Samsung plasma ps-42p2st-i

[STUARTY]

POWER SUPPLY DEAD FUSES INTACT CAPS LOOK OK BUT MAYBE NOT ANYONE ANY IDEAS

 

[duffy]

Trace the line voltage in as far as you can. Past the fuses there will be some filtering (MOV, couple of small caps, common mode coil), a thermistor (current limiter), and then a bridge. After the bridge it's DC. You should see a few hundred volts or so on big electrolytic filter caps in this part of the circuit. This will go to a MOSFET screwed to a heatsink, often the source of the trouble, they can fail open or short.

 

[electronicsfreak]

Could we possibly get a tad bit more information on this? When you say dead, what are the power supplies' symptoms? are you getting anything at all from any of the switching supplies' various outputs?

 

[STUARTY]

Not got circuit diagram,but i will have a look later today ,check if volages marked on board,thanks both of you for help so far

 

[STUARTY]

had a check at the set today,ac present,dc out of bridge there but going amiss into q65 transistor couple of wirewound resisistors there,any help with diagram or advice,cheers STUARTY

 

[duffy]

Do you not see the voltage at the transistor? This is actually a good sign, could be a simple-stupid break somewhere. Find out where that high voltage stops. Take a close look at the pins of the high-frequency power transformer the transistor is connected to, check the solder junctions, might be a broken pin or pad there.