Dell Power Supply fan not coming ON

[sam_sam_sam]

I am working on Dell computer power supply that was totally Dead
I found one bloated cap that was a 3300uf @ 16 volts
I found all of the cap below 100uf @ ten X the ESR value that the new ones are of that value

I recapped the power supply except the two main caps
The cooling fan dose not even tiwitch or move at all

If I need to post photos of this power supply I can but it will have to be later

[sam_sam_sam]

Re: Dell Power Supply fan not coming ON

I will check the fan on another power supply to see if it works
If the fan is good ?
What to check next?

[stj]

Re: Dell Power Supply fan not coming ON

follow the fan supply, one side is going to be ground the other is 12v.
and one is probably going through a transistor to control the speed.

replace the transistor with a jump-wire.

[sam_sam_sam]

Re: Dell Power Supply fan not coming ON

Thanks for your reply

I thought that might be the way they did that or with a thermistor which could also be be bad because I saw one those in there as well what are the ohm value of them as a rule of thumb

[stj]

Re: Dell Power Supply fan not coming ON

no idea,
the inline thermister is a design i'v not seen in years btw, if it's using one then it probably drives a transistor.
they can use a smaller one that way.

[selldoor]

Re: Dell Power Supply fan not coming ON

SAM if you are trying to start it with a paperclip on the bench this might be of interest.
https://www.badcaps.net/forum/showth...ell#post222675

[sam_sam_sam]

Re: Dell Power Supply fan not coming ON

The power supply comes ON and works
The fan is the only thing that is not working

[selldoor]

Re: Dell Power Supply fan not coming ON

OK did you test the fan yet? or the voltage at the pins.

I am not sure if there is a standard for thermistors - is the one you see related to the fan or is it current inrush near the mains socket.

I have seen a table of some NTC thermistors which suggest 3000 ohms at 70c
and goes to zero at 90c but depending on use I suppose the figures could be anything as long as it reached zero ohms at the temperature full speed was required.

Here is a way to test if it actually works at all
http://www.ehow.com/how_5398454_test-thermistor.html