Philips 42PFL6198k/2 sound ok, no picture

[domix]

I have this TV Philips 42PFL6198k/2.

Suddenly it has no picture only backlight is on, it has sound and remote is working, so if i turn on only backlight turn on and has sound from TV program. If i turn off it turn off.

Is it main board faulty or some chip board?

Thanks.

[domix]

Re: Philips 42PFL6198k/2 sound ok, no picture

Anyone?
Thank you

[William1967]

Re: Philips 42PFL6198k/2 sound ok, no picture

Check the fuse on the t-con, there must be 12V available on both sides. You can also check if the display has a problem by disconnecting the FCC cables between the t-con and the display , if the picture is ok on the left or right side the display is faulty.
Also the mainboard can be faulty which is very common with this model.

[Andrew F. Ali]

Re: Philips 42PFL6198k/2 sound ok, no picture

Look for a shorted SMD capacitor on the long panel board where the T-CON Bd. goes. Try disconnecting 0ne side at a time to determine which side the fault lies. With the Power OFF test each SMD cap by setting your DMM on the continuity mode.

[domix]

Re: Philips 42PFL6198k/2 sound ok, no picture

I have only 7~7,5V on both side of F1 fuse on t-con. If i disconnect left or right flat on t-con which goes on long board at the bottom, nothing happend, only backlight on whole screen is on.

[William1967]

Re: Philips 42PFL6198k/2 sound ok, no picture

Mainboard is the culprit, the QFU1.2 is known for mainboard problems. Repairing is not easy.

[domix]

Re: Philips 42PFL6198k/2 sound ok, no picture

If i get used MB 3104 303 54946 (3104 313 66186) from 47PFL6198K/12 it will work?

[Maalobs]

Re: Philips 42PFL6198k/2 sound ok, no picture

Look for a shorted SMD capacitor on the long panel board where the T-CON Bd. goes. Try disconnecting 0ne side at a time to determine which side the fault lies. With the Power OFF test each SMD cap by setting your DMM on the continuity mode.

Do you mean the board that this guy reaches into at the 15:50 mark in this video:
https://www.youtube.com/watch?v=srccct1mDIU&t=15m50s

He is incidentally repairing a Samsung with the same symptoms; backlight and sound works, but no picture.
Maybe Domix should investigate that first before committing to buying replacement PCBs.
The guy in the video doesn't talk anything but he is systematic and shows pretty clearly how he identifies all the problems, and he helpfully adds text-messages into the video about specific details.

There is a big overheat problem with the main processor in this series of systemboards, as has been noted in other threads.
But in this case, maybe the systemboard isn't the issue, because I would expect the TV to fall into protection mode at power-on self-test, and you are not getting any blinking error codes on the power-LED and the TV obviously boots properly since you get sound.

If you are academically curious Domix, you can use a 3.3V USB-to-TTL adapter and listen to the output from both the 8051 standby microcontroller, and from the main processor.
This board has the serial ports available, it's all well documented in the service manual for this chassis.

You can find the pins on the debug-port 1CV5, which in the case in this picture is unpopulated so it's actually easier to solder bodge wires to the pads:


Pin 2 TXD-STANDBY outputs at 57600 BPS.
Pin 8 TXD-SERVICE outputs at 115200 BPS.

Connect your TTL-adapter to the pins before plugging in power to the TV, and enable the "log to file" function in your terminal program (you can use Putty if you don't have anything better), because there is a huge amount of data coming out of the main processor.
Scan for error messages and warnings in the output.
This output will show any issues that the standby POST and the Linux system can identify, at the very least you can warn the owner about them.
The number of lines with mention of "fixable bit-flip" is the number of bit errors in the NAND-chip.

[domix]

Re: Philips 42PFL6198k/2 sound ok, no picture

I dont have TTL adapter :/

I do measurments again, i have 12V on that F1 fuse on t-con. Bedore i forget to te gnd. Now i have 12V with ref to GND when TV is turned on

I unplug the 2 ribbons that lead to the panel one by one and picture doesnt appears on a half screen with the TV on.

Here is a oic of left panel board

[yokoono]

Re: Philips 42PFL6198k/2 sound ok, no picture

Disconnect the ribbons that lead to the screen. Turn on the TV. Look on the T-con VGH (VONE) and VGL (VOFFE) and measure.

[domix]

Re: Philips 42PFL6198k/2 sound ok, no picture

I measured at disconnected ribbon when tv is on and i get, here on picture are marked red where i measure
VGH : 18,4
VGL : -4,99

[yokoono]

Re: Philips 42PFL6198k/2 sound ok, no picture

You can say that the T-con is good. Connect the two ribbons one by one and see if the voltages (one or both) disappear. There are other points of measurement. Measure if they are all and disappear when you connect the ribbons.

[domix]

Re: Philips 42PFL6198k/2 sound ok, no picture

When both ribbons are disconnected values are
VGL: -4,95
VGH: 18,4

1 ribonn cable connected
VGL: -4,98
VGH: 19,6

2 ribbons connected
VGL: -4,98
VGH: 19,6

[domix]

Re: Philips 42PFL6198k/2 sound ok, no picture

Any sugestions?

[champikilo]

Re: Philips 42PFL6198k/2 sound ok, no picture

salut à tous. s'il vous plait j'ai besoin du fichier nand de cette philips. 3104 313 66186 b / 310430354946b MERCI.