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

**kca** · 04-04-2016, 10:01 AM

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

Here is a bit more information:

The PSU board is labeled as BA01P0F0103 2 and the part number is: A01Q0MPW-001. There are small but important differences between the 40" PSU board and the 46".

Attached is a pic of the diodes currently in question near the transformer that is making the problematic squealing/hissing sound.

PHILIPS 46PFL3705D/F7

Diode readings immediately surrounding the SMPS:

D651 = 565
D652 = 566

D656 = 253

D662 = 153

D665 = 525
D670 = 175

D672 = 193
D673 = 193
D674 = 193

The above readings were taken in Diode Mode on a Craftsman DMM, and when I reverse the leads I get a reading of 1 on the left-hand side of the screen. There are no OL readings. Is this the best way to gather the readings?

Also, ..... here is some more info from a post I made on a separate thread a week or so ago:

I am wondering if you know if other boards in the set, if defective, can cause this type of squealing in the PSU transformer?

I ask because when I disconnect all of the cables leading out from the PSU, the tv no longer shuts down and there is no squealing. I only get a "silent" black screen. When I reconnected all of the cables and ribbons one by one, the squealing returns. I haven't done exhaustive testing of this as of yet, but one result is that everything could be plugged in EXCEPT the tuner board and it was still black screen silent. Then, when I made that last connection of tuner board to PSU via the small white ribbon, that's when the transformer would start its familiar squealing/humming again.

The same result, however, occurred when I left the tuner board connected up to the PSU and isolated the board above it (where the HDMI ports are). All black screen silent until I made that connection between this "HDMI port" board (sorry, can't think of its proper name at the moment), and the tuner board via two white ribbons. I think there are other combinations that would likely produce the same result.

So, my question is .... could it be that one or more than one of these other boards in the set is producing the squeal in the transformer, or is it the case that the squeal must be stopped at the PSU level itself and then the other boards are likely to function in their normal manner? It seems like both notions have merit.

Attached Files

**martino** · 04-04-2016, 10:39 AM

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

Take a good look at diode D670,it looks like it is cracked?
When you plug in the tuner board,it is then that the power supply gets activated hence no squeeling till then. The squeeling is often a shorted diode suppressing the transformer mostly secondary side but some times primary side.

**kca** · 04-04-2016, 11:21 AM

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

Hello martino ~

Thanks for your reply. I took another close look at D670, as per your suggestion, by visually inspecting/touching it on the board itself and you are exactly right. It is definitely cracked. Great eye!

In your experience, could this account for the trouble I am experiencing with the SMPS and with the picture/sound in general?

Yes, it is when I plug in either of the two boards on the right-hand side of the PSU that the sound in the transformer occurs. Not until then.

I didn't focus on this particular D670 before because when I did the readings against the 40" PSU I have on hand, the 46" D670 actually read a bit higher (182) than the 40" D670 (which read 166). Whereas the opposite was true with Diode # 662 (175 on the 40" and only 153 on the 46"). So, that's why I purchased the D662 only from Digi-Key.

I think I will desolder the D670 from my 40" unit today and replace the cracked one on the 46". They are both labeled as the following:

D670
DIODE SCHOTTKY SB230BD
NDWZ000SB230

A little strange that the cracked one is actually getting higher readings on the DMM, don't you think? But, still seems prudent to replace the cracked one anyway and see what effect it has on the overall operation of the set.

**martino** · 04-04-2016, 11:32 AM

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

It's probably reading something else as you measuring in circuit. If you get a weird reading,desolder one leg and measure again.
And yes,one diode can cause those symptoms

**kca** · 04-04-2016, 11:48 AM

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

Here is a pic of all the boards involved:

Attached Files

**kca** · 04-04-2016, 11:52 AM

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

Okay.

Will do the readings out of circuit once I have it desoldered.

I'll update the thread as soon as I can. Hoping it's like your D651 fix from a couple of years ago. Nice and simple.

~ kca
David

**martino** · 04-04-2016, 11:56 AM

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

Originally posted by kca

Okay.

Hoping it's like your D651 fix from a couple of years ago. Nice and simple.

