I totally went through my single 47 version model 90 earlier this year. All new caps, all new resistors. It was playing fine. But it's been sitting a few months and now it developed a crackling sound that almost sounds like the crackling interference you get when there's a thunderstorm. It's controllable with the volume but is consistent throughout the dial as you tune. Does this sound like it could be caused by corrosion; that perhaps the trimmers on the tuner developed corrosion from sitting? Full disclosure I didn't remove the tuning capacitor from the chassis when I did the recap but did clean it out good. My other thought is it may be the grommets under the tuner that need replacing. Anyone else encounter this with a model 90? I didn't have this on my model 70 (which I sold after I got the 90).
Electrolysis shorting could be creeping up somewhere, but sounds more like outside interference - anything new in the house?
Living in Florida with all the dampness when turning on a radio that has not been played for a few months just turn it on for a hour and let things dry. Sometimes have to pull the tubes and give the sockets a good cleaning.
Greg
Start with the tubes.
If no luck, see if by touching/rocking components you could see additional crackling or maybe if it stops.
Including the tuning cap.
Start tapping everything you can with some wooden chopsticks and listen for any changes. You might get lucky. Take care and BE HEALTHY! Gary
Thanks for your ideas. There's nothing new in the house to cause the crackling, as none of my other radios do it. I neglected to mention I did try several different tubes in each socket so I eliminated that possibility. However when I pulled the chassis, I heard something rattle within the tuner. So I turned the chassis upside down and out popped a fossilized black piece of grommet. I wiggled on the tuning capacitor and sure enough it's loose. So I spent the night making a wiring diagram (7 wires to the tuner and 2 to the light bulb) and will remove the tuner tomorrow and replace the grommets. While I have it out I'm going to run it through my ultrasonic cleaner. I can see the mica trimmers are very dirty and there's still a lot of dirt within the tuner itself. The one mystery I have yet to solve is how to remove the dial scale from the tuner. I see a set screw but there must be something else holding it to the shaft.
Hello greg,
I really love my ultrasonic cleaner it really comes in handy and tuners look brand new when I clean them with it !
Sincerely Richard
Yep. That's why rocking/tapping tuning cap is one of nice things to do, when things crackle.
Dirty ones also do it.
So seven wires to the tuner and 2 wires to the dial lamps disconnected and I had the tuner unbolted and in my hand. Then I removed the dial scale and tuning knob/drive, and then disassembled the trimmers, carefully counting the number of turns it took to back the nuts off of each. I removed the sheet of mica from each, reattached the copper adjusters and it was time to put it in the cooker, er I mean ultrasonic cleaner. It JUST fit in my Harbor Freight model, and just that I could get the water level over the meshed tuner. So I ran it through four 480 cycles with heat and a bit of simple green, two with the bottom down, and two with the bottom up. I took it out, rinsed it off to get the soap residue out, then took the air compressor and blew it down good to dry it off. Added a few drops of oil to get it moving nice and smooth. Then it was time to reassemble the trimmers, reattach the dial mechanism and scale, install new grommets and resolder the new wires on. Fingers crossed I tried it out and remarkably I received a station! After an alignment it's back to performing like it should with only an occasional pop, nothing like it was. So apparently the heart surgery was a success and the patient survived. Lesson learned I should have just bit the bullet and did this when I did the recapping. Yes it was a lot of work (took the entire afternoon) but judging by how black the water in the ultrasonic cleaner was from 91 years' worth of crud, it needed to be done. Here's how it looks now, all squeaky clean.
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As Ma would say could your lunch off it! Purdy job.
Paul
Hello Greg,
Yes the current model Philco 51-930 I should of done the same but I just did not want to have to restring the tuner but I might have to since it was really filthy I blow it and dusted it we will have to see.
Sincerely Richard
It is rare that I skip full removing of the tuning cap and soaking and washing it in soapy water with soft long paintbrush, going between all vanes.
One radio I skipped it with is my Zenith 9-S-262 console, and even though it tunes fine, it really crackles when being tuned. One day I will take care of it.
Hello morzh,
Yes the good old crackle !
I still might do my Philco before i am finished .
Sincerely Richard
I see that one of the cap sections has a possible metallic washer installed over the shorter (cut off ends) bronze metal plate. Don't know if the insulated washed is under that. A 70 I purchased had that type of shorter plate on the oscillator section and was loaded with several metallic washers that was probably an attempt to add capacitance to get it to align. If this is metal on yours, and if it touches the metal upward tabs on the metal plate, all kinds of pops and static can occur, especially when the metal washer gets gunked up. You can experiment with that area, cleaning the metal washer, trying with and without it. During my experiments, I saw how much difference this one small area can make in gain and alignment.
Good eye. When I disassembled it to run it through the ultrasonic cleaner, I took careful notes as to how and in what order everything went back together, so I'm confident I have it the way it was, but that's not to say there isn't metal touching the upward tabs. I'll dig into it again when I get caught up on a few other things