Good day everyone, this is my first time on a phorum, so I apologize in advance.
I have a 46-1201 radio with a magnet Less speaker, and I can not get rid of this loud hum that over comes the audio. I changed all cas that are accessible an the hum remain strong. Did any of you has had this issue before? I was think of taking some tubes out to see if one was drawing too much current... but all tube filament are in series. Thank you in advance. Marco.
Welcome to the Phorum!
I'm not the best guy for troubleshooting so I'll leave that to others with more skills but for folks to follow along here's the link to the schematic in our library:
https://philcoradio.com/library/download...6-1947.pdf [Link corrected...thanks]
Not sure what you mean when you say magnet less speaker. These originally had an electrodynamic speaker which uses a field coil to create the magnetic field for the speaker.
Thank you.
That is correct, the speaker has a 1200 ohms coil to create the electro magnetic field... Just did not know the lingo for it.
Since the voltage is about 100, that coil gets pretty warn. Nevertheless, I do not get where that hum could be coming from. I even doubled the two 25 uf and the one 40 uf to see if it will reduce the hum... But no cigar.
Yes it is an elctrodinamic coil magnet. I did not know the terminology for it. Nevertheless, I changed all capacitor I could find and doubled the 40 uf and the two 25 uf capacitors just to see if it will reduce the hum and no cigar.
Hi Marco,
Welcome to the Phorum. But first a note to Bob that his link points to a 46-1209. I checked the schematic for your 46-1201 and found two versions so I'm assuming yours is the one with the 50A5 and 35Y4. First off, determine if the hum is controlled by the volume control or is it constant no matter where the volume control is. Now the schematic I'm looking at has no coupling capacitor from the volume control to the grid of the first audio amp. There should be a .01mfd cap. Lots of hum if you don't put it in. It's very easy to install the power supply filter capacitor negative leads to chassis ground where, in this case, they should be connected to the B- bus (voice of experience). You will get a loud hum if connected to the chassis. Check to see if it hums in phono mode or radio mode. That should get you in the right direction .
Thanks Rod
I corrected the link in my post.