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

[budm]

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

"On page 35 of the service manual I traced the AC_OFF_DET circuit back to that crispy looking transistor Q6405"
You need to look at the schematic again, that is not what is shown in the service manual I provided. We need to get correct info first.
You need to trace the circuit from the AC_off_det pin cn6101 pin 7 back toward the front end.

[budm]

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

Your power supply board in your 55" is G6 board, look at page 35 for G6 schematic which is for your TV.
G5 power supply board is not used in your TV, G5 uses Q6405 in the AC_OFF_DFET circuit.
Look at you board, the service manual and then match them up to what you are troubleshooting.
Service manual page 7 shows what boards are used in your TV!

[DXseekerMO]

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

I see that, it traces to pin 3 of PH6302 which has zero volts. Pin 4 has 3.49V. If I am reading the diagram right it looks like pin 3 is the supply line for Q6402 which looks like no volts at pin 3 = transistor Q6402 doesn't turn on?

Also pins 1 and 2 of PH6302 have 18V present, hot ground used

Maybe I should ask how the electricity flows through an opto. I'm guessing there's an electrically conductive photocell in there that when the LED's inside light up it results in electrical flow through pins 3 and 4?

[DXseekerMO]

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

Your power supply board in your 55" is G6 board, look at page 35 for G6 schematic which is for your TV.
G5 power supply board is not used in your TV, G5 uses Q6405 in the AC_OFF_DFET circuit.
Look at you board, the service manual and then match them up to what you are troubleshooting.
Service manual page 7 shows what boards are used in your TV!

I almost made that mistake, I am looking at the G6 board schemo on page 35

Ahhhh, crap.....I was on the wrong page, but the circuit looks identical, save for nomenclature

Now on page 35

[budm]

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

G6 board.
Please pay more attention, I spend lots of time providing you with service info. Schematics, Training manual, etc.
We are up to post 46 now.

[DXseekerMO]

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

G6 board.
Please pay more attention, I spend lots of time providing you with service info. Schematics, Training manual, etc.
We are up to post 46 now.

Yes, I do tend to get the cart before the horse occasionally. but I do try to accept my mistakes humbly

[DXseekerMO]

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

If I am reading the diagram right, if voltage is present at pins 1 and 2 the LED inside the opto should illuminate and close the circuit on pins 3 and 4?

Since 3.49V is already at pin 3 and this is the specified voltage for that circuit, shouldn't jumping pins 3 and 4 activate the AC_OFF_DET circuit if the opto is bad?

[budm]

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

This is where understanding how Transistor and Opto work come into play.
So Opto PH6032 pin 3 (Emitter of photo transistor) is at 3.49V, and you also have about the same Voltage at pin 4 (Collector), so what do you think what is going on with that Opto, is the output ON or is it OFF?

https://en.wikipedia.org/wiki/Opto-isolator

[DXseekerMO]

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

I'll look at the link

[DXseekerMO]

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

If I am reading that right pins 3 and 4 should have continuity?

Between pins 1 and 2 are a diode with arrows pointing at 3 and 4. This has to be light driving pins 3 and 4 correct?

[budm]

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

So is the output of the Opto on or off?

[DXseekerMO]

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

The LED should be on and voltage should be present at pins 3 and 4?

[budm]

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

Good, so that means if you jump pin 3 and 4 will not make a different, correct? since it is already on.
So the output of Opto is on, that means it is providing the bias current to turn on that Q6402 which will cause the Collector Voltage to be low, and that Collector pin is the one that provides the AC_OFF_DET signal to the main board so now you see why you are getting low Voltage on the AC_OFF_DET pin on the connector. Opto needs to be off so Q6402 will then be off then the Collector Voltage will then go high.
If you measure the Voltage on the hot side of the Opto between pin 1 and 2, it should show about 2V for the internal LED, that will mean the IC6501 (pin 26) is driving the LED of the OPTO, in normal condition, the LED should not be driven on right now, so that IC may be detecting and false AC condition, if that is the case then you need to dig deeper to see why. You need to get the spec sheet of that IC6501 (CXA3811M-T6) to read and understand how it works.
Pin 4 (AC_DETIN) of the IC looks to be the one that monitor the incoming AC via a bunch of resistors connected in series, it can be that those resistor have drifted up in value and cause fault condition.
Update: I found the spec sheet of CXA3811.

