TV Samsung LE32B450C4W bad PSU.

[HellasTechn]

Hello friends,

I am looking at this Samsung LE32B450C4W television that would blow the PSU main fuse when connected to MAINS.

I found the bridge rectifier Shorted and a blown mosfet (QP802s K10A60) i replaced both (actually the K10A60 with a K15A60) and the mainboard comes on. I hear the startup sound but the backlight does not come on at all, not even for a second.
A friend of mine tv lend me a PSU from the same tv model and so my samsung worked all right. So i know ccfl lamps are ok and that something else is wrong with my PSU. i have measured all capacitors and transistors (heat sink mounted) also i replaced the sem2006 but nothing changed.

Any advice ?

thank you so much !

 

[HellasTechn]

I have taken pictures and measurements.

Here is a table exactly as shown on the PCB but with the readings i got.

as far as i can tell DET_5V is wrong and i am not sure about I-PWM and E-PWM.

 

[73's de Edd]

'
Sir Constantine . . . . . . .


SOoooooooo hard to find newer sets schematics.
Any chance that your board has this 16 pin IC mounted on bottom, as I saw no LARGER one mounted on your top of units photos.

Give us its ID number as its the driver for your two PSC transistors that popped that generate your HV for the baclplane illumination.

Also, were any of the YELLOW marked in resistors ( 47 ohm surface mounts ?) smoked by voltage punch through to the gates, when the D-S shorts on those power FET pairs occurred ?

QUASI- SIMILAR SAMSUNG PCB :

( http://i.imgur.com/aprPeyf.png )

73's de Edd

 

[HellasTechn]

I think i got your point.

Here are two more pictures. I suspect a bad PCF chip also. (FAN 7530). I will go get a new one later today when shops are open.

samsung is also know to have issues with the power diodes.