Philips 3PFL5606H/12 - good image for 3s / corrupted for 3s and so on

[SuperDuty]

Hi guys,

I've just found this TV at the recycling center. The image is perfect, sound is great, but here is the problem : the image is perfect for 3 seconds, then it's corrupted (like vertically stretched) for 3 seconds, then it's good again, then bad, and so on. The sound doesn't change. The problem occurs on the whole image (including the menu screens, so it's not related to the antenna).
So I'm assuming the problem is located on the logic board and not on the power supply board. I see no buldging caps anywhere. Though there is one "CapXon" lytic cap on the logic board, but it doesn't look bad, and two "Elite" GP with an orange sleeving. It haven't seen any burnt component yet.
Any hint as to where I should look first ?

Thanks !

[tom66]

Re: Philips 3PFL5606H/12 - good image for 3s / corrupted for 3s and so on

Can you show us a picture of the defect, in video form if possible? This might be a tab bond problem.

[SuperDuty]

Re: Philips 3PFL5606H/12 - good image for 3s / corrupted for 3s and so on

Aw the TV is apart right now, but when I look at problems caused by tab bond issue, it's very different. Here the image is fine, it just goes bad for three seconds every three seconds.

[tom66]

Re: Philips 3PFL5606H/12 - good image for 3s / corrupted for 3s and so on

I've seen a thermally sensitive line doubling tab-bond before though the problem did get better after some time.

[SuperDuty]

Re: Philips 3PFL5606H/12 - good image for 3s / corrupted for 3s and so on

Here's a video :
http://www.youtube.com/watch?v=p6JM41pLWKc

I've let it run like that for 20 minutes with no change.
I'm hearing some sort of coil noise (not hiss) on the logic board where there is the CapXon capacitor every time the image gets corrupted.

(I don't know if there a way to embed a video here.)

[tom66]

Re: Philips 3PFL5606H/12 - good image for 3s / corrupted for 3s and so on

Does the menu get corrupted too?
Can we get a photo around the coil and CapXon capacitor?

[SuperDuty]

Re: Philips 3PFL5606H/12 - good image for 3s / corrupted for 3s and so on

Yes everything gets corrupted, that photo is actually a test image from the menu.

After looking closely, that CapXon capacitor seem to be part of the sound system so I doubt it has anything to do with the problem, but I'll take a picture of it and of the board.

[tom66]

Re: Philips 3PFL5606H/12 - good image for 3s / corrupted for 3s and so on

Could be that the power supply feeding it is unstable, causing other unseen problems.

[SuperDuty]

Re: Philips 3PFL5606H/12 - good image for 3s / corrupted for 3s and so on

Here are the pictures.

I've just noticed something by the way, there is a fluctuation at the 12V pin where the harness of the PSU is plugged to the logic board (the two red wires) :
When the image is fine, I get 11.94V with my multimeter, and when the image is corrupted, it drops to 11.89V. It's a slight drop but it might be important.
So it could indeed be a problem from the power supply. But what could make the power drop so regularly ?
At the +12V voltage regulator, I get a drop from 11.98 to 11.94.

[tom66]

Re: Philips 3PFL5606H/12 - good image for 3s / corrupted for 3s and so on

Ugh, this isn't a Philips TV. I mean, it has the badge. But it's just a Unihan OEM.
Check the 5V line too. Maybe that is dropping by too much.

[SuperDuty]

Re: Philips 3PFL5606H/12 - good image for 3s / corrupted for 3s and so on

Ok, well as long as I make it work I'm fine There's no +5V on it, only 3.3V and +24V and they're stable.

I've found a NPN transistor (Toshiba 2SK4003) that seem defective but not shorted, it won't open like others NPN transistors when touching the source and the gate.

[SuperDuty]

Re: Philips 3PFL5606H/12 - good image for 3s / corrupted for 3s and so on

False hope - replaced and no change

[budm]

Re: Philips 3PFL5606H/12 - good image for 3s / corrupted for 3s and so on

Pictures of the T-CON? What are the voltage labels on that connector of the power supply board to the main board? Not all the pins are used so it may not have 5v stby, but it may use 3.3V stby instead.

