Replacing a Field Coil with a PM Speaker - Please Help - Printable Version
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+--- Thread: Replacing a Field Coil with a PM Speaker - Please Help (/showthread.php?tid=9304)
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RE: Replacing a Field Coil with a PM Speaker - Please Help - K7Sparky - 04-16-2014
Good point on getting 89 Ohms for a VC. There is also Ni Chrome
0.89 Ohm VC resistance on a tube amp has a bad smell also.
Can someone with a good 84B measure the VC resistance?
Ron probably knows without looking
RE: Replacing a Field Coil with a PM Speaker - Please Help - codefox1 - 04-16-2014
Once upon a time, eletrolytic capacitors were more expensive than chokes, and coil magnets were better than the "permanent" magnets of their time.
So in fxing up an ld set that doesn't care how how you got there, inexpensive larger value capacitors, resistors if needed, and permanent magnet speakers can be used.
RE: Replacing a Field Coil with a PM Speaker - Please Help - morzh - 04-16-2014
Sparky
why exactly are you going to fry anything? and where is that 11:1 ratio came fom?
Again, the speaker voice coil in 84 is 0.89 Ohm (zero point eight nine), not eighty nine ohm.
And so it is more or less in all old early Philcos: 90, 20, 70, 111, 95 and such.
The transformer they use in 2x71A or 2x45 pushpulls are more or less 100:1 ratio hich will turn 0.89 ohm into 8.9 kOhm impedance that ain't gonn burn anything.
So I m not sure what the post was about, but clearly no one uses 1:11 rAtio an 0.89 ohms there for 42 tube.
RE: Replacing a Field Coil with a PM Speaker - Please Help - vinzer - 04-16-2014
My 84b had hum to it was caused by a bad ground on the detector tube it was the rivet on the the tube socket that was used for the ground.
RE: Replacing a Field Coil with a PM Speaker - Please Help - Radioroslyn - 04-17-2014
Seems like I remember someone having a bad gnd at the rivet on the #42 socket too.
GL
Terry