Model 70 field coil resistance - Printable Version

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Model 70 field coil resistance - Maynardb - 05-08-2020

Hi
Does anyone know what the field coil resistance is for a model 70/570 chassis with 1, 47 tube ?  My field coil opened, and am trying to find a replacement speaker 
Thx
Bruce

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RE: Model 70 field coil resistance - KCMike - 05-08-2020

Hello, 3100 ohms
Here is a link for some information.
https://philcoradio.com/library/index.php/shop-talk/model-notes/the-speaker-problem-in-early-philco-cathedrals-20-21-70-90/

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RE: Model 70 field coil resistance - Maynardb - 05-08-2020

Thx
That gives me what I need ?

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RE: Model 70 field coil resistance - morzh - 05-08-2020

???

It is 3100 ohms. This is what you asked, this is what Mike said.
The replacement is any K-type speaker, they all have the same Field coil and voice coil.
You need any Single ended transformer type, from 70 or 90.
The 20 will also work. But I don't think it should be used, though with the transformer changed it is the same speaker.
I just did exactly that, my 570 had a 20 speaker with bad xfmr, and I had a spare xfmr from a 70.

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