Toshiba 42xv540u no power blowing top right fuse

[gmzombie]

Ok so I bought this tv for 25 dollars from a computer store since they just put items out. I knew it didn't have power and thought I can fix it. Got it to the shop and pulled off back to see that fuse is blown. I replaced fuse and plugged tv in to it blowing immediately. I started thinking and testing diodes and resistors. I've come to the conclusion they it maybe the bridge rectifier as when I take levels from it while it is off and out of circuit I get from positive side to negative side check,on the diode on my meter of course,all other pins against the first pin and 2/3 pin give a .450 but the last pin give a .889 which to what I understand is bad. We want the same across all of the pins correct?. When I check voltage across the bridge while it has power the dc voltage goes up to 160vdc then drops to 120vdc and the ad side of things checks at 114vac and that stays the same. There is no standby power or anything since it blows the 2.5a fuse on top right. Here is a pic of the power board.

[budm]

Re: Toshiba 42xv540u no power blowing top right fuse

We need to see the whole back side of the TV so we can see how all the boards are connected together, and then good clear pictures of each board showing top and bottom side traces.

[gmzombie]

Re: Toshiba 42xv540u no power blowing top right fuse

There are some pics on the backside of the power board and a pic on all 3 boards hooked up how they should be.

[gmzombie]

Re: Toshiba 42xv540u no power blowing top right fuse

Here is the mainboard back

[gmzombie]

Re: Toshiba 42xv540u no power blowing top right fuse

I've seen another post online about a bad r850 and Sr81 so I have taken them out and checked them. The r850 is testing a 2.0 but when I apply power to the board when it is powered up I can see that the relay doesn't switch at all.

[dick_barton]

Re: Toshiba 42xv540u no power blowing top right fuse

What is the part number on the IC to the left of the fuse holder (top right) which is mounted on the black heatsink?

[budm]

Re: Toshiba 42xv540u no power blowing top right fuse

OK, this is the diagram of the power supply version 1. I do not know if you have version 1 or version 2.
I would inspect the power devices for shorts, anything that does not read right on the board should be removed and test off the board.

[gmzombie]

Re: Toshiba 42xv540u no power blowing top right fuse

That ic is str z2589. Thanks for the diagram as I have been searching for about a week for one lol.

How would you go about testing the are z2589?

[gmzombie]

Re: Toshiba 42xv540u no power blowing top right fuse

I guess the repair kit on eBay has this exact item and a fuse so I'm going to purchase that and go from there.

[gmzombie]

Re: Toshiba 42xv540u no power blowing top right fuse

Ok an update I have installed the str ic and I'm still blowing fuses. Hmm when I take readings on the bridge rectifier my dc voltage drops from 160 to 123 and goes back up..is it supposed to do that or is it supposed to be steady? If it is supposed to be steady I may be looking at voltage regulator possibly.

[gmzombie]

Re: Toshiba 42xv540u no power blowing top right fuse

hmm still havent figured this out can anybody answer my question above?

[gmzombie]

Re: Toshiba 42xv540u no power blowing top right fuse

I have replaced the voltage regulator and still blowing fuses. So when testing voltage at that fuse after replacing the voltage regulator i have on one side 37vdc and on the other side using the same ground i have -37vdc but if i swap wires around im getting 37vdc on each side of where the fuse is supposed to be but not in. SHouldnt there be no voltage on the other side of the fuse. im totally lost on this right now.

[gmzombie]

Re: Toshiba 42xv540u no power blowing top right fuse

ok so i have been checking some of the small smd resistors after tracing down some voltage and noticed r8626 calls for a 12k and its a 10.4..not to bad but then we goto where 25v comes in and at r8627 it calls for a 68k and i have 33k almost half. next resistor i see that is bad possibly is r8622 which calls for a 47k and it comes in at 22.7 im thinking that is what could be blowing my fuses but im not sure and would really appriciate some assistance from someone other than myself. im using the schematics from a few posts up.