please help identify burnt resistor, repairing EMACS PSU

[debugtimog]

Hi All,
I am currently repairing an EMACS PSU model: PSA-6700P with a burnt resistor. If anybody can provide a schematic that would be great. Currently the PSU dont have an output after triggering the PS_on. I have found a lot of high ESR caps. The only short I found was the schottky diode just behind the burnt resistor. I have traced this resistor to be connected to the 5v standby.







Thanks in advance!

[R_J]

Re: please help identify burnt resistor, repairing EMACS PSU

Have you removed and checked the resistor value? it could be that due to heat the outer coating cracked and fell off but the resistor is still ok.
Do you have the 5 volt standby voltage?

[budm]

Re: please help identify burnt resistor, repairing EMACS PSU

Please also provide the straight shot pictures of the whole bottom and top side of the board.

[debugtimog]

Re: please help identify burnt resistor, repairing EMACS PSU

Hello Again,
The value of the resistor is 16 ohms. Im not sure if this is the original value. From the transformer, it entered the schottky and resistor and out into the inductor to the 5v standby wire.
I missed to measure the 5v standby that day I checked for the output, but I checked the transformer, it is not open.
Anybody got an equivalent schematic for this kind of PSU base on the picture below?

[budm]

Re: please help identify burnt resistor, repairing EMACS PSU

I cannot tell from your low res picture to see if that resistor is connected in series with the rectifier diode or not. They usually use fusible resistor (2.2 ~ 4.7 Ohms) in series with the rectifier, but I cannot tell from the picture.

[momaka]

Re: please help identify burnt resistor, repairing EMACS PSU

If you have bad caps, chances are the 5VSB wasn't regulating properly and that's one possibility why that resistor burned up. So first order of business, get all bad caps replaced. Then try to measure the 5VSB. If 5VSB is present and stable, then try to see if PSU can come on.