Samsung D580 LCD TV - No Power

[budm]

Re: Samsung D580 LCD TV - No Power

330v dc between main caps (probe on each leg)

OK, you do have main DC for the SMPS power supplies to run, so now we have look at the STBY SMPS section next to see if that section is getting the DCV to run that section, there may be fusible resistor for feed the DCV to that section.

[mikay786]

Re: Samsung D580 LCD TV - No Power

which section is that, by the sc-03b transformer?

[mikay786]

Re: Samsung D580 LCD TV - No Power

ok that 2nd fuse might be bad, taken it out and not getting any continuity. The main near the main caps

[Moreno83]

Re: Samsung D580 LCD TV - No Power

You didnt check all the fuses?

Replace it and see what happens!

[mikay786]

Re: Samsung D580 LCD TV - No Power

it blew up lol

I might have done something stupid, was a ceramic 3.15a time delay fuse. I only had T8a ceramic fuses. so tried it with that and looks like something has blown scaring the day lights out of me!!

transistor below the ac power in

Might just order a replacement power supply, only £25?

[mikay786]

Re: Samsung D580 LCD TV - No Power

5n52u

[Moreno83]

Re: Samsung D580 LCD TV - No Power

Aah that looks bad! Yes get a replacement and see if it works or not. Im almost certain that the ps is bad.

Let us know if it works.

[Moreno83]

Re: Samsung D580 LCD TV - No Power

Happened to me once! Replaced alot of caps and 1 cap i placed the wrong way.....

Turned on tv and BAMMM , damn.....

[mikay786]

Re: Samsung D580 LCD TV - No Power

taken out two of them, and charred the connector going to the light board

[mikay786]

Re: Samsung D580 LCD TV - No Power

do you think it would have worked if I had put in he right amp fuse? or possibly a fault elsewhere too.

I'm guessing fuse let too much current flow which blew the two mofsets?

[Moreno83]

Re: Samsung D580 LCD TV - No Power

Could have worked , maybe the fuse was bad. You used the wrong fuse with the result that TO much current in very short time traveled though the board and it blew up lol

So get a replacement board or those parts on the board with a new fuse. You dont have any spare ps? Like a scrap board? They often use the same fets

[budm]

Re: Samsung D580 LCD TV - No Power

You have blown up PFC Voltage booster power MOSFET. That MOSFET was OK before you replace the second fuse (FM801S) for the output of the boosted Voltage otherwise you would not have 170VDC on the main cap before.
So beside blown up MOSFET for the PFC, you more likely have shorted parts on the output side of the fuse.
Pictures provided by SHOPJIMMY.

[mikay786]

Re: Samsung D580 LCD TV - No Power

Fuse is there to prevent over voltage in case something is wrong, the fact that it sent too much power to blow up the mosfet means something was wrong with the board anyway? Because if I had the correct 3.15a fuse that would have blown again?

[budm]

Re: Samsung D580 LCD TV - No Power

"Fuse is there to prevent over voltage in case something is wrong,' For over current protection, not Voltage..
You have shorted load so it trying to draw too much CURRENT so the fuse blown.
You need to test the parts on the output side of the fuse to see any one of them show low resistance.
The LOAD dictates how much current it will draw from power supply, the power supply must have current supply capability to supply to the load as needed.

[mikay786]

Re: Samsung D580 LCD TV - No Power

I'm just going to order a replacement used part, as I think to repair this its going to cost quite a bit. £5 just for the 2x mosfets and anything else extra damaged. Plus the original problem.

Hope a new power supply does the job!

[mikay786]

Re: Samsung D580 LCD TV - No Power

Replacement board has fixed it, working a treat.

Gutted I blew up the old board, was probably an easy fix too!

[budm]

Re: Samsung D580 LCD TV - No Power

Thanks for the follow up on the repair.