Rca led50b45rq

[budm]

Re: Rca led50b45rq

PS-ON remains a constant 3.54v regardless of the VCC drop out. Also, with the LEDs unplugged, PS-ON is a constant 4.89v.

Is the 5V standby staying at 5V? that PS-ON should not be jumping up to tha level like that.

[x_orange90_x]

Re: Rca led50b45rq

Do note though that it only goes that high if i have the LEDs unplugged; a non-typical condition. I will check 5V Standby tonight . Would you like any other readings while I'm at it? I like to test in STANDBY, ON, and ON without LEDs just to give you the broadest set of readings possible.

[x_orange90_x]

Re: Rca led50b45rq

I went ahead and rechecked all of the voltages on the connector for you.

OFF - Standby:
All +5V - 0v
+5VSB - 5.17v
PS-ON - 3.54v
Both +12v - 0v

ON:
Same reading as above (Standby)

ON - No LEDs:
All +5V - 5.05v
+5VSB - 5.17v
PS-ON - 4.89v
Both +12V - 12.35v

So to answer the question, YES the +5V Standby remains 5v in all scenarios.

[budm]

Re: Rca led50b45rq

Well, since the Voltage for the VCC to run the PFC IC and the SMPS IC is generated by the AUX winding of the STBY power supply, and you also have good PS-ON to turn on the OPTO couple and good STBY Voltage.
So we need to look around the input side and the Output side of the OPTO, and also the section in the picture I had mark as how the switched VCC is controlled and why it drops outs. May be some error signal that lock out the circuit due to fault some where, more in-depth and board tracing will be required, but then I would think it will lock out the PS-ON to shutdown the power supply.

[budm]

Re: Rca led50b45rq

OK, back to this section again.
We need to find out if the Voltage drops out at the Collector (C) of Q8 or not (this one I expect it to be very steady).
The same at the Collector of Q10.
The same at Emitter (E) of Q10.
I need to know if any one of these Voltages come on and then drop out or not.

[x_orange90_x]

Re: Rca led50b45rq

So black probe on HGND-, and the red probe on C of Q8, C of Q10, and E of Q10? Just curious, why does Q8 not look like Q10, or any of the other Q's for that matter?

You mention something about a possible error signal.. Could that be from a bad backlight? When i have them unplugged i have all of my +5V, +12V, and VCC stable (except for PFC VCC drops out anyways). Plugged in I have dropouts and/or no voltage at all.

[vinceroger69]

Re: Rca led50b45rq

yes black probe on hgnd and yes the test points you have mentioned q8 q10 look like there transistors they come in diffrent package stlyes ie some sufaace mount like q10 and some through hole like q8

[x_orange90_x]

Re: Rca led50b45rq

ON:
Q8 (C) - 15.84v steady
Q8 (E) - .5v dropping
Q10 (C) - .5v dropping
Q10 (E) - .5v dropping

ON - No LEDs:
Q8 (C) - 15.36v steady
Q8 (E) - 14.02v steady
Q10 (C) - 14v steady
Q10 (E) - 12.95v steady

Also decided to check EC1 and EC1A voltages without LEDs.. 397v on both.

I'm by no means an expert, but there's a pattern here with LEDs connected - no voltage; LEDs disconnected - normal voltage. The only thing that doesn't stay consistent with this is the PFC VCC voltage dropping out either way.

