Sony KDL-48W600B software update with no picture

[budm]

Re: Sony KDL-48W600B software update with no picture

OK, so the Cathode of that DD1 is not connected to circuit GND.
I can only do so much as far as tracing out the board using the picture, so at this point you just have to find out what else is connected in parallel with the cap CD100.
We now know that we have shorted circuit, it is just a matter of locating it.
I am soory that I cannot provide more help due to not having board in front of me but at least we are getting close in solving the problem.
Remember to use Ohm mode so you can actually see the resistance.

[DXseekerMO]

Re: Sony KDL-48W600B software update with no picture

I added another pic below. Hope this helps?

In parallel is ICD1, number BD8120. Is this the gamma control IC I keep hearing about in these TVs? Could be shorted?

[budm]

Re: Sony KDL-48W600B software update with no picture

It is BD81206 LCD BIAS power supply, I could not find any spec sheet or any application circuit for it. It has similar function as TI TPS65167a.
It generates multiple Voltages (switching power supplies using those inductors LD1, LD2, LD4, LD6) such as AVDD, HAVDD, VCC 3.3V, etc.
The HVIN_12V is the input 12v fed by that switched MOSFET ICD2.
If you look at the Samsung T-CON board PDF attached, you can see similar topology. it may be that the output drive pin of the BD81206 which is connected to the inductor LD1 is shorted out, you will have to remove LD1 to isolated it and see.

[DXseekerMO]

Re: Sony KDL-48W600B software update with no picture

It is BD81206 LCD BIAS power supply, I could not find any spec sheet or any application circuit for it. It has similar function as TI TPS65167a.
It generates multiple Voltages (switching power supplies using those inductors LD1, LD2, LD4, LD6) such as AVDD, HAVDD, VCC 3.3V, etc.

I also looked for a datasheet to no avail. I found them on ebay and Google but none of the vendors have a datasheet listed. If this chip is shorted shouldn't I be able to find low resistance between the circuits you listed above, AVDD etc? Also, can you tell by looking which of those pins is ground?

Interestingly enough, the T-CON board from the parts pile has the exact same number LCD BIAS power supply upon it. If I can find the ground pin maybe I can somehow compare resistance readings between the two and see what I come up with?

[budm]

Re: Sony KDL-48W600B software update with no picture

Read my updated post with schematic.

[DXseekerMO]

Re: Sony KDL-48W600B software update with no picture

The HVIN_12V is the input 12v fed by that switched MOSFET ICD2. If you look at the Samsung T-CON board PDF attached, you can see similar topology. it may be that the output drive pin of the BD81206 which is connected to the inductor LD1 is shorted out, you will have to remove LD1 to isolated it and see.

Or could I lift the pin on BD81206 that is in-circuit with that inductor? EDIT/ADD: It looks like I'll need a hot air station to remove LD1?

[budm]

Re: Sony KDL-48W600B software update with no picture

Hot air or use high wattage soldering iron by adding more solder to both pads while applying solder tip back and forth between the two pads, but you have to be real careful due to you are working close to the tab bonding.

[DXseekerMO]

Re: Sony KDL-48W600B software update with no picture

Hot air or use high wattage soldering iron by adding more solder to both pads while applying solder tip back and forth between the two pads, but you have to be real careful due to you are working close to the tab bonding.

budm, if you had a first suspicion based on experience what component would you suspect first? MLCC cap, transistor or IC?

In most instances do MLCC caps show outward signs of failure, like a line on them or maybe fracturing, or do they more often fail with no outward signs of failure?

[budm]

Re: Sony KDL-48W600B software update with no picture

MLCC failure mode is short circuit, they do crack if not properly handled.
That inductor LD1 and Diode DD1 is part of the Boost converter circuit driven by that IC81206. I have a feeling the short is in the IC, but to verify it you have to remove the inductor or disconnect the IC pin which will be difficult, if you look at that Samsung T-CON schematic you can see how that section works. You can cut the trace going to the IC to isolate it .

[budwich]

Re: Sony KDL-48W600B software update with no picture

not sure if this idea would help, but perhaps you can do a "divide in half" type investigation. By this I mean, can you trace thru the board a bit and perhaps find a "strategic trace" that you can cut (at a point easily repairable later), such that the "cut" divides the components that you need to potentially desolder in half. This might get you to the faulty component a bit faster... maybe.

[DXseekerMO]

Re: Sony KDL-48W600B software update with no picture

MLCC failure mode is short circuit, they do crack if not properly handled.
That inductor LD1 and Diode DD1 is part of the Boost converter circuit driven by that IC81206. I have a feeling the short is in the IC, but to verify it you have to remove the inductor or disconnect the IC pin which will be difficult, if you look at that Samsung T-CON schematic you can see how that section works. You can cut the trace going to the IC to isolate it .