[DXseekerMO]

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

Now I think I know where we are missing each other....there is no voltage present at pin 4, it reads zero volts, but there should be voltage at pin 4 right?

There is voltage at pin 3, 3.44V

[DXseekerMO]

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

Sorry budm, I was measuring pins 1 and 2 to chassis ground, not each other. There is no voltage present at pins 1 and 2 when measured across each other.

Pins 3 and 4 should not have continuity, right?

In other words, the supply voltage for pins 1 and 2 are what is missing?

Sorry this is dragging out like this.

[budm]

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

Now I think I know where we are missing each other....there is no voltage present at pin 4, it reads zero volts, but there should be voltage at pin 4 right?

There is voltage at pin 3, 3.44V

Look at the schematic again, pin 4 of the opto 6302 is connected to stby3.3V, so no way you will not have 3.3V at pin 4 of the Opto unless you have broken trace between pin 4 and the STBY 3.3V pin of the connector cn6101 pin 10.
Use your logic and common sense.
You need to pay attention. Ask yourself how you can have 0V at pin 4 of the opto.

[DXseekerMO]

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

From D6500 to pin 4 of IC6501 there is 1.320 megaohms of resistance. I added up the resistors in circuit and this is the figure I come up with. When I test at jumper wire JW6046 (part of the circuit) I get about 2.16V, hot grounded meter.

It looks like pin 4 AC_DETIN is receiving at least some voltage. This leads me to believe IC6501 may not be processing that signal?

I will pull the datasheet and look

[DXseekerMO]

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

Based on what I see AC_DET_OUT volts are absent.

The AC_DETIN is about the same voltage as what drives the LED in the opto.

This leads me to conclude the AC_DET circuit of IC6501 has failed?

[DXseekerMO]

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

So I am frustrating myself and I have made a mistake. I am getting things transposed.

What you all don't know is about 20 years ago I was seriously injured by a 6500 pound truck on a supposed 10,000 pound rated lift which folded under the weight and came down on top of me. Turns out the cheap lift was over-rated. Of the many injuries I had, I also had a head injury and sometimes this causes me to get things backwards.

I died on that shop floor. I wouldn't be here if it wasn't for the service manager knowing what to do.

Sometimes I feel like "Cousin Eddie" on National Lampoon's Christmas Vacation. Rev up the microwave, piss myself and forget who I am for a while.

I don't mean to do it. It happens on automatic pilot and I'm none the wiser....least for a bit anyhow.

Pin 4 of PH6302 has 3.45V
Pin 3 has zero volts.

[DXseekerMO]

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

I'd like to at least attempt to share my understanding of how the AC_DET circuit functions with the hope I've learned something.

AC power is delivered to a rectifier diode turning 120V AC in to about 165V DC. This DC power is passed through another diode and multiple resistors, regulating it down to about 2 volts and delivering it to pin 4 of IC6501, which if present will pass through this IC and out of pin 26, and arrive at PH6302, illuminate the diode and allow STBY_3.3 voltage through to Q6402 and ultimately to the AC_OFF_DET pin on CN6101, then on to the processor on the main board. With this voltage present the processor allows POWER_ON voltage of 3.3V to be sent to the PSU. By grounding this voltage the processor recognizes that as a power on request and the TV is turned on.

I'm very ready for someone to confirm this or maybe tell me where I missed the mark.

The diagram and conditions present lead me to believe IC6501 is bad. Furthermore if I am reading the diagram right I should be able to connect pins 4 and 26 on this IC which should result in AC_OFF_DET voltage at CN6101?