Finding value of burnt resistor

[daniel1700]

Hello,

I have this Forch LED torch circuit with circuit board number 1100017 and a burnt resistor.

The character above the resistor read “R1”. Using a multimeter to measure its resistance its comes out to 1 ohm. Searched around the internet and someone suggested that the R Value of the actual resistance but I doubt that since the other resistors don’t correlate to their respective value and the R values seems to be in order.

This resistor is directly connected to the battery input which is a 14430 li ion battery, 3.7v 650 mah and followed by a diode.

Please note the resistor didnt burn out with normal use, it short-circuited a new battery put in.

Is there anyone who can tell me how to find the resistor value or what would be a suitable value for a replacement, or is this not even possible ?

Thanks for any help!

 

[sagor1]

A "short circuit" can happen if you put the battery in backwards. Usually that damages the diode and any fuse in line with it. It might be what is called a "fusable resistor", one that is meant to open under heavy current.
Without a schematic or a similar board, no way to guess the value of that resistor.
I notice on the underside, the etch resist seems scrapped off between a ground trace and a trace that connects to the resistor (at the very bottom of picture). It may be that something in the case cause a short across those two traces, which in turn blew the resistor.

 

[unclejed613]

depending on what type of resistor it is, (most likely metal film), you can get a close approximation by cleaning the carbonized paint off it, and look at it under a magnifier. find the break in the metallization, and measure with an ohmmeter from each side of the break to the corresponding terminal on the resistor, and add the two values together.