Philips 46PFL3705D/F7 ~ No picture or sound / transformer buzzing

[kca]

Re: Philips 46PFL3705D/F7 ~ No picture or sound / transformer buzzing

Quick update:

I just replaced the 8 capacitors that most closely surround the SMPS transformer that is buzzing with absolutely no change in the symptoms or behavior of the set.

Does anyone out there have experience with these Philips LCD models circa the year 2010 and could tell me if the Digital Main Board (and/or possible the Tuner Board) can be a direct source of the SMPS transformer not functioning properly.

I have a feeling that if I can solve this "buzzing" issue, the rest of the set will work without a problem. Did some more exacting research and the Digital Main Board I would need is $41 plus shipping. If I can get some type of confirmation that a malfunctioning Digital Main Board can and does actually cause this type of buzzing, I'd be more inclined to spend the money.

Or, is this type of problem almost exclusively solved by attacking the Power Supply Unit components only?

Thanks in advance for any type of advice that can be supplied.

~ kca

[dick_barton]

Re: Philips 46PFL3705D/F7 ~ No picture or sound / transformer buzzing

35+Tuner = 0.00
12v = 0.00
3.3v = 0.00
3.5v = 1.2
and
24v = 0.00
...................................

Given all of this, it does appear that the PSU is indeed not activated until the ribbons and cables are connected from the PSU to the other boards, and in particular from the Digital Main board (through the Tuner Board) to the PSU.
...................................

Have you run the power supply disconnected from the main board
and then connected the standby voltage to the Power_On pin with a 1K resistor so then you can then measure all the other voltages, 24V, 12V, 3.3V, 35v, etc are correct.

[kca]

Re: Philips 46PFL3705D/F7 ~ No picture or sound / transformer buzzing

No, I haven't tried that. I'm not sure how to set that up. Still kind of new to all of this, but am more than willing to learn .... especially if this type of test will end up saving me both time and money.

How is it set up / arranged? What do I need to make it work?

[dick_barton]

Re: Philips 46PFL3705D/F7 ~ No picture or sound / transformer buzzing

You say in post 17 that the 5v is steady so that looks like your standby voltage. You need to connect this pin using a 1K ohm resistor to P_On (or called Power_On or On/Off pin).
This should then bring up all the other supplies which you can verify with your meter.

If you post a clear picture of the connector with the supplies legend alongside then I can see which pin you need to connect the other end of the IK to.

[kca]

Re: Philips 46PFL3705D/F7 ~ No picture or sound / transformer buzzing

Hello d_b and others:

I had to put this project on hold for a few days, but am back at it now. Here is the picture you requested (see below). It's not completely obvious which P-ON pin needs to be connected with the 5v pin, since there are two of these.


Would it be the P-ON+3.3v pin or the P-ON3.5Vf or REG pin?

(I'm thinking it might be the latter because if you look at the pic you'll see the following label along the left-hand side of the image:

P-ON3.5Vf or REG

I haven't tried either yet. I want to ask a couple more questions before doing so:

1) Do you connect the 1K ohm resistor directly to the pins in a certain manner? There are no back holes on this particular connector through which I might normally attack it. So, in order to be safe, I would like to know how best to connect the resistor so that I am not endangering myself or what I hope is a primarily otherwise functioning tv set.

2) I don't have one of these 1K ohm resistors handy at the moment. So, is there another way to do this that would be equally safe and effective?

and

3) If I accomplish this properly, can I expect that the set might actually fire up an on-screen image if the Digitial Main (and Tuner) are essentially taken out of play? Or, am I only doing this in order to take readings with the Digital Main and Tuner not in the picture. If it is the latter, then haven't I already accomplished that in the prior readings I documented in earlier posts here?

~ kca

[budm]

Re: Philips 46PFL3705D/F7 ~ No picture or sound / transformer buzzing

The command signals from the main board are fed to that small black connector for the flat ribbon cable.
The stby is ALL +4.3V, the pwr-on are PON M1, PON M2.
I also see the Protection signal pins, I did not study the board to know what all those function are but at least you can monitor those pins.
You should check the DCV when TV is plugged in but not turn on and the afetr the power switch is activated to see which pin change states.

[kca]

Re: Philips 46PFL3705D/F7 ~ No picture or sound / transformer buzzing

Hello budm ~

Yes, you're right. When that ribbon is pulled out of that black connector, the buzzing stops. But, then again, I can leave that particular ribbon in and pull the ribbons that go into the Digital Main instead and get the buzzing to stop as well. That's why I think it's the Digital Main and not the Tuner.

The tv really can't be plugged in without it attempting to turn itself on. Or, at least this is seemingly what happens.

As soon as I apply the AC cord, the buzzing starts immediately (when all of the cables and ribbons are in place), and then about 10 seconds later the Philips logo appears on what is a rather wildly flickering screen. Then, 4 seconds after that, the HDMI label appears very briefly on screen in the upper left-hand corner and then 1 second after that the entire thing shuts down.

Do you have any insight about whether the Digital Main board is at fault here?
All signs seem to point in that direction.

[kca]

Re: Philips 46PFL3705D/F7 ~ No picture or sound / transformer buzzing

I'm getting a little lost here as to what is best to test next.

Can someone tell me, based on all the information I've already provided, what is the next best single thing I should do?

