Does a fuse prevent over voltage???

[mattdavios]

Hi guys,

I have a guyatone Tube distortion pedal. Its a vintage pedal with in-build fuse and power supply.  I foolishly over voltage the pedal without checking. The pedal auto shut off after I on it for a few second. The fuse broke and I replace the fuse, however it cant be turn on even with the replacement of a new fuse and a transformer to step down the voltage from 220V to 100V. Anybody know why? Would the componets in the pedals get burn out by the high voltage even with fuse protecting it? From what I know, which might be wrong. A fuse would cut of the current to prevent damage to circuit board in case of over voltage. Could the reason of the pedal not functioning be the in-build powersupply had been damage? Need your advise and thanks a lot in advanvce!

[QSQCaito]

Well, not exactly.
Lets define what a fuse is first:
A device designed to provide protection for a given circuit or device by physically opening the circuit. Fuses are rated by their amperage and are designed to blow or open when the current being drawn through it exceeds its design rating.

You could pass 10,000 volt at a very low current, and nothing would actually happen to the fuse.

If you pass to much current the SI of current is the Ampere, so fuses are rated in A(amperes).

If you overload your circuit, using it too much, or too hard really. Or there is a shortcut anywhere making very large amounts of current flow, the fuse will break.

It's most probable you burn something in it. I don't think the transformer broke, but it's the first think in the line. I would suggest you checking it.

[grapefruit]

Sometimes when you apply 220-240V instead of 110V the fuse will blow before anything else. It depends on how robust the circuit is and how far above nrmal operating current the fuse is rated at.

The fuse isn't really there for over voltage but sometimes works. I've seen an Oberheim drum machine and a few other things come in for repair that only had blown fuses after being over voltaged. Other devices had various thing destroyed.

With fuse intact, power switch on and unit diconnected from mains, measure resistance across active and nuetral. This should be less than 100 ohms (if the unit has a power tranny). If it is open, double check the transformer primary winding directly. If this is open then you have blown the power tranny. If not you'll have to start checking the secondary side....


Stew.