Sony Bravia KD-65XE7096 with shorted power supply - SOLVED

[R666]

Hi everyone,

I need some help repairing this power supply. I've been testing it and my conclusion is that it's sorted. Now I don't know how to find the faulty component. Can someone give me a hand?

The model number of the board is:
GL72
APDP-225A1 A
1-474-685-11

This is all the information I've gathered:
The TV does not turn on. When I push the on button a click is heard (the relay) and the red led shows the 2 blinks code (faulty power supply).
I've removed the power supply and these are the tests I've already done:
- when plugged in to mains, stand by voltage is ok.
- when I turn it on, by shorting the stand by and power on pins, REG12V are ok, but there's no voltage at TCON_VCC12V pins. Also, the voltage to the LED arrays is 97V, lower than the 163V expected as per board labels.
- with the board unplugged I've found continuity to ground in places that I believe are not supposed to have it: both ends of D950A; REG12V, TCON_VCC12V and BL_Error pins at CN6401.
- I've desoldered some components,and all have tested ok: Q123, D950A, C950A, C120B&C and C958.

My assumption here is that one or more components are faulty and shorting to ground. Am I right? Maybe one of the small ones on the bottom side of the board? How can I find the culprit?

I haven't been able to find the schematics of the board or a repair kit. I'm attaching hi-res pics of the board downloaded from shopJimmy. I'll try to take others myself if I manage to get the right light to get good pictures.

Many thanks in advance.

[R_J]

Re: Sony Bravia KD-65XE7096 with shorted power supply

See that pin labeled TCON_ON, that pin also needs to be active high, it turns on the TCON_VCC12V. It is best to use about a 1k resistor between the standby voltage and the POWER_ON or the TCON_ON.
The voltage to the led's needs to be checked as soon as the tv is powered on. It will start high then drop to 97v if there is a problem with the backlights. IE led string is open.

I suspect your power supply is ok, and the fault could be elsewhere

with the board unplugged I've found continuity to ground in places that I believe are not supposed to have it

let me guess.. you are using the BEEP function on your meter. THIS DOES NOT WORK. use the meters resistance scale to check the resistance.

[R666]

Re: Sony Bravia KD-65XE7096 with shorted power supply

Thanks a lot for the prompt answer.
If the power supply is ok, then the TV is showing an incorrect error code. Is that common?
Will add the 1k resistors to activate TCON_ON and POWER_ON and report back.

[budm]

Re: Sony Bravia KD-65XE7096 with shorted power supply

BTW, you also need the BL-ON control to run on the LED driver circuit to get the LED Voltage booster circuit to come on.

[R_J]

Re: Sony Bravia KD-65XE7096 with shorted power supply

Where did you find the error code discription? You have the REG12V which is good, The TCON_ON signal controls Q124 which controls Q123. Q123 acts as a switch, and switches the REG12V to become the TCON_VCC12V
It could be that the error is that the power supply led boost circuit detects a led fault in the panel, and sends the BL_ERR signal to the main board.
Connect the main board back up, monitor the voltage going to the led's and turn on the tv. If the voltage goes over 163v (likely around 200v) and drops to 97v, the led string could be open.

[R666]

Re: Sony Bravia KD-65XE7096 with shorted power supply

Hi,
I've just tested the power supply while activating POWER_ON, BL_ON and TCON_ON and all voltages seem right except for BL. I've attached my readings at the connectors to main board and to BL.
+out to BL doesn't go much higher than 97-99V, even when the power on button is pressed. On the other hand, -out is always almost 0.
This is the same no matter if the main board is connected or not.
What can be the cause?

[R666]

Re: Sony Bravia KD-65XE7096 with shorted power supply

Where did you find the error code discription?

Many thanks for your answer.
The description of the errors reported by the TV blinking the red light can be found in Sony's service manuals. I've attached a list of error codes and it's description.

You have the REG12V which is good, The TCON_ON signal controls Q124 which controls Q123. Q123 acts as a switch, and switches the REG12V to become the TCON_VCC12V

Thanks for the info. Now this is solved, I just needed to activate TCON_ON.

