A Beginner's Journey: The Philco 40-190

[TA Forbes]

I would advertise here for an output transformer. Also check out Playthings of the Past and John Kendall's site for your part.

[DeckApe]

It lives.



I'll work on the alignment later, after I inspect my signal generator; so far it would seem that the best thing to do would be to move the dial pointer about a half-inch on the string as that will bring the world into dial scale alignment. I may not even screw with it after that.

THANK YOU to all of you who walked me through my first radio!

[DeckApe]

Upon listening closely to my radio, it has a very low-volume but consistent 60 Hz (B-flat) hum coming out of the speaker, even with the volume all the way down. Is this normal, or indicative of needing the voice coil wires reversed?

[jerryhawthorne]

Deckape, is the hum level changed at all by increasing the volume? If not, perhaps a little cathode to filament leak on one of the tubes in the audio output. The voice coil, a possibility if the wires were switched. If it has a hum bucking coil tied to the voice coil and things are turned around, it won't cut some of the induced hum from the field coil they have to be in opposition. Just my lame ideas. Congrats on getting this far!
Jerry

[codefox1]

Agree, if the hum bucker winding is wired backwards you will get more not less hum. Can't hurt to reverse it and have a listen. All those old sets had some hum regardless. You can beef up the filter capacitors a little bit (say 10%) and as said, make sure your output tubes are not gassy, but there will still be a little hum or more likely interference from modern devices that simply didn't exist way back when.

[TA Forbes]

Rectifiers will also cause a set to hum when they get weak....

[DeckApe]

I all but let the smoke out of the original rectifier by crossing a couple of wires in the rebuild--thankfully, I had a spare hanging about (And a Raytheon-branded tube, at that). The spare tested out stronger even to start with. I'll try swapping the wires out when I'm feeling adventurous (and have a few spare moments to devote to the pursuit). I guess I'm asking a bit of a useless question in wanting quantification when I'm the only one available to listen to the speaker.

All else fails, I'll swap the wires back.