Model 20 speaker rebuild - Printable Version

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+--- Thread: Model 20 speaker rebuild (/showthread.php?tid=3417)

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Model 20 speaker rebuild - mjmont1 - 06-27-2011

Hello all,

I've been looking all over the place and I can't seem to find any data on the inductance value for the field coil in the speaker. I have an RLC bridge but according to my ohm meter, the winding is no longer continuous. The speaker itself is beyond repair. I want to replace it but I need the inductance value for an equivalent value choke.

Thanks to all who can help!
Mike

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Re: Model 20 speaker rebuild - Radioroslyn - 06-28-2011

Hi and welcome to the Phourm!
Don't know if I've ever seen the inductance measurement listed for a field coil. It should be but the norm is resistance. The resistance is important as it will determine the voltage drop a cross the coil. This can be critical if the field coil is in the negative leg of the power supply because it will determine the amount of bias voltage the power supply will develop. The model 20 it's in the positive leg.
Noting the size of the filters I'd take a guess and say between 5 and 10 Henries. Don't think it is really critical.
Terry

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Re: Model 20 speaker rebuild - tdbisel - 07-06-2011

Hi,

Using a BK Precision Model 875A LCR meter - it reads 3540 ohms resistance and 37.4 henrys inductance when connected at the plug for a Philco Model 20 speaker at the field coil connections. It has read pretty close on choke coils that I have measured that had a published value.


Tom

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