[WyTex]

I do receive stations and static above this point on the band. But something new occurred this past weekend. I usually listen to another station, 1210, on Sunday mornings. This station now cuts out completely and the radio was silent with no static anywhere. If I turned it off/on it comes back but eventually cuts out completely again. Probably best not to play it anymore until I can figure this out.

[morzh]

Cuts out ONLY on this station or it stops receiving and goes silent altogether?

[WyTex]

If I tune the dial further below 1210 it usually comes back to life. I can then hear the 1210 station but never 1440.

[codefox1]

A Piece of paper between blades whilst rocking back and forth can detect the flaw, set on with proper isolation transformer, or set off disconnected with ohmmeter observed. When paper binds, you got it, and if just a bit, probably dislodge it. Takes some time as you have to do all the plates, but most likely those on the end will be guilty.

[Raleigh]

My last two restoration projects in a row (not Philcos) had shorts in the tuning caps. FWIW, I found that a long, thin, wedge-shaped piece of card stock (a 5 X 7 file card) worked best to find the shorts. You do have to wiggle them around a lot. In one case that was enough to clear one of the short, some conductive grime, I suppose., but there was another that was harder to find.

I used a beeping ohm meter to help locate the short, radio off. Tune the cap to the very first point the meter beeps, then probe around with the paper. Be sure to probe on BOTH sides of each vane (or whatever they're called.)

In both cases, I eventually had to remove the tuning caps from the radios to get to the lower-most points that could be shorted.

[WyTex]

Update. There is now a dead zone above approximately 1150 or so where nothing comes in. Slight static or humming but only stations below this range come in. Used card stock to clean between the tuning blades and blew it and the entire chassis out with compressed air. No effect. When I adjust the dial from from the range where stations do come in and when they don't, there is a slight pop and then silence. Adjust slightly towards the other direction and stations return so there is a definitive dial location where it goes silent. Is this indicative of a short in the tuning capacitor?

Thanks all for the assistance.

[morzh]

Paul


I probably advised that before but let me do it in case I did not: locate your oscillator tube and change it if you have a spare. Even if it tests fine. Not an unusual reason for the symptom you are having.
It will at least eliminate one suspect.

[jerryhawthorne]

As has been suggested twice, use your ohm meter and look for a short from shell of your variable cap (ground) to each of the gang sections one at a time while rotating your tuner across it's range. Very simple! Make certain you are on the "side" of the trimmer that is attached to the stationary plates of the gang your testing, not the side of the trimmer with the wire coming off of it.
Best, Jerry

[WyTex]

Thank you for both suggestions. New tube on the way and I will learn how to test for a short. This is my first attempt at tube radio repair and I sincerely appreciate the help and patience with my questions.

[Randy H.]

You might try shorting the antenna wire to the chassis, then try for your satation. It might well be an AVC (automatic volume control) problem, and this might send you in the right direction.

Also, listen to the sound of the radio istelf. That kind of a 'shoosh' sound you get between stations. Is it present at 1440? Or does it go silent there? Could be your oscilator tube 'don't wanna' at that frequency. What were the tubes in the 38-62? Large 6 and 7 pin types (6A7, 6D6, 75, 42, 80) or loctals? (7A8, 7A7, 7C6, 50a5, 35Z3)

[jerryhawthorne]

Hey, trying to help a little and I know this is a bit confusing for someone new to this. Seems there are two possibilities for your problem. One a bad oscillator the second some short problem in your tuner. I'm posting a picture of a tuner that I have open to see if I can help. This tuner is much larger than yours from a much earlier radio. You will not see the moving plates on this as I had to tear it apart, removing the rotating vanes as the bearings were froze. The moving vanes are tied to the frame (ground) the stationary ones there are isolated from ground. Note the four adjustable mica trimmers, one on each of the tuning gangs? You have those as well on your radio but not as many. Lucky you. The might not look just like yours but essentially the same. Each of those trimmer have a wire going to them. On the other "end" of them they are attached to the stationary gang associated with it. A good connection would be the adjusting screw of the trimmer as it goes to that stationary set of plates.
Just hook one lead of your meter to the frame of the tuning cap and the other to each screw and rotate the tuning cap looking for a short. Do it on each of them.
Hope it helps.
Oh fudge, nope connect your meter to the the ground and to the wire going in to your trimmer cap. Must have had a brain fart. Sorry, happens often and much easier and right to do it that way. The right way.

Jerry

[Image: http://i303.photobucket.com/albums/nn129...tuner3.jpg]

[Raleigh]

Paul, this may not apply to your radio, but I had a similar-sounding problem with a very different Philco, a 41-81 portable. I replaced a dead oscillator tube, and suddenly the band went dead from about 1200 up. Below 1200, the stations were about in the right place.

I checked the tuning cap, but didn't find a short. Voltages were about right.

I bought yet another oscillator. It made no difference.

On a whim, I repeated the alignment. That fixed the problem and everything worked fine. I can't explain why it stopped working when the old oscillator died, and I can't explain why the alignment fixed it.

On my radio I didn't have the problem of not being able to pick up a single station, only having the band become dead above about 1200.

[WyTex]

I've replaced the 6A8 tube. Same dead zone. The stations that did come in now seem to overlap each other with 2 or more stations heard simultaneously. No station comes in clear. This took place about a week ago. When I tested last weekend with a 2nd replacement tube I now only hear a hum with no reception. I seem to be going in the wrong direction with this. Radio does have newer electrolytics and caps. Should the lamp light dim down on this radio after powering up as it does on an AA5? Will test it on a dim bulb tester tonight.

Randy - no swooshing sound where 1440 should be heard. Just silence. Tubes in this set are 6A8G, 6K7G, 6Q7G, 5Y4G and 6F6G.

I just acquired a signal generator and am studying how to perform an alignment. Does this point to 2 issues, a short and an alignment? Hoping to follow the steps Jerry kindly provided here for the short test this week.

Thanks fellas.
Paul

[morzh]

Paul

try the alignment (it does not take long) and see whether the problem cures itself.

Now as for 6A8 tubes, I had a nightmare experience with buying them when they came three times from three different vendors all very weak in the triode section (oscillator tested fine). There is some plague with them.

Which does not mean that they do not work.
Your change with the 1st tube could be due to the different inter-electrode capacitance which screws the alignment you have.

When you perform the alignment use your generator to produce the exact frequency you are looking for (1440 is it?) and see if you receive.

[PAradiogeek]

Paul,

You say you recapped. Did you check for and possibly change any out of tolerance resistors? I guess I'm just wondering if you've double checked your work. For instance, if in changing a resistor, you put one leg back in the wrong place you might introduce a resistance into an LC tuning circuit. This would negatively affect the selectivity of the set (potentially allowing you to receive multiple stations at once that you mention in your most recent post).

Good luck.
Jon