GE P-9011 Speaker Issues

[YamahaFreak]

I got this nice little radio on that one auction site. Very interesting to me is the fact that it uses a field-coil speaker. Unfortunately, the permanent magnet around the front of the magnet structure has deteriorated, and there are now hundreds of filings living inside the gap, preventing the speaker from moving. I have tried many times to remove the filings, but they are stubborn and I don't want to harm the speaker assembly. Help!

Here are some photos:

http://i3.ebayimg.com/03/i/000/c1/d9/b878_3.JPG

http://img86.imageshack.us/img86/3310/1020799vq0.jpg (This is a fullsize photo; zoom to the center to see the speaker gap)

[glen65]

Don’t think there's much you're going to be able
to do with that except replace it. Measure the size
of the speaker from edge to edge. Also see if there
is an ohm rating printed somewhere on the frame or magnet
assembly.

[YamahaFreak]

Originally Posted by glen65

Don’t think there's much you're going to be able
to do with that except replace it. Measure the size
of the speaker from edge to edge. Also see if there
is an ohm rating printed somewhere on the frame or magnet
assembly.

Are you sure? Kinda disappointing because I paid $57 for a "properly functioning" radio. The speaker works, but it sounds similar to when you play a speaker with a rubbing coil at low volume.

[glen65]

Originally Posted by YamahaFreak

Are you sure?

Not 100% no,
I would have to have the radio here where I
could substitute the speaker with something else. However
if the speaker itself is deteriorated that would be the most
likely culprit especially giving the age of the unit.

[Celt]

If it's actually a field coil speaker, the circuit may need an inductor to replace the coil when replaced with a PM speaker. Might check the DCR of the speaker too. Speaker impedances on those old transistor radios were all over the place back then. I wonder if the existing speaker is actually an output transformer and driver built together? Many of the old transistor radios used OT's.

[YamahaFreak]

Originally Posted by Celt

If it's actually a field coil speaker, the circuit may need an inductor to replace the coil when replaced with a PM speaker. Might check the DCR of the speaker too. Speaker impedances on those old transistor radios were all over the place back then. I wonder if the existing speaker is actually an output transformer and driver built together? Many of the old transistor radios used OT's.

That's probably what it is, there are three leads to the speaker rather than the usual two. I'm almost certain that there's nothing else wrong with the speaker other than those teeny iron shavings inside. The radio has great reception and is nice and strong, only the speaker has issues.

[Don Lindsly]

It is a speaker and output transformer combined. As the loose transformer lamination moves, it modulates the speaker cone. GE also used that concept on some early paging receivers. The communication engineers took the idea from the consumer guys as a cost and weight measure.

Try passing the entire speaker assembly through a color TV degaussing coil or some other strong AC field while shaking it, to release the filings. You may not even need to remove it from the radio.

[YamahaFreak]

Originally Posted by Don Lindsly

It is a speaker and output transformer combined. As the loose transformer lamination moves, it modulates the speaker cone. GE also used that concept on some early paging receivers. The communication engineers took the idea from the consumer guys as a cost and weight measure.

Try passing the entire speaker assembly through a color TV degaussing coil or some other strong AC field while shaking it, to release the filings. You may not even need to remove it from the radio.

Do you think a bulk reel tape eraser would work?

[Celt]

I would think so.

[CUlater]

instead of shaking, perhaps compressed air might work to blow the filings out?

[YamahaFreak]

Originally Posted by CUlater

instead of shaking, perhaps compressed air might work to blow the filings out?

That's another idea I want to try, but I need to get some of the stuff first.

[Bone Yard]

Nice looking radio...How about just taking some Q-tips and getting some out a little at a time? Careful with the compressed air, you might get an eyeful of the filings....

[Don Lindsly]

You might also try a very strong magnet.

[YamahaFreak]

Originally Posted by Bone Yard

Nice looking radio...How about just taking some Q-tips and getting some out a little at a time? Careful with the compressed air, you might get an eyeful of the filings....

Q-Tips won't fit into the gaps. I'm going to try my bulk tape eraser and/or canned air with eye protection to see if I get results.