Samsung plasma tv 50pn5oa450

[thuss]

Hi

I was wondering if someone has come across this problem before- its in regards to a DYP-50W3 psu out of a 50pn5oa450.

The power supply blew the 10amp fuse plus the rectifier - so I just changed those two components and installed the psu.

Then it blew the theristor (Highlighted in red next to the relays) and the bridge rectifier again.

There seems to be a short in the circuit with the mosfets highlighted in yellow(outside legs) on the circuit even once they are removed. (I tried to trace the print and it maybe designed that way)

One of the large filter caps is faulty as well)

Any advice would be appreciated. ( just realised I was in the wrong section)

Thanks in advance

[chrismurphy]

Re: Samsung plasma tv 50pn5oa450

Filter caps the large ones almost never go bad, how did you test?
The mosfets need checking and replacing if faulty ,don't look for shorts at the mosfets points on the board as there are usually transformer winding's that will confuse
You should have no shorts across the filter caps when you have replaced the mosfets
.

[happyade123]

Re: Samsung plasma tv 50pn5oa450

Have you tried testing the power supply on it's own using a lightbulb in series with the fuse holder. (with the fuse removed). I had a similar incident occur with a board I was working on found that the first 4 of the diodes pictured were shorted ( the ones starting below the relay as well as the one facing towards them. and blew the two thyristors. The lightbulb will save anything else blowing up if there are still any shorts present. I would think if the thyristore is blown something further back from the Bridge rectifier will be faulty. Ie the diodes I have mentioned.

[Jodeanss]

Re: Samsung plasma tv 50pn5oa450

first post

[Jodeanss]

Re: Samsung plasma tv 50pn5oa450

samsung power supplies are cheap, did you search for a used one? usually 25-30 bucks

[thuss]

Re: Samsung plasma tv 50pn5oa450

Thanks for the responses -I removed the filter caps completely from the circuit and with my fluke meter (has the function to read capicator values) I read the micro farad readings. One is reading within 10% whilst the other one is in the 10 range.

Ive checked all the diodes they are fine. Mosfets seem fine. Cheapest psu Ive seen is 45 pounds is that about 60 dollars.

[R_J]

Re: Samsung plasma tv 50pn5oa450

The reason the thermistor blows is due to bad relay contacts on RL801s, if the fuse blows as soon as it is pluged in check ve801s and ve803s, they could be shorted, Inspect them for any small cracks, if they are cracked they are bad.

"There seems to be a short in the circuit with the mosfets highlighted in yellow(outside legs) on the circuit even once they are removed"

what are the location numbers of the parts you measure the short? if you measure across the outside legs of dp802, you will measure a short, (you are measuring across lp802s & lp801s windings)
You should not measure a short between the legs of QP802 or QP801, if you do measure a short with the parts removed, then remove BP802s Bridge rectifier and check again. if there is still a short, check CP801

[thuss]

Re: Samsung plasma tv 50pn5oa450

I checked ve801s and 802s they seem fine no cracks.

dp802 is fine.


qs801 and 802 are highlighted in the yellow square box

If I just concentrate on qs801 the outside legs read short - once removed the outside leg holes still read short (qp801 reads fine out side circuit). (As does qs802- theres only one bridge rectifier on this board and I have removed it with the same result)

[R_J]

Re: Samsung plasma tv 50pn5oa450

Are you sure it measures a short or is it more like 10 ohms, the outside legs are Gate & Source, the source is connected to seondary winding of TS802s and then via rs812(10Ω)/DS803 to the gate.

If you removed BP802s (bridge rectifier) and it still blows the fuse, there are only a couple components that are across the line that can do that, VE801s VE803s ( I suggest removing them temporary) ce801s, ce802s, CE806s & CE907s capacitors

I suspect ve801 or ve803, did you measure their resistance?

[thuss]

Re: Samsung plasma tv 50pn5oa450

when I mean a short - I put the meter in continuity? The outer legs on both qs801 and 802 circuit board holes are beeping whilst they are removed.

Ive checked ve801s,ve803s and both read OL and only give me a reading in ohms n s scale.
As do ce801s ce802s ce806s ce806s and ce807s.

I think its time for a new board. Maybe my understanding of a short is wrong........but anyway thanks for your help.

[R_J]

Re: Samsung plasma tv 50pn5oa450

ignore the beep, you need to measure resistance in ohms,
In post #8 you said "theres only one bridge rectifier on this board and I have removed it with the same result"
What do you mean by the same result? do you mean the fuse still blows?

in post #1 you said " Then it blew the theristor (Highlighted in red next to the relays) and the bridge rectifier again."
did you replace those parts with the same part numbers?

[thuss]

Re: Samsung plasma tv 50pn5oa450

post #8 same result -I meant that the outer legs on the circuit board with mosfets removed are is still beeping.

post #1 yes I replaced them with the same part number.

I get 11 ohms when I measure the circuit (the outer holes of the mosfets)