Originally Posted by Low Tech
Ok, I had been testing my power supply mod to fix random power up issues. Parts list at the end.
I had noticed at times my DLP had powered on and off or just had the light flash without producing any picture or startup sound.
As of late I found that the power supply's heating up issue was because of the 12V 2.5A output was being consumed to the point of not keeping up with demand once fully warmed up.
The culperate can be easily found on the bottem side of the Main Board. If know how to solder components, the fix is about $30.00 for all the parts to repair your power supply and faulty main board components.
That is less than the cost of replacing both at over $325.00.
Samsung had used low cost filtering capacitors in the powersupply and revised a critical component change to the power supply in various areas.
What happens is a snow ball effect, filtering capacitor fail, causing higher spikes to hit and weaken the Metal Oxide Varistor at the end of the filtering stage.
The only way to know is to sniff for a slight oder of ozone or BBQ affect when the power supply has warmed up. Once you deturmine there is some oder. Power off and wait a few minutes before removing the power supply. The retangle box things are the poly film capacitors. They are along side the toroid (doughnut shaped) filters. Remove each one and look on the bottem ends for discoloration. Not all will be discolored but might as well be replaced as they have been stressed.
Once the Metal Oxide Varistor becomes too weak to filter, voltage spikes will be introduced into the output stage randomly.
Because of a design change to put the MOV (Metal Oxide Varistor) at the end not the begining near the fuse, and not to follow Fairchilds design guidelines in using proper filtering capacitors for the FSCQ0765RT TV switch to power the DC switched power to the main components.
As for the Main Board, this part is speculation about the parts used in the main board, but has truth to more low quailty parts.
There are two 470 Ohm 1/3w chip resistors powering a LM317 1A adjustable voltage regulator that is to deliver 6.3v to the main controller chip of the Main Board.
Mine were fried because of the voltage spikes, as they were used as surge protection. They were to fail like a fuse, but actually started to short out below the 150 ohm range. Thus over driving the curent capabilities of the 1A LM317 and making it unstable. Mine seemed to become damaged as once it heated up it ran into thermal breakdown causing more and more current to be consumed, and the 12v voltage from the power supply would drop. Because of the higher amount of current the power supply would heat up beyond its normal running temprature.
It was easy to spot without any tools, as it discolored the circuit traces at the resistors and made a blue tent, almost like someone marked the components for QC check.
Ok here is what I accumulated for replacement to keep things tip top. Just because one component will fail, it is best to replace everything associated with the failed components function that could become stressed.
1x MM3Z8V2B - 200ma 8.2v Zener chip diode, location DZ209
1x LM317EMP - 1A adjustable regulator, location IC204
2x ERJ-P08J471V - 470 Ohm 1/3w anti-surge chip resistor, location R232 and R233
1x B32620J681J - 680pf film capacitor for PS, never was installed, location C8110, between main transformer and black heat sink.
3x B32620J471J - 470pf flim capacitor for PS, never was installed, location CS811, C823 & C827, all next to the rear heat sink back side.
2x V250LA40AP - 250 VAC / 330 VDC 6.5 KA MOV for PS and SPS, location GT802
4x V275LA20CP - 275VAC 5KA @ 473VAC 145J MOV, 1 @ location VX8015 and 3 optional for AC power receptical mod.
2x R46KI368000P0K - 0.68uf 275VAC Poly Film Capacitor, location CX8035 & CX8015
1x PHE840MD6680KD18R06L2 - 0.68uf 275VAC Poly Film Capacitor, location CX8025