Repairing JVC 42" LCD TV

[dave.martin]

ok just tested the 200V 1000uF caps and both tested at 170VDC just like you had figured. so then I tested the out put on the schottky Diodes all out put was the same 24VDC

 

[(*steve*)]

As long as you have this meter on a voltage range, and you don't short anything, you should not have anything blowing up.

And you have established that the PSU needs to be in the TV to power up correctly then you're going to have to do tests with it in place.

No need to measure across the capacitors, the measurements you've already done pretty much confirm that.

Now you need to find all of the low voltage DC rails and measure them. They may be marked where the cables from the PSU go to the other board(s).

First with power on, but TV off, then with TV on, bu in standby (if there is a distinction) and then adter you try to turn it on.

I am expecting to see a standby power supply operating with the device in standby.

What will be interesting is what changes happen when the power is turned on.

 

[dave.martin]

OK I think I found the problem... after checking what I could on the power supply board I directed my attention to the main board and pulled it off and pulled the magnafine glass out and started a chip by chip search and found 4 in question. Once the wife gets back with my Ipod ill try to get some pictures through the magnifine glass and see what you think.these might be a bit hard to replace since I do not know what they are... Pictures soon to come.

 

[dave.martin]

ok I found these in question on the back of the main board but I am unsure of what they are or how to test them I did notice that alot of the empty spaces with the same distance between the solder points has a diode symbol but I am just guesing at this point.

 

[(*steve*)]

Gee, that almost looks like corrosion to me.

A sharper (and closer up) image might help if you can get one.

At this point, getting a schematic would be really good too...

 

[dave.martin]

I'll work on getting one but yeh I thought corrosion also when I saw it.

 

[dave.martin]

I do wonder thought if its corosion then could I just resolver the connection to possibly fix it?

 

[dave.martin]

Arg freaking auto correct. I ment solder the connections

 

[(*steve*)]

Hard to say. If it *is* corrosion, you should clean up the board and check for any damage.

It may not be corrosion though.

And how would just this spot get corroded?

 

[dave.martin]

So I ended up finding the short in the TCON board, I also opted to remove the LCD panel from this unit and put it into a Toshiba model LCD TV... Thanks for all the help in trouble shooting this and I will hope to use the knoledge I have gained on the next project, beleave I have alot of them.