The PHILCO Phorum
MODEL 43 - PROBLEMS WITH TUNING CAPACITOR - Printable Version

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MODEL 43 - PROBLEMS WITH TUNING CAPACITOR - jhgrahamjr - 12-21-2014

Hi,

I just finished re-capping the electrolytic and filter bank capacitors, and fired up the radio and was pleased to see a marked improvement (thanks for the assistance of my online mentor, John Goller!)

However, on the AM broadcast band, once I tune past 1050 kHz, I only get awful crackling. The problem seems to be with the rotor/stator plate spacing. I tweaked a couple, and the crackling changed to a consistent, well, sound like a fly passing gas, if a fly could do that.

I notice the plates are very close together. I can't seem to fix the problem.

I have two questions:

1) Are the rotor plates supposed to be centered with respect to the stator plates, or to one side, close to them?

2) If they are supposed to be centered, how can I do that?

Any and all suggestions are welcome!

RE: MODEL 43 - PROBLEMS WITH TUNING CAPACITOR - GarySP - 12-21-2014

Hi,  First thing I would try is pulling the cap out of the chassis and giving it a good washing.  I have had good results putting the unit in my dishwasher with the plates opened out  and running it through a cycle.  Then put it in a very warm oven, or in front of a space heater to completely dry it out.  Once you're sure surface corrosion and dirt aren't the issue you can concentrate on plate spacing.  Remember to lightly lubricate the pivot points before re-installing it.  Good luck. Gary

RE: MODEL 43 - PROBLEMS WITH TUNING CAPACITOR - NostalgiaRadioTime - 12-21-2014

I can't speak for your model 43, but I've had trouble with rotor & stator plates touching on tuning capacitors in the past, causing the same symptoms you're describing. I tried to get an even gap on each side once they are in the closed condition, using a set of narrow width feeler gauges to check the spacing. In one case, I used a set of tiny jewelers files or some fine grit, stiff backed sandpaper to open the stubborn gap when there was corrosion causing the crackling.

RE: MODEL 43 - PROBLEMS WITH TUNING CAPACITOR - jhgrahamjr - 12-22-2014

This capacitor was cleaned carefully in an ultrasonic cleaner. Got off ALL the gunk! Looked almost like it just came from the factory.

I will be taking it out...looking for some kind of set screws on the front end.
Thanks!

(12-21-2014, 10:32 PM)GarySP Wrote:  Hi,  First thing I would try is pulling the cap out of the chassis and giving it a good washing.  I have had good results putting the unit in my dishwasher with the plates opened out  and running it through a cycle.  Then put it in a very warm oven, or in front of a space heater to completely dry it out.  Once you're sure surface corrosion and dirt aren't the issue you can concentrate on plate spacing.  Remember to lightly lubricate the pivot points before re-installing it.  Good luck. Gary


RE: MODEL 43 - PROBLEMS WITH TUNING CAPACITOR - jhgrahamjr - 12-22-2014

Hey,

Thanks for the tips! this one has been ultrasonically cleaned, but the blades were corrosion free to start with. The blades are just too close together, pushed towards the front, and almost (and probably) touching the stator plates.

(12-21-2014, 11:00 PM)NostalgiaRadioTime Wrote:  I can't speak for your model 43, but I've had trouble with rotor & stator plates touching on tuning capacitors in the past, causing the same symptoms you're describing. I tried to get an even gap on each side once they are in the closed condition, using a set of narrow width feeler gauges to check the spacing. In one case, I used a set of tiny jewelers files or some fine grit, stiff backed sandpaper to open the stubborn gap when there was corrosion causing the crackling.


RE: MODEL 43 - PROBLEMS WITH TUNING CAPACITOR - jhgrahamjr - 12-22-2014

Gee, I wish I knew more about radio!
You won't believe this (or maybe you will). It wasn't the tuning capacitor at all! There was oscillation coming from the wire going from the oscillator coil to the grid cap of a 39/44 tube. I noticed if I put my hand in a certain position, the oscillation went away. To cut to the chase, I turned a screw on an ugly trimmer assembly on top of the coil, and the oscillation went away-- I guess turning the tuning capacitor to a certain capacitance set off the oscillation, and I misinterpreted what was going on! Live and learn? After taking out that capacitor 3 times, and spending a day messing with it, do I feel stupid now! Thanks for your kind attention!

RE: MODEL 43 - PROBLEMS WITH TUNING CAPACITOR - klondike98 - 12-22-2014

Don't feel stupid...we all have to scratch around some to find troublesome problems...although some of us scratch more a lot than others who know what they are doing  Icon_biggrin  I've been known to wire up a bakelite block cap incorrectly and then have to back track to find out what the darn problem was  Icon_eek

RE: MODEL 43 - PROBLEMS WITH TUNING CAPACITOR - jhgrahamjr - 12-22-2014

Thanks, Bob! I'm just so relieved to have solved the problem so easily.

(12-22-2014, 08:38 PM)klondike98 Wrote:  Don't feel stupid...we all have to scratch around some to find troublesome problems...although some of us scratch more a lot than others who know what they are doing  Icon_biggrin  I've been known to wire up a bakelite block cap incorrectly and then have to back track to find out what the darn problem was  Icon_eek


RE: MODEL 43 - PROBLEMS WITH TUNING CAPACITOR - thirtiesradio - 12-23-2014

Glad you got it repaired. It really sounded like the stator plates were rubbing. There are so many strange things you run into with these old sets. Some can be very difficult to locate so you did very well.

RE: MODEL 43 - PROBLEMS WITH TUNING CAPACITOR - jhgrahamjr - 12-23-2014

Thanks for your reply! Yeah, it feels good to be able to move on to my first experience with re-capping "tar babies"!

(12-23-2014, 04:15 AM)thirtiesradio Wrote:  Glad you got it repaired. It really sounded like the stator plates were rubbing. There are so many strange things you run into with these old sets. Some can be very difficult to locate so you did very well.