help wiring in field coil speaker in place of a PM speaker

[nosaj]

I'm building a tweed deluxe clone and have a jensen field coil speaker that I would like to mergen into the build. But not quite sure how I'd do it. I've included the schematic the speaker came from and the schematic I'm using for the amp.

This is what I'm thinking
pin1 to pins 3 on the 6v6's
pin2 to pins 4 on the 6v6's
pin3 to rectifier
pin6 to 6v6 pin4
pins 4 5 NC
Thanks,
Jason

[g1]

pin6 not to 6V6 pin4, but to pin3 of other 6V6.
Post the whole of the other schematic.
The field coil probably replaces the first resistor coming off the rectifier.

[nosaj]

Here goes. I have more schematics of the organo but I think these will be what you need.
The speaker I'm using came from the organo.
Thanks,
Jason

[g1]

Ok, so they are running all the current through the choke. So I think you would want to put the choke in series between the rectifier and the 5K resistor. You will want to run the screens off the other side of the 5K, rather than full B+ like the organo does. You may also want to add individual screen resistors at each power tube.
So:
conP1 to one of 6V6 pin3
conP6 to other 6V6 pin3
conP2 to 5K resistor
conP3 to rectifier

If anyone thinks there is need for a further filter cap right at the rectifier, please speak up.

Please make sure the high voltage wires are insulated safely, especially if they are in any user accessible areas!

Edit: this is all under the assumption that the organo speaker has the OT mounted to it, and you will be using it as the OT.

[nosaj]

Here's what I got on the LCR meter DER EE measuring the field coil. The OT is mounted on the speaker also. Was thinking about just keeping the plug on the speaker,coil,Ot. It appears to be in good shape.
LP 3.791 henries
Cp 6.686 nf
Rp 33.44k
Dcr .3318k

Test with the multi .331k

So it's in the 300 ohm range I believe.

[g1]

Agree with keeping the cable/connector.
Looks like it's dropping around 70V across the field coil in the organo circuit, so that may be a consideration.

[Enzo]

There is already a cap right at the rectifier, C14A, so another probably not necessary.

[nosaj]

There is already a cap right at the rectifier, C14A, so another probably not necessary.

Basically the schematic for the organo was included because of the speaker plug connector wires. I was wanting help putting the field coil into a deluxe that i was building.
just to clarify.

Thanks,
jason

[g1]

There are several factors in play here that make this not such a simple prospect. Hopefully there are others here more into design/building who may have comments. Unfortunately, not many will have much experience building with F.C. speakers.
The amount of current through the field coil will affect the speaker in the same way magnet strength would. So you want to get somewhere around the same as what they had in the original amp. That's why I suggested running the OT and everything else through the field coil, like the organo did.
But, the field coil may not be able to handle much more current than that, so you are limited to the same kind of B+ at the power tubes (260V).
For this reason I would suggest not adding another cap right off the rectifier. A cap there will increase the B+, the result will be more power output, maybe too much for the field coil to supply. Depending on your PT, if you find the voltages end up too low, then you could add a filter cap right at the rectifier.
So for now, I'd suggest you put the field coil in series between the rectifier and the first filter, as described in post #4, leaving the first filter connected to the 5K resistor.

[nosaj]

The PT is off the organo, will be using dropping resistors to drop one of the 6.3 taps to 5.0.

Jason

[g1]

If you are going with the organo PT, then you don't have to worry about exceeding the capability of the field coil or the OT.
That is assuming you don't get more voltage with the different rectifier type.
You might want to go with the 100R after the rectifier into 40uf, like the organo. Then the field coil, then the rest of the circuit as in 5E3.

[Tom Phillips]

Jason,
Have you considered building a dedicated variable power supply into your amp to energize the field coil? That would give you a Flextone type speaker set up. An interesting option I'd think at a fraction of the cost of a Flextone speaker. The amp circuitry would then stand on its own and could be optimized without worrying about it powering the field coil.
Tom

[Diablo]

I agree with Tom's post above.
Measure the resistance of the field coil in your speaker and post it here. If you want to build a stand alone or adjustable power supply for the speaker, we'll be able to make suggestions. It will give you more flexibility with the amp design, if you don't have to power the field coil from the B+.

[nosaj]

LP 3.791 henries
Cp 6.686 nf
Rp 33.44k
Dcr .3318k

Test with the multi .331k

So it's in the 300 ohm range I believe.
I like the idea of a variable design if anyone will help me I'll build it an post results

Thanks,
Jason

[nosaj]

Anyone have an ideas i can implement variable or fixed.

thanks,
Jason