Samsung LE52M87BD - CI811 burnt out

[StephenU]

Samsung LE52M87BD

Had this to for over a year now, was watching it the other night and heard a crackle and it just went black, still had volume, so turned off then back on - has standby and can here the power supply working.
Opened it up, thinking maybe transformer on psu. Still the same , unplugged one half inverter and seemed to give me video for a split second then I heard the crackle and the dreaded electronic burnt out smell, tried it on full load with both inverters back together, plugged in power and within couple mins, CI811 had burned out. It's just above the TI801, any help would be greatly appreciated or where in can source the CI811 that has burnt out and also the schematics for PSU. ( bn44-00150B )

Thanks in advance.

[budm]

Re: Samsung LE52M87BD - CI811 burnt out

can we get good clear pictures straight shot of the top side and bottom side of the board?
You should also remove he cap so we can see the print on the body of the cap.
It looks to the coupling cap fro driving the Inverter transformer.

[StephenU]

Re: Samsung LE52M87BD - CI811 burnt out

Thanks budm, wasnt sure what kind they caps were, but will remove it and get better pics to upload, I'm on my mobile at the minute and it's not letting me upload the other pics I have.
Thanks again for the quick response,
Stephen

[budm]

Re: Samsung LE52M87BD - CI811 burnt out

More likely to be Polypropylene type for high frequency switching application.

[StephenU]

Re: Samsung LE52M87BD - CI811 burnt out

Here are the pics i managed to get last night, any input or help would be great, thanks.
I have the cap ordered, but not sure as to what has caused it too fail in the first place.

[Electronic Handyman]

Re: Samsung LE52M87BD - CI811 burnt out

In my opinion from your new pics I can see a few bad solder connections, especially on the coil.I'd recommend taking a real close look at all the soldering connections.Personally I'd re-solder any of the hot spot soldering connections and as many connections that I could.Also look at what connects to that cap two pins and see what's shorted out to cause the cap to go.A coil or regulator , or diode etc might be shorted out.It's quite common for the inverter coils to fail.

[StephenU]

Re: Samsung LE52M87BD - CI811 burnt out

Thanks Electronic Handyman, when i first got this set it did have bad solder joints on the big transformer coil, I have since reflown them and applied some fresh solder. Also when the set made the initial 'crackle' sound picture dissapeared, turned the set off for a while, then back on and it done the same thing, i unplugged the LL and LU inverter boards and it seemed to stay on (the PSU that is...) so decided to plug back in the inverters until something went (another couple of switching on and off of the set the cap gave out), at first i thought it was the transformer as the smell was coming from that area then noticed the damaged cap. So, can anyone help me diagnose what inverter it could be as they both split LL and LU, i think its the LL that has something failing on it but want to debug it and get the replacement part/s ordered. I will also go over the PSU, but was thinking fitting new cap and powering on the set without either LL,LU,RL or RU connected and see if the supply has an output ok.

What the best and easiest way to test the coils on the inverters, do i need to take them off the PCB or can they be tested with them still fitted.?


Many thanks to anyone with advice/support towards my issue.

Stephen

[budm]

Re: Samsung LE52M87BD - CI811 burnt out

That is the DC blocker/coupling cap for the return side of the Inverter transformer, it should have been rated at 630V (or higher, I suggest to use 800V, Notes: the inverter circuit runs on 400VDC) and Polypropylene type for high frequency high current pulse type cap. Same kind of failure in SAMSUNG TV also. The one you have is Metalized Polyester film.
For I.E.

[StephenU]

Re: Samsung LE52M87BD - CI811 burnt out

Thanks for the info budm, i ordered up the 400v and the 630v 1uF cap couldn't find the 800v

Here are some pics of the primary and secondary values i measured from the TI801 transformer. Are these measurements what they should be or am i looking at a faulty transformer?

Thanks again

Stephen

[StephenU]

Re: Samsung LE52M87BD - CI811 burnt out

Parts have arrived this morning so hopefully get some time in over the weekend to install psu back in with new part fitted 600v option. Can anyone point me in the right direction for the Schematics or parts list for this psu.? Also wondering if i should be removing the transformer to test resistance of both sides or wether its ok to do it while installed.

TIA

Stephen