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Help wiring vintage record player speaker

MagicMan5

Jan 30, 2024
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Hi! I’ve been trying to fix a vintage record player, and I was able to get it working, but I’m having some trouble connecting it to the speaker. I think it has a built in AC amp, but when I power the top two pins with ac and the bottom two with the sound output, it doesn’t make any sound. Any ideas?
 

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Bluejets

Oct 5, 2014
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That particular type of speaker arrangement is commonly known as (in Aus at least) an electrostatic speaker.
It does not contain a permanent magnet as most common modern day speakers.
What is does have is a choke coil which is wired into the smoothing side of the line transformer to act both as an inductor and as the speaker magnet.
One then has the speaker coil which is wired into the valve amplifier output.
You will need to know which wiring is which as mains connected to the speaker coil will give you a very high volume 50/60 cycle (best described as VEROOMBA!!!!) followed by smoke and very bad smell.

A circuit diagram of the model and type of amplifier would show the correct wiring but some multimeter testing will be needed as well.
Perhaps one of the older gentlemen radio techs in here will be able to assist with a diagram if you can supply the make and model of the "radio/phonograph please"..... record player.

Note that all would be applicable until you decided to act first and ask later. As it stands you've probably blown the guts out of any remaining working part with your application of whatever form of AC you decided would be a good idea.
Sadly not..........
 

MagicMan5

Jan 30, 2024
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Thanks for your reply! I don’t think that using the ac power broke anything in the speaker. When it was applied, the speaker made a slight humming sound, similar to that of a guitar amplifier when it’s turned on. This was also repeatable after turning the speaker off and back on again, with no visible damage to it.

I still don’t quite understand what each of the two boxes on the speaker do. The ac power was applied to the smaller box in top. Do you mind explaining what both of the components do and what connections would go to each of them?
 

Harald Kapp

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Please supply make and model of the record player. With luck we find a schematic online and can help you much better.
 

MagicMan5

Jan 30, 2024
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The player is really old, and all the stickers and writing on it have faded or fallen off, and I have been unable to find the model. It is make by Gorman, and it is a record player-speaker combo that is inside a cabinet. The radio is beyond repair, and all the power cables and sound cables pass through the radio, so I don't think that the schematic would help that much, as I'm completely rewiring it.

Even knowing what the different components do would help. I'm not sure what either box does, so that's really what I'm trying to figure out.
 

AnalogKid

Jun 10, 2015
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Your image has the speaker magnet assembly (large steel rectangular shape lower left), the amplifier output transformer (transformer-looking thing upper left) and a connector (round thing upper right).

The yellow and yellow-stripe wires from the connector go directly to the magnet. Those are the wires from the power supply section.

Two of the wires from the connector (red and red/grey? go to the back of the transformer. Those are the wires from the audio amplifier output stage to the output transformer input winding.

Two wires (brown and green? brown and black?) go from the transformer output winding to the speaker voice coil.

ak
 

MagicMan5

Jan 30, 2024
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Your image has the speaker magnet assembly (large steel rectangular shape lower left), the amplifier output transformer (transformer-looking thing upper left) and a connector (round thing upper right).

The yellow and yellow-stripe wires from the connector go directly to the magnet. Those are the wires from the power supply section.

Two of the wires from the connector (red and red/grey? go to the back of the transformer. Those are the wires from the audio amplifier output stage to the output transformer input winding.

Two wires (brown and green? brown and black?) go from the transformer output winding to the speaker voice coil.

ak
Thanks! this helps al lot, but I have one more question, what kind of power do the yellow and yellow striped wires take to the magnet? would it be ac or dc, and what amount of voltage?
 

AnalogKid

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It is high voltage DC with AC ripple superimposed on top of it. The DC value depends on the AC mains voltage and the rectifier configuration. The AC ripple is what causes the background hum out of the speaker.

There are several rectifier/filter capacitor configurations. We can't get into your details without a schematic.

ak
 

MagicMan5

Jan 30, 2024
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It is high voltage DC with AC ripple superimposed on top of it. The DC value depends on the AC mains voltage and the rectifier configuration. The AC ripple is what causes the background hum out of the speaker.

There are several rectifier/filter capacitor configurations. We can't get into your details without a schematic.

ak
one of the stickers on the outside of the cabinet that is still intact has a voltage rating on it, but I'm not sure if that's for the outlet it should be plugged in or the speaker.

The humming I got came from when I connected the AC power to the pins you said were for the audio input, not the ones for power.

Are you saying that without the schematic it is pointless to continue as I won't know how much voltage is needed to power it?
 

Maglatron

Jul 12, 2023
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May be completely wrong but I think the transformer is ther to amplfy signals to a voltage that would move the speaker diaphram!
 
