I'm trying to fix a vizio tv model number E500-b1 and I think i've identified a potentially burned out component. I have limited experience so have attached a pic, it's the purple blob looking one above my pointer finger.
MOD: Cleaned up your image.E

 

Hello,

It is a power resistor.
Do you have a schematic of the device?
Than you could lookup the value of R860.

Bertus

 

If you have a meter you could check its resistance.
Want makes you think it is burnt out?

 

Looks like you are in the primary side of a switching power supply, but a wider view will confirm. As above, it does not look burned. Why do you suspect it?

electrotanya might have the manual and schematics.

ak

 

Thanks for the tips!

I suspected it because it has a bulge in the middle along the length of the cylinder, something i've not seen on other resistors of any type.

 

The colour is even along the whole part (and isn't black!) with no signs of any crumbling of the covering. I suspect that it is a wire wound resistor where the coating on the outside is not evenly applied.

 

The colour is even along the whole part (and isn't black!) with no signs of any crumbling of the covering. I suspect that it is a wire wound resistor where the coating on the outside is not evenly applied.

I would concur with this. It looks normal to me. If you put a meter on it, you can tell if it is open, which is the most likely failure mode.

A resistor of that sort would almost certainly show signs of darkening and structural damage if it had been overpowered. If it was over a long period, the board below would also show damage. If sudden, it would be cracked or otherwise broken.

 

Resistors with numerical coding often have the value printed on one side and other numbers, the likes of which I've never bothered to figure out, printed around about the device. What your picture shows is probably one of those manufacturer markings that has no meaning to me. You may see other numbers if you can look closer at the sides and even possibly be able to read other numbers even if they are nearly on the bottom. But in some cases you just can't see all the numbers. As an electronics inspector I've seen what I've described thousands upon thousands of times.

The silk screening on the board identifies it as R860. On a Bill Of Material (BOM) R designates a resistor, the 860 designates a specific resistor. The BOM will specify the wattage and resistance. When inspecting a manufactured board inspectors have to check the BOM and compare the component to make sure it's the correct value. When these parts are placed by machine there is no control of when the numbers are faced up so they can be seen. On the other hand, if they're stuffed by hand the assembly technician SHOULD put the numbers up so they can be verified. But when you're assembling hundreds of thousands of boards a month you get tired of making sure the identification can be read. Then, on Another hand, you could have an assembler who just doesn't care. Bend the leads and stuff the board.

Yours is a resistor. And from experience, none of us see any problem with R860. If you need help diagnosing a problem you can take a picture of the overall board. If you have part numbers and/or schematics this too can aid in diagnostics. Also a thorough description of what the board is (or isn't) doing will also help us zero in on helping you solve your problem(s).

Finally, welcome to AAC.