The PHILCO Phorum
I'm batting 1000 - Printable Version

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I'm batting 1000 - Eric Adams - 09-21-2015

I'm at the point where everything I touch turns to s**t! Icon_confused

I've got a simple Airline model 4705 . Just a simple 6 tube AM radio. Replaced all caps. Tubes and resistors checked OK. Alignment done. Everything is fine except I only get one station . It is WGN, 720 from Chicago (about 40 miles away). It comes in on any dial position. Icon_eek It is just as strong at 55khz as it is at 1600khz.

Any clues as to where to start?

Thanks guys,

RE: I'm batting 1000 - Steve Davis - 09-21-2015

Sounds like the oscillator is not working. Have you tried placing another radio near it to see if you can pick up the oscillator?

Steve

RE: I'm batting 1000 - Eric Adams - 09-22-2015

Well Steve, I just checked it. The oscillator is working, but now WGN is gone and the only thing I can pick up is my SSTRAN set at 1500khz. This would be a step in the right direction except that it is coming in at about 700khz no matter what I do to the osc trimmer on the tuning cap!

RE: I'm batting 1000 - Steve Davis - 09-22-2015

Eric, when you listen to the oscillator on the other radio and adjust the trimmer, does it move up and down the dial?

Steve

RE: I'm batting 1000 - jerryhawthorne - 09-22-2015

Eric, do you have a signal generator? A very nice piece to have to troubleshoot these problems.
jerry

RE: I'm batting 1000 - Eric Adams - 09-22-2015

Sure do, Jerry. I was able to do the IF alignment.

RE: I'm batting 1000 - jerryhawthorne - 09-22-2015

Great Eric, now use it to run AM frequencies into the antenna input but please use an Iso trans on the radio. As you know, this has a potentally hot chassis depending on the plug orientation. Steve is much smarter and there is something wrong in the RF/OSC section. See what you find for a "tone" across the AM band.
Jerry

RE: I'm batting 1000 - jerryhawthorne - 09-22-2015

Sorry, Dup. And sorry Eric if I didn't realize and recognize your experience and knowledge. Best, Jerry

RE: I'm batting 1000 - morzh - 09-22-2015

>>>I'm at the point where everything I touch turns to s**t!


Eric, go save Midas Icon_smile

RE: I'm batting 1000 - Arran - 09-23-2015

 Schematic linked to is an Air King 4705, not an Airline, or is your set actually an Air King? If so try replacing the 22k Ohm resistor on pin #1 of the 12SA7 tube. The 22K resistor, or R3, may test fine cold, but may not when the set is powered up.
Regards
Arran

RE: I'm batting 1000 - Eric Adams - 09-23-2015

Yes Arran, it is an Air King. The 22k ohm resistor is on pin #3 of the 12SA7 tube. It goes from pin #3 to ground. I replaced it. No change, except now it is motor boating.

No big deal. It is time to put it on the punishment shelf Icon_thumbdown and go on to something else.

Thanks for your help,

RE: I'm batting 1000 - Paul Philco322 - 09-24-2015

I think as a kid I wound up on that shelf. I read a story/interview with a guy who worked at Air King, trouble shooter and supervisor on the line and while they did make some decent stuff they did cut some corners. It may be that some manufacturing may not be to spec or done well to begin with. Sometimes taking a break is good, think about it, work on something else for a change.

Good luck.

Paul

RE: I'm batting 1000 - Eric Adams - 09-25-2015

I think we all ended up on that shelf at one time or another Icon_wink  It's just that if this keeps up it looks like I'm going to need more shelves!

RE: I'm batting 1000 - TA Forbes - 10-10-2015

This could be the result of an alignment mis-adjusted to an harmonic of the frequency vice the frequency itself. Also, how do you verify that the F is what it should be.   

RE: I'm batting 1000 - TA Forbes - 10-10-2015

What I mean is do you verify the frequency from your sig gen with a frequency counter?