Samsung LNS4051DX

[budm]

Re: Samsung LNS4051DX

So when the P-ON is present, every functions are OK, the pictures and sounds are good.
What you can do for now is to use a switch to feed force on to the POWER -ON/OFF pin with a switch so at least you can use the TV until it breaks down completely.

[Rmasters3]

Re: Samsung LNS4051DX

I finally located a used--supposedly from a set with a damaged display--main board. I get audio, and occasionally video that sometimes lasts for an hour or more. Then black screen. I have replaced the usual suspect caps in the power supply. I am guessing the next step is to recheck the connector voltages. Is audio-no-video commonly a power supply issue?

[Rmasters3]

Re: Samsung LNS4051DX

Just checked the voltages at the white connectors--both the long and short on the upper right side of the power supply--all check out correctly on the longer one.

Short one at top On/Off 5.4V, A-Dim 2.4V, P-Dim 4.98V, E-Sym 5.3.

4 blinks when turned on, Video occasionally works when I turn it on--then goes black after a few minutes. Audio works, no problems.

[budm]

Re: Samsung LNS4051DX

"Short one at top On/Off 5.4V, A-Dim 2.4V, P-Dim 4.98V, E-Sym 5.3. " So those readings stay the same when it works and when it does not work?

[Rmasters3]

Re: Samsung LNS4051DX

These were the values when the set had audio but the screen had gone black (backlights no longer on). I did not test voltages when set was working correctly

I turned set on, it worked for a few minutes before screen went black and backlights off but audio remained.

[budm]

Re: Samsung LNS4051DX

'E-Sym 5.3' this may be the one that will give me the clue, so when it is working we need to know what is Voltage is.

[Rmasters3]

Re: Samsung LNS4051DX

Tested the 'E-Sym while set was playing a DVD on HDMI2 and got a consistent 5.35-5.37VDC. I used 3 different digital meters, FWIW.

[budm]

Re: Samsung LNS4051DX

OK, the old main board was having the PS-ON problem not present and we were able to force on using the resistor. This replacement main board is in place and now you are getting black screen after an hour or so. I would put the old board back in and use the force on to see if it still goes out (backlights) after an hour. You were getting pictures and sound OK when forced on, right? (see post 21)

[Rmasters3]

Re: Samsung LNS4051DX

I didn't do the force on with the old board. New board is still doing the same. Contacted the new main board seller who said the problems is in the inverter board, which I now have on order.

[Rmasters3]

Re: Samsung LNS4051DX

FWIW: I ordered and installed an inverter board (left side when viewed from rear of set), but still got the erratic shut down to black screen Found another thread indicating the power supply transformers solder joints were sometimes problematic, so I touched up those--none looked questionable, but did it regardless. Also again, swapped out the used 22uf@450 V cap on the PS. I had two 22uf@450V, used caps and tried the second. Set has been working--latest run nearly 12 hours with no issues.