Samsung PN51D550 SMPS question

[ranergeo]

Hey all! Was just given a Samsung PN51D550 with a one click, 5 blink, no power up issue. After pouring over the forum, I've been able to isolate it to, you guessed it, the X-main (and probably Y-sus). I did this by unplugging the Y-sus from the SMPS (which also turned off the X-main), and seeing the logic LED flash normally. I was also able to use the remote to turn the set on/off.

However, I decided to check the SMPS voltages while it was up and running and found my Vs @ 234 VDC, but the sticker says it should be 203 VDC. I tried to adjust, but the pot wouldn't turn it down that low. The Va was ok at 58 VDC.

Two questions:

1. Will the Vs go high with the y-sys and x-main disconnected, or is this an SMPS issue?

2. Do I need to replace both the Y and X boards as a pair? I tried to isolate out the x-main, but it still set the long blink on the logic bard with only the y-sus connected.

Thanks in advance for the input!!

[ajshoe]

Re: Samsung PN51D550 SMPS question

pic of back of set - pics of boards. I would bench test SMPS with 2 100 Watt bulbs on Vs. sounds like Ysus bd is bad

[ranergeo]

Re: Samsung PN51D550 SMPS question

I've added some pics. Let me know if you need others and I'll get them for ya'!

I've never done a bench test on the SMPS with bulbs before. Where should i attach the 100w bulbs, and is this simply creating the "load" that the y and x boards would draw if attached? (or should i simply put the bulbs in series with the meter when testing?)

[R_J]

Re: Samsung PN51D550 SMPS question

If you measured the Vs voltage with it disconected from the Ysus/Zsus it will read high and likely shut down, it needs to have a load, you can use 2- 120 volt, 60w or 100w incandesent lamps in series from the Vs pin to ground to test, and the voltage should be close to spec.

[ranergeo]

Re: Samsung PN51D550 SMPS question

Yup, that worked... a little tricky to set up, but the power leveled out where it needed to be.

Another question, as it looks like I'm buying the Y-sus and x-main. While shopping the x-main, my version is "rev 1.2". I can find a "rev 1.3" more easily, and for less money. The only difference I can find is that it has one less cap on the board. Every number matches otherwise. Does a higher rev # mean it has been improved?? (Or do I need the extra cap due to the set being 3D, and the other board being used for the non-3D set?)

Also, if the y-sus went bad, does it automatically take out the buffer? Capkid had mentioned in a post about making sure they are purchased together, but again, am having a difficult time finding a matched pair.

Thanks in advance!

[ranergeo]

Re: Samsung PN51D550 SMPS question

So, like so many others in this series, the X-Main was the culprit.

After installing it and looking to adjust my voltages, noticed my Ve high at 89VDC (the panel lists it at 83). Using the potentiometer, I can only get it as low as 83.9 VDC. What could cause this, and is it something I need to worry about?

[R_J]

Re: Samsung PN51D550 SMPS question

What voltage do you have on the Ve in pin (CN5001 pin 3) It could be too high and it is supplied by the Y-sus board

[ranergeo]

Re: Samsung PN51D550 SMPS question

I have 105 VDC at pin 3 being supplied...

Is there an adjustment for what's being sent from the y-sus, or am I looking for something failing?