Power Supply Failed - Samsung Plasma PS-42Q96HD (BN44-00162A, PSPF531801A, W2A)

[nogger]

Re: Power Supply Failed - Samsung Plasma PS-42Q96HD (BN44-00162A, PSPF531801A, W2A)

Hey that's excellent news.

You were very lucky to be honest as dry joints on those pins like you had usually result in destruction of the Mosfet transistor . I guess the pin that wasn't really connecting was the GATE pin & therefore the Mosfet was not trying to switch on.If it had been teh high voltage Drain/Source pins it would have gone for sure.

[tom66]

Re: Power Supply Failed - Samsung Plasma PS-42Q96HD (BN44-00162A, PSPF531801A, W2A)

Actually it would usually be the reverse, if the gate were lose, the pin is floating and the device is randomly conducting, often partially, which can be destructive. A drain open would cause no harm, source open could cause no harm too.

[nogger]

Re: Power Supply Failed - Samsung Plasma PS-42Q96HD (BN44-00162A, PSPF531801A, W2A)

On reflection probably correct Tom, i think it's the constant make/break of the solder joint that causes the FET to blow. Either way, he was lucky !

[Jidis]

Re: Power Supply Failed - Samsung Plasma PS-42Q96HD (BN44-00162A, PSPF531801A, W2A)

Glad to see Dailafing's is back up so easily.

Don't mean to change the subject, but Tom, if you or Nogger might happen to know anything about the BN44-00356B power board from this, I'd be interested. I've got an "A" version coming as a replacement, but it might be fun to poke around at the other if there's anything specific to look for. I skimmed over it with a magnifier when I started, but the joints all looked decent.

Thanks!

George

[nogger]

Re: Power Supply Failed - Samsung Plasma PS-42Q96HD (BN44-00162A, PSPF531801A, W2A)

Jidis, not sure if i missed something when i trawled through that posting you provided the link for but you seemed to jump straight from having a dead clicking set to assuming it was an LED backlight fault.

Maybe i missed where you try to power up the board & measure the secondary voltages ? Also, looking at the circuit, the PSU needs the signal from the main board on connector CNM802 to fire the LED driver chip so i don't see how you can expect the backlights to come on ? It was a quick look through the posting so maybe i missed something ?

Nogger

[Jidis]

Re: Power Supply Failed - Samsung Plasma PS-42Q96HD (BN44-00162A, PSPF531801A, W2A)

Thanks Nogger!

No, I'm pretty sure the backlight thing is out of the equation now, and I'm waiting for a power supply board to arrive. There was talk in the thread that when the lights aren't working right, the set will stay in that typical failure state with the clicking, and it was suggested to check them (they were all OK).

According to that troubleshooting "field guide" thing and a few forum members, the lights should work if you disconnect the mainboard and power up. Mine didn't, so I'm hoping this new power board will cure it. I'm just interested in what went wrong with the original (BN44-00356B) board, and maybe trying to fix it for the experience. That's why I was wondering if there were any common failures people knew of (besides the caps).

Take Care,

George

PS- Of course, I probably should wait to see it power up with this replacement board, as there's always the possibility that my PSU isn't the problem. I'm supposed to get that this week.

[nogger]

Re: Power Supply Failed - Samsung Plasma PS-42Q96HD (BN44-00162A, PSPF531801A, W2A)

The circuit diagram for that board is available on Elektrotanya, just enter BN44-00356B Service Manual into Google & it should be the first listing.

With the PSU on the bench, put a link across pin 16 & 18 of connector CNM802 (Stby & PS ON/OFF) & you should have 12 volts on pins 1,3 & 5 & 5.3 volts on pins 11,13 & 14. That's where i would start, make sure you have them & put a load on them (AV board connected ) & make sure they are stable.

Maybe this should be posted in your original thread.

Nogger

[Jidis]

Re: Power Supply Failed - Samsung Plasma PS-42Q96HD (BN44-00162A, PSPF531801A, W2A)

Thanks again Nogger,

I checked voltages 'with' the mainboard connected when I was messing with it, and almost everything was unstable and really low voltage. The standby pin was the only thing that seemed to have a solid correct (5.3) voltage.

I'll try to mess with it out of circuit with 16&18 jumped, but like I say, it would probably be wise not to hassle people about it until I'm pretty confident that the power board was bad. If the other one shows up, and the set does that same clicking mess, I'll be back to square one again (in addition to having wasted 80 bucks).

