Posts: 4
Threads: 2
Joined: Oct 2014
City: United States
Hello,
I'm measuring 470 ohms impedance across the unconnected voice coil. DC resistance measures 430 ohms. I'm sending the speaker out to be re- coned. Doubt if the speaker shop has specs on this.
The audio is very distorted at this point. I'm not above blaming the speaker- I can't find a reference to this in the factory service manual.
Any help appreciated.
Thanks
Cornell
Posts: 16,510
Threads: 572
Joined: Oct 2011
City: Jackson
State, Province, Country: NJ
This is totally wrong resistance, if anything its should be on the order of 1 Ohm to few Ohms.
Are you sure you are measuring what you think you are measuring?
If it were a needle drive speaker.....maybe, but this is a regular electrodynamic job with an output transformer.
Posts: 1,703
Threads: 55
Joined: Sep 2005
City: Evanston, IL
You're probably measuring the field coil.
Voice coil will be 1-2 ohms D.C. resistance, not A.C. impedance.
Chuck
Posts: 13,776
Threads: 580
Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
The 37-9 uses an H-30 speaker.
Field coil DC resistance should be 480 ohms; voice coil impedance 1.25 ohms.
You can find complete specifications of this and other 1929-1938 Philco speakers here:
http://www.philcoradio.com/phorum/showth...hp?tid=215
When you go to that link, look for the link to the file
speakers.zip. This is an Excel 97-2003 file (*.xls format) which can also be opened by newer versions of Excel as well as by OpenOffice.
--
Ron Ramirez
Ferdinand IN
Posts: 4
Threads: 2
Joined: Oct 2014
City: United States
Thanks everyone for your replies. I'm measuring the Red and White wires that go under the frame, and are attached to a coil that is attached to the cone- sure looks like a voice coil to me. The red lead is connected to the secondary of the output transformer, and the white lead goes to a very low resistance coil between the field coil and the frame. The other lead of this coil goes to the other lead of the output transformer secondary.
Ron, I'll check the link you referred to.
Posts: 4
Threads: 2
Joined: Oct 2014
City: United States
Here are the measurements just taken, and compared to the speakers.zip information:
Field coil: spec 480 ohms; measured 469 ohms.
Transformer primary: spec 660 ohms, measured 656 ohms.
Red and White voice coil spec 1.25 ohms; measured 430 ohms (DC) - with one lead disconnected from transformer
What is the flat- wound low resistance coil under the field coil called? It's in series with the voice coil and the secondary of the output transformer.
Posts: 16,510
Threads: 572
Joined: Oct 2011
City: Jackson
State, Province, Country: NJ
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
