Philips PUS6501 - no picture

[betmen]

Re: Philips PUS6501 - no picture

I removed 4 electrolitic capacitors C8120-C8123, all four are good.
I measured two smd capacitors in circuit and they are not in short circuit and R8148 is OK.
Earlier I seen that optocoupler U9306 in stanby circuit have 0V on pins 3-4 on transistor, I wonder is that relevant?

Also there is no intermittent LED light any more, LEDS are not working at all, but when I test it with backlight tester on connector they are working.

Any new ideas?

[nomoresonys]

Re: Philips PUS6501 - no picture

Kind of suspect a capacitor, if it isn't a backlight connection or led.

[nomoresonys]

Re: Philips PUS6501 - no picture

Since things seem to be intermittent. I would heat sections of power board and note any difference. Also check solder joints with a magnifying glass.

+1, heat up the caps with a hairdryer, see if it turns on.

[dskall]

Re: Philips PUS6501 - no picture

Since things seem to be intermittent. I would heat sections of power board and note any difference. Also check solder joints with a magnifying glass.

[betmen]

Re: Philips PUS6501 - no picture

That is first what I have done, few leds did`t work and i changed them, now all leds are working, tested with backlight tester.
On the led connector CN8101, pin +VLED there is no voltage.

[nomoresonys]

Re: Philips PUS6501 - no picture

If you don't have a backlight tester it might be time to tear it down and see whats going on with the leds.

[betmen]

Re: Philips PUS6501 - no picture

I would love to fix this tv so if anyone wants to help let me know.
I did the following, in LED circuit I took out C8116 and C8117 and check them ,both are ok, I measured most of the resistors, all are ok, secundary side of T8101 in LED circuit has no voltage on diodes or capacitors, I made measurements on U8101 according to datasheet, Vcc - 12,07V, FB pin voltage 2,95V, CSS pin 0,71V, VB-VS - 2,5V...it seems fine to me.
There is stanby voltage of 3,5V and when TV is turned on there is 12V on 12V pins, DIM pin have 1,52V, BLon -2,92V, PSON - 3,25V, 3D_ON - 0V.
C9802 and C9803 have 386V, so I think AC input, PFC and stanby circuit are fine, there is some fault in LED circuit.
Correct scheme is in post 17.
Anyone have some idea what to do?

[betmen]

Re: Philips PUS6501 - no picture

So just to be clear, you changed both Q8101 and Q8102, correct? Usually when there are internment backlights it is one of the led's or one of the connections in the panel that is at fault.
IC8101 monitors the led voltage as well as the led current, if the current through the string changes and the led voltage lumps up for a split second, this will trigger the ic to shut down the led voltage.
Sometimes C8109 gave problems on some power supplies, but the cap usually just went open.

Yes I changed Q8101 and Q8102.... but I made one error at the beginning, I put the wrong scheme of the PSU.
I put the scheme for bigger screen PSU
I print for me correct scheme and put on my post wrong one.
In this posts attachment is correct one...sorry for that.

[R_J]

Re: Philips PUS6501 - no picture

So just to be clear, you changed both Q8101 and Q8102, correct? Usually when there are internment backlights it is one of the led's or one of the connections in the panel that is at fault.
IC8101 monitors the led voltage as well as the led current, if the current through the string changes and the led voltage lumps up for a split second, this will trigger the ic to shut down the led voltage.
Sometimes C8109 gave problems on some power supplies, but the cap usually just went open.

[betmen]

Re: Philips PUS6501 - no picture

That voltage was D-G and D-S, not D to earth.
Backlight, when working, have voltage about 35V, when TV is on but backlight and TV not working voltage is low, about 6-7V, sometimes up to 12V it is not stable.
Q8102 was changed in the beginning with the R8101....

[R_J]

Re: Philips PUS6501 - no picture

Measurement from today:
- R8113- 10ohm 1,7V, after some time voltage droping
- R8112 47ohm, 2,6V after some time voltage droping
- D8101 - diode mode 0,029V, probably because of paralel resistor
- Q8101 - D-G 382,7V; D-S - 380,2V; G-S - 0V
- Q8102 - D-G 0,85V; D-S - 0,38,2V; G-S - 0,5V
Voltages are not staedy, after some time drops a litle and wher TV does`t turn on it`s turn of after some time, few minutes and STBY LED lights red.
After some measurement I measured voltage to LED backlight, it is about 35V, I connect connector and backlight lite up and TV powers up. When TV is working voltages on Q8101 and Q8102 are obout 2V , before was abour 382 on Q8101 and under 1V on Q8102.
Leds for backlight are OK I check them with backlight tester and they all worked fine without flickering.
I will change Q8101 when I will have time to do it (first I will test it when I desoldet it), Q8102 is new.
Any advice?

