Samsung PN50A650T1FXZC 50 inch - No Power

[smartjohn]

My latest Craigslist project is a Samsung PN50A650T1FXZC plasma 50 inch TV. The owner got as far as identifying the power board, BN44-0222A as the culprit but finally got tired of the thing in his garage! If you live in a cold climate, fall is a good time to haul away some great deals.

I was told the set was working fine until one night they heard a “pop” and everything shut down. On checking the board, the first thing I found was a green blown apart RTE-802. I found FishFind's thread for the same PS board when I did a search for RTE-802 https://www.badcaps.net/forum/showth...hlight=samsung.
There are two of these green inrush current limiting NTC thermistors side by on the lower left side of the board. From that thread I leaned about the cold solder joint on the relay and sure enough the lower pin on RLYE-801 was nearly hanging free!

Part # for these ICL thermistors is SCK0512, 5ohm, 12 amp rating. I found a cross over at digi-key with Amtherm part # SL22 5R012 for a buck 92 each.

[smartjohn]

Re: Samsung PN50A650T1FXZC 50 inch - No Power

I replaced both thermistors, repaired the damaged traces on the board and fired it up but no action, nothing. I found that the 12A 5mmX20mm fuse (just above the power input connector) was popped and replaced it. Fired it up again and blew the new 12A fuse right off the bat! Thermistors appear to be OK. I am now suspecting some bad active components, MOSFETS, Diodes, etc.....

[tom66]

Re: Samsung PN50A650T1FXZC 50 inch - No Power

Check the bridge rectifiers on the heatsink.

[smartjohn]

Re: Samsung PN50A650T1FXZC 50 inch - No Power

Thanks, Tom and a good call. I checked those pretty early and forgot to mention they were OK. I next went to the IGBT's on the heat sink just next to the relays and ICL's (photo & arrows), and bingo! They both checked shorted, in circuit. I pulled them out and were still reading bad. These are likely used in the inverter section.

So I ran the numbers, 20N60C3 is a 45A, 600V IGBT but is hard to find stock in the US as it's listed by most as obsolete. They are still available from China on ebay, for about $4.00ea US, but I didn't want to wait a week!!

I crossed it to an IRC part IRG4PC40UPBF which was very close (40A, 600V) and was in stock at Digi-Key, and i had them in 2 days. One issue, the lead length was shorter on the IRC part so I had to extend the leads to use the same screw hole in the heat sink.

Popped these in a replaced the fuse with a correct 5x20MM 12A 250V. and fired it up.

Success !! Apparently the constant on/off cycling when the cold solder joint no longer allows the bypass circuit to work, must stress the IGBT to fail? Not sure how but they were both toast. Anyhow, I now have a $68 50inch Plasma !!

Hope this helps some others who may have this same PS board.

[capkid]

Re: Samsung PN50A650T1FXZC 50 inch - No Power

Good work on the fix.

[falcons7]

Re: Samsung PN50A650T1FXZC 50 inch - No Power

When you repaired the trace, did you extend the trail as I've attached?

I don't have the schematic for this part and have the exact same issue as you.

[tom66]

Re: Samsung PN50A650T1FXZC 50 inch - No Power

What's BN## or LJ## number - might be able to get you a schematic.

[falcons7]

Re: Samsung PN50A650T1FXZC 50 inch - No Power

bn44-0222a

[falcons7]

Re: Samsung PN50A650T1FXZC 50 inch - No Power

What's BN## or LJ## number - might be able to get you a schematic.

bn44-00222a

[tom66]

Re: Samsung PN50A650T1FXZC 50 inch - No Power

Wish I could help but I don't have that schematic, sorry.

[elgordo]

Re: Samsung PN50A650T1FXZC 50 inch - No Power

Thanks for this post, the power supply on my PN50A550S1FXZA failed exactly as shown here (down to the cold soldered relay) so I was able to repair it with the equivalent parts listed. I asked a technician from work to help me with the soldering and he used the legs of the thermistors to repair the traces which worked great. Also, the legs of the new IGTBs were too short so we used the legs of the old ones to extend the new ones. The repairs worked on the first try and cost me $20 in parts and a lunch for the tech that helped me. Thanks!

[Logsdon326]

Re: Samsung PN50A650T1FXZC 50 inch - No Power

I hate bringing a old thread back to life but I'm having this same problem does anyone have pics of how they fixed the traces? It would be greatly appreciated

[tom66]

Re: Samsung PN50A650T1FXZC 50 inch - No Power

If you have a picture of the damage it may be possible to trace out the tracks.

[netspace]

Re: Samsung PN50A650T1FXZC 50 inch - No Power

Hello!
I decided to continue this thread since the issue is identical to last post.
BN44-00222A board with burnt RTE 801 and 802 and poorly soldered
RLYE 801 and 802. The board was burnt so much that it lost traces.
My question is where to put new RTE 801 and 802 and use some JPs perhaps with insulation on them and connect to existing board traces.
Also, first I have to solder relays properly to a board. Before drilling new holes maybe it is worth to simulate use of new RTE 801 and 802 away from a board and see if the whole set would work. I attach some pictures to let you see the damage done by high temperature.
Thanks for a suggestions how to fix it and what/where parts to buy .

ps I noticed that pictures open faster in new tab and are bigger

ps2 I found a website with tons of schematics - perhaps it will be useful for you http://www.electronica-pt.com/esquema/

[tom66]

Re: Samsung PN50A650T1FXZC 50 inch - No Power

You will have to remove all of the carbonisation by means of isopropyl alcohol or similar solvent (avoid acetone as it removes PCB silkscreen.)
Then you will need to trace where the connections go. Looking at PCB images on websites such as ShopJimmy may help.

Both thermistors will either be in series or parallel. One relay will switch the input to them on, and another relay will put a short circuit across them once the TV is powered up.

The problem with these boards is one relay get cold solder joints, and so the whole operating current passes through the inrush limiting thermistors. Ergo, they get really, really hot and do this damage. It's alarming to me that the thermistors don't fail open circuit until really late on. I'm guessing the TV worked OK just before it stopped working.

[netspace]

Re: Samsung PN50A650T1FXZC 50 inch - No Power

thank you tom66 for a quick response. Do you know the value of these two relays and limiters if I have to buy them?

[fcisolutions]

Re: Samsung PN50A650T1FXZC 50 inch - No Power

from smartjohn above:
"Part # for these ICL thermistors is SCK0512, 5ohm, 12 amp rating. I found a cross over at digi-key with Amtherm part # SL22 5R012 for a buck 92 each.:"

Relays p/n
SDT-S-105DMR

[JazzyQ]

Re: Samsung PN50A650T1FXZC 50 inch - No Power

Need your help geniuses.....can't believe there is a thread for the specific second (prolly fourth) hand tv I got.........don't have the remote, although my Telus guy hooked it up for power on....I can't change the source on their remote and don't have the original remote......Can I change the source from the tv manually?

[erikinsac]

Re: Samsung PN50A650T1FXZC 50 inch - No Power

Mine blew in the same way today, just wanted to say thank you for the thermmistor part numbers. Gonna tackle this tomorrow