question about part in picture

[kustomdreamz]

New to this broken electronics crap, I like them a lot better when they are working... Anyway, are these resistors? I am assuming they are since the location numbers have R in front of them. I think I need to replace the bottom one because it is burned and from the bands (Y, V, G, G) it should be 4.7ohm@5% tol. and it is 3.1ohm. The top one is 5.3ohm which is over the 5%...

Also, if they are resistors, why are these two green and the rest tan? Are they a different type?

BTW if you are curious, this is off my Sony home theater sub.

 

[kustomdreamz]

I think I found what it is

Maybe a fusible resistor?

 

[eblc1388]

One thing you might not know is that one cannot measure the resistance value accurately when both ends of the resistor are connected to the rest of the circuit.

You have to unsolder at least one end and then measure its resistance.

Resistors come in various sizes, shapes and body color and there is no strict standard on these. However, the 5% or 10% carbon film ones are commonly found in tan body color while the metal film 5% and 1% ones are in light blue.

 

[DigiTan]

Yeah, I'll put my money on 1/8th watt; 1% metal film resistor.

 

[kustomdreamz]

thanks for your help, one more thing

Any idea where I might find a couple of these? I've looked at digi-key, opamp, radioshack, jamesco, mcminone... not finding the 1/8W 4.7ohm metal film 1%

 

[DigiTan]

The closest thing I found was a 4.75 0hm version with Mouser.

 

[kustomdreamz]

I'm assuming that the .05 ohm will probably make a difference. I don't want to mess anything else up by not using the right parts.

 

[zachtheterrible]

Doesn't have to be 1/8watt. Anything above will do.

 

[eblc1388]

...it is burned and from the bands (Y, V, G, G) it should be 4.7ohm@5% tol. and it is 3.1ohm. The top one is 5.3ohm which is over the 5%...

If the band color is as you have said, they are definitely not 4.7ohm but 4.7 megger ohm.

You can try the resistance calculator here:

Resistor Color Code Table And Calculator

 

[kustomdreamz]

I used this calculator

https://www.the12volt.com/resistors/resistors.asp

 

[eblc1388]

And it also correctly shows that the resistance is 4700Kohm.

So, your point is.... :roll:

 

[Nigel Goodwin]

I suggest the confusion arises over him NOT telling us what colours the bands are

(Y, V, G, G)

What does 'G' mean?, could be grey, green, gold - presumably he means gold? - but it's a pretty poor effort at passing information on!.

 

[eblc1388]

Well spotted, Nigel.

My fault of assuming for G he means green.

 

[audioguru]

It should be obvious that a 4.7M/0.1W resistor needs more than 686V across it for it to burn! I think a little 0.1W resistor would arc if it had only 100V across it.

 

[kustomdreamz]

my bad

I guess I should have spelled it out, but I figured since I DID put the 4.7ohm in the text it would be obvious what the colors were.... SO, flame away...

 

[audioguru]

Before replacing the burnt resistor you must find out why it got burnt and fix that problem.

 

[kustomdreamz]

From what I was told by the tech that worked on my other unit, it is just a poor design. They run too much power down that circuit. The other unit popped the capacitor just before the resistors. I'm still not 100% certain the capacitor isn't bad on this one.

 

[Dean Huster]

Those resistors are the least of your problems. Resistors don't just "burn up" because it's a Tuesday. With the possible exception of their reaction to a mains transient, they are nearly always a secondary failure caused by another device (often an output transistor or output IC) shorting. New resistors in that spot without finding and replacing the cause of the overload will most likely result in a picture just like that above.

Dean

 

[Nigel Goodwin]

It's true that resistors don't usually fail without a reason, but it looks like those two may be in parallel? - and fitting resistors in parallel (or in series) often results in their failure. I've been criticising manufacturers for years about it - they show me the circuit, and I point out the parts which are likely to fail (nothing clever about it, it's just the parts that ALWAYS fail!).

However, 4.7 ohms isn't a common value that fails!.

The reason for the capacitor failing is most likely down to a crap capacitor, modern electrolytics are EXTREMELY unreliable.

 

[audioguru]

modern electrolytics are EXTREMELY unreliable.

I've never had an electrolytic capacitor fail in my projects. I use mostly name-brand ones, a few used ones and even a few Chinese ones.

Remember a few (5 years?) years ago when nearly every brand of anything electronic had their Chinese electrolitic capacitors fail when they were new?
I know some guys who made a career of nothing but changing them.