Hello, should the resistance of the field coil change when I touch the outside paper? I would think not. What would be the recommended fix.

Thanks, Len

:Hello, should the resistance of the field coil change when I touch the outside paper? I would think not. What would be the recommended fix.

No, something's not right, shouldn't be any change. Could have wires that are barely holding on. What is the ohm measurement when you touch the field coil vs. when you don't? What is the spec resistance of the coil (if you have that info.)

::Hello, should the resistance of the field coil change when I touch the outside paper? I would think not. What would be the recommended fix.
:
:No, something's not right, shouldn't be any change. Could have wires that are barely holding on. What is the ohm measurement when you touch the field coil vs. when you don't? What is the spec resistance of the coil (if you have that info.)
:
:
Brian, my first measurement of the coil was 1550 ohms, the schem shows a value of 650 ohm, after squeezing the coil the resistance changed to 650 ohms and holding, further squeezing of the coil makes the resistance vari by 15-20 ohms. I believe surgery is required.

If this coil was totally open what effect would it have on the voice coil and chassis.

Thanks, Len

:Hello, should the resistance of the field coil change when I touch the outside paper? I would think not. What would be the recommended fix.
:
:Thanks, Len
:

This is not normal and indicates that you have a corroded section of wire in the field coil. Since it is sensitive to mechanical pressure on the cover paper, it's possible that the problem is in an outer winding layer. You could try carefully removing the paper cover, then examine the visible windings to see if there are discolorations or burnt areas. Damaged windings could be stabilized with transformer dope; but this is a long shot. The "course of least resistance" would be to locate a good replacement speaker on eBay or some other radio-trading venue.

Taking CV's tip a little further and with some luck----If you unwrap the outer paper covering of the field coil to expose the windings...I put a straight pin on one probe of a ohmmeter then connect the other probe to one of the ends of the field coil connections to the circuit. Carefully stick the pin into the exposed wires (to get thru the enamel coating, or lightly scrape off the top coating) and look for continuity somewhere that gives you close to your full listed ohms for the coil. If you luck out, you can bring out that point to your field connection and be in good shape. Make sure the set is unplugged and the caps are dis-charged first.
I also know a good local speaker re-cone guy that has someone who re-winds field coils for him.

::Hello, should the resistance of the field coil change when I touch the outside paper? I would think not. What would be the recommended fix.
::
::Thanks, Len
::
:
:This is not normal and indicates that you have a corroded section of wire in the field coil. Since it is sensitive to mechanical pressure on the cover paper, it's possible that the problem is in an outer winding layer. You could try carefully removing the paper cover, then examine the visible windings to see if there are discolorations or burnt areas. Damaged windings could be stabilized with transformer dope; but this is a long shot. The "course of least resistance" would be to locate a good replacement speaker on eBay or some other radio-trading venue.
:
I managed to remove the jacket on the field coil and found a hot spot on the coil. I then unwound enough wire so as the resistance stabilised at 596 ohms. The schem calls for 650 ohms, will this speaker still function properly or should I install a resistor to bring it up to 650 ohms.

Thanks, Len

:I managed to remove the jacket on the field coil and found a hot spot on the coil. I then unwound enough wire so as the resistance stabilised at 596 ohms. The schem calls for 650 ohms, will this speaker still function properly or should I install a resistor to bring it up to 650 ohms.
:
:Thanks, Len
:

It will probably work OK as is. The new resistance is only 8% low.

::I managed to remove the jacket on the field coil and found a hot spot on the coil. I then unwound enough wire so as the resistance stabilised at 596 ohms. The schem calls for 650 ohms, will this speaker still function properly or should I install a resistor to bring it up to 650 ohms.
::
::Thanks, Len
::
:
:It will probably work OK as is. The new resistance is only 8% low.
:
I will give it a try.

What type of tape can I use to wrap around the coil to hold it all together, it was the original tape that corroded the wire and caused the short.

Thanks for the help.

:What type of tape can I use to wrap around the coil to hold it all together, it was the original tape that corroded the wire and caused the short.

You might want to make a paper sleeve that goes around the coil. Overlap and tape the ends together. That way the tape adhesive doesn't contact the wire. Then you can throw an outer layer of whatever decorative tape you want (I've used black duct tape for this purpose) over this paper layer for additional protection if you want. This will prevent the paper from falling off if the taped joint gets warm enough to cause the tape adhesive to lose its grip.