it. I do have that tiny can from the Shack. Closest to a wire brush is a copper brush in the kitchen, but I don't like that...I have dry Scotch Brite? Naah. I'll figure it out.

Steven (PM me about my Musaphonic 475 though)
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Old 10-23-2004, 08:53 AM
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Chad Hauris Chad Hauris is offline
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Have the paper caps been replaced...could be an intermittent in a cap in the audio circuit. Sets that use 6X5, 6V6 are not series wired, at least I never saw one, the tube filaments are a parallel circuit.
Intermittants in tubes themselves are very rare...you need to replace the old caps to rule that out as a problem, then try the contact cleaner in the pots, switches, and tube sockets.
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  #6  
Old 10-23-2004, 09:44 AM
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asynchronousman asynchronousman is offline
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All I know is the dial light doesn't light and it doesn't start up. I have heard the light in some sets will take the whole thing down, so until I pull it down later (sleep, heard of it? I should have)...I don't have any tools yet, mind you, just Deoxit. It says on the schematic that 6.3 V heater voltage goes through the lighting circuit? I suspected something like that. But the AVC is what generally would create the random volume variations?
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Old 10-23-2004, 10:13 AM
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Chad Hauris Chad Hauris is offline
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The indicator light is powered by the 6.3 volt filament winding...whether it is in or out of the circuit will not affect performance...however if there was a short at the bulb socket that will take down the filament power and could damage the power transformer. You need to go through the power circuit with a multimeter and confirm where you don't have voltage. Personally I wouldn't mess with a VTVM, I find a good digital multimeter easier to use.

The AVC varies the bias on the RF, converter and IF tubes to vary the gain. There is a delay factor on AVC where a filter capacitor stores voltage to allow for a relatively slow change in gain when the signal strength changes. AVC will not cause rapid variations in volume. The 6AV6 is the detector tube...it rectifies the radio signal, removing the carrier wave and leaving the audio variations. Also the rectified signal is fed to a filter system to provide the AVC voltage which varies w/ signal strength. Also the 6AV6 has a triode portion which is the first audio amp.

The variations in volume are most likely in the audio portion of the set.

Again don't go troubleshooting the problem till you replace those old caps, that way you can rule them out as a problem.
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Old 10-23-2004, 11:18 AM
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Paula Paula is offline
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Hi Steven,

For what it's worth...

I have a Motorola radio from around 1949, that had a problem similar to yours.

Paula

Last edited by Paula; 10-28-2004 at 09:47 AM.
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  #9  
Old 10-24-2004, 07:58 AM
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asynchronousman asynchronousman is offline
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Paula: Neither the 15WG-1813B Airline nor my ~1955 GE Musaphonic 475 have an arrangement like that. The GE will no doubt need some caps and both have dial lighting (the GE light moves around the dial to your tuning spot as you turn the dial and the Airline is a square dial with a top mounted light).

I will be able to do a lot more once the VTVM arrives next week and I learn how to use it.

Steven
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  #10  
Old 10-24-2004, 08:22 AM
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asynchronousman asynchronousman is offline
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Quote:
Originally Posted by Chad Hauris
The indicator light is powered by the 6.3 volt filament winding...whether it is in or out of the circuit will not affect performance...however if there was a short at the bulb socket that will take down the filament power and could damage the power transformer. You need to go through the power circuit with a multimeter and confirm where you don't have voltage. Personally I wouldn't mess with a VTVM, I find a good digital multimeter easier to use.

The AVC varies the bias on the RF, converter and IF tubes to vary the gain. There is a delay factor on AVC where a filter capacitor stores voltage to allow for a relatively slow change in gain when the signal strength changes. AVC will not cause rapid variations in volume. The 6AV6 is the detector tube...it rectifies the radio signal, removing the carrier wave and leaving the audio variations. Also the rectified signal is fed to a filter system to provide the AVC voltage which varies w/ signal strength. Also the 6AV6 has a triode portion which is the first audio amp.

The variations in volume are most likely in the audio portion of the set.

Again don't go troubleshooting the problem till you replace those old caps, that way you can rule them out as a problem.
The set has played strongly and loudly since I got it. Conventional wisdom says that if they weren't broken by now, I have a hunch they aren't the deal even if they need and should face replacement. Which leads to the next reasoning...

Will removing the bulb break the short, or will it break the heater string so that no power will get to them anyway? Another thing to consider is that the bulb was lit all the time UNTIL the failure, which suggests no short was present. This I think brings me back to the vicinity of the 6AV6 again.

You are emphatic about a DVOM, yet reality presents me with a VTVM instead. A digital meter is a great tool, but I am going to have to deal with much the same stuff as any 50-70 yo would have had 20 years ago, for I cannot afford many newfangled gadgets; I live on disability benefits and less than $600. Before this fall I had never spent more than $25 on any radio or speaker. I have relied on the kindness of repair people who took interest in me as I was a "nice guy". I cannot travel 200 mi each way to one anymore; too expensive and he now wants money, and the other one has Hepatitis C and is highly unsure of the length of his remaining life. Put simply, I must learn as I'm running out of repairmen

I think I will send to a member for a 6AV6 after I look at the base of the lamp. Something tells me this one will be easier than the GE. Can this PS really be as fickle as the one in my computer?

Steven
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  #11  
Old 10-26-2004, 10:15 AM
mbates14 mbates14 is offline
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BTW, this may be an already-checked item, or a longshot, but did you clean out or replace the pot? the wiper could be hung on dirt and scratchy. Also control switches and stuff develop static and breaks.
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  #12  
Old 11-13-2004, 12:17 AM
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asynchronousman asynchronousman is offline
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I've got an air can and Caig Deoxit (much tinier) and I'm fixing to tackle a number of my sets, Antique or Vintage Stereo just as soon as the fall chores are tackled.
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