High Voltage/Power Supply Issues: Dead Set - No Power at all

There are two basic ‘dead set’ faults. One is no power at all to the set, the red standby light on the back of the projector is completely off and there are no processor lights on on the controller board. This is due to a bad AC input board, or the standby power supply has gone dead, or in rare cases, there’s a short in the set that is shutting down the standby power supply.

The easy fix is a blown fuse on the AC input board. There are two fuses located on the AC input board. If the fuses are original Barcos, they are sand filled, and a meter must be used to measure if the fuses are intact or not. In fact, it’s a good idea to test the fuses for continuity anyways as fuses like this can blow right at the end caps, and it looks like the fuse is OK, yet it has no continuity.

Once in a while one of the fuse holders on the AC input board goes bad and there’s a poor contact made between the fuse and the fuse holder. Usually the fuse holder at one end will become discolored, indicating the bad fuse holder.

There is a main fuse on the SMPS as well. Usually if this fuse is blown, there’s some other kind of problem on the SMPS, but there’s no harm in trying a new fuse (3 amp). If the new fuse blows instantly, there’s no point to installing a second fuse, pull the power supply and send it in for repair.

The standby power supply that powers the controller module and the IR sensors for the remote control is located on the daughter board of the SMPS. There’s a 125mA fuse on this board, and again, it’s a good idea to measure this with a continuity tester to confirm it’s bad. These fuses are hard to find, and will not be stocked at Radio Shack. If the fuse blows a second time, again that indicates problems in the SMPS somewhere.

The standby power supply feeds the IR sensor at the back of the set, the one on the front on the convergence board, the wired keypad, and the controller board. If all fuses check OK but the rear red LED is off, it’s rare but possible that either IR or the controller board has developed a short, thus shorting out the power supply. Try pulling out the convergence board and see if the set will power back up. If not, try pulling the rear IR sensor plug from the motherboard and see if the set powers up. Similarly, disconnect the wired keypad and see if the set will power up with the wireless remote.

If none of these steps cause the rear red LED to light up when the set is off, then it’s safe to assume that the SMPS is bad.

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