Is it:

A) Test the white connector (CN1802) with some kind of resistor or jumper cables?

B) Run tests on the black connector (CN1801)?

C) Address the Digital Main board (numbered as BA01P2G04011 and A01Q2UZ) by either fixing it at the component level or just buying a new one?

D) Look for other faulty caps, diodes, or other components on the PSU?

or

E) Other?

[kca]

Re: Philips 46PFL3705D/F7 ~ No picture or sound / transformer buzzing

Just measured the black connector (CN1801) voltages and they came up as 0.00 on all of the pins except the following three:

Pin 6 - Power Reset - read -1.8 (negative 1.8)

Pin 12 - All + 4.3v read exactly 4.3 volts
Pin 13 - All + 4.3v read exactly 4.3 volts


Does that appear to be in order?

[kca]

Re: Philips 46PFL3705D/F7 ~ No picture or sound / transformer buzzing

Also, I'm not 100% sure now that it is the SMPS transformer that is actually making the buzzing noise. It still sounds like it is when I try to auditorily isolate it, but I got up the nerve to physically touch it while the AC was plugged in and there was absolutely no physical vibration that I could feel.

Is there anything else in this exact same vicinity that is even capable of making such a loud and sustained buzzing noise? It would have to be within a couple of centimeters diameter away from the transformer, at the most, as I can definitely hear it within this range / parameter.

[budm]

Re: Philips 46PFL3705D/F7 ~ No picture or sound / transformer buzzing

The standby Voltage and the command signals are on the black connector so you need to have that cable connected so the power supply will get the PS-ON to signal to turn on the main power supplies but you can disconnect the white connector CN1802 to see if the power supply will still buzz. I am not sure if you have tried that already or not.

[kca]

Re: Philips 46PFL3705D/F7 ~ No picture or sound / transformer buzzing

Yes, I did try that.

With the black connector engaged and the white connector disengaged, the buzzing still occurred. It was a bit more strained and high-pitched than usual. It felt like if I left it on that something might "give".

So, I unplugged it at about 10 seconds instead of waiting for it to shut down on its own. I didn't want to risk blowing any of the new Rubycon capacitors I just put in, any diodes, or any other components on the PSU.

What do you think I should do or test next?

[budm]

Re: Philips 46PFL3705D/F7 ~ No picture or sound / transformer buzzing

So that means it not the loads that causing the power supply to buzz, I really do not know exactly as to what the causes of the problem is since I did not trace out the board to see how it works yet.

[kca]

Re: Philips 46PFL3705D/F7 ~ No picture or sound / transformer buzzing

This link will lead you to the Service Manual:



My model is the YA1A.

[kca]

Re: Philips 46PFL3705D/F7 ~ No picture or sound / transformer buzzing

Many of the schematic wiring diagrams found there are complex and hard for me to decipher, but maybe they shed insight for you. I did, however, find this flowchart (see image below) that is related to the buzzing.

I have already checked all of the suggested diodes, but have not yet examined Q652, Q653, and Q654. Apparently, according to the Parts List also found in the Service Manual, these three are transistors.

Any suggestions on how best to test these three with my Digital Multi Meter would be most helpful.


~ kca

[budm]

Re: Philips 46PFL3705D/F7 ~ No picture or sound / transformer buzzing

OK, I will down load it and see.

[budm]

Re: Philips 46PFL3705D/F7 ~ No picture or sound / transformer buzzing

Many of the schematic wiring diagrams found there are complex and hard for me to decipher, but maybe they shed insight for you. I did, however, find this flowchart (see image below) that is related to the buzzing.

I have already checked all of the suggested diodes, but have not yet examined Q652, Q653, and Q654. Apparently, according to the Parts List also found in the Service Manual, these three are transistors.

Any suggestions on how best to test these three with my Digital Multi Meter would be most helpful.


~ kca

Hmm, so they already know about the potential problem. To test the Transistors properly, they will need to be removed and tested off the board.

[kca]

Re: Philips 46PFL3705D/F7 ~ No picture or sound / transformer buzzing

Thank you for taking time to examine the Service Manual.

and ...

I will take a look at the board soon and see what it is going to take to desolder those.

[kca]

Re: Philips 46PFL3705D/F7 ~ No picture or sound / transformer buzzing

Been looking at how to test MOSFET transistors. Is this video thorough and comprehensive enough:

https://www.youtube.com/watch?v=RkWy1EirEu8


... or should I be testing them in some other way? Any tutorial you can provide would be very helpful as I continue to try to isolate the problem.

Thanks ~
kca

Also included two pics of the three transistors in question (see images below). Note: The Q652 board label is not visible in the photo, but that is definitely one of the two correct MOSFET transistors in question.


And the screen shot from the service Manual describing these three transistors is also included below. Q652 and Q653 appear to be identical MOSFET transistors, and Q654 appears to be what is called an N Channel Low Power MOSFET Transistor. Are these two different types tested in the same manner, or should I be looking to test the N Channel Low Power one in a different manner than the other two?

[budm]

Re: Philips 46PFL3705D/F7 ~ No picture or sound / transformer buzzing

OK, just to be sure, please check those Diodes I marked with yellow boxes (you will have to lift one leg off the board to test), I am looking for low resistance or leakage resistance.