~ kca
David

That tv is still going strong today,gave it to my brother in law.
I read a few of my older posts a few weeks back,was pretty green back then haha,hard to read some of it lol..

**dick_barton** · 04-04-2016, 01:35 PM

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

Excellent call martino.

**kca** · 04-05-2016, 12:34 PM

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

Welcome d_b ~

It was a great call, but I think there are bad caps too unfortunately. I swapped out the cracked D670 with the one from the 40" board. Both read about 165 (see question below) on my DMM both in circuit and out of circuit once I had them both desoldered.

Plugged it in and still the same buzzing/hissing sound. As I mentioned, I have all the caps surrounding that transformer and D662 coming in the mail, and I will update the thread once I have them all in.

Question is:
Am I reading my DMM in the best way possible when gauging the strength/viability of these diodes? I am getting vastly different readings (from appx. 150 to over 900) based on which diode I am testing. However, there are certain patterns that can be detected and deciphered even though I am not sure of the meaning of the format of the numbers themselves. For example, all three of the diodes immediately to the right of the transformer all read 197, so I made the assumption they are all good and in working order since all three are exactly the same type of diode. In this particular case, the service manual labels them all as follows:

D672 DIODE SCHOTTKY SB3A0BH NDWZ000SB3A0

D673 DIODE SCHOTTKY SB3A0BH NDWZ000SB3A0

D674 DIODE SCHOTTKY SB3A0BH NDWZ000SB3A0

Most of the information online is referring to 0.4 to 0.7 voltage drops instead of readings like the three digit whole number ones I am getting. But, when I set my DMM to the diode mode (as indicated by the arrow w/ the vertical line), I do not get anything that indicates it's even capable of reading voltages in this manner. It's a Craftsman DMM 82141. It also has a continuity symbol alongside the Diode symbol, but I don't know if I am supposed to be switching between the two somehow. There doesn't seem to be a way to do that. Am I missing something?

I plan on testing many diodes in the future as I continue on with this hobby, but want to make sure at this point in time that I am doing it properly.

Attached Files

**dick_barton** · 04-05-2016, 12:52 PM

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

The diode test also has continuity so you hear the beep. It's not switchable, just part of the diode test for that and many other meters.

**kca** · 04-05-2016, 12:56 PM

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

Thanks d_b.

And what about the triple digit readings vs. the voltage drop readings? Should I be focused on one or the other? As mentioned, I cannot seem to even get the voltage drop readings to materialize.

**martino** · 04-06-2016, 01:05 AM

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

How is the battery in your meter? A weak battery can give weird readings. Most diodes voltage drop around 0.560ish. Maybe meter is a bit wonky? dunno.Often if you measure in circuit and you don't see what you kinda expect then lift a leg of the component so it reads out of circuit.
Did you measure the fets too?
Did you try and measure the 35volt line to ground for ohms?
How are the solder joins on transformer T601?

**kca** · 04-09-2016, 10:26 PM

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

Hello all ~

I'm back to work on the Philips 46" again, having received the numerous capacitors I ordered and the diode (662) in the mail. But, I want to check with the forum here before proceeding on replacing all of these caps and/or the singular diode.

Note: None of the caps look damaged in any way and the diode, while testing a bit lower than the rest at a reading of 155, actually tests with the same number reading as the new diode I received in the mail as I tested it straight out of the package. So, I have a feeling that the PSU might not be the root of the problem here.

The primary reason for my hesitation is that I am not getting the buzzing/hissing/clicking sound from the SMPS transformer UNTIL I connect it with the Digital Main Board. So, I'm wondering if the Digital Main could be the source of such a problem with the buzzing transformer (i.e., the problem itself).

Here is the sequence of the testing I did: (please refer to the pics attached below)

1. I disconnected the white ribbon cable from the Tuner Board to the Power Supply. Result was that the buzzing would not start up. Complete quiet.

2. Buzzing started immediately when I replaced this ribbon between Tuner Board and Power Supply. Initially I thought, then, that there might be a problem with the Tuner Board, but .........

