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

[kca]

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

Hello budm ~

I know I need to lift the legs in order to be absolutely sure, but first I want to share with you all of the readings I've already obtained from these diodes you've identified and marked when I measured them a couple of weeks ago. It seems to me that some of them are certainly patterned in a way such that their viability is already confirmed. In other words, the numbers match up so perfectly between certain pairs or triads of diodes that desoldering them seems unnecessary.

I have both the 46" PS board (from, of course, the 46PFL3705D/F7 model that I am working on) and a Philips 40" PS board in my possession (from the 40PFL3705D/F7 model), ...... so not only was I able to detect patterns on the 46" board, I was also able to compare them to the 40" diodes and found that none of them were what I would call significantly out of line with one another.

Below, I have listed the 46" readings first, and followed them with the 40" readings. So, for example, Diode 665 is reported as follows:


Diode # 46" and 40"
D665 = 517 and 506


Also, in the list below, I have bolded all of the ones you marked in yellow for me.

Please take a look at these readings and let me know if I can indeed forego and desoldering and leave them in tact according to the patterns you detect. I would like to limit the amount of desoldering and resoldering as much as possible on this board, but will certainly go ahead and do so on any and all of them you tell me still need to be analyzed that way.

Note: I used my Craftsman DMM in the diode setting to obtain these readings. I hope they are in line with what you are expecting to see. If not, I can perform the test in another way.

And another note is that I already replaced D670 on the 46" board with the same one I took off of the 40" board because the original D670 on the 46" was found to be cracked.

HERE ARE ALL OF THE DUAL READINGS OFF OF BOTH BOARDS:

Diode # 46" and 40"

D607 = 747 and 747

D610 = 148 and 148
D611 = 678 and 673

D613 = 530 and 561
D614 = 526 and 553 (See my note below on Diode 614)

D651 = 568 and 564
D652 = 570 and 564

D656 = 256 and 261
D657 = 257 and 261

D662 = 155 and 184 (See my note below on Diode 662)
D665 = 517 and 506

D667 = 703 and 690
D670 = 171 and 166

D671 = Open (no diode there) and Open (no diode there)
D672 = 197 and 209
D673 = 197 and 209
D674 = 197 and Open (no diode there)

D676 = 687 and 695

D606 = This was the most curious case. D606 tested as shorted on the 46" power supply board (a beeping sound when both the red and black DMM leads were applied), but it also tested in the exact same manner on the 40" power supply board so I ignored it as an absolute cause.


Notes:
Diode 614 looked a bit burnt on the 46", but as you can see from the numbers above it registered within 95% of the same diode on the 40" board.

Diode 662 looked to have a relatively significant discrepancy between the 46" board and the 40" board. So, I ordered this from DigiKey about two weeks ago and replaced it. After it was in, I expected that it might read more like the higher number found in the 40" board (somewhere around the 180's, but it in fact read, and still reads, closer to the 160 mark).


Please let me know your thoughts. I really appreciate your help on this project.

~ kca

[budm]

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

D657 is Zener so I expect the VF to be around 600 range.
Do me a favor, test the diodes in 200 Ohm scale mode to see what you get with those you have test above, no need to lift the legs.
BTW, the 40" PS board is a good working board, right?

[kca]

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

Okay, I will do those checks you've suggested.


As far as the 40" board, I am making the assumption that it is indeed a working board. But, it is just an assumption on my part because I ordered it by mistake about three weeks ago off of Ebay. I wasn't too thrilled with myself for making that error, but then decided I could at least use them for the purpose of these comparisons. Right now, I have no way of assuring myself in full that the 40" board is fully functioning.

[kca]

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

Well, I got what may or may not be strange results. Most tested fine in the 200 Ohm range, but a few did not register until I switched it into the 2000 Ohm range.

Here are the 200 Ohm range results:

Diode # followed by the reading itself

D670 = 84.2

D662 = 90.3

D672 = 100.7
D673 = 100.7
D674 = 100.7
(D671 does not exist on the board)

D656 = 127.0

D657 = 126.8 (Q: Are D656 and 657 both Zeners that you might be questioning, since their readings are almost identical?)


D610 = 147.6 (which almost exactly matches the 148 reading on the diode scale I got two weeks ago)

_____________________________________________________________


Now, here are all the ones that I had to measure in the 2000 Ohm scale range because they immediately "topped out" in the 200 scale and the screen would only read 1. _____________ (with the area above the line just being blank).


D611 = 540 (and then, when I switched the red and black leads, the reading would interestingly change to 824. Also interesting that this read so much differently than D610 which gave me a clear reading in the 200 scale as you can see above.)

