[vecher]

Ok On to next problem.. One side of my antenna coil was open.. The Sec of it..

See picture

[Image: https://farm5.staticflickr.com/4460/2639...9061_b.jpg]

The good news is I see where its broken.. NOW how do I reattach it.. Do I try to solder the 2 ends together? I have NO clue how to fix this..

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[Arran]

Skip;
  Often you can simply unwind a little bit of the wire from the coil, such as 1/2 a turn,and then reattach it to the terminal, on an antenna coil it should not make too much difference. If it broke because the wire is corroded, like in a Philco 60 for example, you may be better off rewinding it since it's a small winding anyhow. 
Regards
Arran

[vecher]

Thanks I will give it a try

PS how do you get the insulation off of the wire so you can solder? Do you just scrape it?

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[vecher]

OK, New Problem.. Speaker time.. Seems like the field coil is open..

[Image: https://farm5.staticflickr.com/4529/3764...b71a_b.jpg]



On speaker it say MODEL 237 650 Ohms Is 650 Ohms the field Coli? If so can it be substituted with a resistor.. What Wattage? The other coils seems to be OK measuring about 742 Ohms..

[Image: https://farm5.staticflickr.com/4536/3764...8423_b.jpg]



The other side of speaker look good..

[Image: https://farm5.staticflickr.com/4580/3764...7c0d_b.jpg]

I almost have this put together minus the antenna coil Its coming.. Sure hate to scrap this due to a bad speaker>>>


Any help??

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[vinzer]

You might be able to rewind it if not it could be replaced with a pm speaker and a 650 ohm resistor in place of coil.

[Phlogiston]

Those coils are open more often than Philcos . In the old TRFs it is often the 2nd one. I have always just rewound them. It is not hard. Count the turns.

[Phlogiston]

You can put a resistor in place of the field coil, but your speaker still won't work And you get a hot resistor to deal with and no filter choke. Best to replace it.

Where I said that rewinding the rf coil is easy, rewinding a field coil is not - unless you have a coil winder, then it is easy too. It can be done by hand, but keeping the coil cheeks from bowing outward is the real issue.

[vecher]

How do you even get it apart??

I see no way to get at winding

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[vecher]

Ok, Found a resistor of 650 Ohms at 50 watt.. Have a replacement speaker of 3.2 ohms..

looks like on schematic they are using the transformer for the B+ to the 47 tubes thru the center tap..

So question is what transformer do I use to match the 47 outputs to 3.2 ohms and still get B+ to the tubes??

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[Arran]

So what is wrong with the speaker again? I think that the 650 Ohms denotes the field coil, though it may be inductance rather then DC resistance, if it reads 742 Ohms it's probably fine. I can't think of anything else that would be giving you a 742 Ohm reading, the output transformer primary is usually lower then that, the secondary will be lower, as will the voice coil, and the hum bucker winding. The hum bucker is in series with the secondary of the output transformer, but in opposite phase. The field coil looks like it's connected to the two fat pins on the speaker plug, the output transformer secondary is connected across the two small pins, with the center tap connected to one of the fat pins. I think that the speaker was probably manufactured by Rola, though it could be a Lansing speaker.
Regards
Arran

[vecher]

OK, The field coil is open It supposed to be 650 Ohms .. Stampeded on speaker.. The 767 ohms is the primary of the output Transformer.. The secondary of output transformer measures .2 ohms..

So since I cannot get or rewind the Field coil I am replacing it with a 650 Ohm 50 Watt resistor..But I also have to change speaker.. I found a Speaker from a Motorola radio that measures 3.2 Ohms that fits perfect in cabinet. So I need a output Transformer to match the Dual 47 Tubes to the 3.2 ohm Speaker..


The 767 Ohms doesn't seem right but that's what I measure,.. They get the B+ to the 47's by using the Center tap of the primary of the output Transformer..

PS Schematic of course doesn't give any values..

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[Phlogiston]

The bell that covers the field coil will come off. Sometimes it is difficult. On many of these speakers the spider is on top of the cone with a screw going to the pole piece (round metal piece inside of voice coil). It does not appear that your speaker has this kid of spider - instead being below the cone. But it does look like the pole piece is pressed into the bell. This is not unusual. Either removing 2-4 nuts and bolts or grinding a couple of rivets should free the assembly revealing the field coil windings.

Also, at ~700 ohms, this would be a fairly small FC with less turns of magnet wire than most others.

[vinzer]

Looks like the spider is on the top if you blow up the picture up it looks like it is under the cover on the front of the speaker to me.

[vecher]

ALL< UPDATE: I was able to repair the Field Coil.. I found the 2 ends and was able to solder to them..

So now the field coil is repaired.. Reading 648 Ohms... Now on to the installation of the replacement antenna coil.. and finish up the wiring...

Thanks all to suggestions on how to fix that coil They helped a lot..

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[klondike98]