Samsung LN32B360 No Power....Diodes ok

[awoods8221]

Bought the LN32B360 about two years ago and now the TV will not turn on (NO Red light indicator). Alot of places are out of stock on the BN44-00289B board and I cant bring my self to spend 100-150 bucks for one.

I saw some threads that it might be the diodes on the BN44-00289B board but I checked those and they were fine. Found the FM802S (2A fuse) was blown. Replaced the fuse with a fast acting 250V/2A fuse from radio shack and it pops as soon I put power to the tv. Attached schematic and highlighted the fuse. Any ideas on what is causing the fuse to pop and if there are specific components i should be checking? THANKS

[budm]

Re: Samsung LN32B360 No Power....Diodes ok

Please check the resistance on the parts as shown. I will assume that you already check the Diodes and MOSFET in the circuits before the fuse already.

[multimeter]

Re: Samsung LN32B360 No Power....Diodes ok

Bought the LN32B360 about two years ago and now the TV will not turn on (NO Red light indicator). Alot of places are out of stock on the BN44-00289B board and I cant bring my self to spend 100-150 bucks for one.

I saw some threads that it might be the diodes on the BN44-00289B board but I checked those and they were fine. Found the FM802S (2A fuse) was blown. Replaced the fuse with a fast acting 250V/2A fuse from radio shack and it pops as soon I put power to the tv. Attached schematic and highlighted the fuse. Any ideas on what is causing the fuse to pop and if there are specific components i should be checking? THANKS

check the bridge rectifier,then main filter cap,then the output mosfets,these all blow the main fuse when faulty

[multimeter]

Re: Samsung LN32B360 No Power....Diodes ok

also the fuse needs to be a anti-surge type (t) even if the psu was ok ,with a fast acting fuse it might still blow ,it wont handle the surge current

[budm]

Re: Samsung LN32B360 No Power....Diodes ok

I think the main fuse did not blow but the secondary fuse did blow.

[awoods8221]

Re: Samsung LN32B360 No Power....Diodes ok

budm....it is the secondary fuse. Did that first intial check without the 2A fuse and got 0.6 ohms. But while looking over the schematic i missed DP802 and wasnt sure how to check the mosfets with a multi meter. Either way the DP802 chip/diode (higlighted in schematic) is reading 25 ohms either way. Could this be my problem? If not is there an easy way to check the mosfets???

Thanks Guys for the quick responses!!

[multimeter]

Re: Samsung LN32B360 No Power....Diodes ok

i may be wrong,but i think that is a shottky diode,that reading seems ok,they should have 2 readings but not shorted readings,sorry bout the fuse !,long day ,main fuse is a 5 amp anti-surge yes?

[budm]

Re: Samsung LN32B360 No Power....Diodes ok

Since you read 0.6 Ohms after the fuse circuits, then the problem will not be in the PFC MOSFET DP802, more likely to be the two MOSFET's on the second page. IF you assign the 3 pins of the MOSFET with 1, 2, and 3. The all you hav eto do is to measure resistance between 1 &2, 1&3, 2&3. You should set the meter to 200 Ohm scale. Report back what you read since you mayhave to remove them.

[awoods8221]

Re: Samsung LN32B360 No Power....Diodes ok

Got the following readings:
QI820 1-2 = 0.6ohms, 1-3 = 0.5ohms, 2-3 = 0.2ohms
QI821 1-2 = 113ohms, 1-3 = 0.2 ohms, 2-3 = 100ohms

[retiredcaps]

Re: Samsung LN32B360 No Power....Diodes ok

Got the following readings:
QI820 1-2 = 0.6ohms, 1-3 = 0.5ohms, 2-3 = 0.2ohms
QI821 1-2 = 113ohms, 1-3 = 0.2 ohms, 2-3 = 100ohms

QI820 is shorted. Desolder and verify the readings out of circuit.

QI821 looks like it may be shorted. Desolder and verify as well.

[awoods8221]

Re: Samsung LN32B360 No Power....Diodes ok

Will do.....i got to borrow my buddies soldering iron but will get back to ya

[budm]

Re: Samsung LN32B360 No Power....Diodes ok

Since the MOSFET is shorted badly, you need to check the resistance on the output pins of the IC that drives the MOSFET including the components (Diodes, resistors) that are connected to the Gates of the MOSFET otherwise you end up blowing the new MOSFET's.