The Fine Things are Always Hand Made
Hi, E H Scott radio enthusiast members
My name is Kirk Spalinger and I recently joined as a member, probably like many of you I joined after being allured by a Scott radio. I am more of an audio enthusiast but I like old technology and learning new things. I recently purchased at auction a Phantom AM deluxe 20 tube receiver and 6L6 matching amplifier. I have a couple of issues I need to resolve before I test the radio and wanted to get your feedback. I have spent a little time viewing older threads speaking to speaker combos for the various model Scott radios and have downloaded all the related schematics and information on my radio.
My first issue is mating a correct speaker to my radio or modify a like speaker to work or find a member that would like to work a trade. The Magnavox speaker I posted was purchased separate from the radio but I knew it was used in I believe a couple of other models of Scott radios. The speaker is a coaxial with a strap mounted tweeter, the field coil is 500 ohms and the voice coil is 8 ohms. The field coil is marked 500 ohms I measured 501, I was able to measure the resistance of what I believe is the output transformer between two three points at 94 ohms and 197 ohms respectfully.
The speaker obviously does not have the correct speaker plug for the Phantom, there are five leads coming from the seven pin male Amphenol. Pins 1 and 7 have a jumper between them and not used, pins 2 and 6 are to the field coil and I believe pins 3, 4 and 5 are to the output transformer? My hope was to temporarily makes some leads from speaker to amp speaker socket to test the radio. I don’t want to damage the set or the speaker so I am very leery.
I believe this speaker was used in the 800B and the Laureate and is somewhat rare in that it is a coaxial, my hope is to trade for a 15” speaker for my radio.
I will post my second issue in a separate post.
Be sure you have the 14 tube Deluxe receiver, the receiver tube count of 14 includes the magic eye and a VR-150 voltage regulator. I ask because your dial appears to lack the vernier dial window at the top middle of the dial. I do see the additional control - noise limiter control below the tuning dial. The Phantom Deluxe lacked the vernier dial only briefly initial production late 1939. I can see you do have the Phantom Deluxe 6L6 amp.
Study the speaker information for both the Phantom Deluxe and also the Philharmonic (essentially the same speaker(s)) using 6L6 output tubes. Not sure what to say about your coax speaker, but do proceed carefully.
The STANDARD speaker for your Phantom Deluxe has 1) a 38 ohm voice coil and 2) the 925 ohm field coil tapped at 525 ohms with 3) output transformer mounted on the speaker frame. Have seen both 12 inch and 15 inch examples. But no tweeter.
The 1940-41 OPTIONAL multi unit high fidelity system featured an outboard crossover containing the 1) output transformer, and 2) sockets into which the 8 ohm woofer and one or two 16 ohm tweeters each plugged into. The woofer had a small 5 pin plug, no output transformer and each tweeter had a 2 pin plug. the woofer had the same tapped field coil as the standard speaker. Tech data is in Riders Vol 14 , Scott section, page 15. The crossover had a small cable fitting a small socket on the receiver which your receiver would lack. (I have a late 1939 Phantom Deluxe which lacks the vernier dial and is not equipped to control the crossover.) Parts for the optional speaker system do show up from time to time.
You will need to deal with the your field coil being only 500 ohms, vs 925 with a tap.
And, whether your output transformer is correct to match for the push-pull 6L6's for your voice coil.
Scott used a 2 mfd cap in series with tweeter voice coil to limit the tweeter to high frequency audio.
I think I will wait and get the correct speaker for the set, I would not be happy unless the set is right. I do not have experience with field coil speakers and do not want to damage either the amp or speaker.
That pins 1 and 7 have a jumper, likely carried 115 house voltage to the power switch, acting as an interlock to prevent the original radio from powering up without the speaker (to avoid risk of damage). I doubt your coax speaker was from a Scott 800-B - documentation says a Stephens or Jensen speaker. I have never seen the Stephens, I have seen several of the dark teal painted 15 inch Jensen coax.
Scott speakers from 1935 to 1941 were special design Magnavox speakers in silver paint. The post war 800-B coax speaker and the pre-war Scott Laureate coax speaker look similar BUT are not the same and are not interchangeable. Your 8 ohm voice coil would not be used in combination with an output transformer mounted on a late 1930's Scott Magnavox speaker - such speakers have a 38 ohm voice coil. The only 8 ohm 15 or 12 inch speaker would be for the 1940-41 high fidelity speaker system, but the output transformer is not on the speaker, but is on the outboard crossover. No late 1930's Scott (Magnavox) speaker had a simple 500 ohm field coil from my experience.
A 10 watt 400 ohms or so power resistor in series with your 500 ohm field coil would approximate the 925 ohm tapped field coil of the correct speaker to provide satisfactory B+ voltages. Again, study the Scott Phantom Deluxe diagram with respect to speaker and the amp. Copy the diagram and trace the Phantom speaker wiring and note the reduced voltage at the field coil tap feeds a lower B+ voltage to certain circuits and even lower B+ from the low end of the field coil. Suggest you color code the circuit with colored pencils - red for highest 350 volt B+ to the field coil, orange for the lower voltage at the tap 300 volts, and yellow at the even lower B+.
From your readings above, your output transformer is center tapped. Again, study how the Scott diagram has the output transformer wired. Of the 3 wires, the largest resistance identifies the two ends of the primary. The other wire should be the center tap, but verify that the center tap to each of the other two wires should be close but not exactly equal resistance.
For comparison, look at this pre-war Scott 15 inch coax on eBay:
Dave you are correct I went back to the source I acquired the speaker from, I knew it was pulled from a 6L6 amp but was told it was pulled from a Magnavox radio. Thanks for the information, I am on the lookout, I will try to be patient and wait for the right speaker with the correct amphenol.
Your Phantom Deluxe may have had a 12 or a 15 inch speaker with curved cone, may have depended on the original cabinet.
Because you confirmed your speaker came from a Magnavox radio using 6L6 output tubes, then you should have a sufficiently correct output transformer to match the Scott's output tubes to the 8 ohm voice coil of your 15 inch speaker. You should be able to use a power resistor to substitute for the other half of the field coil as I mentioned above. That would give you a working speaker for now meeting the B+ requirements and you can proceed with restoration of your Scott Phantom Deluxe and power up the radio for testing and playing until you source a correct Scott speaker.
Maybe also try the tweeter across the speaker voice coil but in series with a 2 MFD cap - similar to the Scott diagram for the Philharmonic's optional tweeters.
You have the challenge of sourcing a suitable 7 pin speaker plug to fit the amp socket. Note the 2 fat pins are not next to each other but opposite, which precludes using a base from a 7 pin tube unless you are able to modify the pin arrangement somehow. I would discourage you changing the amp speaker socket.
Curious what you will use for a cabinet (or speaker enclosure) for your Phantom Deluxe?
Again, great information, that just made my day!
First thing I would like to recap the set, I am working on what I need to do that. As far as the speaker it sounds like the hard part will be to find a connector. Dave that was one of the first things I noticed on the amp was the speaker socket was different than the receiver socket, I guess that makes it idiot proof. I will still work on getting the correct speaker but will probably need to come back to you regarding the field coil. As far as the cabinet, I did not want to get too far down the rabbit hole but I think that I already have. Yes I will definitely want a cabinet but I wanted to get the radio working before I got to far. That being said, if one of the members here has a cabinet for sale I would love to hear from them.