Samsung LA26C450 E1D no power led

[petersdrz400]

I have this samsung tv with no power led. Here is a link to the service manual



but it does not have any schematics & my PSU is different
When I disconect the main board I get all good 13v & 5v at cn802 (connecter from psu to mian board) & the back lights come on, as soon as I connect the main board the 5v at cn802 drops to 0.5v, also the pin to the front led only has 0.5 volts (should be 3.3v) all other pins to the front switch panel have 3,3v. without schematics im not really sure where to start

[budm]

Re: Samsung LA26C450 E1D no power led

Can you check the resistance on that 5V line and chassis ground to see if it has really low resistance?

[petersdrz400]

Re: Samsung LA26C450 E1D no power led

yes it only has 5ohm, in fact all the power lines are shorted, except for 1 (also 5v) which i guess supplies the 3.3v to toe front buttons

[petersdrz400]

Re: Samsung LA26C450 E1D no power led

here is a pic of the power input on main baord, all ic's seem to be shorted

[budm]

Re: Samsung LA26C450 E1D no power led

The 3.3v will be generated from the LDO regulator that drop the 5V down to 3.3V.
Well since 5V will be feeding a lot of circuits and LDO, it is not going to be easy since you are not going to be able to cut traces unless you know how the 5V traces are distributed.
"in fact all the power lines are shorted" not really sure on you mean, all the B+ lines, same if the power cables from the power supply board is disconnected?

"all ic's seem to be shorted" not sure how you go about checking them.

[budm]

Re: Samsung LA26C450 E1D no power led

Service manual:

[petersdrz400]

Re: Samsung LA26C450 E1D no power led

when i say all power lines are shorted i mean all 5v exept for 1 & the 13v lines on the mainboard

[budm]

Re: Samsung LA26C450 E1D no power led

OK, I see, you can download the service manual in post6

[petersdrz400]

Re: Samsung LA26C450 E1D no power led

that is the manual i have (see original post but it does not have schematics

[budm]

Re: Samsung LA26C450 E1D no power led

OK, I did not know that is the same one, there are 4~5 of them and not sure which one matches yours.

[petersdrz400]

Re: Samsung LA26C450 E1D no power led

thanks for your help, not really sure where to go from here