BTW- ShopJimmy replied again yesterday and said that it sounds as if I may have a problem in the LED backlight driver part of the board. He said there should be an IC feeding an array of FETs and I can check them to see if any are shorted. Actually, I believe there may be two ICs on this board, but ShopJimmy didn't have the schematic.

I'll post an update to that other thread when the PSU board gets here (should be within the week).

I also never got an answer as to whether I was making a mistake in ordering an "A" version to replace my "B" board, so if anybody knows, I'd be interested (even though I've already ordered).

Take Care

George

[ecu971]

Re: Power Supply Failed - Samsung Plasma PS-42Q96HD (BN44-00162A, PSPF531801A, W2A)

Hi
I got this board to with no powerup clicking, i got 8V on VS, rest testpoints is OK. All boards are connectec. Do i have to short "power-on" to test vs? What can cause just 8v.

[Cricky]

Re: Power Supply Failed - Samsung Plasma PS-42Q96HD (BN44-00162A, PSPF531801A, W2A)

OK guys i'm going to (hopefully) bring this thread back to life since i'm having a similar fault on the same board (i.e. the relays clicking and no power coming to the TV).

I've followed both nogger and Tom's fault finding guidance as far as measuring the resistance across the FETs. My VS FETs are dead on with 11ohms across them but my VA FETs had been completely blown apart and i replaced them. I'm getting 10Kohm across them both. These replacements are Fairchild FQPF 9N50C FETs on QX801 & QX802.

Before i go any further though, i'll go back and explain the fault so far...

The TV is my mum's and when the fault started it was just the clicking and the tv still worked then it died completely after a while. They asked me to have a look so after a bit of researching online, the fault seemed like it would be blown caps.
I checked it out and there were a few blown caps (which i'll mark on an attachment) and the two VA FETs had blown themselves to bits. There were also some scorch marks on the underside of the board which i'll also include pictures of below.

Another strange thing i found, was that one of the tracks coming from one of the big huge caps (CP803) had stripped off a lot of the solder resist and the bare copper was showing and it had also been stripped off in parts. So i've bridged this with a bit of wire between the pin of the big cap to the next solder joint on that track. I did test this cap by sticking the meter across it in ohms to charge it then switching it to Volts DC and it did charge and discharge though i didnt make note of these values and i didn't bother taking it out of the board either but the cap looked ok on the top side so i'm guessing/hoping its ok.

The fuses are OK too.

So going back to the readings across the FETs being 10Kohm, clearly there must be a problem here! I'm going to go ahead and assume there's a problem with the resistors and those diodes(?) (DX804 and DX803). I can't make out the markings on them to order new ones. Can anyone help me out here?

There may also be other issues with this board so if there's anything else i should check out, please let me know! And as with dailafing above there, i'm just a bit of a hobbyist and by no means an expert but i'd really like to fix this thing myself. I do quite a few electronics repairs but nothing too major so it'd be good to bring a TV back to life!

Re: the attachments, the caps i replaced are circled in red and the FETs in blue.

Thanks for any help anyone can provide!

[tw2005]

Re: Power Supply Failed - Samsung Plasma PS-42Q96HD (BN44-00162A, PSPF531801A, W2A)

OK guys i'm going to (hopefully) bring this thread back to life since i'm having a similar fault on the same board (i.e. the relays clicking and no power coming to the TV).

I've followed both nogger and Tom's fault finding guidance as far as measuring the resistance across the FETs. My VS FETs are dead on with 11ohms across them but my VA FETs had been completely blown apart and i replaced them. I'm getting 10Kohm across them both. These replacements are Fairchild FQPF 9N50C FETs on QX801 & QX802.

Before i go any further though, i'll go back and explain the fault so far...

The TV is my mum's and when the fault started it was just the clicking and the tv still worked then it died completely after a while. They asked me to have a look so after a bit of researching online, the fault seemed like it would be blown caps.
I checked it out and there were a few blown caps (which i'll mark on an attachment) and the two VA FETs had blown themselves to bits. There were also some scorch marks on the underside of the board which i'll also include pictures of below.

Another strange thing i found, was that one of the tracks coming from one of the big huge caps (CP803) had stripped off a lot of the solder resist and the bare copper was showing and it had also been stripped off in parts. So i've bridged this with a bit of wire between the pin of the big cap to the next solder joint on that track. I did test this cap by sticking the meter across it in ohms to charge it then switching it to Volts DC and it did charge and discharge though i didnt make note of these values and i didn't bother taking it out of the board either but the cap looked ok on the top side so i'm guessing/hoping its ok.

The fuses are OK too.

