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

[R_J]

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

When the conditions of ac detect of ic6501 are met pin 26 logic is HIGH. Since VCC of that ic is ~18 volts I would believe +18 on pin 26 would be considered HIGH,
PH6302 (led) is off, transistor between 3 & 4 open, Q6402 off (open) +3.3 applied through R6403 and R6404 to AC_DET_OFF = 3.3 volts.
If you are getting 0 volts on AC_DET_OFF, Q6402 could be shorted.

[DXseekerMO]

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

Ok here's what I see when looking at my board:

Q6301 is the one that looks crispy. I think it is on the primary side of the board.

[R_J]

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

Q6301 is the switch controlled by the power on opto, you could diode check it or check the voltage on the base and the collector
Its collector connects to pin 28 of IC6501
Mode select input
GND connection: Normal sequence
VCC connection: Standby mode

[budm]

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

So +18 volts on pin#2 of the opto = +18 on pin 26 which is not low but high
So AC_OFF_DET should be 3.3 volts?

Yep, that is what should happen.

[budm]

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

when the conditions of ac detect of ic6501 are met pin 26 logic is high. Since vcc of that ic is ~18 volts i would believe +18 on pin 26 would be considered high,
ph6302 (led) is off, transistor between 3 & 4 open, q6402 off (open) +3.3 applied through r6403 and r6404 to ac_det_off = 3.3 volts.
If you are getting 0 volts on ac_det_off, q6402 could be shorted.

+1

[DXseekerMO]

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

Ok I looked at the board. It looks like I can test collector voltage at one side of R6307, on top of the board. I see no way to test base voltage from the top of the board.

The board needs to be screwed down so it is grounded, correct? If so how am I going to test base voltage?

Thanks for hanging in there R_J

[DXseekerMO]

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

+1

I was so busy typing and looking at the schematic I didn't see you jump in there. Thanks budm

[DXseekerMO]

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

So are we transitioning away from Q6301 and more towards Q6401?

When testing Q6401 is that in diode mode and which probes on the meter go to which pin?

[R_J]

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

You can check the base voltage on pin 3 of opto PH6301, I'm more interested in the collector voltage and the condition of this crispy transistor.

[R_J]

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

Q6401??????????????


Q6301 is the switch controlled by the power on opto, you could diode check it or check the voltage on the base and the collector
Its collector connects to pin 28 of IC6501

[DXseekerMO]

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

You can check the base voltage on pin 3 of opto PH6301, I'm more interested in the collector voltage and the condition of this crispy transistor.

Pin 3 of opto PH6301, base voltage is zero volts, measured against hot ground
Resistor R6307, collector volts is 18.67 volts measured against hot ground

Q6401??????????????

Thank you for issuing correction, I meant Q6402. I asked if we were transitioning away from Q6301 and more towards Q6402 because budm gave a +1 on the possibility of it being shorted

[R_J]

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

Ok so that crispy Q6302 transistor is likely ok, it has 18 volts on the collector which means the power supply is in standby mode. (not on)

So just to refresh, what is the voltage on CN6101 pin 7 (AC_OFF_DET)?

[DXseekerMO]

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

Ok so that crispy Q6302 transistor is likely ok, it has 18 volts on the collector which means the power supply is in standby mode. (not on)

So just to refresh, what is the voltage on CN6101 pin 7 (AC_DET_OFF)?

Voltage at pin 7 of CN6101 is .47V

[R_J]

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

Unplug CN6102 and check it again.

[DXseekerMO]

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

Unplug CN6102 and check it again.

No change in voltage. Maybe you were thinking something on that board was pulling down the AC_OFF_DET volts?

[R_J]

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

Yes I was, but its not so Re check the voltage on PH6302 pin 3, it should be 0 volts

[DXseekerMO]

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

Yes it is zero volts

[R_J]

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

Check Q6402, It must be shorted e-c

[DXseekerMO]

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

with the red probe on C and black on E it tests open
Reverse the probes and the reading is 1.297

Diode check mode used. Confirmed I tested the right transistor

[R_J]

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

If you disconnect CN6101 from the main board, does the voltage come up to 3.3 volts? Somethings killing it