Secondary LCD Supply Voltage

[jkb242]

I am looking at the power board from this sharp LCD set and would like some input as to what voltage I should measure at the connector that feeds the CCFL's. All connectors of the LCD lamp feed are connected in parallel and are directly connected to the secondary coil of the LCD lamp transformer. I have attached the power board circuit where this connection is made.

I'm using a DMM Fluke Meterman which can measure frequency (up to 40MHz) and AC voltages up to 1500.

Appreciate any information that can be provided.

Thanks!

[retiredcaps]

Re: Secondary LCD Supply Voltage

1) Your pdf file is corrupt.

2) Which is it? A Fluke or Meterman? What model?

3) What is the problem that you are having?

4) We usually never ask people to measure the high voltage AC side of inverter transformer. Most multimeters will not survive as voltage can be anywhere from 600 to 2K AC voltage.

5) If this is the same TV as your first post, keep everything in one thread so people like myself who are trying to help don't get confused with multiple threads and answers.

https://www.badcaps.net/forum/showth...553#post225553

[jkb242]

Re: Secondary LCD Supply Voltage

Thanks for alerting me that the file is corrupt. It is a pdf and it looked fine to me when I viewed it. It is supposed to be backward compatible to earlier versions of Acrobat reader, but perhaps not. I will repost the schematic as a picture.

The DMM I am using is a 33XR Wavetek/Fluke Meterman.

Yes this post is related to the same set as the previous post you referenced--sorry for not linking and the confusion. I have progressed a bit further in trouble shooting since the original post and was trying to update my latest question to the current question I have now. Not using a HV probe but did not think the voltage would exceed 1kvac.

Thanks for your reply and information and please reply again after reviewing the new picture.

[jkb242]

Re: Secondary LCD Supply Voltage

I am looking at the power board from this sharp LCD set and would like some input as to what voltage I should measure at the connector that feeds the CCFL's. All connectors of the LCD lamp feed are connected in parallel and are directly connected to the secondary coil of the LCD lamp transformer. I have attached the power board circuit where this connection is made.

I'm using a DMM Fluke Meterman which can measure frequency (up to 40MHz) and AC voltages up to 1500.

Appreciate any information that can be provided.

Thanks!

Please see updated PDF file attached----



New Picture attached 3/24/12

[retiredcaps]

Re: Secondary LCD Supply Voltage

The DMM I am using is a 33XR Wavetek/Fluke Meterman.

The 33XR was originally made by a company called Meterman. Then Meterman got bought by Amprobe.

Danaher Corporation owns Fluke and Amprobe.

The 33XR is sold today as an Amprobe 33XR-A.

http://www.amprobe.com/amprobe/usen/....htm?PID=73030

We still don't know what the problem is? Does the power LED come on? Any sound or video? 5V standby present?

[jkb242]

Re: Secondary LCD Supply Voltage

The 33XR was originally made by a company called Meterman. Then Meterman got bought by Amprobe.

Danaher Corporation owns Fluke and Amprobe.

The 33XR is sold today as an Amprobe 33XR-A.

http://www.amprobe.com/amprobe/usen/....htm?PID=73030

We still don't know what the problem is? Does the power LED come on? Any sound or video? 5V standby present?

All standby voltages present. No LED's on with power supplied after pushing power on button. The relay on the power board will not pull in to apply AC
VOLTAGE to the run part of the power supply. The reason is that there is no power latch from the LCD controller when the power on button is pressed. The power switch is applying a momentary 5.0vdc to the controller on the LCD board, but this is not being output to the system board where latching occurs. I have replaced power board(didn't suspect it to be bad, but encouraged to do so from techs who have worked on these sets for years) then was advised to replace system board, that still did not allow the relay to pull in. I have believed all along that the LCD controller is the source of the problem.

I have biased the PS-ON, D-POWER and E-PUA-POWER LEADS so that ~4.5vdc is applied to the power board which closes the relay and allows the power board to produce all run voltages , but still no LED's or power on switch working BECAUSE all of these latches originate from the controller chip on the LCD controller board. I am still being told the problem is somewhere else. I think I should have gone with my first diagnosis and simply replaced the LCD controller board. That board is now on the way to me--there's not left as I see it!! Luckily, I am using a great supplier who will allow me to return the power board and system board once I determine the original boards were OK.
TV PARTS NOW is a great source I could strongly recommend.

If you can advise further, would very much appreciate your input.

Thanks!

[retiredcaps]

Re: Secondary LCD Supply Voltage

Post a picture of the main board following the instructions in my sig file exactly as in post #2.

I suggest checking all the voltage regulators on the main board to make sure they are within spec and outputting the correct voltage.

[cashkennedy]

Re: Secondary LCD Supply Voltage

You think its the lcd controller? which is the part that comes with the lcd panel, and is tv brand agnostic (as in its made by the panel maker and could be used in many different tv brands), also called a tcon?

Because that part has never been involved in the tv's ability to power on in anything ive seen or heard of. Infact usually you can leave it compleatly unplugged and still the tv will turn on the indicator LED's and backlight.

