I have small problem in my LG700S monitor, any help?

lg studioworks heater 6.3 volt

Hello all,

It's almost my first post to this forum (Repair tips forums)..
I have a 17" LG Studioworks 700S monitor (like the shown in picture below)


I have a small problem with it.. The problem is that its colours are some how darker than usuall (more than one year ago ), it's not very bad thing, but it'll be better if i found a method to solve this brithness issue (of course it couldn't be solved from the front-pannel keys, even after setting them to maximum brightness)
Can someone suggest a solution?

Thanks in advance,
Ahmad,

service manual or the schematic for lg700s

hi ahmad_abdulghany


check heater voltage normal voltage is 6.3volt dc

Resolder the joints!!

cyber1 said:

hi ahmad_abdulghany


check heater voltage normal voltage is 6.3volt dc

Click to expand...

I'm not a monitor technican, hence i don't understand what u both mentioned!

Can u clarify more? Some detailed steps will be much helpful!

P.S. I may be only able to make tests with AVO meter, no TV-pattern gen, or other TV troublshooting instruments!

Thanks and regards,
Ahmad,

hello Ahmad
well, u don't need more than a soldering iron and AVO ( Multimeter)
just open the back cover of ur monitor and also u need to remove the shilding metal from the CRT (Cathod Ray Tube) base unit to be able to resolder all joints there and u can measure the heater voltage from there also as shown in the attached pic .
hope this is enough to guide u there , if u need the schematic for this model i can upload for u.
Kind Regards

sawwa7 said:

hello Ahmad
well, u don't need more than a soldering iron and AVO ( Multimeter)
just open the back cover of ur monitor and also u need to remove the shilding metal from the CRT (Cathod Ray Tube) base unit to be able to resolder all joints there and u can measure the heater voltage from there also as shown in the attached pic .
hope this is enough to guide u there , if u need the schematic for this model i can upload for u.
Kind Regards

Click to expand...

Yes, please, upload schematic of my monitor...

Also what if i found heater voltage greater or less than 6.3V ??

And what let you sure that the problem is in heater voltage specifically??

Thanks for help,
Ahmad,

[quote="ahmad_abdulghany

Yes, please, upload schematic of my monitor...

Also what if i found heater voltage greater or less than 6.3V ??

And what let you sure that the problem is in heater voltage specifically??

Thanks for help,
Ahmad,[/quote]

hello Ahmad
here's the complete service manual for ur monitor and it has a good service information that will help u repair ur monitor .
well, supposed to find the heater voltage less that 6.3V not more that 6.3V and that's the reason why the brightness is dim and in this case u have to check the supply rail to the heaters and may be u will need to replace the electrolytic caps on this rail , i have also attached a pic for the components that mostly responsible for causing that and hope it'll help u solving this problem.
about ur second question , i'm not sure that the problem is in heater voltage specifically , but this is the first thing we check before going further, may be u have a video output problem , may be u have to change some caps or a resistor that goes high in value or leaky transistor or diode , it'll be easier to have the problem here rather than checking the video output circuit.
i hope it'll be solved soon
Kind Regards

i know this fault and monitor

you need to look on the tube base panel
{unscrew its tube neck clamp and pull it off gently}

on this pcb is a driver ic for the tube emittion guns

this ic is fed with low tension +12v and a resoviour cap
replace this cap {usualy 220uf or 300 or 470uf type}

you will also find that there is three small 1uf
{or 2.2uf 4.7uf or sometime 10uf capacitors}

they couple the red green and blue signals to this driver ic
the ic then amplifies them and drives the tube guns

you must replace these low value caps
becouse inside them was a liquid called an electrolyte

this has simply dried out

and you wont get as much drive to each input
to this driver stage as you had before they dried up

now
once youve done this fit a fan to your monitor
i recon you live in a hot country or the montitor is in a high tempreture area of the home
or... left on all day in standby


totaly ignore the heater supply its a red hearing
in over 20 years of bench work
ive seen two faults with heaters both were the filiments
even if the filiments were supplied with less voltage this wouldnt affect the brilience of the picture
right down as low as 3v lower than this maybe
a quick look at the base panel in a dark room
will confirm good heaters
three bright orange dots inside the tube

or low heater supply 3 dull red dots
but i still would replace the associated caps 10v circled above anyway

....

VSMVDD said:

i recon you live in a hot country or the montitor is in a high tempreture area of the home
or... left on all day in standby

Click to expand...

I leave it almost all the time in stand-by mode! It may remain for more than a month ON

I didn't think that this may harm it!

Thank you all ...
I will begin to fix and feedback..
Ahmad,

so first

its a very bad idea to leave monitors flashing and in standby
esp 24hrs a day

this is what caused the caps to dryout
most {80%} of monitors leave the psu running or part running
when its in standby


and it costs you about 1/3 or 1/2 the amount of energy to do this
as it normaly uses when its in use

ill also add this is a stupid thing to do for any equipment
maybe it will go on fire as often happens and burn you to death

SO DONT LEAVE IT ON STANDBY AGAIN EVER.......

also this increases your carbon footprint and is bad for our planet


....

VSMVDD said:

also this increases your carbon footprint and is bad for our planet..

Click to expand...

Ok, for this point espesially, I won't again ...
hehe

Yes, please do not leave your equipment on when you are not using it.
You may or may not be personally paying for the electricity, but the rest of us all are paying for the environmental problems that this may cause, however small an impression that your monitor makes on the problem.

Global warming is all Ahmad's fault... lol

Sombody pleas gift me value of R342, 341,3345 on LGF700, my resistor monitor is burning.

yenhanso said:

Sombody pleas gift me value of R342, 341,3345 on LGF700, my resistor monitor is burning.

Click to expand...

hello
hope this could help u
Regards