can the psu be removed for testing

[terry681]

i was wondering if its possible to remove the psu from my lcd tv and have it on the table so that i can get a better idea of the volts around those small smd at the solder side of the board on the 32lc2d lg, and if so how i have a idea how it may be done but not a 100 percent

[newtothis]

Re: can the psu be removed for testing

Yes but use a bench power supply as power source at a lower voltage. Will give you what you need for testing but remember that it isnt grounded.

[terry681]

Re: can the psu be removed for testing

just my luck ehh i dont have bench power supply as im at the end of my tether with this psu as im not prepaired to purchase another one so my aim is to try and repaire and learn more if possible and fix this and i belive iv narrowed it down to those small smd on the solder side of the board and it is this, i would like to check their voltages those components as i think the low 3.4 v is down to those being bad thank you very much for replying.

[newtothis]

Re: can the psu be removed for testing

just my luck ehh i dont have bench power supply as im at the end of my tether with this psu as im not prepaired to purchase another one so my aim is to try and repaire and learn more if possible and fix this and i belive iv narrowed it down to those small smd on the solder side of the board and it is this, i would like to check their voltages those components as i think the low 3.4 v is down to those being bad thank you very much for replying.

Ive done them off chassis mind you... croc clip a common ground. Just be damn careful!

[newtothis]

Re: can the psu be removed for testing

Just check the ohms of the SMD components, See what resistance you get etc... I never test them whilst live

[terry681]

Re: can the psu be removed for testing

i dont know if iv tested these components correctly as im reading on q204 source to gate=.181
source to drain=.308
q205 source to gate=1.655 and rises
source to drain=.308 and rises both are irf 3037 smd ic using my dmm on the diode setting have i done this correctly to test those mosfets ty again guys

[tom66]

Re: can the psu be removed for testing

I think it's usually the 3.4V controller IC on the power boards that fails not the fets.

[terry681]

Re: can the psu be removed for testing

tom mate im learning as i go so the iru3037 is the controller how would i test check this smd ic as i rekon this area hold the key to the low 3.4v issue i think lol

[tom66]

Re: can the psu be removed for testing

Yes it's a controller IC; I can't see an easy way of testing it though.

[terry681]

Re: can the psu be removed for testing

and for the life of me i couldint find the power supply schematic but that item must be somewhere how do the lg techs get by for their info any way the reason i think the fault lies in that area of those 3 smd ic 1 ic controller3037 and 2 ifr7807 mosfets as this is for the 32lc2d lcd tv and the voltages for both broken psu are roughly the same with the origianal showing on its 3.4v =1.00v and the replacment now the same as the original broken lol shows on its 3.4v line=1.39v. did the numbers look ok when i tested those mosfets i mean did i do them right as i said mate im still got a load to learn but by hook or by crook ill fix this tv

[tom66]

Re: can the psu be removed for testing

No schematic for most LG power supplies.
The techs follow a flowchart which will end up in board replacement -- very rare for component level repair to happen nowadays.

[terry681]

Re: can the psu be removed for testing

tom do i need anything special in the soldering department for replacing those small ic the controller and the mosfets as iv got nothing to lose by trying to replace those components starting with the controller 3037 and see what that does for me or do u have any idea of how i should proceed without getting a new psu lol and again cheers mate for ure input

[tom66]

Re: can the psu be removed for testing

Generally a small tip works good, though not too small.

Temperature controlled iron is preferred, rather than one which just plugs into the mains.

Flood the pins with solder, then push side to side to remove the device.

[terry681]

Re: can the psu be removed for testing

im not getting off to a good start i have 3 solder irons and all wall mains type diffrent wattage thou from a weller 15 watt mains power and 30 watt skytronic mains iron and a other 15 watter.. ill try and get by on what i have iv sent for the replacment ic anyway as i said ill try that and before they arrive ill pratice on some old board with smd ic similar and go from there as iv taken every capacitor out except the largest one on the board and they all looked good their uf microfarad and esr and iv read a few other forums and that fault looks to originate to that area of the board .ill post a pic of the repaire that was done to the board when i got it but it worked but the solder job looks awfull i thought and its in that 3.4v area

[tom66]

Re: can the psu be removed for testing

Minimum 30W really to do that job, I use 65W w/ temp control which works well.

[terry681]

Re: can the psu be removed for testing

ill give it a go when i receive those parts and heres a pic of my original board in that same 3.4v area u can see that some one repaired that area of the board on my replacment from the ebay so ill wait and report if i get any good news cheers mate