SAMSUNG - PS51D550 - Power Board Question

[manowar]

Hey Guys,
Scored a SAMSUNG - PS51D550 Plasma 50" TV that was destined for landfill. The unit refuses to power up and makes a clicking noise.
I have identified what I believe to be the fault on the power board, component CM853 which is a 10V 3300uF cap appears to be open circuit I have attempted to source a new cap from my local Jaycar but unfortunately for whatever reason they do not stock any caps in 3300uF (regardless of voltage). My initial thought was to swap this component out for a 4700uF @ 16V as i *think* this cap is only used as a filter.

Can anyone shed any light as to whether my fix is acceptable or should I do the right thing and order the correct value of cap from RS and be patient

Cheers

[Skepticist]

All capacitors are 'open circuit' being 2 electrodes separated by an insulating material and the 'clicking' points to the supply detecting an overload causing it to shut down immediately on every startup IE something has gone low impedance rather than high impedance. The more valid test for a cap is to measure its ESR.
Shouldn't be any issues temporarily substituting 4700uF for the 3300uF for a test apart from physical size - the larger one might not fit on the PCB as a permanent replacement.

Is that 3300uF cap on the standby supply?
(You didn't mention any lights being on and usually the standby condition has at least 1 dim light indicating, usually that is)

[manowar]

Hey Skepticist,
Wrong terminology my apologies I tried to measure CM853 with my multimeter on uF and couldnt get a reading, other caps got a reading close to their values. I swapped the 3300uF cap out for a 4700uF and unfortunately no luck.

When powered you can hear the relays clicking but it cannot fire up the TV, the standby light is blinking 3 times when its sitting idle.

[Skepticist]

At least the standby supply seems to be running OK
Is the blinking an error code?

I see a lot of info on troubleshooting plasmas online - simplest test is to unplug the 'Y' board from the power supply and power up. If the set starts up then you need a replacement 'Y' board, if no change then re-connect the 'Y' board & unplug the 'X' board and repeat the power up test. Should be a start-up tone if successful and if it sounds ok with 'X' board disconnected then you appear to need a replacement for that board - seems a fast method of determining which, if either, of those 2 boards is faulty. Check the power supply output voltages too (correct values should be marked on there somewhere).

And take extreme care - don't go energizing yourself in the process :O

[tw2005]

As suggested I'd lean towards checking the sustain boards, predominately the xmain for shorted IGBTs( transistors)

also search for a training / quick guide on fault finding this series. I think with these later models this is the case:
"Will not be run with the “X” or “Y” main disconnected. The SMPS will shut down immediately. However if a meter is first connected to the test point when power is applied it will read the correct voltage briefly before shut- ting down.(You have enough time to check key voltages)"

CAUTION: Do not reconnect any connectors to SMPS or Y/X Boards until power has been turned off long enough for Vs to drop below 10V or damage will occur to X or Y Boards.

Check the part numbers on the ymain and xmain and see if these match.
BN96-16523A
X Main

BN96-16524A
Y Main

If so then google PN51D550C1FXZA Fast Track Troubleshooting Manual. You should get some hits and download. That shpould help you get ontrack

Good luck.

[kevviek]

As suggested I'd lean towards checking the sustain boards, predominately the xmain for shorted IGBTs( transistors)

also search for a training / quick guide on fault finding this series. I think with these later models this is the case:
"Will not be run with the “X” or “Y” main disconnected. The SMPS will shut down immediately. However if a meter is first connected to the test point when power is applied it will read the correct voltage briefly before shut- ting down.(You have enough time to check key voltages)"

CAUTION: Do not reconnect any connectors to SMPS or Y/X Boards until power has been turned off long enough for Vs to drop below 10V or damage will occur to X or Y Boards.

Check the part numbers on the ymain and xmain and see if these match.
BN96-16523A
X Main

BN96-16524A
Y Main

If so then google PN51D550C1FXZA Fast Track Troubleshooting Manual. You should get some hits and download. That should help you get ontrack

Good luck.

I know this is an old thread but hoping for some tips too. I have a PS51D550 which has had very little use in a spare room. We tried to turn it on last weekend and nothing - no lights at all. I have had a look and there is power to the unit, the fuse is ok and reads 240V to ground, but there is zero voltage on the test points Vs and Va. I disconnected the X and Y boards and still nothing, there are no shorts that I could find. I have checked all the main diodes, resistors and capacitors and everything seems ok. I found the troubleshooting guide mentioned above but it is not much use as it assumes there is some voltage at the test points. I guess the only option is to replace the power supply board?

[kevviek]

After a bit more troubleshooting I have found there is a signal from an IC labelled PS On, which is reading at 4.8v and from another video it seems that needs to go to ground for the other power sources to be enabled. I know it's a smart power supply but I don't know if that trigger to ground is not happening because of a fult on the power supply board or because it has sensed a fault on one of the connecting boards. But plugging and unplugging things doesn't help :-)

[wotnot]

I guess the only option is to replace the power supply board?

IF you could get one ~ they're pretty thin on the ground these days ... probably your only hope is to repair it.

[kevviek]

IF you could get one ~ they're pretty thin on the ground these days ... probably your only hope is to repair it.

Thanks. I have been poking around on the board today but with no circuit diagram it's a bit of a lottery. None of the FETS are turning on.

There seem to be a few boards around but they are overseas, there's a local supplier that has one but they want $264 for it.

[wotnot]

Thanks. I have been poking around on the board today but with no circuit diagram it's a bit of a lottery. None of the FETS are turning on.

There seem to be a few boards around but they are overseas, there's a local supplier that has one but they want $264 for it.

Yeah..bit of an expensive 'parts cannon' with no guarantee it'll fix the issue.

Have you checked/found the 5volt standby power section? If that's dead, it probably never receives the SMPS start signal. (might explain why it doesn't start even with boards unplugged)

edit: this may help -->>