Re: HP W2408 No Power
Looks like the power supply has a problem starting up. There's a few things that can cause this:
1) Shorted output diode(s)
To see if this is the problem, check schottky diodes D853 and D854. First turn OFF and unplug the monitor. Next, let's say you're checking D853 - put red (+) multimeter probe on middle pin (pin 2) of diode D853 and black (-) probe on either outer pins (pin 1 or 3). Measure the resistance with your multimeter and report back what you find. Repeat for D854.
2) Bad component in the start-up circuitry
To see if this is the problem check the following items:
- Check that resistor R855 (next to the big yellow transformer) is not open circuit or reading much higher in value than what it should be (check color code on it)
- Verify that diode D852 (it's close to R855) is not shorted. See what value it gives you with the diode setting on your multimeter.
- Test electrolytic caps C872 and and C884 with an ESR meter. If you do not have an ESR meter, then replace those caps. Make sure the new caps have identical voltage and capacitance values.
Originally posted by kjspylite
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1) Shorted output diode(s)
To see if this is the problem, check schottky diodes D853 and D854. First turn OFF and unplug the monitor. Next, let's say you're checking D853 - put red (+) multimeter probe on middle pin (pin 2) of diode D853 and black (-) probe on either outer pins (pin 1 or 3). Measure the resistance with your multimeter and report back what you find. Repeat for D854.
2) Bad component in the start-up circuitry
To see if this is the problem check the following items:
- Check that resistor R855 (next to the big yellow transformer) is not open circuit or reading much higher in value than what it should be (check color code on it)
- Verify that diode D852 (it's close to R855) is not shorted. See what value it gives you with the diode setting on your multimeter.
- Test electrolytic caps C872 and and C884 with an ESR meter. If you do not have an ESR meter, then replace those caps. Make sure the new caps have identical voltage and capacitance values.
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