Toshiba 50L5200U backlights but no picture.. Tcon?

[102mm]

JUst picked up a 50L5200U that turns on with a back-light but has no image all the power supply voltages work fine and the but i seem to have an issue with the T-CON. I am getting 11+ volts at the fuse, but i don't get any voltage at UP4 or any of the 3V points.. It's less than $20 online, but i wanted to confirm that was my real issue.. any thoughts?

[CapLeaker]

Re: Toshiba 50L5200U backlights but no picture.. Tcon?

that says nothing. the only way to proof that the main board or the t-con is at fault, is to check the LVDS with the oscilloscope.

[102mm]

Re: Toshiba 50L5200U backlights but no picture.. Tcon?

Understood.. it was just a rough process of elimination since i have sound and backlight.. I figure i should have some kind of voltage at U4 since the set is on.. and i do have 12Volts at the Lvds cables. thanks tho. do you happen to have a data sheet for CM3805A or a service manual for this set?

[tibimakai]

Re: Toshiba 50L5200U backlights but no picture.. Tcon?

The fuse at the T-con is good?

[102mm]

Re: Toshiba 50L5200U backlights but no picture.. Tcon?

Yes, The fuse is good 12 is present. I also have 3V at the ribbon cable at CON1.

[budm]

Re: Toshiba 50L5200U backlights but no picture.. Tcon?

Since you do have Voltage deeding the T-CON, then you should look at the test points of the sub-power supplies on that T-CON first with the ribbon cables cables between the T-CON and the panel, then without. There are 3 switching power supplies on that board
As you look at the board you can see these test points:
V12V = 1.2V by inductor LP3
V25C = 2.5V by inductor LP3
V33V = 3.3V by inductor LP1
VGHP = XXXV by UP1,
GAMMA Voltages GMA1~GMA18

[102mm]

Re: Toshiba 50L5200U backlights but no picture.. Tcon?

Since you do have Voltage deeding the T-CON, then you should look at the test points of the sub-power supplies on that T-CON first with the ribbon cables cables between the T-CON and the panel, then without. There are 3 switching power supplies on that board
As you look at the board you can see these test points:
V12V = 1.2V by inductor LP3
V25C = 2.5V by inductor LP3
V33V = 3.3V by inductor LP1
VGHP = XXXV by UP1,
GAMMA Voltages GMA1~GMA18

I had to put the TV back together for the night but before i saw this message i checked the V12V, V25V and V33V with the T-CON connected and there was no voltage at any of those points.

I will try to get back into it later today and check the other spots.. I found a T-CON for $13 so i ordered it. it'll be here Friday, but i still want to find out where and how this one went bad.

[budm]

Re: Toshiba 50L5200U backlights but no picture.. Tcon?

I had to put the TV back together for the night but before i saw this message i checked the V12V, V25V and V33V with the T-CON connected and there was no voltage at any of those points.

I will try to get back into it later today and check the other spots.. I found a T-CON for $13 so i ordered it. it'll be here Friday, but i still want to find out where and how this one went bad.

At this point the T-CON board is dead.
When you get the new t-con board you should not having those two flat ribbon cables to the panel in place yet, take the DCV readings of those test points to see if there are OK, if the Voltages are present then you can have those cables back in place and then check and see if the Voltages are still present. What we do want to do is to damage the new board in case there are shorted circuits in the panel that will damage the new T-CON.