Philips 37MF321D No power no LED

[Horty24]

Re: Philips 37MF321D No power no LED

Here are some pics of the PS.

[Horty24]

Re: Philips 37MF321D No power no LED

I found an answer to this,4.2v is required on pin 5 of connector 1089 when the power supply is
Is plugged into the wall socket. Apparently someone removed jumper 9052 on the power supply.
Anyway with that jumper replaced I do see the standby voltage of 1.3v on pin 9, and the 24v section comes alive.
I wonder if there is a problem with the panel and the service tech disabled the power supply to try to make the power supply useless?

I too do not have voltage on pin 4 and 5. I don't believe there needs to be a jumper at 9052. All my caps do look good but I know just because they look good does not mean they are. One thing I do find odd looking at my PS board is solder built up on these pins. Look normal?

[dustinlof]

Re: Philips 37MF321D No power no LED

I spoke to soon on suggesting to check the SMPS,If I am reading the schematic correctly we should try to find out why there is no 24A voltage. I think that is the voltage that is always on when the set is plugged in.
Honestly this is over my head; hopefully someone else will jump in and help

I would assume I would need to see some sort of output voltage on transformer 5071 before the 24A voltage can be present?

I just printed this schematic out on 4 sheets of paper and taped them all together to hopefully help me understand this better.

[dustinlof]

Re: Philips 37MF321D No power no LED

I am confused, are we talking about troubleshooting alexanna's TV or dustlinlof'sTV.

we were talking about my TV

[budm]

Re: Philips 37MF321D No power no LED

I am confused, are we talking about troubleshooting alexanna's TV or dustlinlof'sTV.
If the (alexanna's TV) PFC Voltage boost circuits are not working then the 24vdc will not be fucnctioning, as stated in post #2.

[alexanna]

Re: Philips 37MF321D No power no LED

at the smps I have on pin 1 Vcc - 186mvdc, pin 2 gnd - 0v, pin 3 ctl - 0v, pin 4 - dem 28mvdc, pin 5 isense - 0v, 6 driver 180mvdc, 8 drain - 158.7vdc. If I am reading the data sheet correctly I should have 1 - 1.5vdc on pin 3 ctl. I am not sure what cap you mean when you say small start up cap.

I spoke to soon on suggesting to check the SMPS,If I am reading the schematic correctly we should try to find out why there is no 24A voltage. I think that is the voltage that is always on when the set is plugged in.
Honestly this is over my head; hopefully someone else will jump in and help

[dustinlof]

Re: Philips 37MF321D No power no LED

at the smps I have on pin 1 Vcc - 186mvdc, pin 2 gnd - 0v, pin 3 ctl - 0v, pin 4 - dem 28mvdc, pin 5 isense - 0v, 6 driver 180mvdc, 8 drain - 158.7vdc. If I am reading the data sheet correctly I should have 1 - 1.5vdc on pin 3 ctl. I am not sure what cap you mean when you say small start up cap.

[alexanna]

Re: Philips 37MF321D No power no LED

You might want to look at the SMPS start up IC. I haven't looked at the schematic yet this morning but I think it's the 7 pin through hole chip on the hot side of the PS.If you look up the data sheet it will give you minimum voltages for it to start. The small start up cap is critical also.

[dustinlof]

Re: Philips 37MF321D No power no LED

Yes, that's what I was referring to as ground(-), I maybe should have referenced to it as negative.

[budm]

Re: Philips 37MF321D No power no LED

When you work on the HOT (primary side) side of the power supply, you do not use the chassis as the ground ref point for the voltage measurement, you need to use the Negative leg of the main DC filter cap (the large one with 350~450Vdc rating), that is the circuit ground ref point for the primary circuits. The cold side circuit ground ref is commonly tied to the chassis.

[dustinlof]

Re: Philips 37MF321D No power no LED

I have the same TV with the same symptom, no power, no LED, I however do not have any voltage available to any pin on 1089 as referenced on page 90, I have determined that there is 164.4 VDC across rectifier 6051. And at transformer 5071 pin 1 - 164.2VDC, pin 2 - 163.3VDC pin 3 - 163.4VDC, pin 6 - 163.6VDC and 7 & 8 are at 0v, voltages to 1089 were measured to earth and voltages at transformer were measured to ground(-) at rectifier. I thought at some place in the manual I read there should be 300 some volts at some point in the power board, I cannot however find where I read it and at what point it pertains. Any insight would be greatly appreciated, I do have plenty of electrical knowledge it just applies to automobiles.