Yeah those pins are short and narrowly spaced....I can see lifting one of those pins being a pain. I might add solder and use two soldering irons to melt solder and pluck the inductor off the board. This is how I remove MLCC caps, seems to work ok?

not sure if this idea would help, but perhaps you can do a "divide in half" type investigation. By this I mean, can you trace thru the board a bit and perhaps find a "strategic trace" that you can cut (at a point easily repairable later), such that the "cut" divides the components that you need to potentially desolder in half. This might get you to the faulty component a bit faster... maybe.

I think with my small soldering skills needing work I may just pull that inductor and see if the short drops out.

[DXseekerMO]

Re: Sony KDL-48W600B software update with no picture

MLCC failure mode is short circuit, they do crack if not properly handled.
That inductor LD1 and Diode DD1 is part of the Boost converter circuit driven by that IC81206. I have a feeling the short is in the IC, but to verify it you have to remove the inductor or disconnect the IC pin which will be difficult, if you look at that Samsung T-CON schematic you can see how that section works. You can cut the trace going to the IC to isolate it .

not sure if this idea would help, but perhaps you can do a "divide in half" type investigation. By this I mean, can you trace thru the board a bit and perhaps find a "strategic trace" that you can cut (at a point easily repairable later), such that the "cut" divides the components that you need to potentially desolder in half. This might get you to the faulty component a bit faster... maybe.

Inductor plucked, short still exists at both CD100, ICD2 and ICD1. I re-tested the test points on the board (vone, vcc3.3, 15 and 18, AVDD etc) and the only one that indicates short now is HVIN12V at 12ohms. A couple of the others had resistance in the thousands of ohms but all indicate infinity now after removing the inductor.

[budm]

Re: Sony KDL-48W600B software update with no picture

'Inductor plucked, short still exists at both CD100, ICD2 and ICD1.'
That does not make sense to have ICD1 (BD82106) pin that is connected to the LD1 pad still showing short and CD100 also still showing short.
Can we see the picture of the board now since LD1 is removed?

[DXseekerMO]

Re: Sony KDL-48W600B software update with no picture

'Inductor plucked, short still exists at both CD100, ICD2 and ICD1.'
That does not make sense to have ICD1 (BD82106) pin that is connected to the LD1 pad still showing short and CD100 also still showing short.
Can we see the picture of the board now since LD1 is removed?

Here you go budm:

[budm]

Re: Sony KDL-48W600B software update with no picture

https://www.badcaps.net/forum/attach...9&d=1549486060
So based on the picture of the LD1 not in place so if you check the resistance between GND and each empty pad, you are saying they both show <10 Ohms?

[DXseekerMO]

Re: Sony KDL-48W600B software update with no picture

https://www.badcaps.net/forum/attach...9&d=1549486060
So based on the picture of the LD1 not in place so if you check the resistance between GND and each empty pad, you are saying they both show <10 Ohms?

On the left side pad of LD1 (as pictured, next to HVIN12V) the resistance to ground is 11.9ohms. The right side pad (goes to anode side of DD1 and that pin on ICD1) to ground is 1.4ohms.

Chassis ground was referenced

EDIT ADD: I would have thought the short at ICD2 would have disappeared after LD1 was removed. It is showing short direct from the two top left pins to the two bottom left pins.

[budm]

Re: Sony KDL-48W600B software update with no picture

"The right side pad (goes to anode side of DD1 and that pin on ICD1) to ground is 1.4 Ohms." That tells me that pin of the IC is really shorted out. Just to be sure, check the Cathode of DD1 to make sure it does not show about the same Ohm either.

[DXseekerMO]

Re: Sony KDL-48W600B software update with no picture

"The right side pad (goes to anode side of DD1 and that pin on ICD1) to ground is 1.4 Ohms." That tells me that pin of the IC is really shorted out. Just to be sure, check the Cathode of DD1 to make sure it does not show about the same Ohm either.

Cathode of DD1 to ground shows infinity

I see a path from ICD2 to that pin. Is it possible ICD2 is short as well? It shows short, see previous post.

[budm]

Re: Sony KDL-48W600B software update with no picture

Since the LD1 is removed then there is not path for the ICD2 to get to the pin of ICD1 or Anode of DD1.

[DXseekerMO]

Re: Sony KDL-48W600B software update with no picture

Since the LD1 is removed then there is not path for the ICD2 to get to the pin of ICD1 or Anode of DD1.

Yes you are right, sorry I did a lousy job saying what I meant. With LD1 in place there is a direct path from that pin on ICD1 to the two pins on ICD2 that indicate short to ground. If I measure between either of those pins and the pins directly opposite I get a reading of short direct.

I also get a reading of short to chassis ground on both sides at the same pins.

I believe this may be a transistor