Help identifying a 5 band resistor

[Hambag]

Hi guys, my pc power supply gave up on me last night, and instead of throwing it away I want to give t a crack and try and fix it.

On opening the case I noticed the only faulty looking component, a resistor that has burst.

I took it around to a couple of electronics stores and had no luck with finding one as even the experienced tech guys were stumped.

It's a 5 band resistor with the following stripes:
White
Gold
Gold
Red
Red

If you guys could help that would be greatly appreciated.

 

[davenn]

That's an easy one

you are reading it around the wrong way

put Rd Rd Gd Gd Wh into an online resistor calculator

eg
http://www.hobby-hour.com/electronics/resistorcalculator.php

cheers
Dave

 

[chopnhack]

Way faster than me dave! For what it's worth, make sure the silver, gold or white band is on your right - makes it easier to i.d. your resistors.

 

[davenn]

or white band is on your right

Not always for white there are values of resistor that start with 9

 

[chopnhack]

Not always for white there are values of resistor that start with 9

ah, good point - when white is directly next to gold or silver then?

 

[Hambag]

Thanks for your replies. So having entered the colors in that calculator I get a result of 2.2 ohm and 5% and it's telling me that the value is calculated as a 4 band resistor.

So can I go back to the tech store and ask for a 2.2ohm resistor?

 

[chopnhack]

Thanks for your replies. So having entered the colors in that calculator I get a result of 2.2 ohm and 5% and it's telling me that the value is calculated as a 4 band resistor.

So can I go back to the tech store and ask for a 2.2ohm resistor?

That would be a direct replacement. The other value to know would be the resistor's power rating - 1/4 watt or 1/2 watt. It's hard to judge size in the photo, can you measure the resistor?

 

[Hambag]

It's about 6 mm.

 

[chopnhack]

It's about 6 mm.

From axial end to end or from between where the lead enters the pcb?

 

[Hambag]

From end to end of the resistor it's self, do you need the pcb dimension?

 

[chopnhack]

My best guess is that it's either a 1/2w or 1w resistor. I have found both available in 6.5mm body lengths. Last detail would be whether this was a fusible type resistor. I am leading towards no since the PCB just shows R (no special designator for the part number). Are you able to find a schematic for the circuit? One thing we can tell for sure is that it was not flameproof

 

[chopnhack]

1/2 watt flameproof and fusible
1 watt

Have you any clue why it failed?

 

[Hambag]

Brother had a laptop charger plugged into the wall, he pulled out that plug and went to plug in the power brick with the pc stuff plugged into it without turning off the wall plug (if you know what I mean). There was a pop and a bright flash that I saw come from the back of the pc.

I had a look at it since we built it some 5 yrs ago, and noticed that nothing is powering up. I then had a look at the psu as it seemed the most logical problem, and as soon as I opened it I noticed the blown resistor.

 

[chopnhack]

Brother had a laptop charger plugged into the wall, he pulled out that plug and went to plug in the power brick with the pc stuff plugged into it without turning off the wall plug (if you know what I mean). There was a pop and a bright flash that I saw come from the back of the pc.

I had a look at it since we built it some 5 yrs ago, and noticed that nothing is powering up. I then had a look at the psu as it seemed the most logical problem, and as soon as I opened it I noticed the blown resistor.

Well, maybe it was a fusible resistor after all! Best of luck, I hope it works out, post and let us know.

 

[Hambag]

We had the ac on in the house and the pc was slightly more dusty then usual, but don't see why that would cause it to fail. It is an oldish unit now, but we have the whole pc set up so I would like to keep it if I can till I redo the rest of the pc.

 

[Hambag]

So just to clearify, I need a 1/2 w flame proof and fusable link resistor?

 

[davenn]

flame proof and fusable link resistor?

there's no confirmation that it was either of those ... only a schematic or parts list would confirm
If you cannot get one with either or both of those I wouldn't panic too much, at least for an initial trial


Dave

 

[chopnhack]

Agreed, those power ratings are my best guess. You can always try the 1/2 watt and see if you can power up again. The resistors are cheap, I would buy a couple of each rating and see if that is not the only problem. Sorry, I can not give you more advice than that.

 

[BobK]

It is better to err on the side of higher power rating. If a 1W would fit, I would use it, rather than trying a 1/2 W.

Bob

 

[chopnhack]

It is better to err on the side of higher power rating. If a 1W would fit, I would use it, rather than trying a 1/2 W.

Bob

But what if its purpose is to provide some protection to the circuit?
At the low resistance value of 2.2Ω, a resistor of this small size can't have much voltage across it, correct?