Perhaps you have some rare, bizare, design where they routed power switch through the lcd controller, but i wouldnt believe it till i saw extremly clear pics showing that. It would be extremly complex for the lcd panel manufacturer to know how the rest of the tv was going to be designed when they made the panel, as the panel and tcon is usually designed before the rest of the tv and by completly different people...

You also said the lcd controller receives the 5v? but in every design ive seen the main board is connected to the power supply, and not to the lcd controller. So if the lcd controller is gettign 5v its getting it through the main board. Perhaps you can post a pic of the whole back of the tv showing all the boards, because ive never seen a design where the lcd controller got power fromt he power supply.

[jkb242]

Re: Secondary LCD Supply Voltage

Cashkennedy,

Thanks for responding and providing comments. I have posted several full resolution pdf files directly from the service manual that I believe depict the reason for my feelings that the root of the issue with this set lies on the LCD Controller board.

On the LCD controller board is the main processor IC2004 where the key signals all connect (Power on, chan +/-, vol+/-, and input. These outputs do in fact to the main or system board where the other IC 1001 provides T-CON control as well. Of particular interest on the LCD controller board IC 2004, pin 15 is SMPOW which is connected to PS_ON on the system board is I believe the primary signal that enables latching of PIN 117 on the main board processor IC 1001 that enables ~4-5vdc bias for the PS_ON feed which is also connected to the relay on the power board connecting AC to the "run" part of the power supply.

I would appreciate your feed back looking at the main block diagram which shows PS_ON/SMPOW connected to pin 117 of the processor IC1001, which appears to supply the latching voltage mentioned above to keep this line high, necessary for the relay drive and for enabling D_POW and E_U_POW biasing to turn on the remainder of the DC voltage regulators/inverters on the power board. Also note that IC 1501 shown on this diagram, supplies bias for the D_POW and E_U_POW feeds from pins 6 and 7. I am a little puzzled at the However if you he diode in D1504 seems to be backwards or is a mistake on the schematic since if pin 117 does in fact provide the latching high for PS_ON, the diode seems backwards.

However look at IC 1001 pin 117 again and note that the series components of Q1508, Q1507 and D1504 appear to provide the latched high bias that is the PS_ON signal. It appears that there is a mistake in the way that the diode of D1504 connects to Q1508. It appears to be backwards, unless I am looking at this incorrectly. Do you agree?

Looking at the LCD controller board also attached, note the 0 VDC on pin 15, of IC 2004 at the SMPOW feed. I have to assume that these voltages are shown while the set is not in standby. It appears from this that this pin is not the source of the latch after pushing the power button if this voltage is correct as shown in the run mode.

Note too on pins 55 and 56 both supply 5 vdc to the LED feeds POWR and POWG. AT the LED board, on the 5vdc buss voltage is available. There are no other components between these pins of IC 2004 and the LED board so again, I am suspicious of this controller, which also provides the SMPOW feed for the remainder of the start up bias to the power board.

Please look these comments over and provide your input. I would most certainly like to know if you agree with my reasoning that the LCD Controller board is indeed the source of this set showing no LED's and the missing PS_ON, D_POW and E_U_POW biases necessary to run the set.

Thanks so very much.

[budm]

Re: Secondary LCD Supply Voltage

“However look at IC 1001 pin 117 again and note that the series components of Q1508, Q1507 and D1504 appear to provide the latched high bias that is the PS_ON signal. It appears that there is a mistake in the way that the diode of D1504 connects to Q1508. It appears to be backwards, unless I am looking at this incorrectly. Do you agree?”

If you look at MAIN Unit-9/11, the following happens:
SMPOWHOLD (the print is real small, hard to read) goes HI, it will cause the logic transistor inverter Q1507 output to go LO which will turn on the PNP Transistor Q1508, this will allow the BU+5V to go through the Emitter of Q 1508 and then through the ANODE of the bottom diode D1504, this +5V then will be present at PS_ON pin.
This +5v is also fed logic transistor inverter Q1503, causes its output to go LO, this LO is fed into logic transistor inverter Q1502, which causes its output to go HI (+5V) which is fed into D1500, the output on the Cathode side is then fed the +5v to D_POW.
So PS_ON and D_POW will be HI to activate the power supply, they are active HI mode.

[jkb242]

Re: Secondary LCD Supply Voltage

Budm,

Thanks very much for your input. I follow exactly what you are saying to D1504, but the diode that connects to the PS_ON feed, is backwards to allow +vdc from cathode to anode. If the diode was reversed what to described would be correct. Obviously the circuit did work, but I think this a matter of the schematic being incorrect. I should look up the part number to be sure this is the case, but I don't think there is any doubt, as shown, it couldn't work.

One additional point I failed to mentioned is that the system board has been replaced which has produced the same issue as the original board

Finally, because all boards in this set contain about 1/2 of the components on both sides, component probing/measuring is significantly impacted. That has really slowed down the repair, almost forcing board level replacement. impacting component level confirmation.

