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TV LG RZ 29FB51RX no picture.

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burt007

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I doubt the problem with microcontroller, and even if you check the dc voltages, it should be checked with an oscilloscope to see the quality of dc voltage, no ac component should be present, it should be pure DC. Poor filtering could cause all kinds of problem and with a multimeter it will indicate what it should be.

Another problem could be bad firmware or corrupted firmware it receives the command to go into standby and thus goes into stand by or error is coming from somewhere and firmware is programmed to go into standby. This could be tricky to troubleshoot.

find the voltages on microcontroller ic001 sda5555 described as below.
1) pin 9 vdd2.5v
2) pin 11 vdd3.3v
3) pin 13 vdd2.5v
4) pin 30 vdd3.3v
5) pin 33 rst
6) pin 37 vdd2.7v
7) pin42 vdd 2.5v
find these voltages it should be matching & find the voltage on rst pin33
8) pin44 vdd 3.3v
 

nnaveli

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all replies relevant,just remove standby pin on the micro and fire the set,it should work except remote switch off and if not download a virgin bin and write it on a new eeprom.
 

piotrekn95

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I replaced LM7845, but nothing helped.

nnaveli - what do you mean remove standby pin ? It's about SDA 5555 IC or DDP 3315 ?
Could I removed this standby pin, and tv should switch on even if the bin is broken ?
 

piotrekn95

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Question is - could I check these voltages when tv is in standby mode?|


ps. sorry for not being on forum but studying, studying :D
 

pradeep.g.belchada

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yes you can check the voltages in stand by mode. if voltages are corect as mentioned above then open the resistor r040 conected to pin31 of
ic sa555. now tv should switch on. find voltages on reset pin of icsa555.
 

piotrekn95

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Well, I checked voltages, and look:

pin9 =2,46V
pin11=3,29V
pin13=2,46V
pin30=3,28V
pin33=3,29V
pin37=2,45 (It should be 2,7V so there is voltage drop)
pin42=2,46V
pin44= there is a problem, its 0,45V, should be 3,3V.

I removed resistor R40 and when I plug tv to main socket, only LED is lighting. Nothing more. No reaction for pressing any button.
 

pradeep.g.belchada

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ok in pin 44 you are getting less voltage then check l012 inductor . if pin 33 is 3.3v then pin 44 should get the same voltage. i think L012 is open

check by dmm for continuity.
 

pradeep.g.belchada

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now here pin 3.3volt is fed to pin 33 & pin 44 if pin 33 is getting the 3.3v then pin 44 also get the same voltage. check the track of pin 44
& again remove the one end of r040 conected across microcontroller & conect a wire on open end of resistor and ground it. now tv should switch on
 

piotrekn95

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OK, if I understood, I should connect through resistor r40 the output of IC to ground?

Cheers
 

pradeep.g.belchada

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  • INSTRNS.JPG
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piotrekn95

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OK, I connect like in schematic.

TV now is starting on, hearing coil. But there is still no picture. Even the filament is not glowing.

Maybe it's something with Horizontal/Vertical positioning?
 

pradeep.g.belchada

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OK, I connect like in schematic.

TV now is starting on, hearing coil. But there is still no picture. Even the filament is not glowing.

Maybe it's something with Horizontal/Vertical positioning?

you said hearing coil , what is coil ? i not understood.
Well, I checked voltages, and look:

pin9 =2,46V
pin11=3,29V
pin13=2,46V
pin30=3,28V
pin33=3,29V
pin37=2,45 (It should be 2,7V so there is voltage drop)
pin42=2,46V
pin44= there is a problem, its 0,45V, should be 3,3V.

I removed resistor R40 and when I plug tv to main socket, only LED is lighting. Nothing more. No reaction for pressing any button.
but do you solved the voltage problem of sda5555 ic.
 

piotrekn95

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It's a sound like a starting TV .

TV won't start if pin 44 has 0,45V ?
 

pradeep.g.belchada

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but pin44 should get a 3.3v , check the conitinuity on pin44 & ic014 pin1 which is o/p 3.3v& also check continuity pin 44 & pin 30 it should show
0 ohms
 

piotrekn95

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OK, I was checking for bad soldering. And I check the voltage again. I've got +3,3V on pin 44. But there is still no picture.
But tv isn't going to standby, it's working, but no picture, filament no glowing.
 

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