[budm]

Re: Philips 37MF321D No power no LED

If the MOSFET 7071 is not installed, then I can see why you have to have jumper installed, if 7071 is on the board, then it means that the Gate is not getting the signal to turn on 7071 which function as a switch, and the jumper is used to force the 24vdc to come on, that way the tech can tell that the 24vdc is OK but the turn on signal for the 7071 is not functioning. It is like having a relay to turn on the light, but you can jump the replay contact and make the light to come on, then you will know that the relay is not working instead of trying to find out if the lamp is good or not. Same principle as applying voltage to the PS_ON pin to force the power supply to come on, if it does, then the power board is OK but the PS_ON is not coming through from the main board.

[Jasgriff]

Re: Philips 37MF321D No power no LED

Maybe the jumper is there to allow you to check other parts of the board without the inverters getting power? and they forgot to put it back?

[alexanna]

Re: Philips 37MF321D No power no LED

I found an answer to this,4.2v is required on pin 5 of connector 1089 when the power supply is
Is plugged into the wall socket. Apparently someone removed jumper 9052 on the power supply.
Anyway with that jumper replaced I do see the standby voltage of 1.3v on pin 9, and the 24v section comes alive.
I wonder if there is a problem with the panel and the service tech disabled the power supply to try to make the power supply useless?

[alexanna]

Re: Philips 37MF321D No power no LED

This is kinda like a double post but there is some stuff added.
I am hoping someone will look at the troubleshooting flow chart and see if I am interpreting it correctly.
I am getting the correct voltages on pins 1 through 3,but no voltages on pins 4 and 5.The way I am reading it if any of the voltages are incorrect on pins 1 through 5, it appears they want you to look at the power supply for problems.
Attached is the link that I believe to be the correct service manual.http://elektrotanya.com/?q=showresul...oria=&kat2=all
It is the very last manual listed
Page 90 is the flow chart, and 110 is the schematic for the 37” model.

[alexanna]

Re: Philips 37MF321D No power no LED

I think I am taking the wrong path in troubleshooting this?
Looking at the flow chart for no power and no led, it is asking to verify voltages on pins 1 and 2 and Pin 3 these are OK.
There is suppose to be 1.8v on the dim pin #4 and 4.6 v on pin #5 the inverter on off pin.
If any of these are incorrect its directing me to check the power board.
The Schematic I posted in my first post is correct for the 37” model.
I have been beating my head against the wall ,and I just do not see what has to happen for the correct voltage to be on pins 4 and 5

[budm]

Re: Philips 37MF321D No power no LED

@retiredcaps: OK, that is a good idea, I will do that. Too bad badcaps.net does not have one place for the TIPS&TRICK where people can upload the instructions to it, and sorted and organized by the type of products.
I am beginning to like this place more than FIXYA. Thanks!

[retiredcaps]

Re: Philips 37MF321D No power no LED

You can read my basic guide if you want, it has the same idea but voltage value may be difference.

Suggestion for budm.

Create a new thread in the Troubleshooting TVs and Video Sources section and call it

Basic LCD TV and Monitor trouble shooting guide by BM.pdf

Put the pdf file in that thread and then provide a link to it for future people. That way, you don't have to upload the same pdf over and over again. And if you make revisions, you can tack it on to the same thread.

[budm]

Re: Philips 37MF321D No power no LED

That is good the 24 PS is OK, and it sounds like you on the right path on the main board to find out you are not getting the PS_ON signal.
You can read my basic guide if you want, it has the same idea but voltage value may be difference.

[alexanna]

Re: Philips 37MF321D No power no LED

In this case, per SCH, the HI signal from main board will turn on Q7076, which will turn on the OPTO, which will turn on Q7063 which will supply the VCC voltage to the PFC Cotroller IC.

Just an update on this television,
Appling right around 3.3 volts to the stand buy pin causes the other 24 volt portion to come alive.
Checking voltages going to the main board, I am loosing 16 volts to the 3A 1u101 fuse on the main board.
I can trace the path of what should be the 16 volts to the 7003 L5972d switching regulator.
It is easier to see in the photo but it has a very small pin hole in it.
I will let you know what happens when I get the regulator. I am fortunate that it's a good number and Digi- Key has them.
The two pictures Show the 24volt section that comes up with the 3.3 volts applied to the standby pin, and the 8SOIC regulator on the main board.