Philco 38-4 chassis ith no speaker - Printable Version
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+--- Thread: Philco 38-4 chassis ith no speaker (/showthread.php?tid=3274)
Philco 38-4 chassis ith no speaker - Dennis tiernan - 05-16-2011
Hi all,
I just joined the site an am looking forward to learning a lot about these old Philcos. I had a 38-4 in my cellar when I was 10 years old. It worked great. Just picked up a chassis that needs recapping and a speaker. I changed the power cord and all the tubes light up and I measured the two terminals on the plug for the speaker that are closer together, ( they measure approx. 350V) Can someone tell me how to convert this to a PM speaker? Also, does anyone know the correct illumination lamp that plus into the back of the dial? Alos where to get ot would be good to know too. ((is teh elctromagnet for the speaker also called the Field Coil?) Thanks for your help with these questions. I also have a Philco portable radio that plays great but has a little hum to it. I', using the AC line because I don't think they make the batteris for it anymore.
Dennis
Re: Philco 38-4 chassis ith no speaker - BILL - 05-16-2011
You need to find out what the resistance was of the original the original field coil was and use a resistor or a choke between the B+ ,then you need to find out if you still have audio out put transformer and if it's push pull or not, quite offen the out put transformer was mounted on the speaker.
Need obsolet batterys? build your own, I have several vintage portables , I've got another Portable Philco coming in now, one I have, Philco, has 1 1/2 volt "A" and 90volt "B", I use two "D's" in paralle. and 10 9 volts in series, I also have a Zenith Transoceanic Clipper 7G605[1942] I use 8 "D's" 6 in series two parallel= 9volts and then 10 9volts these radios will play over 50 hours on Dollar Store batterys!
Re: Philco 38-4 chassis ith no speaker - Arran - 05-18-2011
Dennis tiernan Wrote:Hi all,
I just joined the site an am looking forward to learning a lot about these old Philcos. I had a 38-4 in my cellar when I was 10 years old. It worked great. Just picked up a chassis that needs recapping and a speaker. I changed the power cord and all the tubes light up and I measured the two terminals on the plug for the speaker that are closer together, ( they measure approx. 350V) Can someone tell me how to convert this to a PM speaker? Also, does anyone know the correct illumination lamp that plus into the back of the dial? Alos where to get ot would be good to know too. ((is teh elctromagnet for the speaker also called the Field Coil?) Thanks for your help with these questions. I also have a Philco portable radio that plays great but has a little hum to it. I', using the AC line because I don't think they make the batteris for it anymore.
Dennis
A filter choke is the best substitute for a field coil on a speaker, unless it's a smaller set then a wire wound resistor is good enough, there is a way to make a solid sate substitute for a filter choke if you can't find an iron one.
With regards to the portable, if it hums excessively during AC operation, assuming it is a three way portable with a built in AC power supply, then very likely the filter capacitors need to be replaced.
Regards
Arran