Issue on DC/DC chip on Samsung UE55MU9000 motherboard

[totof]

I have a problem with my Samsung UE55MU9000T TV, which is out of order. The TV starts up normally, but after about a minute, horizontal lines begin to appear on the screen, and after another minute, only horizontal lines remain.

I noticed that the DC/DC converter on the motherboard (BN41-02570B) gets slightly warm, and when it reaches approximately 43 degrees Celsius, the horizontal lines appear. If I cool the converter with a freeze spray, the lines disappear, but of course, they reappear after a few seconds. I disconnected the LVDS cables and observed that the temperature of the DC/DC converter increased, just as it does when the LVDS cables are connected.

I installed another motherboard initially without connecting the LVDS cables to monitor the temperature of the DC/DC converter. I observed that the converter did not exceed approximately 32 degrees Celsius. Next, I reconnected the LDVS cables, and the TV worked well for 5 minutes before horizontal lines appeared. I concluded that the original motherboard was faulty due to the panel, which also burn the replacement motherboard.

I would like to perform further tests, for example, to verify that a SMD component on the panel is not the cause. To do this, I would like to replace the DC/DC converter, part number VPM1GMA, but I can't find it. I only find part numbers VPM1RT, VPM1R0A, VPMS2RT, or VPMS3RT.

Since I haven't found a datasheet for this component, do you know which ones are compatible with the VPM1GMA model ?

Thank you

[Diah]

you have short inside the Display Glass at CKV rail.. nothings you can do only Tape masking.. try first with top LVDS

[totof]

you have short inside the Display Glass at CKV rail.. nothings you can do only Tape masking.. try first with top LVDS

Thank you, I willl try tomorrow. I can try without replacing VPM1GMA component on motherboard ?

[lotas]

What makes you think that the problem is in the T-CON controller (VPM1GMA)? Install a jumper between the FB_TRDY_1 and FB_TRDY_3 test points and check each half of the panel by disconnecting one LVDS cable.

[Davi.p]

Try to resolder the PMIC (VGMA...) , first try a simple pass with fresh solder on the sides of it, without removing it , if the situation improves needs a complete resoldering, this on the original board, but before connecting to panel, erase the serial flash on the panel, or better get a salvaged content from the net.. (save the previous content before,)

[totof]

Thank you Diah and lotas.

I started by masking the CKV signals on the top LVDS, but it didn't change anything; the display is fine for about a minute, then vertical lines appear.
Then, by masking the CKV signals on the bottom LVDS, I immediately get vertical lines.
The same thing happens if I only mask the CKV signals on the bottom LVDS, I also immediately get horizontal lines.

By only masking the top CKV signals, once the vertical lines have appeared, if I spray the VPM1GMA component with a cooling spray, the image becomes fine again until the temperature rises above 44 degrees Celsius, at which point the vertical lines reappear.

[Diah]

show please yours MB photo,, to tell you where are the feed back Points Lotas mentioned it to bridge them,, then you disconnect one LVDS at time with out masking to know whish side are defect

[totof]

Yes of course, some photo of the MB

[Diah]

FB_TRDY_1 on this socket, the other one FB_TRDY_3 need to located at other one

[lotas]

These points need to be connected with a jumper, a thin wire.