Re: HP LP3065 black screen, LED lighted, USB works
For the two diodes, unsolder one end and repeat the test. Either one could be causing the problem.
Retiredcaps gives much better instructions than T do, but here goes.
I prefer a two step approach for measuring diodes and transistors. On a transistor arbitrarily number the leads 1, 2, and 3. First, set your DMM on the lowest range, usually 200 ohms. When I indicate 2 pins, place the red lead on the first, the black lead on the second.
For a transistor, measure the resistance 1-2, 1-3, 2-3, 2-1, 3-1, 3-2. A good transistor will read open on all six readings. Sometimes other components will interfere, in that case unsolder the transistor and repeat.
Now set the meter to the diode test range. Repeat the measurements 1-2, 1-3, 2-3, 2-1, 3-1, 3-2. On a bipolar transistor 4 of the six readings should indicate open, two should indicate about .7 volts. Again, other components may interfere, unsolder the transistor and repeat.
On a diode number the pins 1 and 2. Measure the resistance 1-2 and 2-1. It will usually indicate open in both directions. Switch to the diode test range and repeat. It should indicate open in one direction, about .7 volts in the other. (Schottky diodes will read lower).
PlainBill
Originally posted by freddyfena
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Retiredcaps gives much better instructions than T do, but here goes.
I prefer a two step approach for measuring diodes and transistors. On a transistor arbitrarily number the leads 1, 2, and 3. First, set your DMM on the lowest range, usually 200 ohms. When I indicate 2 pins, place the red lead on the first, the black lead on the second.
For a transistor, measure the resistance 1-2, 1-3, 2-3, 2-1, 3-1, 3-2. A good transistor will read open on all six readings. Sometimes other components will interfere, in that case unsolder the transistor and repeat.
Now set the meter to the diode test range. Repeat the measurements 1-2, 1-3, 2-3, 2-1, 3-1, 3-2. On a bipolar transistor 4 of the six readings should indicate open, two should indicate about .7 volts. Again, other components may interfere, unsolder the transistor and repeat.
On a diode number the pins 1 and 2. Measure the resistance 1-2 and 2-1. It will usually indicate open in both directions. Switch to the diode test range and repeat. It should indicate open in one direction, about .7 volts in the other. (Schottky diodes will read lower).
PlainBill
I worked in the Computer branch in our company since 15 years and repair and maintain every equipment that we have here (hundreds of caps....) Before this time I worked in a Company that repaired Helicopter and I was the responsible person for repairing the Electronic Components.
Its a little time consuming and pretty dangerous with a 300+ volt mains.
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