Samsung PS51D550 mura like effect

[maxvalutech]

Had this given to me in going order but with screen centre top giving a pool of slightly different colour than that broadcast. This happens from switch on. The model is from 2011 so probably 6/7 years old and I found owners have had it in store mode since purchase!! Entered service menu and did factory reset to home and retuned etc. Display is bright enough and set goes well otherwise. Even had remote with it. Pics show the problem and also faces in that area may have a slight grey cast. So is it a screen problem or something else. I lean to the former.
In the pics greenish tinge seen in centre and clouds darker than actually were in other pic.

[freakaftr8]

Re: Samsung PS51D550 mura like effect

I would 1st check all voltages it make sure they match the label on the panel especially VS. If all voltages check out you could try raising VS about 5v. This is controlled on a potentiometer off the power supply. Could just be dealing with a worn out panel

[maxvalutech]

Re: Samsung PS51D550 mura like effect

Well I got back to this set to check voltages etc but before removing to workbench I tried to start it again to carefully check picture over for any clues. Set doesn't start !! What I get now seems to be a fault code being 2 blinks x 5 times, pause, repeat ongoing. Not really able to find anything definitive in various posts but may be 12v line problem - anyone know what that code really points to??

[freakaftr8]

Re: Samsung PS51D550 mura like effect

I would remove the power supply and check soldering connections on all the mosfet transistors connected to the aluminum heat sinks also check and re solder transformer soldering connections.

[maxvalutech]

Re: Samsung PS51D550 mura like effect

Thanks freakaftr8 I will do that but going out west today and be a month until I get back to this set. Have packed a couple in the car to work on while away.

[maxvalutech]

Re: Samsung PS51D550 mura like effect

Got back to this set today. PSU only has 5v sby and 3.2v pson. Nothing else happens and front led blinks 2 times x 5 continuous. One strange thing is main caps read 417v when power connects then runs down 1v at a time shutting down. I don't hear any clicks at any time. So looks like a definite PSU problem and time to follow above advice.

[maxvalutech]

Re: Samsung PS51D550 mura like effect

OK it seems that this series set has a separate transformer to supply 5v standby and therefore main caps are not in play. This set is in what looks to be a permant state of trying to turn PSU on with 3.2v constant at pson but that signal is not being accepted so the standby led flashes a code. At first start attempt the control board green led does give a few flashes but not the one per second when all well - just a few intermittently then no more. The 3.2v pson needs to go to ground to activate so I tried forcing PSU on with mainboard disconnected but no joy. Can't find a service manual for this model as yet but have been looking at other around same era. Did run heat gun over the solder joints on rear of psu board but no change. Has to be a PSU problem surely??

[maxvalutech]

Re: Samsung PS51D550 mura like effect

What a dummy - first I got the model wrong and was searching with little result, second I was focussed on PSU due to secondary voltages not starting but these depend on logic board readings from other boards. So went back to square one and disconnected X board from Y feed and up came the required voltages. When I searched for the correct model its apparent the X side was a problem in this series.