[SuperDuty]

Re: Philips 3PFL5606H/12 - good image for 3s / corrupted for 3s and so on

The T-CON board, you mean the one that controls the LCD panel ? As far as I can see, there are only two small boards for left and right display under the panel. So there's no other board than the two I've shown above.
If there were a problem with one of the LCD panel boards, I doubt I'd get a problem on the whole screen since each one of them are for one half of the panel if I understand correctly.



I'll try to update the firmware.

[SuperDuty]

Re: Philips 3PFL5606H/12 - good image for 3s / corrupted for 3s and so on

Ok here are the labels of the connector on the PSU board :
+3.3V - blue wire
STB - grey wire
GND - black
GND - black
+12V - red
+12V - red
+24Vsnd - orange
GND - black
ENA - yellow (mesuring 4.91V stable)
DIM - white (mesuring 2.94V stable)
POK - three empty slots
GND - black

I can't update the firmware...I need the remote to start it...that's stupid cause I can move into the menu with the buttons in front of the screen, but not for the firmware update :/

I'm getting very unstable voltages at the Q9121 and Q9122, not sure what I'm supposed to get there.

[tom66]

Re: Philips 3PFL5606H/12 - good image for 3s / corrupted for 3s and so on

Do you know any friends with Philips remotes; or with supermarket-brand TVs? If the supermarket brand is made by Vestel, it will work with Philips TVs. They copied the remote codes for some reason. Maybe it's a somewhat industry standard set of codes.

[SuperDuty]

Re: Philips 3PFL5606H/12 - good image for 3s / corrupted for 3s and so on

No, I don't know anyone with a Philips or Vestel TV.

Do you think it could be a good idea to test the TV by replacing the +12V from the power supply with one from an ATX PSU or is it a different kind of power?

[tom66]

Re: Philips 3PFL5606H/12 - good image for 3s / corrupted for 3s and so on

Might work, as long as your PSU outputs more than 11.89V or so.

[SuperDuty]

Re: Philips 3PFL5606H/12 - good image for 3s / corrupted for 3s and so on

I've just done the test with a +12V from an ATX PSU...no improvement. Still that same problem.
So I guess the PSU board is fine after all.

Could it have something to do with a component that would have a timer in it, or some sort of regular switching ?

[SuperDuty]

Re: Philips 3PFL5606H/12 - good image for 3s / corrupted for 3s and so on

I've made some further tests and found the slight coil noise wasn't coming from the area around the CapXon cap, but on the opposite side, on the lower right of the 9th picture.
I've noticed huge losses of power on the D7106 and D7107 diodes (just above the small mosfet), going from 22.2V when the picture is good, to 14.8V when it goes bad.
And the power increases on the small inductor (L7105, the one at the very bottom of the picture) from 1.70V with the good image to a 2.60~2.80V range when it goes bad.

All of this is located around the TI TPS65168 IC : http://www.ti.com/product/tps65168#technicaldocuments

High Resolution, Fully Programmable LCD Bias IC For TV
The TPS65168 provides a simple and economic power supply solution for a wide variety of LCD bias applications. The device provides all supply rails needed by a TFT-LCD panel. VI/O, VCORE and RST for the T-Con. VDD and HVDD for the Source Driver and the Gamma Buffer. VGH and VGL for the Gate Driver or the Level Shifter. The VGH voltage can be compensated for low and high adjustable temperatures, if GIP technology is used. The transition from one programmed VGH value to another is made using an external thermistor connected to the IC. All output rails and delay times are programmable by a Two-Wire interface: a single BOM can cover several panel types and sizes whose desired output levels can be programmed in production and stored in a non-volatile memory embedded into the TPS65168.

BTW, the problem persists when the screen is on standby mode (no image is shown, backlighting is off, red led is on)