Samsung PN59D550C1FXZA, X-sustain, shorted fets from bad panel?

[DXseekerMO]

Hello everyone, I hope you had a happy Thanksgiving! This TV comes from the free pile. It's a Samsung PN59D550C1FXZA. The complaint was the previous owner was watching TV, they heard a buzz/pop and lost video with audio present. After trying to re-boot the TV it appears to wake-up but isn't responding to the remote or key controls. No picture and no response to commands are confirmed.

The health light indicated a problem on the sustain boards with a very long on-time when flashing. The main cap voltage comes up when plugged in then immediately drops off, so do VS and VA. I Tested the Y-sustain for VS short to ground, none present then tested the X-sustain for same. VS is shorted to ground on the X-Sus board. When removing the X-Sus the screws were all loose, and after inspecting the ground pads and chassis contact points there is evidence of arcing. Both sustain boards have loose screws right along with the PSU.

The bank of FET's circled all indicate short and are right by the output header connectors to the X-buffer.

The conclusion I have drawn by this is the poor ground plane and evidence of arcing grounds on the X-Sus board is probably what popped the FET's.

The question I have, is there another possible explanation for the popped FET's, such as a short in the panel itself or maybe the lousy "D" series panel cracked and took them out?

Thanks everyone for your input!

[DXseekerMO]

Re: Samsung PN59D550C1FXZA, X-sustain, shorted fets from bad panel?

Bump

[DXseekerMO]

Re: Samsung PN59D550C1FXZA, X-sustain, shorted fets from bad panel?

bump

[DXseekerMO]

Re: Samsung PN59D550C1FXZA, X-sustain, shorted fets from bad panel?

bump

[DXseekerMO]

Re: Samsung PN59D550C1FXZA, X-sustain, shorted fets from bad panel?

Bump

[DXseekerMO]

Re: Samsung PN59D550C1FXZA, X-sustain, shorted fets from bad panel?

GUYS!!!!!

Can I get an answer here??

[DXseekerMO]

Re: Samsung PN59D550C1FXZA, X-sustain, shorted fets from bad panel?

Over 3 days in and no help?

Guess I'll just order the board and hope for the best.

I sure wish I knew why only a few of you help me anymore, or why no one wanted to help with this one at least. I thought we were here to LEARN??

Thread done.

[DXseekerMO]

Re: Samsung PN59D550C1FXZA, X-sustain, shorted fets from bad panel?

Thread done.....I lied!

I just removed the IGBT's of concern with the heat sinks, they all indicate direct short from collector to emitter and close to short from gate to emitter save for two. Fusible resistor R4004 is open.

After they were removed a short still exist on the board at U4004 which is part number FAN73611, a Step Down DC-DC converter, testing short across pins 1 and 8.

Pin number 1 of U4004 was de-soldered, isolated from board contact and re-checked. The short is on the board. The pinout for terminal 1 is supply voltage and pin 8 is the high side floating supply.

Bottom line, this last short eludes me. Can anyone help me find it?

https://cdn.badcaps-static.com/pdfs/...cc8b1d2bb1.pdf

[DXseekerMO]

Re: Samsung PN59D550C1FXZA, X-sustain, shorted fets from bad panel?

I have found that those two pins are apparently tied together on the back of the board. This explains the short I was seeing.

After considering the cost of parts, their locations and time to ship along with my time to fix the board I will be ahead to just buy a replacement board and stick it in there.

This thread is now done. I've been talking to myself here anyhow.

[DXseekerMO]

Re: Samsung PN59D550C1FXZA, X-sustain, shorted fets from bad panel?

X-Main board on the way. Yay

[DXseekerMO]

Re: Samsung PN59D550C1FXZA, X-sustain, shorted fets from bad panel?

So the X-main board arrived today. I installed it, hooked everything up, turned the TV on and the next thing I know I see a flash on the Y-main and hear a loud POP.

I thought "oh shart...the Y-main just took out my new X-main". I checked the VS line on the X-Main for short to ground (thinking it would be shorted) but thankfully it tested open line.

After inspection the cap circled in the picture below is what gave out, blown to smithereens. I checked the nearby components on the Y-main and none indicated short. Thinking it was just a crappy cap I swapped it out with one of the same spec from the old X-main BUT I proceeded carefully this time, leaving the X-Main unhooked from the Y main.

I plugged the TV in with the X-main disconnected, the relay on the PSU clicked and the Y-Main did not go pop, so I unplugged the TV, hooked the X-Main back up and plugged the TV back in. About a second after VS came up the Y-Main popped and there was another flash, but just behind the cap I replaced and under the heat sink. The cap I replaced appears to be OK if judged by appearance.

Thankfully VS is not shorted to ground on the X-Main after this, but I am concerned that something on the X-Main is causing a problem on the Y-Main since it popped again. On the other hand, what I saw EXACTLY matches the description of the person I got it from, a loud POP and no video.

What I really, really need here is direction, and I mean I really need help with this. Can anyone suggest what to check on these boards, or elsewhere to find out why the Y-Main popped the way it did?

[bman4]

Re: Samsung PN59D550C1FXZA, X-sustain, shorted fets from bad panel?

Something might be shorted on that cap circut. Check everything that corelates with those igbts and cap. Samsung like to put low voltage controller circuts on back . when blowing up a board there might be more dead parts. If it was one of those blue caps it might of just been faulty. Theses boards do look verry similar to mine and verry complicated compared to others

[DXseekerMO]

Re: Samsung PN59D550C1FXZA, X-sustain, shorted fets from bad panel?