It could be that the error is that the power supply led boost circuit detects a led fault in the panel, and sends the BL_ERR signal to the main board.
Connect the main board back up, monitor the voltage going to the led's and turn on the tv. If the voltage goes over 163v (likely around 200v) and drops to 97v, the led string could be open.

I've connected again the main board and the voltage never goes higher than 97-99V at power on. With the main board and BL disconnected the voltage is the same.
BL_ERROR reads 3.3V after pushing power on button, even with both BL cables disconnected.
Could be an fault in the led boost circuit you mention? What other tests can be done?

[R_J]

Re: Sony Bravia KD-65XE7096 with shorted power supply

Does the tv ever turn on (give sound) or just stay off flashing the 2 blinks?
Does the tv flash the backlights for a split second when first turned on?
I guess it is possible that the led boost circuit has a problem, I have not worked on this particular power supply.

Check Q750A and check that R770A,R772A are not open. I'm not sure what the dca-162 is (looks like a driver ic) but it drives Q750A which seems to be the boost output fet.

[budm]

Re: Sony Bravia KD-65XE7096 with shorted power supply

https://www.badcaps.net/forum/attach...9&d=1580005552
So at what condition are readings were measured?
How can you have no Voltage on T-CON on but you have 12V on TCON_VCC12V?
Are you sure about all those Voltage readings?
What happen if you leave the meter probe on the BL-ON pin then turn on the TV while watching the meter?
The Dim controls also not present?

[R666]

Re: Sony Bravia KD-65XE7096 with shorted power supply

https://www.badcaps.net/forum/attach...9&d=1580005552
So at what condition are readings were measured?
How can you have no Voltage on T-CON on but you have 12V on TCON_VCC12V?
Are you sure about all those Voltage readings?
What happen if you leave the meter probe on the BL-ON pin then turn on the TV while watching the meter?
The Dim controls also not present?

Sorry, maybe the picture is confusing. Pins POWER_ON, BL_ON and TCON_ON have 3.3V because I connect them to STBY.

[R666]

Re: Sony Bravia KD-65XE7096 with shorted power supply

BTW, you also need the BL-ON control to run on the LED driver circuit to get the LED Voltage booster circuit to come on.

Thank you. Done, but BL voltage is not getting higher than 97-99V, even when the power supply is out of the TV.

[R666]

Re: Sony Bravia KD-65XE7096 with shorted power supply

Does the tv ever turn on (give sound) or just stay off flashing the 2 blinks?
Does the tv flash the backlights for a split second when first turned on?
I guess it is possible that the led boost circuit has a problem, I have not worked on this particular power supply.

Check Q750A and check that R770A,R772A are not open. I'm not sure what the dca-162 is (looks like a driver ic) but it drives Q750A which seems to be the boost output fet.

The TV has no sound. Also backlights never get to be on, probably because the voltage doesn't get high enough. It only starts with a solid white led for 1-2 seconds and then makes a click sound and starts a secuence of 2 blinks of the red led. When the TV is turned on BL voltage goes to 97V. After 1-2 seconds, when the relay is heard (or maybe just before), it goes to 99V for a split second and then it drops slowly to 0.

I'll test the components you suggest and report back. Thanks a lot.

[R666]

Re: Sony Bravia KD-65XE7096 with shorted power supply

Check Q750A and check that R770A,R772A are not open. I'm not sure what the dca-162 is (looks like a driver ic) but it drives Q750A which seems to be the boost output fet.

I think I've found two broken resistors: R765A & R766A. They show no continuity, should be 100 kOhm). The rest of the resistors in the area are good.
Mosfets and diodes of the secondary seem good to me. I've tested them by measuring DS resistance:
Q750A: 400 stable
D751A: 550 stable
Q123: 500 and then increasing
D120A: 130 stable
D120B: 130 stable

Seems like I need to replace R765A & R766A.

NB: I've attached a picture of this area on my actual board.

[R666]

Re: Sony Bravia KD-65XE7096 with shorted power supply

Ooops! No, these resistors are ok. I just rechecked then because I was not confident that I did it right yesterday. My multimeter doesn't have multi range and it was set to read ohms, not I ohms.

