Philips 46" LCD (46PFL3705D/F7) ~ Temporarily back from the dead zone

[kca]

Hello all ~

I have a thread on this already that I started back in February 2016, but had something pretty unusual happen so I decided to start a new thread and put the link to the old information here:

https://www.badcaps.net/forum/showthread.php?t=53388


So ......

After having this Philips 46” tv on the shelf for several months and having almost given up on it altogether, I pulled it out again this week and got the following surprising results:

I put the original PSU back in and got the familiar buzzing on what still appears to be the transformer (see the last attached photo on this post). Although, there is no physical vibration on this transformer whatsoever, which I found and still find odd.

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 came on, flickered for about 2 seconds and then the picture suddenly and firmly "locked in". The buzzing sound concurrently disappeared. Beforehand, this flickering and buzzing would go on for 30 seconds or so, then the tv would shut itself down. But at this semi-miraculous moment, everything was rather instantaneously perfect.

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 came back. Ended up taking the back panel off once again. Disconnected and reconnected all the ribbons and connectors, much to no avail. There was one, singular attempt I made about 5 minutes after that where the picture suddenly locked back into place again, but it was very short-lived. When I shut it down after about 10 minutes (as I would have had to do at some point in time anyway in order 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 (meaning, allow for several hours (two days, really) of perfect play, then revert to a flawed picture accompanied by the buzzing sound)?
  
• 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. However, I don't think that's likely the case with mine because when it does lock in the picture is absolutely perfect. But maybe one or more of the lights is just barely malfunctioning? Anyone ever experienced that scenario?

NOTE: Below is one photo of the actual tv after it roared back to life, and the rest are stock photos of the set and the PSU. I’ll try to take some actual photos of the boards in my set this weekend. I am also going to replace two more capacitors that sit slightly above and to the left corner of the suspect transformer, but I don’t think that will likely fix this problem. I’ll update soon. For now, just curious if someone can help me nail down the likely cause as I’d rather not spend $75 - $85 for a new PSU when it might be a single component (or even one of the other boards).

~ kca

[petehall347]

Re: Philips 46" LCD (46PFL3705D/F7) ~ Temporarily back from the dead zone

repeated attempts warmed something up and got it working for a while .. capacitors work better warm if they are failing . thing is as found out is sometimes when capacitors completely fail they can take out other innocent components .
maybe some gentle heat might get it on again .then freezing suspects to find it .

[petehall347]

Re: Philips 46" LCD (46PFL3705D/F7) ~ Temporarily back from the dead zone

bad connections can behave the same .. have had transistors work when warmed up . also had ic.s work when frozen ..

[kca]

Re: Philips 46" LCD (46PFL3705D/F7) ~ Temporarily back from the dead zone

Thanks, Pete ~

I think it’s likely that one of the original capacitors was failing and affected another component on the PSU that I haven’t tracked down yet. I’m thinking it’s a diode. If you click the link above in my first post here you’ll see that a Badcaps member named martino pointed out that Diode 670 (D670) looked cracked on the original thread. It was indeed cracked. So, I replaced that and almost all of the caps around the transformer with new Rubycons. All to no avail.

Yesterday, I replaced two more capacitors (the two that sit up above the left-hand corner of the suspect transformer), but that resulted in no change either.

Here is a YouTube link to a short video that shows both the flickering and the buzzing, and then the recurring automatic shut down that always occurs (most of the time around 30 seconds or so, but every once in a while the whole thing will stay on with the flickering + buzzing in effect for appx. 3 or 4 minutes). Sorry it’s a little dark in the back when I’m zooming in on the PSU. Just filmed it quickly to show the overall problem(s).

https://youtu.be/X0psPRKoQJ8

[kca]

Re: Philips 46" LCD (46PFL3705D/F7) ~ Temporarily back from the dead zone

Tried heating up all the boards with a hair dryer. Did this for several minutes and several tries. No change.

Took some more close up pics of the boards in question. I'll post the PSU pics first on this post (the first 5), then the CBA Jack (next 3) and the Digital Main Board (the final 2), respectively.

Note: They all uploaded upside-down. Again.
If anyone knows how to change or avoid this, please let me know.

