[Les Dickson]

I have a Viking chassis 652-E that I just opened up and I’ve never seen an item like this patched into the speaker connection. I assume someone has spliced in a replacement part – a choke?
If in inject an audio signal into the plug I get a nice tone on the speaker so I guess whatever it is is working?

Attachments:

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   speaker-part1.jpg
   

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   speaker-part.jpg
   

[Rick D]

Hello Les
If you look at the schematic for that set I am sure it had a electromagnet speaker and some one replaced it with a PM speaker ,it looks like they took off the coil
from the electromagnet speaker and used it instead of resistor ,when ever you replace a electromagnet you should use a resistor in place of the coil ,you can do it this
way ,just use the coil instead of a resistor , but some coils are a lot harder to separate from the original speaker than yours,have a great day all the best Rick

[Dan Walker]

Rick, I was going to say the same thing. In fact I have done that with a speaker that was very bad, but the coil was still good so
I attached the coil in the chassis and used a permanent magnet speaker.
A word of caution Les,, The field coil should be the same ohms as the schematic calls for.
Dan in Calgary

[Jean Marcotte]

DC resistance will remain the same if you use the original field coil alone but the inductance will be much lower without the iron in it. I dismantled a 12in speaker to measure the difference. With the field coil in place I get 7.5H and with the field coil alone I get only 1.85H. I guess that it can affect the quality of filtering.
Jean in Montreal

[Gary Albach]

Hi Les – instead of replacing the field coil from an electrodynamic speaker with a resistor, I have had good results using a solid-state field coil replacement. Here is a link to the circuit and original construction article published by the Antique Wireless Association:
http://www.antiquewireless.org/uploads/1/6/1/2/16129770/37-a_solid-state_filter_choke_or_field_coil_replacement.pdf
As stated in the article, the circuit provides 60 Hz ripple suppression in excess of 60 dB, far in excess of the original field coil acting as a choke.
Gary

[Les Dickson]

Thanks for the feedback. As it turns out the coil from the original speaker that had been left in was bad so I’ve got it running by using a resistor. However, I think I may try the solid state solution suggested by Gary Albach.

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