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

[tom66]

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

The supply is for Vg, 5.3V, Va, etc.
It's odd that Samsung do not use sequencing for Va. Most plasmas, the Va must be switched on after the 5V/3.3V or the panel can be damaged (vertical lines, bars, etc.)

[dailafing]

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

ok cool, what next guys... and thanks for everything so far guys.... team effort

[tom66]

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

Check cold joints as Nogger says...

[dailafing]

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

ok cool...
So whats the procedure on charged caps then?
Do I need to do anything to make sure im not gonna get buzzed?

[tom66]

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

It would be wise to discharge the large 450V capacitors - a light bulb across the terminals works well.

[dailafing]

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

It would be wise to discharge the large 450V capacitors - a light bulb across the terminals works well.

really? any other method?
I've seen people just shorting over?

Could I use the DMM?

Or am I gonna rip out a light bulb? (none spare)
also does the type of light bulb matter?

[tom66]

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

Well, you can use a screwdriver, but it has the potential to damage the capacitors and other components.

[nogger]

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.

[dailafing]

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

ok, im currently uploading the HQ images now.

I can see now that you've pointed them out that they are looking a little nasty.
Additionally, when seeing your above attachment, I had to look back at my copy of it because I couldn't believe the two really bad looking ones up the top left!! Any comment on them?

Ok, they are all coming in at 11ohm exactly... good news right?

So, is this really down to just crap solder?

Because, even though its looking bad on those particular points, surly there's enough there to get a connection?

[nogger]

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

Scrape back the etch resist on all the pins (both transistors) & flow fresh solder on them). Measure again for 11 ohms (you checked the Vs as well right ?) At this point you can either just pop it back in the TV+ & test or hook a mains lead onto it on the bench & test. If you want to do that let me know & i iwll tell you which pins to short etc.

[dailafing]

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

I checked the 4 points you circled in the picture? is there more?

Ok what do you mean by,

Scrape back the etch resist on all the pins (both transistors)

Do you mean, just remove the current solder?

Also here are the close ups

[dailafing]

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

looking at them here they look like they're forming a circuit?

Do you really think putting more solder on here will help?

[vinceroger69]

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

in the pictures i would certainly reflow/add more solder theres a few bad looking joints imo

[dailafing]

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

Here's the closups of the whole back of the board

[nogger]

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

Ok, the tracks connecting to those pins are covered in a green film called solder resist, it stops the solder flowing onto the copper below. To make a good connection to these pins i always scrape off about 5 mm of this film around the pins using the tip of a small screwdriver to expose fresh copper below (try it , you will see what i mean). When you get good clean copper reflow the solder on those pins & make a good connection onto the fresh copper.

11 ohms is good news, means the FETS have not blown, the FETs we are interested in are the ones with the smaller pad areas,(2nd image above) not the ones in the first image you posted above (they are the Vs Fets). On that last image you posted of the Va FETS i can clearly see a sort of 'corona' mark around teh base of one of the pins, that's a dry joint.

By last image i am referring to the one in your post #51

[dailafing]

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

Ok, the tracks connecting to those pins are covered in a green film called solder resist, it stops the solder flowing onto the copper below. To make a good connection to these pins i always scrape off about 5 mm of this film around the pins using the tip of a small screwdriver to expose fresh copper below (try it , you will see what i mean). When you get good clean copper reflow the solder on those pins & make a good connection onto the fresh copper.

11 ohms is good news, means the FETS have not blown, the FETs we are interested in are the ones with the smaller pad areas,(2nd image above) not the ones in the first image you posted above (they are the Vs Fets). On that last image you posted of the Va FETS i can clearly see a sort of 'corona' mark around teh base of one of the pins, that's a dry joint.

Ok, im warming up m 40w now, and getting the solder out...

Nervous to hell....

So im gonna scrape some of this green cover off, and slap some solder on there...

and while im there, if I see anything obvious like how these points are to me now, then i'll do the same to those...

any words of advice before proceeding?

Also, see updated images of higher quality...

[nogger]

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

Dont be nervous, scrape around the pins to expose the copper underneath the etch resist Make sure you have a good solid solder joint between the pins & the tracks . Measure again between the pins A & B as before on each FET (actually on the pins of the FET & NOT just the track) so you can be sure your connections are good & confirm 11 ohms

[nogger]

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

post a pic of your connections if you like before you apply power

[dailafing]

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

while waiting for the video of my solder work to upload, I started doing some point to point testing with the ohm mode. and I could see my solder work wasn't shorting.... I still had my 11ohms....

so I thought, its not gonna go bang if im not shorting anything, so since its only a 2 min job to reconnect 5/6 wires and a couple of screws (only 2 screws holding for testing), I put back together and its working...

I cant thank tom & graham enough for the tips, support and confidence inspiring words that gave me the courage to fix my tv...

youtube video soon to follow showing my progression through the fix...

thanks again

[tom66]

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

Nice one!