field coil speaker question - Printable Version
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field coil speaker question - murf - 12-17-2025
Hello guy's,
Have a 1938 GE floor model G-97 with the clock that I picked up today for free.
Would like to restore this radio, but the 12 inch field coil speaker has no cone. totally bare naked to the frame.
Question is, if I tape off the 2 leads to the speaker cone, can I safely plug in the speaker to the chassis and still power up the chassis?
Trying to find another field coil speaker for this or find a suitable method of replacing it if I can't find a good used one.
Any suggestions from the group?
murf
RE: field coil speaker question - Arran - 12-17-2025
Murf;
As long as the field coil, and the output transformer are good it should be fine to fire up the set, I assume you are going to hook up a test speaker to try it? The O.T transformer secondary doesn't have any real voltage across it, so as long as they are not shorted together I can't see a problem. If the spider and voice coil are still intact you could have a go at reconing the speaker, though I have noticed that console speakers don't seem to be that hard to come by. Someone was mentioning that many radio clubs end up with consoles donated to them, along with parts and other junk, so that may be another place to look.
Regards
Arran
RE: field coil speaker question - klondike98 - 12-17-2025
There are a list of speaker repair shops listed in our resources pages in the library. Scroll down to "Speaker Repair".
https://philcoradio.com/library/index.php/resources-services/resources-categorized/
RE: field coil speaker question - MrFixr55 - 12-18-2025
This is a rather interesting radio. Link to Schematic from Nostalgia Air below:
https://www.nostalgiaair.org/pdfs/General-Electric-Co/General-Electric-Co-G97.pdf
The set was designed and built by GE. As a result of an antitrust suit that separated RCA from GE and Westinghouse, and RCA's acquisition of Victor Talking Machine and their commencing manufacture or radios (Prior to 1930, GE and Westinghouse built radios and RCA marketed them), RCA built GE sets from about 1930 to about 1935. It has several unique features including Automatic Frequency control, 2 IF stages, separate detector and 1st AF tubes instead of a 6Q7 or equivalent, all octal based tubes, except the 42 (I am sure that the 6F6 octal equivalent was available), and a built in clock / timer to turn the set on. This would be a rather sensitive set. Single ended output instead of Push-Pull but should e a good performer, especially for AM. Not exactly a Scott Philharmonic, but a good performer. Consider adding a "Radio / Aux" switch and input.
Funny that the speaker is bad. There is a picture of the set on RadioMuseum, with the grille cloth and speaker cone destroyed.
First off, before even thinking about powering up this radio, you must replace all electrolytic capacitors and audio coupling capacitors. Standard practice in repairing these radios is to replace ALL capacitors. It is vitally important to replace the electrolytics because some electrolytic caps, especially "wet" electrolytic caps will short as they age, blowing the rectifier tube, power transformer, field coil, etc.
You have several options for dealing with the speaker. First off, for testing, disconnect the remnants of the voice coil and hook up any 8 ohm speaker to the voice coil connections. Leave the "Hum Bucking" coil in the circuit.
Permanent replacement is a little more interesting. The field coil resistance is 800Ohm as opposed to the 1000 -1300 Ohm speakers. Unlike many earlier Philco sets, all "B" power flows through this field coil. Your options are:
- Getting the speaker re-coned
- Substituting another vintage speaker with close specs
- Replacing with a modern Permanent Magnet (PM Spraker and replacing the field coil with an 800 Ohm 10Watt or 20Watt resistor or with a choke. If replacing with a resistor, consider "upping" the capacity of the capacitors C60 and C61 to about 30uF and 47uF to compensate for the lack of a choke. Be careful to not have the input cap (the one across the rectifier output to be much higher than 30 uF, as it will strain the rectifier tube and power supply. Per the RCA receiving Tube Manual, the max input cap value is 40uF. Since chokes are rated in Henrys (Henries?) and not in ohms, it is hard to select a filter choke with only info from the schematic. Maybe one of our experts with an EE background can chime in here.
RE: field coil speaker question - Brad Winder - 12-18-2025
Another option: if the field coil is ok, and you don't want to pay to have the speaker re-coned (or find a suitable replacement) you can keep the original speaker in circuit, placing it sideways in the cabinet, attached to one of the sides or the bottom of the speaker board if there is room. Then install the PM speaker onto the board and wire it in and all should work!