This is impossible, the backlights can not operate if the voltage on Q8101 Drain is 2v. R8101 (0.1Ω) supplies 385vdc to Q8101 Drain

I changed Q8101 today, old one was ok but I chaged it anyway

Like I said If Q8101 was shorted, Q8102 may have been damaged so try changing it.

[lotas]

Re: Philips PUS6501 - no picture

If Q8102 struck, then the U8101 SSC9522S PWM controller and its strapping could have suffered

[betmen]

Re: Philips PUS6501 - no picture

I changed Q8101 today, old one was ok but I chaged it anyway.
All is the same, TV can not be turned on.

Anybody have idea what to do next?

[betmen]

Re: Philips PUS6501 - no picture

Measurement from today:
- R8113- 10ohm 1,7V, after some time voltage droping
- R8112 47ohm, 2,6V after some time voltage droping
- D8101 - diode mode 0,029V, probably because of paralel resistor
- Q8101 - D-G 382,7V; D-S - 380,2V; G-S - 0V
- Q8102 - D-G 0,85V; D-S - 0,38,2V; G-S - 0,5V
Voltages are not staedy, after some time drops a litle and wher TV does`t turn on it`s turn of after some time, few minutes and STBY LED lights red.
After some measurement I measured voltage to LED backlight, it is about 35V, I connect connector and backlight lite up and TV powers up. When TV is working voltages on Q8101 and Q8102 are obout 2V, before was abour 382 on Q8101 and under 1V on Q8102.
Leds for backlight are OK I check them with backlight tester and they all worked fine without flickering.
I will change Q8101 when I will have time to do it (first I will test it when I desoldet it), Q8102 is new.
Any advice?

[CapLeaker]

Re: Philips PUS6501 - no picture

Weird. Check the back light connector and the wiring? Maybe there is cracked solder / broken wire. LED flickering on and off could be also a flakey LED.

[R_J]

Re: Philips PUS6501 - no picture

I had made a mistake in post #4, Q8101 was NOT the pfc mosfet, but is one of the backlight driver mosfets.
If Q8101 was shorted, check the gate driver circuit, D8101, R8112 (47Ω) and R8113 (10Ω), Q8102 may have been damaged as well. Note: D8101 is in parallel with R8112.

I suspect C9131 is C9313, C9809 & C9313 are on the VCC supply for U9801 (pfc ic) This 0.5v would be normal since the main board was disconnected (no PS_ON) If you want to work on the power supply with the main board disconnected you need to connect about a 1K resistor between +3.5v/5v and PS_ON. This will turn on the power supply without the main board connected.
Voltages on post #7 suggest the pfc circuit is working ok.

[betmen]

Re: Philips PUS6501 - no picture

Rest of the mausurement are:
C9809-0,52V
C9304-14V
C9305-13,45V
C9131-0,52V

I performed the measurements so that the connector from the motherboard and the LED backlight is disconnected, because the measurement lead can only be reached from the back of the PSU.

Does anyone have any idea?

[betmen]

Re: Philips PUS6501 - no picture

Today TV turn on when I measured voltage od backlihgt LED connector, first flickering then stable LED light and everything working again.
Measurements are:
1.C9802-STBY-387V, STBY-after few minutes-322V, ON-screed not working-387V, ON-screed working-387V
2.bridge rectifier BD9901-STBY-235V, STBY-after few minutes-322V, ON-screed not working-225V, ON-screed working-216V
3.LED connector CN8101-pins +VLED and -VLED 36V, +VLED and chassis, not working - 12,5V, then start flickering, after that 40-43V
Rest of capacitor I did`t measured because I must have access from behind, I did`t have tools to disassemble it near at hand, will tray it tomorrow I hope.

Help.....

[betmen]

Re: Philips PUS6501 - no picture

Did you measure each led string vled+ to the corresponding vled- for each string?

I measured on the connector +VLED on the left and rigth side according to the grond(chasis).
The rest of measurements I will do after the work today.
I try to turn it on today but it did˙t, after some time like it˙s turn of by itself, ambilight turn off and red led for standby turn on.

[CapLeaker]

Re: Philips PUS6501 - no picture

Did you measure each led string vled+ to the corresponding vled- for each string?