Sharp LC-42D62U Inverter board

[budm]

Re: Sharp LC-42D62U Inverter board

I do not use anything less than 40 Watts Iron.

[FlipTV]

Re: Sharp LC-42D62U Inverter board

Ok good to know. I was looking to buy a 60 watt iron possibly one that is adjustable.

If yiu go too high on the wattage, could it damage the board?

[budm]

Re: Sharp LC-42D62U Inverter board

You use in 60 Watts mode when you work on piece of work that has lots of mass that will cause the temp to drop due heat sinking effect. You will develop your skill when you solder lots of works.

[FlipTV]

Re: Sharp LC-42D62U Inverter board

Ahh, okay. So the wattage used depends on the mass of the object you are working on.

If I buy an adjustable 60 watt iron, and am bout to solder the fuse I should lower the wattage to around 25-30

[budm]

Re: Sharp LC-42D62U Inverter board

Set it too about 40 Watts, what happen when you set to low wattage is that you will be heating the circuit traces for a long time due to heat sinking of the solder tip and you will end up lifting the traces. You should practice on junk board and try using different setting to see what happen. It is the real hands on learning.

[cashkennedy]

Re: Sharp LC-42D62U Inverter board

If you buy a soldering station it will have a temperature selection , If the part your desoldering has a lot of metal / is attached to a thick metal section of the board, youll have to turn the heat up higher then youd normally solder at. Leaded solder also melts at a much lower temp the lead-free, so when soldering you might adjust your temperature up 50 or 100 degree Celsius based on what you run into.

[retiredcaps]

Re: Sharp LC-42D62U Inverter board

So when I put the MM into continuity mode, touch the 2 ends of the fuse, should it beep if it is good??

It helps if you think of continuity (beeping) not in terms of good or bad, but as a tool that shows resistance readings of 25 ohms or less.

As I wrote before, a good fuse measures less than 1.0 ohm. Your Fluke 12 will beep.

A fuse that measures 20 ohms is bad and your Fluke 12 will beep.

[FlipTV]

Re: Sharp LC-42D62U Inverter board

Thanks everyone for all the helpful information.

[FlipTV]

Re: Sharp LC-42D62U Inverter board

So i replaced the fuse and the fuse gets 24v on both sides. I tested the 2 white fuses below and they are getting 24 volts as well.

II am now getting 2 seconds to black.

When I test the voltage on the test points near the transformer, it reads. 03 volts.

The slave board acts the same way as the master.

I'm banging my head on the wall now lol.

Please help

[FlipTV]

Re: Sharp LC-42D62U Inverter board

Also, when I take the reading of the rest point on the inverter when powering on the tv it reads 12 v then goes to. . 03 volts.

[budm]

Re: Sharp LC-42D62U Inverter board

So are you using the old boards and you also seat all the lamp connectors, clean the burnt connector real well? If one of the lamp does not turn on or will not fire up, or not connected or stays conducting, it will also shutdown the inverter.

[FlipTV]

Re: Sharp LC-42D62U Inverter board

I did buy a new slave inverter originally due to the burnt mark i saw. It does it with both the new and old slave inverter.

Can I clean the connectors using rubbing alcohol?

Also what could explain the. 03 voltage reading I am getting now?

Prior the the fuse install it was getting 24 volts

[budm]

Re: Sharp LC-42D62U Inverter board

Can you show me that test point in the picture? This thread is getting long and hard to keep track now.

[FlipTV]

Re: Sharp LC-42D62U Inverter board

Here you go.

[budm]

Re: Sharp LC-42D62U Inverter board

OK, I see the picture of the transformers but I do not see the marking where the test point is. Is it right on the leg of the transformer?

[FlipTV]

Re: Sharp LC-42D62U Inverter board

Right next to c326 and below it.

Prior the to the fuse install, it read 24v
Think I might have a cold solder on the fuse?

[budm]

Re: Sharp LC-42D62U Inverter board

OK, you were looking directly at the primary side of the transformer, which when the MOSFETs that are driving the transformers are not on yet when in TV in standby mode which you should see 24V on the transformer pins, when the inverter circuits start driving transformer by pulsing the DC with real high frequency, then you will need meter that can read AC (the voltage at the transformer pins are no longer at steady, but pulsing) at very high frequency it can be as high as 80,000 Hz, which your meter can not response that fast. When the lamps flash on and do the 2-second to black, one it is black out, that 24V should be there again, unless the inverter board tells the main board to shutdown the 24V power supply.

[FlipTV]

Re: Sharp LC-42D62U Inverter board

Here's the thing, I no longer get 24 volt reading on the test point in the pic I attached above.

Thinking it was a bad solder job, I removed the fuse and tested the test point and received 24volts

Resolder the fuse and got. 03 volt on the test point.

So there is a line of caps going down the center and one side when you take readings is 24 v the other side is. 03

Is there something faulty going on which is causing the voltage to go from 24 to 03v as soon as it crossed the line of caps?

[budm]

Re: Sharp LC-42D62U Inverter board

But that blown fuse is for the PWM IC which drive the MOSFETs that drive the transformers, the white fuses are the one that supply the 24V to the primary winding of the transformer. You can verify by measuring the resistance between the white fuse and the primary side winding of the transformer. Beside you did not have the backlights on at all before replacing that black fuse. omething has to short out real bad to drop the 24V power supply, which if that is the case, the white fuses should have blown.
Just to be sure, what do you get at point 1 and point 2?
At this point the inverter is sensing something to cause it to go into shutdown.

[FlipTV]

Re: Sharp LC-42D62U Inverter board

What would you suggest to be the next thing to troubleshoot on the inverter?

II have a whole new respect for people in the electrical field.

I work in IT and man this is such a learning curve.

It's very intriguing though.