OK here is the problem when the unit won’t power up but the standby light goes off:
The power supply board has failed.
The good news is that it's not difficult to repair, however, the problems were a bit difficult to locate without a schematic.
I was not able to find a schematic anywhere, but I design power supplies for a living, so I was able to work through it.
One note of caution.
DO NOT ATTEMPT TO REPAIR THE POWER SUPPLY UNLESS YOU ARE QUALIFIED.
When the power cord is plugged in, lethal voltages are present, even when the unit is turned off.
ALWAYS UNPLUG THE UNIT BEFRE ATTEMPTING ANY KIND OF SERVICE.
Now, on to the problems and solutions.
PROBLEM #1.
Remove the power supply board from the unit by the 6 mounting screws.
Flip the board over and in the back towards where the connectors are mounted, you will see 3 SMT transistors in SOT-23 packages.
Q1, Q2 and Q3.
Q3 is blown and must be replaced.
The original part # used is unknown, however, I was able to figure out by the surrounding circuitry that it is a P Channel MOSFET.
I replaced it with a Si2301CDS (
http://www.vishay.com/docs/68741/si2301cd.pdf) because I had quite a few and the specifications are adequate.
You can get these from Digikey for about 50 cents.
PROBLEM #2.
There are 3 electrolytic capacitors on the power supply board that need to be replaced.
SC13, SC15 and SC18.
SC13 and SC15 are the same (1000uF @16VDC) and SC18 is 1uf @ 50VDC.
Note:
USE HIGH QUALITY aluminum electrolytic specifically designed for high temperature and high ripple in switching power supplies.
Using poor quality capacitors will cause the unit to fail again.
Here is what I recommend and they are inexpensive from Digikey.
For SC 13 and SC 15 use Panasonic EEU-FC1C102S ($1.03) and for SC18 use Panasonic EEU-FC1H1R0 (27 cents).
This should bring the unit back to life.
Remember to install the new capacitors with the polarity marking(s) in the correct position on the board, otherwise they will explode and you are back to square one.
And most importantly, be careful when working around high voltage.
If in doubt, allow a qualified person to make the repairs. It's not worth the risk of getting hurt or killed.
Good luck and take care.
