1933 Philco 89 update

I fixed the main problem with the low volume^^

Category:

Science & Technology

Tags:

• radio
• antique
• philco
• cathedral
• 1933
• 89
• tubes
• vacuum
• tube

[debo693]

Great job!! looks great. I have one that was my wifes Grandfathers. It needs work I would love to restore it, I'm just starting to read about it, and trying to find out the year and model. what forums have you found to be helpful. Thank you!!

[coolbluelights]

@debo693 Antique radio forums all the way! good luck

[Radiosnmore5]

It squeals because it needs an alignment. The IFs as well as the front end and oscillator. Nice Job so far!

[Destry7]

Chassis "ground" connections are also sometimes bad. If they use a screwed solder lug, built-up oxidation and dirt, can cause a problem. Often, just backing it out & re-tightening will fix it as the screw/lockwasher re-bites into the metal. Cleaning the contact point first is best. Also, old solder joints can fail as the exposed wire oxidises. Look for noise, a loose-feel or a little dark ring-shaddow around the wire-end joining the solder. Re-heat using a dab of rosin-core flux or new solder.

[Destry7]

Right. Resistors often get overlooked. You'll find many @ more than 2x their original value. A good rule is that any resistor >20% off the marked value should be replaced. Carbon resistors connected to old, leaky capacitors or shorted tube elements may get hot & partially burn or disintigrate to a much lower value. Sometimes the evidence isn't easy to see, so you pretty much need to check them all with an Ohmmeter (de-soldering one end), or by checking voltage test points if you have that info.

[coolbluelights]

Thanks for all the advice! I did replace all the paper caps except the one in the tone control, I'll have to go and look at the resistors again, because many of them are origional

[Destry7]

You're right about the old paper dielectric capacitor in series with the tone pot. It's probably leaky & causing distortion as the pot's resistance is reduced.

Usually all the old caps, (other than the silver mica "postage-stamps") need to be replaced and also many of the old carbon comp resistors. I had to do this with a '49 National HRO-50. Most resistors will actually be 1/2W (old parts are always larger). If the original is >1/2W you'll see it's much larger than the others.

[Destry7]

Nice work! Old radios like this are among my favorite things on the planet.

The 5k pot was loading the

1st audio stage too heavily & causing low volume & amplitude distortion. The squealing is likely caused by regenerative feedback in an I.F. stage, causing oscillation which manifests as a beat note or heterodyne as you tune across a signal's carrier frequency. The culprit is probably either a bad screen bypass capacitor in that stage, a screen resistor that's drifted to too high a value.

[coolbluelights]

Thanks! good to know, I'll watch out for that when working on future radios

[OldTimeRadioGuy]

Well its good that it dosen't... Lot of wooden radio's had a layer of asbestos under the chassis which is not a fun thing to get rid of lol. Just wanted to know before my 89 arrives...