Sharp Aquos 70" LED LC-70LE632U does not power on

[Teletubbie]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

You need to check the main PFC capacitors with the power plugged in. Black lead to negative on capacitor and positive with red lead. You should have about 170 volts DC across each of those capacitors

Checked the voltages with the power plugged in and it measured 170V DC for all three main capacitors.

[budm]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

Diode D7951 is the half-wave rectifier, C7951 is the filter cap, this feed the 5V regulator IC7590 for the BU5V (STBY 5V) PD pin 15.
So did you lift one leg of the diode and retest it?

Sharp RUNTKA857WJQZ (DPS-222BP, 2950284203) Power Supply Unit
http://www.shopjimmy.com/sharp-runtk...pply-unit.htm#
Pictures provided by shopjimmy.

[Teletubbie]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

Does it matter which one end of the diode I desolder to test it?

[budm]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

Does it matter which one end of the diode I desolder to test it?

No.

[Teletubbie]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

While I desolder the diode and test it, here is a high resolution image of the back side of the power board with the diode D7951 marked in red in the lower left corner.

[budm]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

I uploaded the pix from SJ on post 22.

[Teletubbie]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

Desoldered one end of D7951 and it still measures 0.0 on the multimeter diode test. The following name is marked on the diode SB2100 (first row) and 050 (second row). Not sure of the letter 1 or I in "SB2100".

[budm]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

SB2100:

[Teletubbie]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

I cannot seem to find where to source this part online. Would it be available in a Radio Shack store?

Should I test more parts on the board while I source this diode?

[budm]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

I doubt you will find this Diode at Radio Shack.
Good ideas to might as well test the other devices, you should resolder the transformer legs and devices mounted on the heatsink, you can see that they use the rivets for some of the legs which tend to have cold solder joints, make sure to use Flux.

[Teletubbie]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

I can order it here for $3.50 (lot of 10) with free shipping but it takes 10-15 days for delivery.

[budm]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

You can get the sub from digikey, just have to match the spec, it will be faster but more expensive.

[Teletubbie]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

I doubt you will find this Diode at Radio Shack.
Good ideas to might as well test the other devices, you should resolder the transformer legs and devices mounted on the heatsink, you can see that they use the rivets for some of the legs which tend to have cold solder joints, make sure to use Flux.

Can you please point to me the numbers marked on the board to know where these legs and rivets are located? Thanks.

[budm]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

Through hole rivets samples.

[Teletubbie]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

Ordered the diode, it will take 10-15 days for delivery.

When I get it, should I do the following?

• Desolder the old diode and remove it
• Cut the ends of the new diode to the same length as the old diode
• Orient the new diode the same way as the old diode and solder it
• Install the board
• Connect the cables back and plug in the power cord

Is there any thing else I need to know?

Budm: Thanks a lot for all your tutorials. Very well written. I read all your troubleshooting and getting started guides before I posted this thread. It was very helpful!
Thanks.

[budm]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

You should make the diode legs longer so when it is mounted the body will be above the circuit board may be 1/4 inch or so to help aid cooling of the Diode, diode legs are part of the heatsinking.

[freakaftr8]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

Good find! Hopefully replacing the diode does the trick. I had seen some power supplies for the transformer get so hot that it makes other semiconductors around it like diodes and resistors overheat and they like to short circuit or open

[Teletubbie]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

You should make the diode legs longer so when it is mounted the body will be above the circuit board may be 1/4 inch or so to help aid cooling of the Diode, diode legs are part of the heatsinking.

I am fairly new to soldering. A couple of questions:

1. To desolder an existing diode from a board, do you heat the joint from the front side or the back side of the board to melt the solder? A youtube video said you should add some new solder to help desolder an existing component. Is this true?
2. When you install a new diode, do you solder on the front side, back side or both?

[calimark]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

I am fairly new to soldering. A couple of questions:

1. To desolder an existing diode from a board, do you heat the joint from the front side or the back side of the board to melt the solder? A youtube video said you should add some new solder to help desolder an existing component. Is this true?
2. When you install a new diode, do you solder on the front side, back side or both?

Yes its true, it helps to get things flowing much faster. If you don't have a solder sucker or wick, you might have a harder time removing it.
It may be easier to clip the diode out and then just de solder the two small pieces left behind. Less metal and no diode eliminates the heat sinking ability and lets you get more heat to the solder joint.

When installing, if you get a good flow- you probably wont need to touch the front side, just the back.

[Moreno83]

Re: Sharp Aquos 70" LED LC-70LE632U does not power on

If you don't have solder wick/solder sucker you can heat up the solder and stick a toothpick in it to create a hole. ( as the solder won't stick to wood ).