Regarding the amplifier, are there any considerations to replacing a field coil speaker with a permanent magnet speaker? Do you need to install a choke in the circuit, or can you just install a modern day speaker as a direct replacement?
Thank You
Field Coil
Moderators: pompeiisneaks, Colossal
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Andy Le Blanc
- Posts: 2582
- Joined: Sat Dec 22, 2007 1:16 am
- Location: central Maine
Re: Field Coil
The field coil is part of the power supply.
I don't see very many, and I'm not a restoration shop, but I believe you
have to find the right choke or resistance value to maintain the right B+
and G2 voltages in the circuit, you cant just use any old speaker until then.
I'm very sure there are juke box ,organ and radio restoration specialists, but your
gonna have to search.
I have seen some replacement Idea's floating around the web.
I don't see very many, and I'm not a restoration shop, but I believe you
have to find the right choke or resistance value to maintain the right B+
and G2 voltages in the circuit, you cant just use any old speaker until then.
I'm very sure there are juke box ,organ and radio restoration specialists, but your
gonna have to search.
I have seen some replacement Idea's floating around the web.
lazymaryamps
-
Andy Le Blanc
- Posts: 2582
- Joined: Sat Dec 22, 2007 1:16 am
- Location: central Maine
Re: Field Coil
After some digging......
It looks like it'll depend on how the field coil is energized.
Sometimes it serves the dual purpose as the choke in the PS.
Sometimes its as a simple PS bleeder.
If its a low resistance its also the choke, and if it has a high resistance its a bleeder.
That 88 on my bench has a 10k field coil, a bleeder, two 5y3 are used, one on
each leg of the HT secondary of the PT to supply enough current to keep the
field coil energized.
Some old amps were half way, the OPT was mounted on the spk frame,
and might just look like a field coil.
It looks like it'll depend on how the field coil is energized.
Sometimes it serves the dual purpose as the choke in the PS.
Sometimes its as a simple PS bleeder.
If its a low resistance its also the choke, and if it has a high resistance its a bleeder.
That 88 on my bench has a 10k field coil, a bleeder, two 5y3 are used, one on
each leg of the HT secondary of the PT to supply enough current to keep the
field coil energized.
Some old amps were half way, the OPT was mounted on the spk frame,
and might just look like a field coil.
lazymaryamps