3. I "backed that up" one more step and disconnected the two ribbons between the Digital Main and the Tuner Board, while leaving the ribbon between Tuner Board and PSU in. Result was that there was no buzzing at all. Complete quiet. This led me to believe that the Tuner Board itself was not the source of any problem related to the buzzing transformer. I then reconnected only one of these two ribbons (did the left first, and then the right in order to test them both) between the Digital Main and Tuner Board, and no buzzing. It wasn't until I connected that 2nd white ribbon between Digital Main and Tuner that the buzzing came back.

4. I repeated all of the same steps with the other two boards that rest above the PSU disconnected, and therefore taken out of the picture, with the same results. This appears to have isolated the Digital Main.

So, all of this led me to one of two conclusions:

Either the Digital Main has a defect that is causing the PSU transformer to malfunction ......

Or, the transformer is malfunctioning due to a cap or diode (probably close in proximity to the transformer), and that those caps or diodes are simply not being activated and "put into play" until the physical connection from Digital Main through Tuner Board to the PSU is made.

Can anyone help answer this question. Which one is more likely to be the case, and is it even possible for another board to be responsible for the transformer malfunction?

Attached Files

**kca** · 04-09-2016, 10:35 PM

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

martino ~

In response to the questions you posed a few days ago (sorry for the late reply), please read the following:

How is the battery in your meter? A weak battery can give weird readings. Most diodes voltage drop around 0.560ish. Maybe meter is a bit wonky? dunno.Often if you measure in circuit and you don't see what you kinda expect then lift a leg of the component so it reads out of circuit.

My DMM is okay, as it gives consistently patterned readings/comparisons between by Philips 40" PSU and 46" PSU. Again, I am not getting any readings whatsoever that are decimal based (nothing like 0.5 or in that range). My readings are all triple digits ranging from the 150's to the 900's when testing all of the various diodes on the entire board. Does the power need to be on in order to obtain the decimal-based readings? All of mine were taken with the power off.

Did you measure the fets too?

I did not measure the fets. Not sure what readings I am to look for there, or what setting to use on the DMM. Never attempted to measure those before.Any advice would be appreciated.

Did you try and measure the 35volt line to ground for ohms?

Not sure what you mean by this. Can you be more specific? Where is the 35 volt line.

How are the solder joins on transformer T601?

All of the solder joints on the transformer look solid. They are a match for the 40" PSU which is in working order.

**martino** · 04-09-2016, 11:08 PM

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

If you look at the psu,study the little jumper wires you see all over the board,some will have markings on them,especially around the cables running to the tuner board etc. You will find markings saying 5volt stby,35 volt et.etc.
Those are your test points,red lead on the jumper,black on the chassis of tv,dmm in dcvolts.
With tuner unplugged,psu doesn't squeel(bd spelling,lol)could make sense:
-either your right and the tuner bosrd is shorting the psu
-tuner is trying to activate psu,hence making it squeel.

Maybe test the 5volt standby without the tuner,then with the tuner,repeat for the 35 volts and other voltages you find,see if one gets pushed down when tuner gets plugged in?(you prob wont have the 35 volts till tuner gets plugged in,still good to see if 35 is indeed 35)

35 volt to ground means:with power off,dmm in ohm,red lead on 35 jumper,black on chassis,read ohms.

fets you can measure in the ohm setting,power off,red lead and black lead on all combinations,1-2,1-3,2-3 see if you get a short on any of them. (unlikely but you never know)

**kca** · 04-10-2016, 08:56 PM

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

Hello martino, et. al. ~

Below are the initial voltage measurements I just took with all of the cables and ribbons hooked up throughout the entire set. Then, I did the same tests with only the PSU in play and all of the other boards disconnected from it.

Note: Every time the AC is applied, the set buzzes for a total of about 15 seconds before shutdown. This has been true from the very start. So, the information below is timed out over that 15 second span.

WITH EVERYTHING CONNECTED:

35V+Tuner = Started out at 34.5, then over the course of the 15 seconds it rose to and past 35 (took about 8 seconds to do so) and then stopped at about 36.8 just before the system shut down.

3.3v = Rose immediately to 3.4 and stayed until shutdown

3.5v = Initial rise to 3.2, then quickly to 3.3 and then hung at 3.4 until about the 10 second mark. It then finally climbed up to 3.5 but no higher and that only lasted the final two or three seconds of the 15 seconds before the ritual shutdown.