So going back to the readings across the FETs being 10Kohm, clearly there must be a problem here! I'm going to go ahead and assume there's a problem with the resistors and those diodes(?) (DX804 and DX803). I can't make out the markings on them to order new ones. Can anyone help me out here?

There may also be other issues with this board so if there's anything else i should check out, please let me know! And as with dailafing above there, i'm just a bit of a hobbyist and by no means an expert but i'd really like to fix this thing myself. I do quite a few electronics repairs but nothing too major so it'd be good to bring a TV back to life!

Re: the attachments, the caps i replaced are circled in red and the FETs in blue.

Thanks for any help anyone can provide!

I'd be cleaning that board. First thing I notice is it's a 50" Samsung this PSU is from.

If it's a 50" TV you're working on then the FETs you used are under rated compared to the originals.

F802 T8AH, 250V

QS801,QS802 FQA18N50

DS801,802 kds184

( RX867, RX869), (RX862 and RX878). 20ohm (2012)

RX863 and RX868 10kohm (2012)

DX803,DX804 KDS184

RX802, RX803, RX832, RX833 100 (2012)

QX801 and QX802 FQPF11N50

RX804 and RX805 10k ohm (2012)


I was making a list for the same board which blew the Va and Vs ccts but I'll probably never get to it.

From what I've read and the kits I've seen , the KDS184 diodes will need replacing and there's a few of them under the board.

schematic if you don't have it, covers the 42/50" PSUs

Video on another PSU variant for these TVs
https://www.youtube.com/watch?v=dVaC2KVVLvs

https://www.badcaps.net/forum/showth...ht=BN44-00162A

[Cricky]

Re: Power Supply Failed - Samsung Plasma PS-42Q96HD (BN44-00162A, PSPF531801A, W2A)

Oh! Thanks! That's very helpful. I think I'll reorder the FETS, replace the diodes and resistors just to be sure and see how it goes then.


...and yeah, I forgot to mention this is a 50" version.

[know]

Re: Power Supply Failed - Samsung Plasma PS-42Q96HD (BN44-00162A, PSPF531801A, W2A)

I also have a problem with this Power board, well it is a PSPF531801A

And when i check the Va FETS i get 50 ohms
When i check the Vs FETS i get the magic 11 ohms

So where to next? tom66 and nogger never get there, due to dailafing got 11 ohms cross the board.

What do I check next, did remove the Va FETS and still got the 50 ohms on the board so i guess its some other component I should bee looking at?

[know]

Re: Power Supply Failed - Samsung Plasma PS-42Q96HD (BN44-00162A, PSPF531801A, W2A)

Ok now i actually followed the whole "guide".

I has to admit that i skipped the VS and AS readings before.

But now when I did do them it shows normal 207 VS and 63 VA, both with and without X and Y mainboards connected.

My TV only click once and blinks five times then no picture. So I guess my problem isn't in the psu.

Anyone have any idea what i can check next? Like how to i check if it is the backlight in some way?

Sorry for bringing old post back when is even wasn't that problem!

[comptek]

Re: Power Supply Failed - Samsung Plasma PS-42Q96HD (BN44-00162A, PSPF531801A, W2A)

check all fuses on x-y boards look for small green fuses called pico fuse
theres one near the heatsink on y-susi had found that had failed

[nickj32]

Re: Power Supply Failed - Samsung Plasma PS-42Q96HD (BN44-00162A, PSPF531801A, W2A)

Pop yourmeter across the caps & you will see the voltage drop (might take a while). I have modified the image to show the pins to measure across (A & B) . You can confirm with the Vs FET's (Blue circle) that they also read 11ohms. The reason its 11 ohms is because there are 2 22ohm resistors in parallel on the PCB (surface mount) across the FETS. When the FETS blow they take a hit but usualy you can tell visually, i would say that from your image they are ok & its just dry joints on the Va FETS. If it is dry joints (very hard to see usualy) you need to scrape back some of the green etch resist to bare copper & reflow all 3 pins, in fact i would do it anyway.

Quick note of thanks... reflowing the pins called out in the photo seems to have sorted my 50" plasma

[matyka]

Re: Power Supply Failed - Samsung Plasma PS-42Q96HD (BN44-00162A, PSPF531801A, W2A)

Hi,I have the same power board 50Inch, Clicking.
I have done sime testing on it,removing all the connectors from the power supply and jump the PS-ON to the ground and VS-ON to StBY I have measured VS-208V
The problem is that VA has only 46v and should be 65V . Any advice please .