[budm]

Re: Rca led50b45rq

Post 71:
"Just finished checking. I've got 171.8v on EC1 and 171.4v on EC1A. D4 diode reads 000 one direction and 461 in the other. I did the flashlight test and CAN see the menu on screen, so I'm pretty certain now its one or more bad LED backlights."
Post 148:
"Also decided to check EC1 and EC1A voltages without LEDs.. 397v on both. "
So after all these times I try to find out why we do not have Boosted Voltage after D4 was replaced.
At the beginning of the project we know that the PFC is not working so it has to be fixed first before moving on to other section if the TV is still not working after we get the boosted Voltage to run other circuit. So I spent times tracing the board to see if we have the VCC to run the SMPS IC and the PFC IC or not, But in fact the PFC does work after D4 was replaced but something else caused the VCC to the SMPS and the PFC IC to drop out so now we will need to find out if the SMPS for the LED driver, LED wiring (shorts wiring to the chassis?), or LED are causing the shutdown or not since now the SMPS does have the Boosted Voltage to run. If I would have known that we do have Boosted Voltage after D4 was replaced then I would have check other section of the circuit to find out what causes the shutdown to occur.
But I have to take a break from this threads for now since lately I have been given wrong DATAs from so many threads and caused me to go the wrong direction and it is getting very tiring for me. I am very patient person when trying to help people but right now I am very tired.

[dick_barton]

Re: Rca led50b45rq

So are you now saying that you have all the voltages when the leds are not connected.

If so with the leds disconnected do you have sound and can you see a picture if you use a bright light shone on the screen at an angle? Press the menu on the remote.

[x_orange90_x]

Re: Rca led50b45rq

So are you now saying that you have all the voltages when the leds are not connected.

If so with the leds disconnected do you have sound and can you see a picture if you use a bright light shone on the screen at an angle? Press the menu on the remote.

That is EXACTLY what I'm saying. And yes i CAN see the menu onscreen using a flashlight.. I stated this a couple of times already.

Budm, i apologize for using so much of your time, and i do appreciate it. However, the only time i have mistakenly given wrong data was when i used a safety pin to check resistance. BUT, to correct you.. I do not have BOOSTED VOLTAGE when the LEDs are connected. When i stated this earlier you moved on without really saying anything about it. I am sorry that you feel misled by my data, but I've been saying some important things for a while now that are apparently being overlooked.

[dick_barton]

Re: Rca led50b45rq

Sorry but 150 odd post to read through is too many.

Can you give the voltages on the pins of Con5 when you switch on out of standby
They should initially go high and then very quickly fall. You need to catch the maximum voltage.
Pin 1 Led- = xxx
Pin 3 Led+ = xxx
Pin 6 Led - = xxx
Pin 8 Led+ = xxx

[x_orange90_x]

Re: Rca led50b45rq

Sorry but 150 odd post to read through is too many.

Can you give the voltages on the pins of Con5 when you switch on out of standby
They should initially go high and then very quickly fall. You need to catch the maximum voltage.
Pin 1 Led- = xxx
Pin 3 Led+ = xxx
Pin 6 Led - = xxx
Pin 8 Led+ = xxx

I'll get those for you this afternoon. Which point do I need to touch my black probe to this time?

[dick_barton]

Re: Rca led50b45rq

Initially use chassis for your ground connection.

[x_orange90_x]

Re: Rca led50b45rq

Pin 1 - 47v then drops to 0v
Pin 3 - 55v then jumps to 130v, then drops to 0v
Pin 6 - .1v then drops to 0v
Pin 8 - 55.4v then jumps to 138v, then drops to 0v

They don't instantly drop to 0v, but rather steadily decline.

[budm]

Re: Rca led50b45rq

"Pin 6 - .1v then drops to 0v" Open LED string.
But check the resistance between pin 6 and GND to be sure.

[x_orange90_x]

Re: Rca led50b45rq

"Pin 6 - .1v then drops to 0v" Open LED string.
But check the resistance between pin 6 and GND to be sure.

So a string has one or more burnt out LEDs?

[budm]

Re: Rca led50b45rq

Check pin 6 and GND first , if it does not show <100 Ohms, then you have open circuit in that LED string.

[x_orange90_x]

Re: Rca led50b45rq

Check pin 6 and GND first , if it does not show <100 Ohms, then you have open circuit in that LED string.

Pin 1 & 6 are both 1548k.

[budm]

Re: Rca led50b45rq

Good, you have to open the panel next.