[Diah]

Re: Philips 46" LCD (46PFL3705D/F7) ~ Temporarily back from the dead zone

buzzing at PSU 99% short circuit at MB TO t-con lvds OR t-con, or ribbon cable between T-CON & LCD or at LCD its self

[kca]

Re: Philips 46" LCD (46PFL3705D/F7) ~ Temporarily back from the dead zone

I’d normally agree, but in this case I can isolate the T-con board altogether and still get the loud buzzing.

If I connect the thin, white ribbon from the PSU to the CBA Jack, and the gray cable from the PSU (at the 15 pin connector labeled CN1802) is also in place, that’s all it takes for the buzzing to occur. The T-con can be completely disconnected from the PSU and from the Main Board as well and the buzzing will still begin.

If the thin, white ribbon is disconnected, all buzzing stops and there are no voltage readings at CN1802.

Now, if I leave the thin, white ribbon in and take the gray cable out of CN1802 (with the power off), then when I power it back up the buzzing decreases dramatically and becomes more of a soft “hiss” instead. Still seems to be coming from the same transformer on the PSU.

Through a long process of deduction this afternoon, I decided that since the CBA Jack is integrally tied to the powering of the PSU, that it was worth $20 to buy one of these and see if it is really the sole source of all this trouble. I’ve put some pictures of it here, with the first image being mine. Just found it on eBay for $17.95 + tax.

[kca]

Re: Philips 46" LCD (46PFL3705D/F7) ~ Temporarily back from the dead zone

I also took a long series of voltage readings today. Maybe they will provide a clue to someone out there who can decipher them.

The 1st number is with both the thin, white ribbon in and the gray cable in. So, the set was buzzing / screen flickering, and constantly shutting itself down as I took these readings over the course of several attempts to get them all.

The 2nd number (i.e, the middle number) are the actual #'s and words which are printed to the right-hand side of Connector 1802 (CN1802). It's a 15-pin connector. Please see the attached photo.

The 3rd number is with the thin, white ribbon still in and the gray cable now OUT. So, I had to take these readings directly off the pins of CN1802 itself.

Here we go:

Pin #1 = 37.9 [Tuner + 35v] 43.7
Pin #2 = 12.1 [LCD+12v] 12.1
Pin #3 = 12.1 [LCD+12v] 12.1
Pin #4 = 0.0 [GND] 0.0
Pin #5 = 0.0 [GND] 0.0
Pin #6 = 3.3 [P-On+3.3] 3.3
Pin #7 = 0.0 [GND] 0.0
Pin #8 = 7.5 [6.5 Vf or 1 V] 10.7
Pin #9 = 0.0 [GND] 0.0
Pin #10 = 3.2 [P-On 3.5 Vf or Reg] 7.6
Pin #11 = 0.0 [GND] 0.0
Pin #12 = 5.2 [P-On+5.0v] 5.2
Pin #13 = 0.0 [GND] 0.0
Pin #14 = 25.2 [24 Vf or Amp] 2.8 (and then only 1.4 upon a 2nd reading)
Pin #15 = 0.0 [GND] 0.0

So, there is a HUGE anomaly at Pin #14, and also what I thought to be odd, almost reversed results at Pin #1 and Pin #8 and also Pin #10.

Do these results jump out and mean anything to anyone?

[Diah]

Re: Philips 46" LCD (46PFL3705D/F7) ~ Temporarily back from the dead zone

did you check closely all these white ribbon silver pad weather they remain tight and no cut at the end of them. if they are not tight the pins could move aside and make SC
between you wrote as T-CON total disconnected the buzzing remain, i would think to remove more load at the main boards, for example the Audio Amplifier 24 volts and check

[kca]

Re: Philips 46" LCD (46PFL3705D/F7) ~ Temporarily back from the dead zone

It’s possible that the ribbons are problematic. They are not perfect. But I have carefully bent the silver tips back into place each time a few of them have gotten slightly out of shape and I have tried to make sure they are not touching one another before reinserting them. However, they may be folding in a way that is incorrect once inside the connectors and in a way that I cannot visually see.

Is there a way to affix these tips back down onto the plastic so that they hold tighter there and operate in a more “like brand new” manner?

There are a couple where the very tops of the tips have broken off, but I didn’t think it was enough to prevent contact with the metal inside the connector itself. Maybe just 1/16th of an inch at most. Is that enough to make a difference?

Can these ribbons be cut across the entire width to eliminate any places where the very tips are gone, or would this simply be a counter-productive act?

