Sony KDL-37XBR6 Black Screen :(

[budm]

Re: Sony KDL-37XBR6 Black Screen

I was thinking around 12V. I did measure one side of the fuse and it was 12.06V and then went to 12.26V when the power button was pressed to on. The other side of the fuse shows no voltage. So if I change this fuse out with same, will this fix the problem? Thanks!

Good, please do as Vince suggested.

[Gammaray]

Re: Sony KDL-37XBR6 Black Screen

OK, I'm getting around 314 ohms on the same side of fuse I measured the 12V. On the other side I get 0 ohms.

[vinceroger69]

Re: Sony KDL-37XBR6 Black Screen

you need too test that transistor budm has marked in post 54 as looks like you have a short on that side of the fuse

[Gammaray]

Re: Sony KDL-37XBR6 Black Screen

you need too test that transistor budm has marked in post 54 as looks like you have a short on that side of the fuse

OK, thanks! But not sure how I can test it. Can this be done with the transistor on the board? Thanks!

[vinceroger69]

Re: Sony KDL-37XBR6 Black Screen

yes it can is there any writing on that part? so we can see if we can find a data sheet
im still learning electronics im sure budm will confirm if infact there is a short and what too check next

[budm]

Re: Sony KDL-37XBR6 Black Screen

Disconnect the cable between T-CON and the main board and see if the 0 Ohm reading goes away on that one end of the fuse that goes to the switched MOSFET.

[Gammaray]

Re: Sony KDL-37XBR6 Black Screen

Disconnect the cable between T-CON and the main board and see if the 0 Ohm reading goes away on that one end of the fuse that goes to the switched MOSFET.

I disconnected as you said, still shows 0 Ohm.

[budm]

Re: Sony KDL-37XBR6 Black Screen

If you look at the schematic, the input side to MOSFET (pin 123, Gate pin 4) has no path for the circuit to show 0 Ohm reading.
I want to make you check the resistance correctly, you need to check resistance between GND and pin 1 or 2, or 3 of Q1423 to see what you get.

[Gammaray]

Re: Sony KDL-37XBR6 Black Screen

I grounded to where I have been grounding from the DMM. I placed other red wire of DMM to pins 1, 2, and 3..Still no reading in ohms. I also tried checking the resistance of FET from pins 1, 2, 3, and 4 to the other side, pins 5,6,7, and 8. The readings from pins 1, 2, and 3 are all the same at around 2.6Mohms. Pin 4 was a little higher at around 3Mohm. Not sure if this will help, but just wanted to let you know. I even tried grounding to the BU board when checking pins 1, 2 and 3..but the same 0 Ohms.

[budm]

Re: Sony KDL-37XBR6 Black Screen

I grounded to where I have been grounding from the DMM. I placed other red wire of DMM to pins 1, 2, and 3..Still no reading in ohms. I also tried checking the resistance of FET from pins 1, 2, 3, and 4 to the other side, pins 5,6,7, and 8. The readings from pins 1, 2, and 3 are all the same at around 2.6Mohms. Pin 4 was a little higher at around 3Mohm. Not sure if this will help, but just wanted to let you know. I even tried grounding to the BU board when checking pins 1, 2 and 3..but the same 0 Ohms.

That is why I suspect that you did not test the fuse but something else because one end of the fuse is connected DIRECTLY to pin 1,2,3 of that MOSFET so all those pins should also show 0 Ohm, you can see that in the diagram I provided.
So are you 100% sure that you test the fuse no something else.
At this point you need to show close up pictures of the fuse that you test.
I have a feeling that you test the capacitor not the fuse.
You need to check the Voltage on either pin1,2, or 3 against GND to see what you have.
BTW, you can uninstall/install SMD devices, correct?

[Gammaray]

Re: Sony KDL-37XBR6 Black Screen

I have attached a photo with a red circle around what I thought to be the fuse. This is where I measured for continuity and didn't get any. I also have marked what I believe is the FET for pins #1-4. Is this correct? You can also see in this photo that the other fuse listed as F1421 on the schematics isn't there. Not sure why?

I have soldered some smd components before, but not sure if I did it correctly. I used 2 soldering irons on each side and was able to get the smd's off that way. Is there another way that may be easier? Please let me know. Thanks

[budm]

Re: Sony KDL-37XBR6 Black Screen

As you can see the bottom pin of the fuse is connected to pin 1,2, 3 of the MOSFET. Top pin of the fuse has 12V, correct?
So how can you have 0 Ohm on that bottom pin of the fuse but not at pin 1, 2, 3 of the MOSFET?

[vinceroger69]

Re: Sony KDL-37XBR6 Black Screen

in post 69 when said still no reading in ohms on pin 1 2 3 what is it reading? maybe re test the pins and take a photo of your multimeter screen then we can advise you more.
we are just trying too find whats blown the fuse so that you can buy all the parts needed.

[Gammaray]

Re: Sony KDL-37XBR6 Black Screen

OK, I measured again from ground to the top side of the fuse (F1422) and still getting 12V, but no voltage on other side of fuse. I also did another continuity check on the fuse, but still no continuity. So the fuse is bad.

Setting my DMM on Ohms, I measured from ground to Pins 1, 2, 3 and 4. My meter shows OL, or nothing Zero. The meter doesn't show any ohms, just OL.

When the power cord is plugged in, I measured each pin #1-4, and it is showing a voltage of .655V for each of those pins. I guess when I said it shows 0 ohms, perhaps I should have said I'm getting no reading at all.

[budm]

Re: Sony KDL-37XBR6 Black Screen

So one side of the fuse does show 0 Ohms. You have to be presise when reporting the DATA, it takes many many Q & A just to find out what resistance you have on one end of the fuse. So there is no 0 ohm any where on the input side of the MOSFET or on output side of the MOSFET.
Next to be sure, verify the resistance between GND and either end of the fuse on the T-CON just to be sure it dose not show low resistance.

[Gammaray]

Re: Sony KDL-37XBR6 Black Screen

The front side of the fuse (F1422) is where the voltage (12V) must enter. This does show 12V when AC is plugged in. When unplugged the Ohms on that front side are showing 313.5 Ohms. On the other side of that same fuse is nothing! No voltage or Ohms. The MOSFET has no Ohms showing for all of the (8) pins I checked.

I measured the resistance for the 3A fuse on the T-CON board and it reads 74.1K ohms. Both sides of that fuse were the same (74.1K ohms)

[budm]

Re: Sony KDL-37XBR6 Black Screen

At this point based on you report, you just need a new 5A fuse, you may have to use substitute since I have no idea where you will get the micro fuse from, you will have do the research on that.

[Gammaray]

Re: Sony KDL-37XBR6 Black Screen

At this point based on you report, you just need a new 5A fuse, you may have to use substitute since I have no idea where you will get the micro fuse from, you will have do the research on that.

So I take it that the MOSFET is still good? I'm wondering what caused this fuse to blow in the first place. I can try and search for that fuse..Perhaps digikey may have a replacement. I guess any 5A smd fuse that size should do.

I really appreciate your help and time budm! Also a big Thank you to the rest here that also helped! I shall make a donation to this website, as I want to continue to see it stay around for others that are in need!

CHEERS EVERYONE!

[Gammaray]

Re: Sony KDL-37XBR6 Black Screen

P.S. I take it that this 5A fuse should be rated at 12VDC, not 12 volts AC? Thanks again!

[neilc6]

Re: Sony KDL-37XBR6 Black Screen

https://www.digikey.com/products/en?...s=P121391CT-ND