1504fp no power despite new MOSFET

[kturnerga]

Hi!
I replaced a MOSFET on a Dell 1504FP power supply (everyone has one or knows someone who has a 1504FP that doesn't cut on . It still won't power on or indicate it is getting juice. I am about ready to recap but the caps aren't swollen or even bulging. I also noticed that the inverter board (board in upper corner w/ 2 two-pin plugs) is covered in some sort of coffee-like spooge. If the power supply still functions would the coffee-laden board still preclude a power-on LED?

Sadly I'm not privy to anything other than a digital voltmeter but I do have another 1504fp sans power supply. If this fails I plan to get my paws on an HP that does the two-second tango with the power.

Thanks. You fellas do good work for us board-swappers/admins out there in geekland.

[PlainBill]

Re: 1504fp no power despite new MOSFET

Hi!
I replaced a MOSFET on a Dell 1504FP power supply (everyone has one or knows someone who has a 1504FP that doesn't cut on . It still won't power on or indicate it is getting juice. I am about ready to recap but the caps aren't swollen or even bulging. I also noticed that the inverter board (board in upper corner w/ 2 two-pin plugs) is covered in some sort of coffee-like spooge. If the power supply still functions would the coffee-laden board still preclude a power-on LED?

Sadly I'm not privy to anything other than a digital voltmeter but I do have another 1504fp sans power supply. If this fails I plan to get my paws on an HP that does the two-second tango with the power.

Thanks. You fellas do good work for us board-swappers/admins out there in geekland.

The first step is to measure the output voltage of the power supply. In general terms, there are two acceptable methods of troubleshooting.

The first I like to call 'Divide and Conquer'. It involves testing at points chosen so as to eliminate large portions of the circuit. (If the power supply is putting out 5V and 12V there is no point in checking the line cord or the power fuse).

The second is called 'Walking through the circuit'. This would involve checking the outlet, verifying line voltage is present at the diode bridge, measuring the voltage across the filter cap, etc.

Notice that neither of these involve blindly replacing parts because 'they might be bad.'

PlainBill