Samsung ps51d550 no sound no picture

[1967tux]

Hi all have a samsung ps51d550 which i am having problems diagnosing what board or boards are at fault.i have read the other posts on this subject but am still unable to confirm the problem. with everything connected when i turn the tv on there is one click and that is all i get the control board led goes into 5 secs on 2 secs off. there is no change with power disconnected to zsus or when power disconnected to ysus (power is linked from ysus to xsus). it is only when ysus ribon cable to the control board is disconnected that the power supply fires up as it should and i get the 1 sec on 1 sec off led on the control board. but still no picture and no sound (i dont know if the Samsung chime was disabled as i inherited this tv).i have also tried to force the tv on to get the test patterns with no success. i have inspected boards for obvious signs of damage and have also tested across the testing points on each board and have found no shorts. i am sure the power board is ok as all the voltages check out when ysus ribbon cable is disconnected and think that the fault lies in xsus / ysus or both.(or possible bad panel but looks ok no signs of damage) i see that ohm supplies do repair kits for both boards but i would like to confirm that components on my boards have failed, do the fets always show as sorted on the test points of the board or do i need to remove them and test them off the board to diagnose? any advice or help would be appreciated.

[ReeceyBurger123]

Re: Samsung ps51d550 no sound no picture

Yes remove, use search feature to find out how to test.

[Andrew F. Ali]

Re: Samsung ps51d550 no sound no picture

When you said you disconnected the Y-sus cable from the Ctrl Bd the PSU fired up. Did you measure Vs and Va on the PSU to determine if these voltages were being produced?

[1967tux]

Re: Samsung ps51d550 no sound no picture

yes when ribbon and ysus cable disconnected all voltages were as they should be.

[sordids999]

Re: Samsung ps51d550 no sound no picture

Posting pictures of the back of your tv showing the boards with clear pictures may help you more with fixing your problem

[Andrew F. Ali]

Re: Samsung ps51d550 no sound no picture

There are 2 other voltages derived by the y-sus bd: -Vy and Vsc. Also there is a voltage labelled Vzb generated in the z-sus bd. In the PSU there is M5V produced. If all these voltages are active then you could replace the control bd for an easy fix or get into the gut and fix the control bd.

[1967tux]

Re: Samsung ps51d550 no sound no picture

will try to take some pics and post. don't think it is the control board as i have changed that im convinced it is ysus / xsus think my next move will be to remove fets and try testing them out of circuit.

[Hamie]

Re: Samsung ps51d550 no sound no picture

You can test them in circuit first. It'll be pretty obvious if they are shorted.

[1967tux]

Re: Samsung ps51d550 no sound no picture

have tested between all the test points on the board and no shorts ( beween ve, xout svc vs,svc gnd ect) however i have got low Resistance on 1 leg of the fet to gnd is this a shorted fet or is part of the circuit it is in?