Find replacement resistor

[magneh]

Hi there!

I know this can seem to be a stupid question, but how do I find a replacement for this resistor of a TV power supply?

If I check the band resistor colour code, It's 1 ohm, but on the schematic its marked as 3.3R

Anyone can clarify ?

Thanks!

[Andrew F. Ali]

Re: Find replacement resistor

There are no stupid questions on this forum What are the coloured bands on your resistor??

[CapLeaker]

Re: Find replacement resistor

the sanken pdf for the IC sez for that resistor to be 1.5 Ohm 1/2Watt in their test circuit.

[magneh]

Re: Find replacement resistor

There are no stupid questions on this forum What are the coloured bands on your resistor??

Hi there!

Well, I know that the resistor coloured bands should mean 1 ohm resistor...

Not sure about the wattage...

Thanks!

[magneh]

Re: Find replacement resistor

the sanken pdf for the IC sez for that resistor to be 1.5 Ohm 1/2Watt in their test circuit.

Ok, interesting.

If I check the coloured bands I get 1 Ohm resistance as value

Feel kinda tempted to get an 1 Ohm resistor 1/2 watt ...
Worst case scenario, Ill watch it burn when I turn it on

[Andrew F. Ali]

Re: Find replacement resistor

the sanken pdf for the IC sez for that resistor to be 1.5 Ohm 1/2Watt in their test circuit.

Yes, I would go for the 1/2W resistor also.

[budm]

Re: Find replacement resistor

That Source resistor for the Internal MOSFET of the SMPS IC will go open circuit if the MOSFET shorted out. Is that resistor tested open circuit?

[magneh]

Re: Find replacement resistor

Thanks for the inputs

The resistor is shorted and clearly burned underneath it.

I will go for the 1/2W 1 ohm ... most likely

Cheers!

[Andrew F. Ali]

Re: Find replacement resistor

The resistor would be open and not shorted. The reading would be infinity or increased.

[R_J]

Re: Find replacement resistor

I agree with Andrew, The resistor is ok, and the board is likely discolored do to heat from the resistor. hard to tell without a picture.

[magneh]

Re: Find replacement resistor

Hi there!

Finally had time to take a look again at the resistor.

You guys are totally right, the resistance is OPEN not shorted

Some pics attached.

Should I definitely go with a 1 Ohm 1/2W?

Ty all!

[dick_barton]

Re: Find replacement resistor

As Budm says in Post #7 there's every possibility that the IC is damaged and replacing the resistor without checking out the IC may just result in it burning out again. Check the mosfet with the meter in diode mode between Source/Drain (Pins 1 and 8) reversing your leads for the second measurement. Set OFF.

[budm]

Re: Find replacement resistor

I would replace that IC.

[redwire]

Re: Find replacement resistor

I would replace that IC.

+1 the IC is shorted, replace it first. Otherwise a new resistor will just burn up.
It should be a flame-proof, fusible-type resistor to prevent fire.

[magneh]

Re: Find replacement resistor

Thanks for all the inputs!

Yes, I forgot to mention that the IC was also burned and replaced.

Only thing missing is to find a correct replacement for that resistor.

Fusible type resistor, 1 Ohm, 1/2W this is what Im going for

Why do they put 3.3R in the schematic for this resistor? any idea?

[Andrew F. Ali]

Re: Find replacement resistor

Could be an update on the board design. 3.3ohm maybe an original design flaw that was never updated.

[SLK001]

Re: Find replacement resistor

It looks like a 1.5 ohm resistor to me. The second band looks green, not black. However, it could be how colors show up here - you decide which it is.

[budm]

Re: Find replacement resistor

Looks like 1 Ohm.
You can use MOX (Flame proof Metal Oxide) non inductive.
Measure the dimension to get rough idea what the wattage is.

[jeeptechfred]

Re: Find replacement resistor

https://www.digikey.com/product-deta...69H-ND/3661844

the IC is cheap and available