lg 47LB585V help to identify ic please

[jimbofz]

ok thanks will do .i will post results

[jimbofz]

Well tiny tps54319 ic arrived
removed s/c one
checked all pins for s/c on board, prepared board
fitted replacement , checked resistances
i/p pins 1 and 2 had 5k to deck which was caused by zd2403 on 3.3v i/p
powered up ,standby led ok 3.5v ok
powered on no o/p from i/c no 1.5v on pins 10,11,12, no backlight
no short on o/p
so i suspect enable pin 15 not turning on
this is proving to be a headache
not giving up yet though
trying to work out the start up sequence

[dick_barton]

The data sheet says "pull below 1.2V to disable" so I gues a voltage greater than 1.2V will enable it.

[lotas]

The microcircuit may not fit well on the seat, it will not contact.

[jimbofz]

removed ic checked all print connections
cleaned underside of ic, retinned the print
refitted ic.
same as before except i now have .2 volts on o/p pins
before i had 0v on o/p
enable pin has 3.2v on it
im going to try another ic in case i used too much heat to flow the solder.
(clutching at straws)

i preheat the board underneath to approx 200 deg
then fit chip
then use s/station to melt solder and wait for flow
i suppose something else on panel could have been damaged due to original faulty psu
putting out more than 3v this is why the 5v zener failed

[lotas]

See the diagram for what else the standbay + 3.5v_ST bus powers

[jimbofz]

some progress .
i supplied 1.5v to o/p and tv works ok
so as Lotas said chip must not be seated correctly
this has been my first time working with these sub minature ics
i suppose practice makes perfect .ive ordered a couple more of this ic
and im ordering another type of liquid flux
ive used the same flux for years without any problems
it wont do any harm to try another flux
i will report back with results

[lotas]

You may also have suffered a MICOM (standby controller and it contains the firmware that controls it) 33 pin. gives the command to turn on just on it.

[jimbofz]

Originally Posted by lotas

You may also have suffered a MICOM (standby controller and it contains the firmware that controls it) 33 pin. gives the command to turn on just on it.

thanks for advice ,
but as tv works fine with 1.5v injected from bench psu
i assume ic is not making good contact ,
or i may have damaged it with too much heat
i have ordered another

[jimbofz]

while i am waiting for chips to arrive ive been running tv with a LM317 as shown in pic
i know the original chip is rated at 3 amp and the lm317 is 1.5 amp
the 2 resistor values allow correct 1.5v o/p
i just wanted to confirm tv had no other problems ,and it seems fine.
the temporary reg only gets slightly warm
dont understand why pic is upside down?