[budm]

Re: Secondary LCD Supply Voltage

No that Diode is correctly used in the circuits, that PNP Q1508 is fed with the + 5vdc at the EMITTER, when it is turn on the +5vdc will be at the collector which will FORWARD bias the diode, then the +5v will be at the Cathode side which is an out put PS_ON.
Cathode is an OUTPUT. Believe me, that circuits works just fine.
PS_ON and D_POW are OUTPUT signals.

[budm]

Re: Secondary LCD Supply Voltage

One way to prove the theory:
Ground the left side of R1508 which is connected to the Collector of Q1507 while monitoring the Collector of Q1508, you should see +5VDC there and about 4.4v at the Cathode D1504. Make sure you do have +5VDC at the Emitter of Q1508 first.

[jkb242]

Re: Secondary LCD Supply Voltage

Budm,

I see why we were not able to agree on the proper representation of the D1504. I posted the system board schematic and the overall diagram of the system board. On the overall diagram, D1504 is shown as a common ANODE not the common CATHODE that is actually is. I discovered this by looking up the generic part which is a DAN222. It's made by RHOM and Motorola. No question it is a common cathode. On the main board schematic, D1504 is depicted correctly. I had been using the overall diagram as my reference since I had several boards and paths that I was examining. So in fact I do agree with you completely on this basic circuit operation.

Now on to the reason that I have no PS_ON.

If you look at the LCD Controller schematic, you will see an output pin on IC 2004 labeled SMPOW which is connected to the main board and then becomes PS_ON. This is the only source I can find for a high going pulse from pushing the power switch to get the set out of standby. IC 1001 on the system board knows that the power switch was pressed from the IC 2004 on the LCD controller and latches smpowhold that provides PS_ON, then IC 1501 on the main provides the 5vdc from pins 6 and 7 to supply the bias to provide D_POW and E_U_POW so that all voltages are produced on the power board.

Please provide your input if you have time and note that the LED power on and OPC bias originate from IC 2004 on the LCD controller. Since I don't have any LED's lit, this too leads me to believe that this IC is defective.

Do you agree?

Thanks again for your input and sorry about the fact that we were looking at different diagrams that should have been the same. There is indeed a mistake on the overall diagram.

[budm]

Re: Secondary LCD Supply Voltage

So when you hit the power button, the power LED does not even flash on once?
IC200 PIN 55, 56 for driving the LEDs through the transistors.
You do not need to have the PS_ON working for the LED to be on since they are using the always on +5V. I would check the reset IC's 7709, 2001, 7705 as shown in the Display block diagram. Not sure if it suppose to be active HI or active LO when the reset occur, need to look up the spec of those Rest IC's. You can still force the power supply to come on by shorting out the resistor as I mention before. At this point PS_ON in not the problem for now until we get the LED to come on.
I also see that the Overall block diagram for the Diode was not correct as you said, I trust the actual diagram for each section than the block diagram since they will use the actual diagrams to generate the netlist and do DRC (DESIGN RULE CHECK) for designing the PCB, not the block diagram. If the netlists are wrong, the PCB will be made wrong. I always check and double check the SCH and run DRC before laying out the PCB.

[jkb242]

Re: Secondary LCD Supply Voltage

I completely agree with you, PS_ON at this point is not the issue. I have jumpered 5vdc a few weeks ago to ps_on and the other two sources to full confirm the power board is producing all run voltages.

Remember too that the system board has been replaced after this all began and it isn't likely that two system boards would have the same issue. I am pretty sure it's the microprocessor on the LCD controller board since it controls the LED's and is where the power on switch is connected. Should have controller board tomorrow.

Regarding your question, the run LED doesn't even blink when the power button is pushed. Can you determine how IC 2004 communicates with IC 1001 when the power switch make momentary contact when attempting to turn on the set?

Thanks again.

[budm]

Re: Secondary LCD Supply Voltage

Yes I believe that something is going on with this controller and it should be running since it supposes to blink the LEDs for the error codes, right now it cannot even tell that itself is not working. I have no idea on the inner of this of this system setup, that is why I wonder if the reset chips may have gone bad which I have seen before which caused the controller to be stuck mode. I also wonder if the firmware is corrupted.

[jkb242]

Re: Secondary LCD Supply Voltage

I believe the reset chips you mentioned are on the main/system board. *Wouldn't these have eliminated when the system board was replaced?

I wonder if there's is any way or even a requirement to reset the new system board for it to work I'm this set. *Would the firmware be stored in IC1001 on the system board? No idea which firmware would be on the replacement board as opposed to the board I removed. *On the LCD controller, would there be any system firmware stores on that, IC 2004?

Thanks!

[budm]

Re: Secondary LCD Supply Voltage

I do not know, is the new board good for sure?

[jkb242]

Re: Secondary LCD Supply Voltage

Budm,

The problem was the LCD CONTROLLER, a very early suspicion I had when I discovered the key input signals and LED DRIVE, all originate from IC 2004 on the LCD controller board.

For some reason however, audio is muted or there is at least no audio on the HDMI input. Trying other inputs tomorrow.