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Broken Spring Reverb


hessodreamy
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I've got this fender solid state amp but the reverb doesn't work. You turn the reverb level up and it just hums a bit, but no verb.

Anyway, I opened things up. The cables from the main amp to the spring unit at the bottom of the chassis are ok. One thing I did notice when I checked inside the spring unit (a simple 3 spring unit, pic attached) is that there's no resistance between the inner and outer lugs of the input socket ie they're connected somehow. Is this right, or does it point to something being shorted?

reverb.jpg

Edited by hessodreamy
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Did you check that with the tank completely removed from the amp? And when you say no resistance, is it literally zero or is it like 8 or 10 ohms or something like that?

Yup, I removed the tank from the amp and checked the resistance across the 2 lugs on the input. Absolutely zero. Also i measured just before where it gets to the transducer. Zero there, too.

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I think I understand now. Never looked at these things before.

Basically the resistance I measure across each of the connectors is the impedance of the in/out coils, right? When I said there was no resistance across the input, it was actually about 35 ohms. (must've set multimeter wrong)

And where the output was showing infinite - further inspection shows the coil wire has snapped.

So rather than a short, it's a break.

Now let's see if I can get the bugger back on...

Edited by hessodreamy
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Can't seem to get enough of the wire free to re-solder.

I would try to unwind a turn or two of the coil. If it's well-potted though, that may be impossible. Worth a try, since you can't screw it up any more than it already is. :D

Or if the piece you have to work with is long enough, you can scrape off some of the coating on the transformer wire and solder an extension on it.

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