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What is "VSR1" on a circuit board.

edony

New Member
Hi All,

I plugged a 110V device into a 240V outlet and blew a fuse. I opened the device and found the main fuse (20A) blown. But something else was blown too.

It is marked VSR1 and looks like a capacitor. The below photo shows it blow with two parts of it broken off from it. Also there is a symbol under it i dont recognise. (sorry its partly obscured)

Does anyone know please?


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KeepItSimpleStupid

Well-Known Member
Most Helpful Member

edony

New Member
awesome thanks very much!

The funny thing is that the radial fuse to the bottom right of it is 250V?
 

ronsimpson

Well-Known Member
Most Helpful Member
The funny thing is that the radial fuse to the bottom right of it is 250V?
Fuses are grouped by low voltage or line voltage.
Low voltage includes automotive. Automotive is built very differently and must handle vibration.
Line voltage fuses might say 120V but more often say 220 or 250 which works well at 120V.
High voltage fuses are longer than low voltage fuses. They use different types of filament inside.
It is common to use 250V fuse in a 120V circuit.
 

edony

New Member
Thank you!

BTW, i think i have found the exact component label. V7221U. But am not 100% sure. Looks right though? An Im not sure if its specific to panasonic or its a generic industry label?

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JWCC

New Member
That part that looks like a disk capacitor is a varistor, and is there to blow the fuse if the power bus (AC power) experiences a voltage surge , transient that exceeds a set voltage over a certain time duration, usually expressed in Joules.
In most electronic circuits just replacing the blown fuse would allow the power supply to work, if the remains of the varistor are not shorted, and the rest of the circuit was not damaged.
Ok for testing, but not replacing the varistor would leave the circuit unprotected from surges and transients. Too low a value will blow again the fuse, too high a value would Not protect. The correct value will absorb most surges without blowing itself up.

JWCC
 

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