Something might be shorted on that cap circut. Check everything that corelates with those igbts and cap. Samsung like to put low voltage controller circuts on back . when blowing up a board there might be more dead parts. If it was one of those blue caps it might of just been faulty. Theses boards do look verry similar to mine and verry complicated compared to others

Thanks for the reply! I had a look at the nearby components and didn't find anything obviously shorted with the meter. I put the TV back together due to space limitations and I have a power board coming tomorrow for a 48" TCL. As soon as I put it together I'll break the Sammy back out and get some real good pix up of that Y-Drive. I should have done it earlier but I was a little choice after the second POP.....and yes it was LOUD! Heck even my little Dog ran for cover! lol

Again I appreciate your reply. Any luck with your D6500 yet?

[bman4]

Re: Samsung PN59D550C1FXZA, X-sustain, shorted fets from bad panel?

No luck, i think it something more complicated than just a fauly nand chip.im gonna have to keep on testing and next is those blue caps! I

[DXseekerMO]

Re: Samsung PN59D550C1FXZA, X-sustain, shorted fets from bad panel?

Today I did some more work on this TV. I pulled the Y-sustain out and started checking components.

If you remember I replaced the X-Sustain board due to shorted IGBT's. I hooked everything up, turned the TV on and once VS came up there was a loud POP and a flash of light. One of the caps had blown, arrow on picture 3. I replaced that cap and tried again with another pop and flash of light. I'll continue that part below.

The only suspicious readings I saw in-circuit on the Y-Sustain were the three IGBT's under the heat sink, next to the same row of caps where that one popped. Once I got the IGBT's out of circuit they tested fine. None of the caps next to those IGBT's indicate short but only have about 723ohms of resistance across each of them in-circuit with those IGBT's removed. As I understand it there may be some continuity but it should be in the megaohms range across them, if any.

Under the heat sink next to that same row of caps are 4 SMD diodes. It was under this heat sink I saw the second flash of light. I tested these and found them to operate in one direction and in good range, about .420 I tested these by placing the red probe on each of the two legs of every diode and the black probe on the VS test point. Reverse the probe leads and they test open.

The only other suspect items I saw are some of the green resistors test in-circuit at about half the resistance of their specification. I believe this could be from other items in-circuit nearby or their placement in the circuit causing this?

So my question at the time is, does anyone find the 723ohms across those little blue caps suspect, or maybe I'm I getting that reading from other items nearby in-circuit?

Also if anyone has any further insight on this issue I'd appreciate the help.

[DXseekerMO]

Re: Samsung PN59D550C1FXZA, X-sustain, shorted fets from bad panel?

bump

[DXseekerMO]

Re: Samsung PN59D550C1FXZA, X-sustain, shorted fets from bad panel?

Bump

[drussell]

Re: Samsung PN59D550C1FXZA, X-sustain, shorted fets from bad panel?

I'm not sure what you're expecting people to be able to do for you...

Since you obviously have shorts and faulty components, you're on the right track by trying to find all the shorts and defective components but you can't tell much about many individual components while they're in-circuit without looking at the circuitry in question and understanding what the component is doing, what it is connected to.

Seeing actual flashes means you have one or more severe faults and probably multiple defective or blown components. You will have to test everything thoroughly individually before power-up or risk further destruction.

I would start by trying to figure out what could be going on with the area where your capacitor blew up. That should be virtually impossible unless it was installed backwards or got a voltage far in excess of the ratings. Something is seriously wrong there but you have not provided any measurements or good photos so it is impossible for anyone to give you any specific advice. Repeatedly bumping the topic is not going to remedy these shortcomings.

Edit: Sorry, had missed the photos on the more recent post, that does help a bit.

[llonen]

Re: Samsung PN59D550C1FXZA, X-sustain, shorted fets from bad panel?

Not sure what you are using to test the IGBT's but to test these effectively it may be necessary use a component analyser capable of driving them as a DVM in diode mode wont always catch a failing device. You might need to construct a test jig for this purpose and that not withstanding you may also need to review the source of the replacement semi conductors you are using.

[DXseekerMO]

Re: Samsung PN59D550C1FXZA, X-sustain, shorted fets from bad panel?

I'm not sure what you're expecting people to be able to do for you...

Since you obviously have shorts and faulty components, you're on the right track by trying to find all the shorts and defective components but you can't tell much about many individual components while they're in-circuit without looking at the circuitry in question and understanding what the component is doing, what it is connected to.

Seeing actual flashes means you have one or more severe faults and probably multiple defective or blown components. You will have to test everything thoroughly individually before power-up or risk further destruction.

I would start by trying to figure out what could be going on with the area where your capacitor blew up. That should be virtually impossible unless it was installed backwards or got a voltage far in excess of the ratings. Something is seriously wrong there but you have not provided any measurements or good photos so it is impossible for anyone to give you any specific advice. Repeatedly bumping the topic is not going to remedy these shortcomings.

Edit: Sorry, had missed the photos on the more recent post, that does help a bit.

Thanks for replying. I will re-think this whole thread and try to make improvements.

Not sure what you are using to test the IGBT's but to test these effectively it may be necessary use a component analyser capable of driving them as a DVM in diode mode wont always catch a failing device. You might need to construct a test jig for this purpose and that not withstanding you may also need to review the source of the replacement semi conductors you are using.

At this time I've installed no new components, other than the X main. The best I can see right now I find no direct shorts on the Y main. Then again I am only using a DVM.