What else can I check?

[R666]

Re: Sony Bravia KD-65XE7096 with shorted power supply

Oh, and I haven't located R770A and R772A.

[R666]

Re: Sony Bravia KD-65XE7096 with shorted power supply

To summarise:
Sony TV that turns on for 1-2 seconds and then it turns off by itself. No sound and no backlights. Starts with a white status led, then a relay is triggered and the TV is shut down, left with a red led that blinks 2 times. According to Sony's documentation (attached) this code means that the power supply is bad.
I've taken the power supply off of the TV, no other boards are connected to it. I've connected POWER_ON, TCON_ON and BL_ON pins to STBY_3.3V pin to simulate the power on state of the TV. I've attached a picture with the readings at the connector to main board and the connectors to back-lights.
-STBY3.3V, TCON_VCC12V and REG12V voltages are ok.
-BLINKING, DC_DIMMER and PWM_DIMMER have 0V, which I presume is not normal. Am I right? Not sure what is the function of this pins.
-BL_ERROR is set to 3.3V, which I presume is what tells to the main board that there's a problem with the back-lights and to stop the normal power on process of the TV. Then the relay at the power supply switches it off.
-Voltage to back-lights only gets to 97-99V, but 163V was expected.
-components around Q750A seen to be ok.

Any suggestion?

I've also attached the service manual for reference. It's for KR and AMERICA, not EU, but close enough. It refers to a second document with troubleshooting info and diagrams, which I've not been able to find. I'm also looking for the schematic of the GL72 power supply.

[R666]

Re: Sony Bravia KD-65XE7096 with shorted power supply

Also, located at the main board there's this tiny connector. Probably it's a service port. Could TV logs be accessed through this port? Anyone happen to have it's specs?

[R666]

Re: Sony Bravia KD-65XE7096 with shorted power supply

It could be that the error is that the power supply led boost circuit detects a led fault in the panel, and sends the BL_ERR signal to the main board.
Connect the main board back up, monitor the voltage going to the led's and turn on the tv. If the voltage goes over 163v (likely around 200v) and drops to 97v, the led string could be open.

This weekend I've managed to test the backlights with an led tester and they are all ok. Each pin of CN6801 controls one vertical array of leds (pin1 corresponds to the rightmost 1/4 of the screen).
After testing successfully all of them I tried to turn on the TV while keeping on one of the central arrays. Now I can see for a second the Sony logo in the center of the screen, just before the TV turns off again.
Now I know that TCON, backlights and panel are all ok. The fault must be on the power supply or on the main board.
I've also tried to remove BL_ERR, BLINKING and DC_DIMMER pins from the connector to the main board CN6401. TV kept shutting down, but I was able to measure 3.3V on BL_ERR from the main board side, so this is a signal generated by the main board not by the power supply. This makes sense, since this signal is not present when I turn on the power supply out of the TV.
One curious thing I've discovered is that once the TV turns off (after hearing the relay), the power supply goes to the stand by state, thus turning off all the voltages but the stby. BUT, if then I keep pressed the on button on the TV for 2-3 seconds then all the voltages come back.

I still don't know what's the function of BLINKING and DC_DIMMER pins. Should I try to set any of them to on by connecting it to 3.3V stby?

[R_J]

Re: Sony Bravia KD-65XE7096 with shorted power supply

Does your led tester show the current each led string is drawing?

I was able to measure 3.3V on BL_ERR from the main board side, so this is a signal generated by the main board not by the power supply

All this means is there is a pullup resistor to the 3.3 volt3 on the main board side

[R_J]

Re: Sony Bravia KD-65XE7096 with shorted power supply

Oh, and I haven't located R770A and R772A.

If this is a picture of your board, the resistors look ok.

Do you know the number on the ic DCA-162? If your led's are indeed ok, It could be this ic that has an issue. OR that the main board is not sending the PWM, blinking and dimmer signals to the drive the ic.

The BL_ERROR, seems to be controlled by Q761, It is possible that when the led circuit is working ok, then the BL_ERROR would be low (0V)