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crutschow

May 7, 2021
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So do you plan on hooking up the speaker electromagnet to the radio circuit or use an external DC source?
If you want to use an external DC source, you would just have to apply an increasing DC voltage with audio to the voice-coil until the audio output sounds normal.
The normal DC current through the coil is likely in the neighborhood of a couple hundred mA, so if you measure the coil resistance, you can calculate about what DC voltage you would need.
 

hevans1944

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Many years ago, I ran across a similar arrangement of a loudspeaker with a paper cone diaphragm attached to a voice-coil that was inserted over the pole piece whose magnetic field was created by an electromagnet, whose two pole pieces surround the voice-coil. The image the OP attached fits this description.

The loudspeaker in question IS NOT an electrostatic speaker. The attached transformer is an audio output transformer that performs the function of impedance matching the output resistance of the vacuum tube audio power amplifier (typically several thousand ohms) to the low impedance of the loudspeaker (typically a few tens of ohms). The electromagnet not only creates the magnetic field against which audio currents in the voice call react against to move the diaphragm, it also serves as an inductive filter for the B+ plate supply. This inductance is large, and there is superimposed on its current an AC ripple component. This AC ripple or "hum" (usually 120 Hz) should be barely audible in a quiet room, even at full audio amplification.

My experience with this technology came as a teenager who "rescued" and restored a discarded console broadcast and shortwave band radio receiver from the trash behind a radio and television repair shop in Denver, CO, sometime in the late 1950s. I used this radio to learn a lot more about electronics back then. I remember using the inductance of the loudspeaker electromagnet to create fat, hissing, DC arcs in air. Why? You may ask. Just for fun, after I accidentally discovered the phenomenon one day while disconnecting one of the two wires feeding current to the electromagnet. Of course, being young and somewhat foolish for a wannabe "sparky" I did this without first removing power to the circuit.

You don't really need a published schematic for these old vacuum tube electronics. Everyone used the same superheterodyne system invented by Edward Howard Armstrong, with only minor variations in how the superhet radio receiver was implemented. Here is a link for a more detailed description: https://www.microwaves101.com/encyclopedias/superheterodyne-receivers. Make your own schematic by reference to a vacuum tube description of your existing audio amplifier, using a multimeter to trace out the wiring and connection to other components such as resistors, capacitors, and (if the record player has a radio) intermediate frequency (IF) transformers. Lots of fun doing that, and you will learn a lot of practical things if that is your goal. If not, you will still end up with a schematic you can work from. It may not be "pretty print" but hand scrawled schematic diagrams are nevertheless still useful.

If you are truly restoring your record player to "like new" condition, I think that is a waste of time unless it is done as part of a "learning electronics" exercise. If all you need to do is get the record player functional again, while keeping its cabinet and speakers, you are in for a bit of work. Personally, I would keep the turntable and ditch the rest of it. Modern PM (Permanent Magnet) loudspeakers are inexpensive, and solid-state amplifiers are readily available in power ratings from a few watts on up to truly awesome power levels.

OTOH, this is a hobby forum... so build an unregulated, electrolytic capacitor filtered, power supply for the loudspeaker electromagnet (several hundred volts at maybe one hundred milliamperes should work). Then buy an audio output transformer similar to the one already mounted on your loudspeaker and wire it backwards to the existing transformer: the high impedance input winding of this new transformer is connected to the input terminals of the existing transformer, and the low impedance winding is connected to the low-impedance output of your audio amplifier. This effectively removes both transformers from consideration, with some loss of audio fidelity, but those old loudspeakers were pretty awful at audio reproduction anyway (ask our resident expert @Audioguru who knows far more than I ever will about it). Better yet, if you can gain access without destroying the loudspeaker, remove the existing transformer entirely and connect your audio amplifier output to the voice-coil terminals directly. Do this ONLY if you fail to find another suitable transformer as it is likely the existing transformer has very short but flexible leads connected directly to the voice-coil.

I no longer have the fine, almost antique, console radio with its huge loudspeaker. It disappeared after I graduated high school and joined the Air Force. Mom and Dad were in the process of getting a divorce while I was serving, so I suspect that Dad discarded my radio. No harm, no foul. I went on to bigger and better things.

I should caution you NOT to use your restored record player to play new vinyl records. The steel needle stylus used on those old players was designed to survive the harsh punishment dealt out by the 78 rpm shellac records that were prevalent before World War II. Vinyl records recorded in stereo need an elliptical diamond stylus and only a gram or so of pressure to avoid ripping off the tracks like a snowplow. And there is a protocol, used by those with Golden Ears, for handling vinyl record pressings. My ears are far from golden, if they ever were, so I do just fine listening to digital streaming audio from a compact disc or online via the Internet.
 
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