Samsung HP-T5054 ysus and buffers

[capkid]

Re: Samsung HP-T5054 ysus and buffers

I use a heat gun and use Kapton tape to protect the surrounding components.

Yeah, I bought some Kapton tape after I'd destroyed a couple boards

[capkid]

Re: Samsung HP-T5054 ysus and buffers

They may have suffered secondary damage that is not obvious under the test current of your meter. But you may get away with replacing just one.

With regard to the meter possibly not revealing secondary damage to the transistors, are you saying that this type of damage would only be evident in a typical live circuit, or is it dependent on the quality of the meter? I typically use my Fluke 87 III to test.

[capkid]

Re: Samsung HP-T5054 ysus and buffers

To add: I found what appears to be the same damaged FETs as JeffJ - One K2837 FET, one 88N30W FET, and the burned B20NK50Z FET.

[tom66]

Re: Samsung HP-T5054 ysus and buffers

One user discovered their board tested OK, but that when they applied a voltage of 5V, it drew around 50mA; at 12V, it drew about 200mA, and it quickly got worse.

[capkid]

Re: Samsung HP-T5054 ysus and buffers

One user discovered their board tested OK, but that when they applied a voltage of 5V, it drew around 50mA; at 12V, it drew about 200mA, and it quickly got worse.

So, is this why you're advocating replacing all five FETs in the bank of FETs on the heat sink? Has this proven to resolve the issue? The second T5054 I picked up a couple days ago appears to be exhibiting the same FET failures as the first one I picked up.

[tom66]

Re: Samsung HP-T5054 ysus and buffers

Usually I'd replace all FETs in a bank where one failed. If they're in parallel damage could have been done to the others. FETs are cheap, buffers are not.

[capkid]

Re: Samsung HP-T5054 ysus and buffers

Usually I'd replace all FETs in a bank where one failed. If they're in parallel damage could have been done to the others. FETs are cheap, buffers are not.

Ok. Really, I guess I'm just being cheap myself, and I know better . I'm going to go ahead and replace all of them.

[tom66]

Re: Samsung HP-T5054 ysus and buffers

Also if the FETs are used for the sustain portion (positive and ground), I'd replace both upper and lower FETs. If they are for ERC (energy recovery) or Yrr/Yfr I wouldn't usually do so.

[capkid]

Re: Samsung HP-T5054 ysus and buffers

Also if the FETs are used for the sustain portion (positive and ground), I'd replace both upper and lower FETs. If they are for ERC (energy recovery) or Yrr/Yfr I wouldn't usually do so.

Good info. Thanks. It also looks like a couple resistors next to the FET on one of the two Y-Sus boards I'm repairing are damaged (the board with the fried B20NK50Z FET). This is turning out to be a more extensive repair than I expected.

Also if the FETs are used for the sustain portion (positive and ground), I'd replace both upper and lower FETs. If they are for ERC (energy recovery) or Yrr/Yfr I wouldn't usually do so.

Good info. Thanks. It also looks like a couple resistors next to the FET on one of the two Y-Sus boards I'm repairing are damaged (the board with the fried B20NK50Z FET). This is turning out to be a more extensive repair than I expected.

How do I find the wattage of the surface mount resistors? Is there a standard wattage that's used with these TVs? I don't have a service manual with a parts list.

[capkid]

Re: Samsung HP-T5054 ysus and buffers

I wish there were a way to edit an older post (unless I'm just unaware of how to do so). Anyway, it looks like the resistors are fine. Once I removed the damaged B20NK50Z FET, I was able to get more accurate resistor readings. How does this pad look from the front side of the board? The gate and source pads are fine.

[tom66]

Re: Samsung HP-T5054 ysus and buffers

Looks OK, clean it with some flux before soldering though.

[capkid]

Re: Samsung HP-T5054 ysus and buffers

Looks OK, clean it with some flux before soldering though.

The more I examined it, the portion in the middle of the pad is burned through a good deal of the PCB. I scraped some of it away, but I didn't want to go too deep. I'm a little concerned about a burning odor being given off when the TV is operational. I did solder on a new mosfet after cleaning the pad with alcohol, but I can redo it if necessary.

I saw this PCB repair procedure online, but I'm not sure I need to go this extreme: http://electriciantraining.tpub.com/.../14186_128.htm

[tom66]

Re: Samsung HP-T5054 ysus and buffers

It's only going to burn if it's got a fuel source. If that is just contamination it'll just make the MOSFET run hotter.

[capkid]

Re: Samsung HP-T5054 ysus and buffers

It's only going to burn if it's got a fuel source. If that is just contamination it'll just make the MOSFET run hotter.

Ok. I'll just leave it as-is for now and see how it performs. Would a small heat sink help? I'm not sure I can find one that small or if it would make that much of a difference.

[tom66]

Re: Samsung HP-T5054 ysus and buffers

Probably not going to work that well... then again I have seen Panasonic do it on their new thin plasmas (1" thin, all SMD) so maybe it could work.

[tocold4u2]

Re: Samsung HP-T5054 ysus and buffers

most of them 5054 tv s that your gona pick up will have the upper buffer board bad and the y main or the power supply board bad,,,atleast 4 out of the 5 i have have upper buffer boards bad!!

[capkid]

Re: Samsung HP-T5054 ysus and buffers

most of them 5054 tv s that your gona pick up will have the upper buffer board bad and the y main or the power supply board bad,,,atleast 4 out of the 5 i have have upper buffer boards bad!!

Changing those ICs isn't fun, either. The good thing is that the last T5054 I picked up came with a set of working buffer boards and an extra working lower buffer board. The previous owner kept saying, "I read online that the Y-Sustain board goes bad, so I changed BOTH of them. The TV's still not working." LOL

[tocold4u2]

Re: Samsung HP-T5054 ysus and buffers

vent tried to change the icu s yet i want to get a hot air station,, and try to change them,,that would be the cheapest route,,or get someone on here to do it 4 me.thats prob gona be my next thing i'm going to order is a hot air station,,but not sure what kind yet,,been looking at xtronic and 2 other kind.

[capkid]

Re: Samsung HP-T5054 ysus and buffers

I found this blog post by Coppell TV Repair - I'm figuring it's been brought up previously, but I didn't search the forum. He mentions that early Samsung plasma TVs usually have the buffer(s) fail, which also causes the Y-Sus to fail: http://blog.coppelltvrepair.com/2011...d-buffers.html

Was there a known design change that caused the opposite to happen? I'm a bit reluctant to fix and resell one of my HP-T5054s without changing out all buffer chips or the boards themselves. I know it can be an expensive proposition. I saw what appeared to be a Philips I'd sold on CL a couple months ago that failed recently and was being sold for parts. I had the Y-Sus done by Coppell, but a replacement buffer board came from a parts TV I had.

Edit: Better link: http://blog.coppelltvrepair.com/2012...d-with-no.html

[capkid]

Re: Samsung HP-T5054 ysus and buffers

I attached a heat sink to the mosfet using some compound and Momentive RTV. I'm letting the RTV cure overnight. I also used some 2000-grit sandpaper to gently clean up the burn marks on the PCB. I scraped away as much of the burned PCB underneath the mosfet as I could without making a hole through the board. Thoughts?

vent tried to change the icu s yet i want to get a hot air station,, and try to change them,,that would be the cheapest route,,or get someone on here to do it 4 me.thats prob gona be my next thing i'm going to order is a hot air station,,but not sure what kind yet,,been looking at xtronic and 2 other kind.

I'm actually getting pretty good at changing the chips. I also just bought a microscope so I can closely inspect my work.