D614 = 422

651 = 449
652 = 452

and

D665 = 418


Did I miss any important ones? What do you think of those results?

[kca]

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

Almost forgot ......

That D606 that tested as shorted (beeping) in the Diode mode on the DMM tested as only 1.0 (in the 200 Ohm scale), and did so no matter if I reversed the leads on the DMM or not.

A very different result from any of the others. It first registered as 1.3, and then slowly over the course of about 5 seconds it lowered itself down to the 1.0 I just reported above.

[kca]

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

And, it looks like I didn't report D613 to you in the Ohm scale.

I just read it. You'll have to mark that as another one that had to be interpreted in the 2000 Ohm scale and its reading was 424.

[budm]

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

D606 is in parallel with <1 Ohm resistor so it will show low resistance both ways.
Something is not right to see 100 and <than 100 Ohms readings since there is no resistance in the circuit that can make the meter shows such low resistance readings.
These reading are done without the white connector CN1802 in place, right?

[kca]

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

All of those readings were taken with the white connector in, actually. I did not know it was necessary to disconnect it.

I can do that, and get the new readings to you.


Are there any other connectors I should disengage, or purposefully engage, in order to get the most accurate Ohms-related readings?


~ kca

By the way, I believe that all of the Diode mode readings I took two weeks ago were also taken with the white connector in place.

[kca]

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

Well, I remeasured all of the diodes in question (the ones you had marked in yellow, budm, and the results did not change significantly at all.

First, with the white connector now disengaged, essentially all of the readings remained the same as I reported in Post #44, with the numbers below 150 only going up by about 3 (so, for example, D670 went from 84.2 to 87.7 and D656, as another example, went from 127.0 to 131.1).

The values on the diodes that originally had to be read in the 2000 Ohm scale still had to be read that way. These went up by about only 8 to 10 (so, for example on these, D665 went from 418 to 428.


These did not appear to be the changes you were alluding to, budm, so I then pulled the ribbon that comes from the CBA Jack (what I have been previously calling the Tuner) and goes into the PSU at the black connector. I did all of the readings again, now with both the white connector and the black connector pulled simultaneously, and there were no significant changes. All in all, the values below 150 dropped by a point or two, and the values above 150 dipped back down by about only 5 points.

What do you think is happening, budm, if there really shouldn't be any values less than 100 on the 200 Ohm scale?


Note: The only two that did not change at all were D610, which remained at exactly 147.6, and D606, which remained at 1.0. Also, on my DMM, I put the red lead into the Ohm scale port (the one on the left-bottom instead of the traditional right-bottom) and did all of the readings one more time. There was no significant change with this arrangement either.

[kca]

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

Does the next logical step, budm and/or others, now involve desoldering and testing those mosfet transistors?

Or, is all of this leading anyone to the conclusion that it may indeed be the Digital Main Board that needs to be replaced as it is somehow emanating a voltage or voltages that is causing malfunction in an otherwise good Power Supply Unit?

[kca]

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

Hello all ~
After having this Philips 46” tv on the shelf for several months, I pulled it out again and got some surprising results.

I put the original PSU back in and got the familiar buzzing on what still appears to be the transformer. Although, there is no physical vibration on this transformer whatsoever.

Took it out, hooked up the PSU from the 40” version of this tv that I mistakenly bought. Got nothing, just as before.

Then, I put the 46” original PSU back in one more time and suddenly it came to life. The Philips logo canme on, flickered for about 2 seconds and then the picture locked in. The buzzing sound concurrently disappeared. Before, this flickering and buzzing would go on for 30 seconds or so, then the tv would shut itself down.

Since it was acting normally, I ran it all day on Tuesday. And then again on Wednesday and had it completely powered down and the power cord pulled out during the nighttime hours in between.

All the was good for 2 full days. But then this morning I put the back cover on and when I was done with that operation, both the buzzing and the flickering cane back. There was one, singular attempt I made after that where the picture locked back into place again, but it was short-lived. When I shut it down (as I would have to do to put this particular back panel on again because of its design), it proceeded to buzz and flicker again.

Question is:

What could possibly be responsible for this erratic behavior?

Can a faulty capacitor do this?
Can a faulty diode do that?
Can a faulty transformer do that?

Or, is there some other component or board that can be the source of this off / periodically on / mostly off again behavior?

I also read another, similar thread here in Badcaps that was suggesting faulty CCFL’s? That seems like a fairly valid theory as well, based on the patterns of behavior I am dealing with.

~ kca