01-28-2018, 10:35 PM
I'm new here, and am enjoying this treasure of information. I have been restoring a 37-8, replacing caps, trying to undo some previous "fixes", etc., and am learning a lot. It actually works, but is weak, so I hope to correct the weak links step-by-step.
I am puzzled by the speaker. Can anyone explain what the speaker circuit is doing? The speaker itself is unusual, with a flex section both at the rim and one pinned at the center of the cone. I've never seen that before. There is a big coil on the back of the speaker, but the output transformer feeds two small wires underneath that big coil, into what I suspect is the actual speaker coil. The big coil on the back of the speaker looks like the traditional speaker magnet, but it is not driven by the OT, so I think it must be the inductor shown on the schematic in series with the speaker. But it isn't wired up consistent with the schematic, so I can't make sense of it. It has 1000 ohm impedance, while the OT has about 400 ohm.
What is that big coil on the back of the speaker do? This obviously is a Philco speaker, so it must have been widely used. There are three wires that feed the transformer, one from the +HV (350v) one from the plate of the 6F6G (~270 v). That makes sense. There is a third wire that goes to the big coil on the back of the speaker, and it is at about 70 v.
It is a very unusual speaker, I've never seen anything like it. Has anyone posted a description of this speaker and its driver? It seems to work, but I'd like to understand it.
Thanks!
Clif
I am puzzled by the speaker. Can anyone explain what the speaker circuit is doing? The speaker itself is unusual, with a flex section both at the rim and one pinned at the center of the cone. I've never seen that before. There is a big coil on the back of the speaker, but the output transformer feeds two small wires underneath that big coil, into what I suspect is the actual speaker coil. The big coil on the back of the speaker looks like the traditional speaker magnet, but it is not driven by the OT, so I think it must be the inductor shown on the schematic in series with the speaker. But it isn't wired up consistent with the schematic, so I can't make sense of it. It has 1000 ohm impedance, while the OT has about 400 ohm.
What is that big coil on the back of the speaker do? This obviously is a Philco speaker, so it must have been widely used. There are three wires that feed the transformer, one from the +HV (350v) one from the plate of the 6F6G (~270 v). That makes sense. There is a third wire that goes to the big coil on the back of the speaker, and it is at about 70 v.
It is a very unusual speaker, I've never seen anything like it. Has anyone posted a description of this speaker and its driver? It seems to work, but I'd like to understand it.
Thanks!
Clif
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