5v = Rises to 5.1 immediately, gets to 5.2, and holds there until shutdown

24v = Rose immediately to 25.5, then continued to rise until 26.7 and stayed there until shutdown.

WITH ONLY THE PSU IN PLAY
Important Note:
During this set of tests, all of the other boards were disconnected from the PSU in various ways and manners, including the Tuner Board and the Digital Main. It did not matter which boards were disconnected, how many were disconnected, or in what order. The result was always the same:

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

Also, I measured the connectors in the upper-left hand corner of the PSU that lead to the inverter boards, and while several of those pins on the bottom half of each connector read 1.4, none of them ever read higher than that when the other 4 boards were disconnected from the PSU.

Retest: 2nd try with all ribbons and cables reconnected to the PSU once again

All of the readings above came back as expected and as follows (just as before):

35V+Tuner = Started out at 34.5, then over the course of the 15 seconds it rose to and past 35 (took about 8 seconds to do so) and then stopped at about 36.8 just before the system shut down.

3.3v = Rose immediately to 3.4 and stayed until shutdown

3.5v = Initial rise to 3.2, then quickly to 3.3 and then hung at 3.4 until about the 10 second mark. It then finally climbed up to 3.5 but no higher and that only lasted the final two or three seconds of the 15 seconds before the ritual shutdown.

5v = Rises to 5.1 immediately, gets to 5.2, and holds there until shutdown

24v = Rose immediately to 25.5, then continued to rise until 26.7 and stayed there until shutdown.

---------------

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.

Is that normal in an LCD tv? I have only worked on plasmas for the last couple of months. Or, is this particular to Philips or this model?

Either way, I still don't think it answers my question if the caps/diode are bad on the PSU surrounding the SMPS transformer ...... or if the Digital Main Board is bad. I took the Digital Main out and got the Part # off of it in case I need to order one. They run about $25.

Would you just replace the caps and diode at this point and see if that fixes or alters things? And then replace the Digital Main Board if necessary?

One other note:
I measured the 35v to ground that you asked for, martino, and that came up as a reading of 43.5 when I put the DMM setting to 200k in the Ohm range.

Or, is there a better approach for me to take based on the voltage data above?

Do some of those initial readings in the first few seconds of the 15 second time span matter in that they are not getting up to the expected values immediately? In particular, the 35v line only gets to 34.5 and takes about 8 seconds to reach 35 and above. However, the squeal from the transformer always starts right away as soon as AC is applied and doesn't stop until the set shuts down.

I really don't want to replace the caps and diode right now if the only problem is the Digital Main board. How can I tell for sure?

**martino** · 04-10-2016, 09:46 PM

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

What happens if you have everything plugged in except the inverter board?

**kca** · 04-10-2016, 10:09 PM

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

Hadn't tried that before.

Just tried it now, and got the same results as before. Namely:

35V+Tuner = Started out at 34.5, then over the course of the 15 seconds it rose to and past 35 (took about 8 seconds to do so) and then stopped at about 36.8 just before the system shut down.

3.3v = Rose immediately to 3.4 and stayed until shutdown

3.5v = Initial rise to 3.2, then quickly to 3.3 and then hung at 3.4 until about the 10 second mark. It then finally climbed up to 3.5 but no higher and that only lasted the final two or three seconds of the 15 seconds before the ritual shutdown.

5v = Rises to 5.1 immediately, gets to 5.2, and holds there until shutdown

24v = Rose immediately to 25.5, then continued to rise until 26.7 and stayed there until shutdown.

I really think if there is a fault outside of the PSU itself, it lies in the Digital Main board based on what happens when I disconnect it. No squealing occurs until that Digital Main is put into play.

**kca** · 04-10-2016, 10:23 PM

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

There is a small ripple on one of the two ribbons coming out of the Digital Main and into the Tuner Board. It's not quite a slit, but it is definitely pronounced. Based on my prior testing, I didn't think it the cause of the trouble.

But, in your experience (anyone), is this enough to cause the transformer to malfunction?

I don't seem to have a perfect match on hand with any of the other tv's I'm working on in order to do a swap/test.

~ kca

Attached Files

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

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

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