Resistor question

[1supertech]

Hello everyone
I am not to familiar testing resistors would like some help
I have a resistor 0.39 ohm 2 watt I get a reading of 000.5 on my
millimeter I assume this resister is bad?

My problem is no power on power supply ACER 1906 no power to mainboard Large cap has 165v test all fuses, diodes, mosfets all new capacitors

If 0.39 ohm 2w resistor is bad is their a difference between this type of resistor and color coded resistors

[selldoor]

Re: Resistor question

May not be bad 0.39 plus the resistance in your leads wont be far off 0.5 what is the
tolerance on the resistor ?

On the back of the board there is fuse F902 (looks like) have you tested it?

[1supertech]

Re: Resistor question

Fuse F902 is good
How do I find the tolerance of resistor? marking on resistor are 2WJ, F063P F&0 overlap could be P

[budm]

Re: Resistor question

"j" = 5%

[1supertech]

Re: Resistor question

Thanks budm

[Phoenix83]

Re: Resistor question

For measuring resistor with low resistance is much better analog ohmmeter. It's not expensive, you can buy it for €10.

[selldoor]

Re: Resistor question

OK so with it ALL connected up you get NO voltages on CN902?

Pictures of Main Board?

[1supertech]

Re: Resistor question

NO voltages on CN902
large cap now show 0.635 volts last test showed 168v have no idea what happened

[budm]

Re: Resistor question

That resistor is for the Power MOSFET (on the heatsink) Source pin which is part of the SMPS circuit, that should not affect the DC reading on the Main filter cap. Did you check that small red rectangular main AC fuse? If that resistor shows open (high resistance), then you need to check the MOSFET to see if it shorted out.

[1supertech]

Re: Resistor question

fuse is good will test mosfet

[1supertech]

Re: Resistor question

MOSFET tested good large cap is back to 167v dummy me forgot to turn on the power to board.

[1supertech]

Re: Resistor question

For measuring resistor with low resistance is much better analog ohmmeter. It's not expensive, you can buy it for €10.

I do have one tried it tested 0.39ohm resistor meter went just past 2 on the ohm scale. would that be good.

[selldoor]

Re: Resistor question

So was the power on when you tested at the connector?

[budm]

Re: Resistor question

Touch your meter probe together and read the probe wires resistance, then add .39 Ohm to the reading, that is what you should have (about). This type of resistor when it goes bad, it will have open circuit.

[1supertech]

Re: Resistor question

With resister removed from board I get 000.5 or .50? which is a higher resistance then
.39 assuming this not good

[1supertech]

Re: Resistor question

So was the power on when you tested at the connector?

still no power to CN902

[selldoor]

Re: Resistor question

With resister removed from board I get 000.5 or .50? which is a higher resistance then
.39 assuming this not good

You are not understanding this - I have said it and budm has said it - it is a problem we all have with testing low ohms- The 0.50 includes the resistance
of the wires and probes which could be 0.1 Ohms. Add that to the 0.39 Ohms
gives 0.49 ohms and add the 5% say .01 ohms so 0.5 ohms could well be correct and as budm has also said they tend to fail open.

[selldoor]

Re: Resistor question

still no power to CN902

You did have the main board connected?

Ok Budm would be better at saying what to test next - I dont know so would have to do it the long way - testing everything. Starting at the big cap.
I would try D 901 D902 then R 908

[budm]

Re: Resistor question

Check the voltage on CN902 with nothing else connected to the power supply board and see if you do get any reading. Are you hearing any ticking sound from the power supply board?

[1supertech]

Re: Resistor question

D901 04.44 one direction
D902 0.505 one direction
R908 101.1
I also pulled diodes out of circuit tested with atlas dca55 showed no shorts