Friday, April 27, 2012

LG 32LB4D / 32LC5DC-UA / 32LC7D does not turn on - power board EAY33058501/13 repair procedure

A major motel chain recently sent us a bunch of power boards EAY33058501/13 coming out of LG 32LB4D, LG 32LC5DC-UA or LG 32LC7D LCD TV models.

They had all worked in climate controlled indoor rooms and all had the same or similar issues - standby light coming on, but TV refunding to completely turn on or turning on for a short while or turning itself off shortly after coming on; sometimes the TV may come on, but without an image.

All power boards had the same set of capacitors visibly swollen at the top.

Below is the picture of the board:


The bad capacitors were C221, C222, C223, C232 (located below the upper right heat sink saying CTVR 32'' on the picture), also C203 in the same group, and C207 and C204, C205 located under the lower right heat sink.


When replacing the capacitors make sure to use same or better values for them, specifically same or better temperature rating and same or higher voltage!


Generic electrolytic capacitors found at RadioShack retail stores are usually of lower quality than the ones you need and I recommend against using them yet when nothing else is available they can be used as a temporary patch.


If you want the set of capacitors you can order it directly from here:










I've seen this power board also have other issues.
At least twice I've seen it being completely dead, usually as a result of a power surge that causes damage in a power component on the primary side, usually leading to a blown main fuse (next to the power plug). 

I can remember at least one case where the two power FETs Q150 and Q151 were blown and had to be replaced, possibly along with some smaller components around them too.


And there was at least another case where the +5V standby voltage would come on and the TV would respond to turn on command, but will shut itself off as a result of overvoltage in the mail power lines.


You should test the voltages that the board produces when it is activated. It is not hard to do.


The connectors with power outputs for the main board are at the lower right corner of the board and look like this (click to enlarge):


 
You can see where the constant +5V standby output voltage is and right next to it is the pin that is used to tell the power board to turn on all other voltages, well, except a specific 3.4V output that is regulated separately.


To test the power board you can put it on a bench and manually short the POWER_ON and the +5V SB pins.


You can then measure the rest of the voltages as printed on the board, right by the connectors, including the 24V output at the P204 and P205 connectors not shown on this picture.


Note there are some control pins that do not produce output voltages; for example on P204 there are  4 pins at the right side labeled BRI, I-C, DIM and ERR. 


The same can be found on P201 and in fact the power board is simply being used to bridge the signal from one connector to the other.


Normally the output voltages are slightly *above* the declared values: 19V is 19.7V, 6V is 6.5V to 7V and 24V is closer to 25V.


This is OK as long as they are stable and within 5% to 10% of what's printed on the board.


When they are missing or significantly off or when the primary fuse is blown as mentioned above then the board has a more serious failure and needs to be serviced or replaced.

If interested in a repair service do not hesitate to contact us!

3 comments:

Marjan bavdek said...

Great post. I'm having similar problems with same board. When I've got this LCD, two capacitors were missing. I think C203 and C204 ( two green ones lower-middle area on the first picture). To put a TV on standby I've put there, what I have in stock of 35V capacitors (1x820uF 35V and 1000uF 35V). When I've turned ON a TV, backlight lights normal,but when OSD comes on panel, backlight dimms and inverter buzzes. Then TV turns OFF to standby. I've also noticed, that 5 capacitors C221, C222, C223, C232 were been replaced, but with funny specs ( 2x470uF 10V ????
3x 1000uF 25V)and that area is litle darker (smoked). I'm pretty sure, that I have wrong capacitors on it, so I'm asking you to give me specs of those electrolytic capacitors. Please give me specs of C203,C204,C205,C221,C222,C223 and C232. Thank you.

Marjan bavdek said...

Sorry a've already got specs for those capacitors. If anyone will look for same thing there are:
C203 470uf/35v
C204 3300uf/10V
C205 3300uf/10V
C221 1000uf/35V
C222 1000uf/35V
C223 1000uf/35V
C232 1000uf/35V

Raymond Isbill said...

So I have a 32" LG 32LCD7D or I thought that's what I have but the PS board looks different.

Post a Comment