I tried to look for replacements for all three of these ribbons both online and in 2 separate local electronics stores over this past weekend. No luck so far. They are unusual in that the thin one that goes from PSU to CBA Jack has 13 pins and the two large ones that go from CBA Jack to Main Board are both 29 pins. I recounted them several times to be absolutely sure.

One of the two 29 pin ribbons also has a slight fold in its plastic covering, where I thought it possible that the wires inside were touching. But, I largely (if not completely) rejected that idea because this particular ribbon has looked like that for two years and it doesn’t explain why, then, that the set would come to life for 48 hours at the end of last week.

Same is true for the thin ribbon. I don’t fully trust it either, but after it worked flawlessly for 2 days at the end of last week I did not remove either it or the other two when I went to put on the back panel. They stayed put, but after I had the back panel back on, the television started in with the buzzing and flickering again. I did have to remove the HDMI cord and the Component cord from the CBA Jack, of course, before putting the set back together.

[kca]

Re: Philips 46" LCD (46PFL3705D/F7) ~ Temporarily back from the dead zone

Well, I was reluctant to cut any of these Flat Flexible Cables before the CBA Jack got here in the mail, but it’s not due til Thursday and the curiosity got the better of me.

There was one end of the thin, 13-pin ribbon cable that had suffered more damage than I remember from a couple days ago, so I severed it across the width and got rid of any area where the silver tip ends had been lost or compromised.

The result was that not much of anything changed. It still began to buzz immediately upon the power being applied (per usual), and the flickering on the screen was still there (per usual). I plugged in DirecTV via one of the three HDMI ports and the screen images appeared (also per usual), but still flickering just like the so many times before.

While this wasn’t the result I was hoping for, I am happy that the flickering picture was there and “stable” in its flicker. I think this more or less proved that the ribbons were not the source of the problem, as all of the other ends were and are pretty well straight and in tact.

Below are images I took of all the ribbons before the cutting of the left end of the thin one.

The first one is the problematic one I cut, and the last one is the small cut off piece itself.

I’m a little concerned about one of the pins on Image #6 and maybe a couple on Image #8 also, but have not cut either of those 29-pin ribbons at all as of yet. I don’t think either of these are missing enough silver to be truly problematic, but please correct me if I’m wrong.

[kca]

Re: Philips 46" LCD (46PFL3705D/F7) ~ Temporarily back from the dead zone

Three more images:

The first shows where I made the cut on the thin, 13-pin wire.

The second shows where one of the 29-pin ribbons has a slightly raised or, as I described in an earlier post in this thread, a slightly “folded over” look and feel to just one of the wire traces inside the plastic coating.

The third shows the exact same “fold”, just this time with the camera’s flash turned off. As you can see, it shows up a little more pronounced in this image.

Does anyone think this “fold” is a problem? Maybe the pins at the bottom of that same image are too compromised and also need to be cut? Let me know what you think.

[Diah]

Re: Philips 46" LCD (46PFL3705D/F7) ~ Temporarily back from the dead zone

if you want to cut make it at the recovered with while plastic, then with shave plate bring the end of them clean so you will have new tight silver pins, measure first if the cable had enough long size

[petehall347]

Re: Philips 46" LCD (46PFL3705D/F7) ~ Temporarily back from the dead zone

pins at bottom then test continuity

[kca]

Re: Philips 46" LCD (46PFL3705D/F7) ~ Temporarily back from the dead zone

Well, not great news.

I got the new CBA Jack yesterday, put it in, connected everything back up and it is still behaving very much like it was before. A bit worse, in fact, because now I can’t even get the flickering screen as the backlights do not turn on. The pitch of the buzzing is a little different too. A bit more intense and seemingly at a higher frequency.

It’s ckearly not the answer. So, I think I’m back to searching for problems in the Power Supply itself. It could be the Digital Main Board as well, I suppose, but I don’t think so.

This buzzing is still emanating from either the same transformer or in the immediate area surrounding it. Just like before.

The only diode I can find that doesn’t appear to be reading the same as the 40” PSU Board is the one directly above the transformer. It consistently reads about 8% to 10% lower. For example, this morning I measured both again and the one on the 40” board is reading 199 and the one on the 46” board is only reading 183.

My question is:

Can a diode like this be approximately 10% “off” of its spec and be the cause of the problems like I am experiencing? In particular, since the tv usually does generate a flickering picture and on those rare occasions when the picture actually “locked in”, can a partially faulty diode be responsible for such erratic behavior?