Philco 90, The final chapter, I hope

[Thermionman1970]

This is very helpful!

[AllAmericanFiveRadio]

Thanks Thermionman1970

[watcher818]

Lockmeister,

I have had the same issue before. A set would play, then go down in vol. When I sparked something, or flipped one of the switches, the signal would come back strong. It wasn't a contact issue either. It was like a cap had to be 'reset' or something. Power on/ then off quickly also reset it. I did find a bad mica cap once, and that solved the issue.

[AllAmericanFiveRadio]

The weakest part of the early Philco radios is the oscillator. Part time problems are always fun.

[Lockemeister]

Well, I might have made a coupple of cold joints myself. I have found that Kester Solder flows a lot better then Radio Shacks brand. I was not happy with some of the chassis stud ground connections I made. the chassis was pretty rusty and I did scrape the chassis studs down resonably well, but I still wasn't thrilled with some of them. We shall see in about a month or two!

[AllAmericanFiveRadio]

Oh I hate when that happens, lol. Yep the true test is time. I hope you got them all!!

[Lockemeister]

Happy New Year Rick!

[Lockemeister]

Rick, my RCA 262 developed an intermittant. The volume goes way down when playing. this can be fixed by switching the band switch from the band it's on to another band then back again. It happens on all bands and whether the radio is cold or has been playing for awhile. Wiggling the tubes has no effect. Only by clicking the band switch fixes the problem. Your video gave me a good number of things to look for! Thanks! My next project, fixing this problem!

[AllAmericanFiveRadio]

Thanks. If you have not found the problem yet I would signal trace it at the output of the detector (the high side of the volume control). If at that point the signal changes with the problem the trouble is in the front end. If it does not change with the problem the trouble is in the audio amplifier.

[Lockemeister]

Thanks, that's good advice. Have to complete Mr. Philco 16b first before looking at the 262 beast. I'm leaning to the front end. Maybe a really old mica cap is having a problem. More likely a cold solder joint. I found that Kester 60/40 solder flows SO MUCH bettter than the Radio Shack solder! The 262 has a rediculous amount of solder joints. Also lots of soldering to chassis studs.

[AllAmericanFiveRadio]

That very possible. The last Philco I worked on had lots of cold solder joints and other loose connections. That was the one where someone had plugged in the tubes so that every other one was in the wrong socket.

[watcher818]

Hi Guys, Great Video RIck. Gmcjetpilot, I agree with checking the resistors, especially the dogbone type, They are almost always high. Especially the higher Ohm units.I'm having trouble with a Philco 89 right now, OSc issues and coil windings that were worked on before.

Maybe I can message you Rick for some ideas I haven't tried yet.. I"ve done a lot so far, but at a standstill for the moment. WIll talk later. Gary Rabbitt.

[AllAmericanFiveRadio]

I will be glad to try to help with some ideas. I did do some reading on the web and there seems to be a natural built in problem with that Philco model. I think I have a chassis on the floor somewhere. I have been thinking about redesigning the oscillator circuit.

[pochodelaribera]

Hi Rick! I am Horacio from Argentina, when injecting signal with the capacitor the "open" resistance work again? Thanks!

[AllAmericanFiveRadio]

Yes, there were a number of things wrong with this radio. The Philco 90 is a very collectable and desirable radio. The owner did a great job on the cabinet work and he is going to have a beautiful Philco 90 to use. THANKS!

[gmcjetpilot]

A great who-done-it mystery.

Rick you say kick starting the oscillator? How did touching the circuit jump start the oscillator and what was your probe connected to?

You determine it was several things, resistors and loose tuning Cap connections. How did you determine to change resistor, just a hunch and processes of elimination?

[AllAmericanFiveRadio]

The resistors were over their 10% tolerance by quite a lot. They may have been 20% but they out enough to replace them and I like closer tolerances in the oscillator. When oscillators are borderline like this one was a little more energy moving the magnetic field in the oscillator coil is enough to get to oscillate. It is like hitting a bell with a hammer.

[gmcjetpilot]

Thanks for the reply Rick; like all your explanations, they're clear, concise and informative, but I surmise there's "magic smoke" in there... ha ha. You put the smoke back in ;-) It's like the time honored whack it on the side. Many of the weird electrical problems I solved where "soft" loose (but not too lose) connections.

I am restoring 50-60 yr old tube radios and awaiting parts for a few radios. I was lazy about checking all the resistors, but I AM GOING BACK AND DOUBLE CHECK.

[AllAmericanFiveRadio]

This one was unusual. Most of the time you would expect one or two loose connection, but not seven. I like the difficulty in getting to the last three screws too, they must have installed the variable capacitor before they welded the three aluminum cans to the chassis. But I thought this radio would be different because right from the start every other tube was plugged into the wrong socket and had one wrong altogether.

[gmcjetpilot]

Congrats the feeling of satisfaction and job well done it quite a reward! Bravo! If it was easy everyone could do it, but they can't.

It's a mental, technical and a mechanical challenge, analogous to solving a cold case crime mystery, all rolled into one. Some one'(s) "repaired" that radio over the yrs. That's why I like unmolested modified radios. New to old radios, it's clear many are tinkered with by amateurs. Thanks for posting the video, it's an inspiration and informative. Cheers.

[AllAmericanFiveRadio]

Most of the old radios have been repaired before and I have seen some interesting repairs. Some of them redefine the word "repair". But it is pretty neat getting them working again and this Philco 90 will be treasured by the owner.

[JimmerSD]

I hate intermittents.

[AllAmericanFiveRadio]

YES!! There was a real danger of going bald.

[JimmerSD]

Going! LOL!

[BassmasterBling]

I toured the Thomas Edison Birthplace in Milan, OH. On display they said they had the first radio tube ever made.

[AllAmericanFiveRadio]

If I remember correctly Edison did put a plate inside a light-bulb and noted that electrons flowed from the filament to the plate, but only in one direction. I think he even called it the Edison effect. Fleming is the guy that put it to work.

[gmcjetpilot]

Edison abandoned work on the "edison affect" (1883) "etheric force", never came up with practical use. John Ambrose Fleming developed the "oscillation (Fleming) valve" (diode) 1904. His patent was invalidated and often gets left out of history.

De Forest credited with the Audion tube 1908, forerunner of the triode but not capable of linear amplification, is my least favorite person in radio history. He screwed Fleming & Armstrong, patenting other peoples ideas. History of radio is convoluted.