Samsung FP-5084 Plasma tv Power supply issues

[jeffecor]

I picked up the TV today from a guy who say he replace a blown cap and first thing I did was check hes work. Well he solder the cap in backwards so I un-soldered it and put it in right.


When I plugged in the TV and it clicks about 5 times and it give up. So pulled the board again and check the fuses found a blown fuse. So replaced the fuse then one mosfet burn out on the board and one next to it was shorted. I order new mosfet's is there anything also i should replace?

[tom66]

Re: Samsung FP-5084 Plasma tv Power supply issues

What is the BN44- or LJ44- number printed on the power board?

[jeffecor]

Re: Samsung FP-5084 Plasma tv Power supply issues

Its a BN44 on the board.

[tom66]

Re: Samsung FP-5084 Plasma tv Power supply issues

BN44-012345A... I need the full number.

[jeffecor]

Re: Samsung FP-5084 Plasma tv Power supply issues

okay Its a Bn44-00175A


Thanks corey

[tom66]

Re: Samsung FP-5084 Plasma tv Power supply issues

Unfortunately I don't have a schematic in my library...

A picture of the underside of that area would be useful - I'd advise replacing the small SMD resistors and diodes, if present, around those devices. I'd also replace both devices at the same time.

[jeffecor]

Re: Samsung FP-5084 Plasma tv Power supply issues

There is anther number it's a longer one CN07BN44000175ADA90BB3166.


Thanks Tom66

[jeffecor]

Re: Samsung FP-5084 Plasma tv Power supply issues

Thats the only other picture I have on my phone. I well get more of the whole board if need.

[tom66]

Re: Samsung FP-5084 Plasma tv Power supply issues

I'd replace RX801,802,803,804,805,806 and DX801,802 (these will be 1N4148-type diodes, SMD package SOD323)

Check QX801,802 for shorts too.

[jeffecor]

Re: Samsung FP-5084 Plasma tv Power supply issues

The Qx802 was shorted out all sides and the Qx801 burn out when I replaced the fuse. They are a 11n60c3 mosfet.

[tom66]

Re: Samsung FP-5084 Plasma tv Power supply issues

Sorry, I mean the small little transistors just above the big ones - QX80#? Two of them, small devices, through hole, just above the transformer.

[jeffecor]

Re: Samsung FP-5084 Plasma tv Power supply issues

I well check them to night and place a order in to get all the parts I need.

Thanks tom

[jeffecor]

Re: Samsung FP-5084 Plasma tv Power supply issues

I checked the transistors no shorts and I unsoldered RX801,802,803,804,805,806 and DX801,802 they all tested in spec. So I soldered them back in the circuit.

[tom66]

Re: Samsung FP-5084 Plasma tv Power supply issues

Generally I replace them regardless - they can have unseen damage due to the failure mode.

When you replace the MOSFETs it's worth building a "lamp tester" before you power the set up, this will let you limit any potential fault current. Essentially you'd place a 100W or so filament/incandescent light bulb in place of the mains fuse.

http://www.antiqueradio.org/dimbulb.htm

In this case, I'd use it in place of the fuse that was blown as the rest of the PSU is probably working ok.

[jeffecor]

Re: Samsung FP-5084 Plasma tv Power supply issues

I know what you mean on replacing the parts. But if I did that with every tv I fixed. I would have a ton of money wrapped up in them. I have checked all other Mosfets last night they all check fine and most of the cap's too which I'm going to pull the all 1000uf 10v cap's or anything that has a 10v and step them up to 16v or 25v.

I'm starting to think that the one MOSFET shorted and cause the other one to over load then burn up since they are link together.


I can build a Lamp tester good Idea.:-) I'm pretty sure I have that stuff laying around the house.


Thanks Corey

[tom66]

Re: Samsung FP-5084 Plasma tv Power supply issues

Heh, surface mount resistors are so cheap. Like 10 cents for 10 of them. I don't see your point? I didn't mean to replace ALL the MOSFETs - just the opposite pair AND all the resistors/SMD diodes in the gate circuit. Wouldn't cost more than a dollar.

I would not bother upgrading the cap voltage rating - the originals were in spec - I would just replace them with like-for-like higher quality caps like Panasonic or Rubycon.

[jeffecor]

Re: Samsung FP-5084 Plasma tv Power supply issues

I need to get a Surface mount resistors kit not buy them one at a time the shipping alone its 3-7. I'm not really worried about the money I have a good job as a pc tech.
I'm slowly build spare parts up with out pissing the wife off. She all ready on me for having four 50 inchs plasma tv's, 42 HP plasma inch, 39 inch vizio and westinghouse 32 inch in the house. lol


Thanks Tom

[tom66]

Re: Samsung FP-5084 Plasma tv Power supply issues

Well, if you buy them from Digikey along with your MOSFET, you'll pay no extra shipping charge.

Digikey would be a few bucks for each MOSFET, then a few -CENTS- per resistor, and $2.50 shipping for the full order. Well worth it.

[jeffecor]

Re: Samsung FP-5084 Plasma tv Power supply issues

All ready order mosfet from mouser couple days ago. So I order http://www.ebay.com/itm/321482294384...%3AMEBIDX%3AIT order on the next row boat to the US.

[Shinju]

Re: Samsung FP-5084 Plasma tv Power supply issues

Just incase you see this issue after your power supply rebuild!

One thing you want to watch for on this unit is the 5v return from the mainboard. These mainboards also fail in a way that simulates a bad power board by clicking over and over as the PS is trying to send/receive the 5v from the mainboard.

Here is my thread, I thought mine was a power supply issue and replaced almost all the components that were showing signs of age and all the caps on the powersupply (minus the high voltage ones) I recommend doing that too as they are poor quality caps.

https://www.badcaps.net/forum/showthread.php?t=40326

Good luck! The 5084 is a fickle beast but when she is working its a great looking TV, I have had a couple of them!