Samsung LN-T4042H

[heavymachines]

Hi all working on this set 40". it was brought to me with the typical clicking and nothing. I was told it used to click constantly till it warmed up and then it stayed on. They pushed it till that didn't work anymore. Now it just clicks and nothing.


Tore it apart sure enough bad caps on top right of power board. Replaced those with rubycons and panasonics. STILL just clicks and nothing. I am afraid something else was damaged due to pushing it. I will update with voltage readings and anything else i find. Has anyone dealt with this problem? There is absolutely no backlights not even a flash.

[budm]

Re: Samsung LN-T4042H

Power supply board P/N? BN44-?????

[dick_barton]

Re: Samsung LN-T4042H

The power supply repair kit contains 9 capacitors. Have you changed them all?

[heavymachines]

Re: Samsung LN-T4042H

power supply board p/n? Bn44-?????

bn44-00167a (sip400b)

[heavymachines]

Re: Samsung LN-T4042H

The power supply repair kit contains 9 capacitors. Have you changed them all?

Replaced 7 of them. Wonder the last 2. Kit on S.J.?

[dick_barton]

Re: Samsung LN-T4042H

Replaced 7 of them. Wonder the last 2. Kit on S.J.?

https://www.amazon.com/Samsung-LN-T4.../dp/B00EOIKXOM

[heavymachines]

Re: Samsung LN-T4042H

Wonder what caps are in the kits it doesn't say. Must be one of the little start caps. Will probably go ahead and replace those from digikey. Going to check voltages soon here.

[heavymachines]

Re: Samsung LN-T4042H

cn801 On/Off

Pin 1 2.7v 0v
pin2 N/C
STBY pin3 5.17 5.11
pin4 N/C
pin5 N/C
pin6 N/C
pin 7,8 12.18v 0v
pin 9,12 GND
pin13,16 5.35v 0v
pin19,21,22. 12.82v 0v

[heavymachines]

Re: Samsung LN-T4042H

CN806

on/off

pin 1 12.18 0v
pin 2 .001 0v
pin3 GND
pin4 N/C
pin5 10.35v 0v

[heavymachines]

Re: Samsung LN-T4042H

connector above cn801 can't find legend to name of connector. goes from main to power supply not seeing names to the pins.... Will look around might be on backside. OK edit, found connector name is CN803


On /Off

Pin 1 .036 .020
pin2 N/C
pin3 N/C
pin4
pin5 5.35v 0v

[heavymachines]

Re: Samsung LN-T4042H

Pics provided by shop jimmy top and bottom view

[heavymachines]

Re: Samsung LN-T4042H

oh crap i did the check wrong. will relist voltage reading again correctly hold on.

[dick_barton]

Re: Samsung LN-T4042H

With the readings shown above it looks like Inverter On/Off voltage is missing.

I don't know if this will be of use to you.

[heavymachines]

Re: Samsung LN-T4042H

pin layout and names, ignore above voltage readings earlier in thread will relist correct voltage pin names etc. stay tuned.

[heavymachines]

Re: Samsung LN-T4042H

With the readings shown above it looks like Inverter On/Off voltage is missing.

I don't know if this will be of use to you.

Thanks . Yes it appears inverter on/off voltage is really low .036volts

[heavymachines]

Re: Samsung LN-T4042H

CN801 voltages are good we have all voltages on this connector and correct.


Cn803 needs attention voltage as follows

pin 1 inv/on/off reads .036volts
pin 2 dim reads 3.46 volts
pin3 n/c
pin 4 ground
pin 5 is detect reads 5.36v



cn806 reads

pin 1 VCC12V reads 12.18v

pin2 FB reads .001v

pin3 ground

pin4 N/C

pin 5 is LD reads 10.33v

[budm]

Re: Samsung LN-T4042H

Main board is not sending the signal to turn on the Inverter circuit, you can disconnect the INV going back to the main board first and then try forcing on the inverter using the resistor, if the only problem you have is the bad INV ON/OFF then you should see backlights, pictures, sound, and all the TV function should work normally.

[heavymachines]

Re: Samsung LN-T4042H

Main board is not sending the signal to turn on the Inverter circuit, you can disconnect the INV going back to the main board first and then try forcing on the inverter using the resistor, if the only problem you have is the bad INV ON/OFF then you should see backlights, pictures, sound, and all the TV function should work normally.

Ok i jumped 5volts with resistor to inv and yes the backlight came on on first try of relay click however thats all it does no picture, no response via remote. After 60 seconds er so it turns itself off and back on but still no response. so it's safe to say main is cooked. i removed the heat sheild and found the the ati graphics chips has been very hot before and some voltage regulators output tabs are shorted to ground.

[heavymachines]

Re: Samsung LN-T4042H

Now the challenge of finding right or compatible main the board number is BN41-00817F on board, on the barcode sticker it is BN94-01400G.

[vinceroger69]

Re: Samsung LN-T4042H

there s this one after a quick search
https://www.tvpartstoday.com/BN94-01...n94-01400g.htm