Help with circuit board resistor

[MattVette89]

Hey guys, hoping you can point me in the right direction. This is for my Streamlight charger. The piggyback portion doesn't work. I think I've narrowed it down to this resistor. I can do the replacement but with limited experience I want some help identifying the right part to get.

The charger itself reads:
Input 12-15vdc .2A
Main out regulated .18A
Aux out 3.6vdc .14A

It seems to be a 4 band. I've used the online calculator but not sure if I have the right colors.

Any help is appreciated.

 

[dogdog]

looks to me it's a 41 OHM 1/2 watt maybe 1 watt current limiting resistor... most like a 1 watt one... I thought steam light have life time warranty on their thing... if your cells are 10650 just google it.

if your cell is a single cell lithium ion battery, you are better off buying a charger from ebay... cheaper.


not even a cheapo micro chip charge controller for the price of that thing... hmmm cheesy...

 

[RPH]

What makes you think the resister is the problem? Most of the ones that I have found have been cooked, some more than others! Only a few times on equipment that was twenty plus years old have I seen resistors drift enough to affect circuit operation. Other components tend to be more unstable. Is something else dragging the power supply down? Have you isolated things?

 

[jismay]

Agreed, it should be a 41ohm current limiting resistor. Have you put a meter across it and checked the resistance?

Those sort of resistors are unlikely to just drift, they should be relatively close to spec or completely open. Honestly, for that application even the specific resistance probably isn't all that important as long as its in the ballpark, so al long as the resistor isn't either open or dead-short then I would look elsewhere. Have you verified that the diode is working as expected? You can use the continuity feature of a multimeter on a diode (or an LED for that matter) it will only beep with the leads in one direction, so check it one way then switch the leads and check the other.

 

[RPH]

What’s on the other side?

 

[theoldwizard1]

Those sort of resistors are unlikely to just drift, they should be relatively close to spec or completely open.

The fourth band is gold so it is a 5% resistor.

As stated, a bad resistor usually has "let the magic smoke out" and leaves an obvious burn mark on the board.

 

[MikeF2316]

It looks like white brown black gold to me. That would make it 91 ohms, +/- 5%. Note that 91 is an IEEE 5% standard value whereas 41 isn't.

 

[LXCam]

I'd suggest looking at the other side of the board adjacent to that diode at the led. That looks like it got hot.

 

[dogdog]

It looks like white brown black gold to me. That would make it 91 ohms, +/- 5%. Note that 91 is an IEEE 5% standard value whereas 41 isn't.

41 OHM makes more sense if it is used as a voltage dropper from 12-15v down to a voltage that is safe for the zener diode as a voltage regulator.... that is for the aux out 3.6V @ .14A

and besides that pic 3 and 4 shows more yellow than white... at least on my screen it is....

 

[Stuart in MN]

I'd suggest looking at the other side of the board adjacent to that diode at the led. That looks like it got hot.

I think you may simply be seeing the shadow lines of the PC board traces on the back side.

If all there is on this board are those two resistors and a diode, even using the parts cannon method and replacing all three components won't cost much.

 

[MattVette89]

Edit - I think MikeF is correct. I rechecked and now it's testing around 90 ohms. From moving things around it seems like cold solder joints could be to blame.

Thanks for the help, guys.

The charger is over 13 years old, by the way

 

[LXCam]

I think you may simply be seeing the shadow lines of the PC board traces on the back side.

If all there is on this board are those two resistors and a diode, even using the parts cannon method and replacing all three components won't cost much.

Quite possible. I still haven't mastered the art of seeing details off a phone. And then there's that glasses thing, it's well past time for a new prescription.

 

[Stuart in MN]

From moving things around it seems like cold solder joints could be to blame.

If you haven't done it already, you should re-flow the solder joints.

 

[MikeF2316]

Edit - I think MikeF is correct. I rechecked and now it's testing around 90 ohms. From moving things around it seems like cold solder joints could be to blame.

Thanks for the help, guys.

The charger is over 13 years old, by the way

Keep in mind there can be an intermittent between the guts of the resister and the lead that you see sticking out. I've seen that more than once.

 

[MikeF2316]

41 OHM makes more sense if it is used as a voltage dropper from 12-15v down to a voltage that is safe for the zener diode as a voltage regulator.... that is for the aux out 3.6V @ .14A

and besides that pic 3 and 4 shows more yellow than white... at least on my screen it is....

I guessed white over yellow because 91 is a IEEE 5% value and 41 isn't. It doesn't look yellow enough to be yellow, but too yellow to be white.

 

[dogdog]

I guessed white over yellow because 91 is a IEEE 5% value and 41 isn't. It doesn't look yellow enough to be yellow, but too yellow to be white.

going to needed new eye balls

 

[MattVette89]

If you haven't done it already, you should re-flow the solder joints.

I did already. Works now.

 

[Stuart in MN]

I did already. Works now.

excellent.

 

[Bert_]

Cracked solder joints is a problem fairly often. I'm not real well versed with electronics repair, but I have fixed thousands of dollars worth of stuff just by reflowing the solder joints. Or other simple stuff.

If you can tap on it and have it work for a while it is almost certainly a cracked solder joint.