Another Vizio VW42LHDTV10A Inverter thread

[PotShotScott]

Okay so I've been doing some reading on this set (VW42LHDTV10A).

I believe I have a bad master inverter. With the power plug pulled out of the inverter I have 3.3VDC, 5VDC and 24VDC/grounds to run the modules. With the power connector plugged into the inverter I have 3.3VDC and a dismal 2.9VDC (24VDC and ground are still good). Blue inverter LED comes on for a second or two and then goes out. TV never really turns on (no backlights). There's a repair kit on ShopJimmy.

http://www.shopjimmy.com/lg-philips-...repair-kit.htm

Has anyone used this kit? I cannot find any references to low 5VDC but something has to be bringing it down on the board. I've already replaced the capacitors but I only had 470uF@25V not 35V. Should be fine for testing but it's just not coming on. Forgot to mention fuse is good too.

Any thoughts/suggestions on this would be appreciated - thanks!

Forgot to mention I have a Rev 1.3 master board.

[cyberhack]

Re: Another Vizio VW42LHDTV10A Inverter thread

Quick test connect a external 5v to see if it pulls down

[budm]

Re: Another Vizio VW42LHDTV10A Inverter thread

Those Voltages on the 4 copper pads are the control signals, as long as they are not <1V they are not off, >2V = ON for the BL-ON, the Dimming control can vary.
So the fuses are good and that SMD IC with bunch of pins is not blown?
Did some one replace one of the cap on that Master board? one is blue another one is black.
BTW, did you see the backlights even flash on for seconds?

[PotShotScott]

Re: Another Vizio VW42LHDTV10A Inverter thread

I replaced those caps with some used ones that I had laying around. 470uF@35 VDC came out and I put in 470uF@25 VDC. Am planning on ordering the right caps. The IC does not look burnt to me - no weird smells either. The first turn on line I measure is 3.3 VDC solid. The other voltage is 2.93VDC with all the cables connected but 5VDC with the cable disconnected. Fuses are good.

[budm]

Re: Another Vizio VW42LHDTV10A Inverter thread

The DC Voltage is fine, that 3.3V and drops down to 2.9V is probably the Dimming control signal.
If the Master board is good but the Slave board is bad then when you turn on the TV you will see backlights come on for seconds and the screen will be lit up half way, if the Master is bad (but the IC is good) and the Slave is good then only the other half will light up. At this point you need to fix the Inverter board or replace them since you do have the 24VDC and the Control Voltages to run the inverter boards.

[PotShotScott]

Re: Another Vizio VW42LHDTV10A Inverter thread

Still reading and learning. Measured my MOSFETs with a VOM tonight to see how they reacted. All of them reacted the same when measuring resistance from drain to source. However, one MOSFET on the slave board measured 0 Ohms from gate to source while none of them rest of them did this. Is that sign of failure?

https://cdn.badcaps-static.com/pdfs/...c50f07a0bb.pdf

[PotShotScott]

Re: Another Vizio VW42LHDTV10A Inverter thread

Got the inverter repair kit from ShopJimmy today. Am going to try Voltage regs and new caps before I do the IC's.

[budm]

Re: Another Vizio VW42LHDTV10A Inverter thread

You have to be careful, if the IC that drives the MOSFETs is bad, it can take out the new MOSFETs, so it is a gamble.

[PotShotScott]

Re: Another Vizio VW42LHDTV10A Inverter thread

I destroyed the Master board attempting to remove the IC. I need a better magnifier and a smaller iron. Ordered an inverter on eBay. Hope it's just the Master than I need. Thanks Budm. Merry Christmas!

[PotShotScott]

Re: Another Vizio VW42LHDTV10A Inverter thread

So I got the Slave board and all is well. This TV looks halfway decent. Thanks for the help.

[budm]

Re: Another Vizio VW42LHDTV10A Inverter thread

Thanks for the follow-up on the repair.