LG42LC55 sound from main board

[andrewblueboy]

hi all

i picked up a tv,but it comes with a problem. it can stay on for 10 -mins to half an hour then can turn off yet sometimes it can be seconds. i ve changed one bulging capacitor.
ive also notieced the black box on the power supply makes arc sound before it goes off,yet when running ok its quite.
so what i like to know is the black box the problem ,is it easy to change or am i better off getting another board. anyinfor appricated

thannkyou

[petehall347]

Re: LG42LC55 sound from main board

check the soldering

[andrewblueboy]

Re: LG42LC55 sound from main board

check the soldering

will do thanks

[andrewblueboy]

Re: LG42LC55 sound from main board

ive tried the resolder and it seems to be the same so ive takin the black thing off and used a multimeter in diode mode

1 to 2 nothin

3 to 4 beep

5 to 6 beep

could someone confirm ive done this right or wrong

oh and i think it might be a transformer

thankyou

[nomoresonys]

Re: LG42LC55 sound from main board

Did one of these not long ago, had the samwa caps, you probably should have at least changed all the caps in that area where one was bad, never hurts to go up a little in voltage, keep the same uf, in my case I went up from 1500 to 2200 uf, seems to be working ok.

[andrewblueboy]

Re: LG42LC55 sound from main board

Did one of these not long ago, had the samwa caps, you probably should have at least changed all the caps in that area where one was bad, never hurts to go up a little in voltage, keep the same uf, in my case I went up from 1500 to 2200 uf, seems to be working ok.

hi there i did check caps with my meter all were in there limits . although no harm in changing them as there only pennys. you say up the the volts a little but keep the same uf spec the same, wouldnt the 1500 to 2200 uf be to much.

ive takin the black box and looks ok but needing advice on this and were to get a replacement if need. thanks for your input

[nomoresonys]

Re: LG42LC55 sound from main board

the one I went from 1500 to 2200, was surrounded by 2200 uf caps, so I put in a 2200, seems to work ok, not sure if someone maybe put a different one in before I got it or not, will know better after a month or so, I don't expect any issues but you never know.

[nomoresonys]

Re: LG42LC55 sound from main board

An Indian guy? testing transformers. https://www.youtube.com/watch?v=GW_-ycgJXhg

[R_J]

Re: LG42LC55 sound from main board

On your transformer you should measure resistance between, 1 & 2, 3 & 4 , 5 & 6
Beeps only mean there is some continuity but every meter beeps at different resistance,
So measure the resistance on either the 200Ω or 2000Ω scale
recheck 1 & 2

[budm]

Re: LG42LC55 sound from main board

hi there i did check caps with my meter all were in there limits . although no harm in changing them as there only pennys. you say up the the volts a little but keep the same uf spec the same, wouldnt the 1500 to 2200 uf be to much.

ive takin the black box and looks ok but needing advice on this and were to get a replacement if need. thanks for your input

So the caps ESR are all OK?

[andrewblueboy]

Re: LG42LC55 sound from main board

very informative video there. going off that i think my transformer my be faulty between 3-4 pins no beeb in diode

[andrewblueboy]

Re: LG42LC55 sound from main board

So the caps ESR are all OK?

hi yes i have a meser-100 meter .only just got it and becoming very handy

[andrewblueboy]

Re: LG42LC55 sound from main board

On your transformer you should measure resistance between, 1 & 2, 3 & 4 , 5 & 6
Beeps only mean there is some continuity but every meter beeps at different resistance,
So measure the resistance on either the 200Ω or 2000Ω scale
recheck 1 & 2

hi there
right here goes
1-2 27.2

3-4 OL

5-6 0.5

this done on fluke 113 so my ohms is auto

thankyou for input

[R_J]

Re: LG42LC55 sound from main board

So the winding between 3 & 4 is open (OL), it should read the same as 1 & 2
5&6 is the primary, 1&2 is one secondary and 3&4 is another secondary
Check where the wire from the winding connects to the pin it could be broken at the pin, if not the winding is open.
On your meter you can push the "range" button to select the resistance range. 600Ω, 6kΩ, 60kΩ

In post #4 you said 1&2 were open (nothin)

[andrewblueboy]

Re: LG42LC55 sound from main board

So the winding between 3 & 4 is open, it should read the same as 1 & 2
5&6 is the primary, 1&2 is one secondary and 3&4 is another secondary
Check where the wire from the winding connects to the pin it could be broken at the pin, if not the winding is open.
On your meter you can push the "range" button to select the resistance range. 600Ω, 6kΩ, 60kΩ

In post #4 you said 1&2 were open (nothin)

thankyou for that information now im slowly getting a understanding of this. hopefully i could fix the pin if not time to look for another one.

[petehall347]

Re: LG42LC55 sound from main board

An Indian guy? testing transformers. https://www.youtube.com/watch?v=GW_-ycgJXhg

his transistors are diodes

[nomoresonys]

Re: LG42LC55 sound from main board

his transistors are diodes

Indeed and his bridge rectifiers are diodes too, lol.

[andrewblueboy]

Re: LG42LC55 sound from main board

ive found were the wire has snapped near the pin,although not longer enough to solder direct to the pin. so is it possible i could solder a new pieace of wire in to make the connection. if thats possible what could i use to cover the pin from as i had to remove sort of hard glue type stuff which covered the pin .

thankyou

[petehall347]

Re: LG42LC55 sound from main board

extend it or see if a turn can be removed for more length

[andrewblueboy]

Re: LG42LC55 sound from main board

extend it or see if a turn can be removed for more length

tried to unwind the wire to make it longer but it so tightly wrapped also i put meter on the piece off wire and theres no reading at all on that winding. been trying to dismantle but no joy. do you know were i could get a replacement as im having no joy except ebay and thats a complete board.

thanks for infro tho