Fine cracks in bobbins - problem, or not?

Musha Ring

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A friend of mine had me install an older set of Dimarzio PAFs in his SG the other day and the bridge pup had a fine crack that ran through four or so of the hex screws down the length of the bobbin.

The pickup sounded great and performed well, but he asked me if that would be a problem and I wasn't quite sure what to tell him. Although I've seen pics before of similar cracks, I'd never seen one in person.

Is it one of those things that isn't a big deal as long as the pickup isn't falling apart and the pole screws turn fine/stay seated? Can it become a problem down the road?
 

cooljuk

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Old DiMarzio plastic is pretty awful. It will shrink and crumble, eventually. If the bobbins get warm enough, I've seen them shrink to about half the size the started as.
 

Musha Ring

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Old DiMarzio plastic is pretty awful. It will shrink and crumble, eventually. If the bobbins get warm enough, I've seen them shrink to about half the size the started as.
Interesting. Why would one be heating a pickup that much?

I have a set that's 42 years old and in fantastic shape. I can't imagine them cacking out any time soon. Would be a shame, because they sound incredible.
 
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efstop

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Plastic is not forever. It ages out, sometimes to a point that a moderate blow could shatter it. I have an acrylic chair made from 1/4" sheet that sits outside. I expect it to crack eventually. I've had it 6-7 years.
 

CheopisIV

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Stage lights? Window display? Left in trunk? I'm with you. I can't see how even these scenarios could bake plastic.
Heat cycling in cars is a major one, extreme climates and moving between them if you travel. Add to that the off-gassing depending on the type of plastic used. Right up there with heat though would be UV exposure. Direct sunlight will kill any plastic given enough time and it's shorter than you might think, especially when there's tensions and pressures on that plastic.
 

Musha Ring

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Plastic is not forever. It ages out, sometimes to a point that a moderate blow could shatter it. I have an acrylic chair made from 1/4" sheet that sits outside. I expect it to crack eventually. I've had it 6-7 years.
Would a rewind be possible on a pup that needs a new bobbin?
 

CheopisIV

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Would a rewind be possible on a pup that needs a new bobbin?
Maybe. If it's been potted like most Dimarzios, it's not possible. Honestly, those are a dime a dozen so not worth the time even if it were unpotted.

On other pickups, it'll depend how far gone the bobbins are. I've had pickups from the 50's here with bobbins so rotten that they disintegrated in my hands; that can get the wire knotted up and make it completely unusable if the proper precautions aren't in place. That kind of operation takes a lot of time and costs to recover can get higher the worse things are.
 


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