Sony KDL-55EX620, no stand-by volts from one bad resistor?

[DXseekerMO]

I bought this TV today with the complaint of appears dead, confirmed. I removed the back and tested the A/C in fuse which was OK. Main cap voltage at 165V. After further testing it looked to me like the whole secondary side of the board was dead with no 3.3V stand-by present.

I pulled the PSU and had a look, nothing obvious showing, so I went to ShopJimmy and looked for a PSU repair kit which they had, here is the link: https://www.shopjimmy.com/sony-1-474...repair-kit.htm .

I checked the components the kit called for. None of those transistors checked short ( I could not locate Q6123 and 6124) and all of the resistors were OK save for R6201 which checks open in one direction and very high resistance in the other.

When I look at the trace it appears voltage comes from the main caps, goes through R6201 to what appears to be a 12V transformer. When I trace the circuits off of R6201's circuit it looks like they all wind up at that transformer.

Based on what I see it looks like this single resistor being open will result in no voltage to the transformer down range and the secondary side of the board?

Can someone have a look at the pix and see if you draw the same conclusion? I put arrows on R6201 to make it easier to see.

Thanks everyone!

[DXseekerMO]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

It looks like part of this circuit ties in to the drain pin of IC6201 which ties in to the SB 3.3V regulator. Picture of pinouts and schematic for IC6201, number MIP2H2:

[budm]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

It is fusible resistor, low Ohm, it will go open circuit if the SMPS circuit shorted out.
Check the resistance between S and D pin of the SMPS IC to see if it shows low resistance reading.

[budm]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

It is fusible resistor, low Ohm, it will go open circuit if the SMPS circuit shorted out.
Check the resistance between S and D pin of the SMPS IC to see if it shows low resistance reading.

Chassis AZ2F

[DXseekerMO]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

The resistance across S and D is 170ohms. Seems low?

[neilc6]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

Fixed the same model recently but it had standby voltage and was giving a 2-blink code. Shorted Q6101, Q6102 and blown R6540. May not apply if you don't have standby voltage.

[budm]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

The resistance across S and D is 170ohms. Seems low?

That does not look good. I would replace that IC.

[DXseekerMO]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

budm, do you think there could be more damage on circuits leading away from that IC? I suppose that IC could tap out on its own?

EDIT: If I de-soldered that IC and tested resistance across the bare pads S and D with the same ohms value I'm guessing I need to look further?

[DXseekerMO]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

Fixed the same model recently but it had standby voltage and was giving a 2-blink code. Shorted Q6101, Q6102 and blown R6540. May not apply if you don't have standby voltage.

I checked those and none indicated directly shorted. I think the values seemed normal.

[budm]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

budm, do you think there could be more damage on circuits leading away from that IC? I suppose that IC could tap out on its own?

EDIT: If I de-soldered that IC and tested resistance across the bare pads S and D with the same ohms value I'm guessing I need to look further?

You can check the resistance of the two IC legs once you remove it from the board..

[DXseekerMO]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

I thought I'd post this pic of a couple suspect items near the suspicious IC. In the red circle, at the top solder joint of this resistor? it looks more like a solder ball than a solder joint. Right next to it circled in yellow appears to be a capacitor with a scraggly looking solder joint on the bottom. Circled in orange, down and to the right there's a transistor that also looks like it has scraggly solder joints.

All of these are making me wonder if there was some kind of over-voltage event on the A/C side?

Does anyone have an opinion about these items?

[DXseekerMO]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

I successfully de-soldered IC6201. The low reading follows the chip. Testing across the pads on the board shows infinite. There's no shorted caps or resistors nearby, but the cap between pins 1 and 8 (VDD and SOURCE) tested short...until I removed IC6201. This short follows the IC as well.

Could the no stand-by issue simply be a bad IC6201 and the fusible resistor R6201?

Also, the transformer isn't 12V, it is for the 3.3V stand-by circuit?

[DXseekerMO]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

bump

[R_J]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

The ic is shorted, replace it and the open resistor

Whats with the BUMP on all your threads?

[DXseekerMO]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

The ic is shorted, replace it and the open resistor

Thanks for the reply R_J, I'll be ordering the parts today.

[DXseekerMO]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

Whats with the BUMP on all your threads?

Didn't see this question R_J, I'm trying to get a parts order together before I hit the sack tonight.

Used to be many folks would input on my threads, now just a few. I guess I'm wondering where I'm going wrong. Maybe someday I'll figure it out.

On R6201, what wattage of resistor is this, and how does one tell? It looks like the letter "J" must be the tolerance, best I can tell 5%. The only other letter printed on the thing is X.

If anyone would tell me I'd appreciate it. The service manual does not have component level info for the G8 board.

[R_J]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

It should be a 10Ω 1/2 watt fuseable flameproof
Here is digikey page of a few https://www.digikey.ca/products/en/r...=1&pageSize=25
If you check page 30 of the manual (post#4), it is listed as [R6202] as the diagram is slightly different

[DXseekerMO]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

Thanks R_J, I appreciate it.

[DXseekerMO]

Re: Sony KDL-55EX620, no stand-by volts from one bad resistor?

I ordered the control IC and fusible safety resistor this morning. It looks like they will be here sometime early next week. Soon as they make it they're going in there and the board is going back in!

[DXseekerMO]

Installed parts, occasional stand-by power restored

The parts came in today so I installed them, put the PSU back in, flipped the on switch on my power strip and the TV came on....but just for a couple seconds. The backlights flashed and that was it. I checked for stand-by volts and it was there. The orange stand-by light was flashing two blinks, pause, two blinks and so on.

I turned the power strip off, re-checked my work and found all to be OK so I flipped on the power strip and no stand-by volts were there. I checked for volts at the connector pin, pin 5 of the IC and on both sides of R6201 and no voltage was present. The orange stand-by light was not flashing or on.

The next thing I know, all of a sudden the TV pops on by itself and stays on. I lifted the TV to look and see if a picture was present, it was. I tried lifting it a bit more to get a better look at the picture, then it shut off on its own.

So I left the power strip turned off for about 10 minutes while I was writing this. For the halibut I turned the power strip on just now and whaddya know, the TV turned on and stayed on for a good 45 seconds. I was able to turn the TV off with the button and turn it back on. After that it shut itself off again with no stand-by light or signs of life.

I'm waiting another 10 minutes now to see if it will come on again.

It did come on, but this time I was ready with the meter. Stand-by voltage was present, but as soon as it disappeared the TV turned itself off.

Apparently the stand-by circuit has another problem somewhere. Can anyone point me in the right direction? The screen has a real good picture when the TV does come on and I think I may be super close to getting this thing fixed!