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Old 07-11-2021, 08:31 AM   #1
betmen
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Default Philips PUS6501 - no picture

Hello,
I have a Philips PUS6501 TV that I got as defective. The TV has no picture. I first tested the power supply and made a short circuit during the measurement on Q8101 between D and S. Therefore, the Q8102 and resistor R8101 burned out, which I changed. After that I went to test the LED backlight and one LED was burned out on each strip. Now I doubt that the LED backlight was a major malfunction and that the power supply was good.
After repairing the LED backlight, the TV did not work again. I managed to turn it on when I was measuring the voltages on the power supply with an instrument, but it turned on so that initially the LED backlight flashed for a few seconds and the TV turned on. Then everything worked, the TV could be turned on and off, everything worked. After that I unplugged it overnight and it didnít work again, it couldnít turn on.
Ambilight lights up but there is no picture.
On schematic I circled with red on page 4 which part I changed and the one I shorted.
Does anyone know what else needs to be checked or what is wrong?
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File Type: pdf PUS6501-power supply.pdf (164.2 KB, 19 views)
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Old 07-11-2021, 04:24 PM   #2
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Default Re: Philips PUS6501 - no picture

No blinking of the backlight, nothing? Turn the Tv on and measure each LED string with the LEDs connected and without. Make sure that all the turn on voltages are provided from the main board to the PSU, like PSon, BLon, Dimm…
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Old 07-12-2021, 04:34 PM   #3
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Default Re: Philips PUS6501 - no picture

I measured the voltages and when the TV is connected to the power supply, the voltages are: STBY-3.74V, 3D_ON-1.24V.
After I turn on the TV with remote voltages are: STBY-3.7V, DIM-2.55V, BL_O / F-3.08V, PS_ON-3.4V, 3D_ON-0.01V, + 12V and + 12VA- 12.2V .
The LED voltage connector is 0V and there is no picture.
When I touched the leads G and D of the Q8101 transistor with the electrodes of the voltmeter, the LED backlight came on briefly, then I touched the G and D leads a few more times and the LED backlight started flashing for about half a minute and the TV turned on and everything worked.
After that I turn off the TV for half an hour and it will not turn on again.
It remained so "on" but without a picture and after 6-7 minutes the LED backlight started flashing for about half a minute and the TV turned on and everything works again:
I turn it off again and turn it on right away and then the TV turns on and works.
I turn it off again for a few minutes and it won't turn on right away but after a few minutes the LED backlight starts flashing and the TV turns on.
As if some part needs to be heated for the TV to work, and when it cools down, the TV doesn't work or that part works a little, it doesn't work a little.
When the TV was working, the voltages on the LED connector were 45V, then 44.6V, then 40.6V on the end connectors left and right in relation to ground.
I suspect transistor Q8101 is not working properly, but I have to unsolder it and test it.
Does anyone have any idea what it might be?
Attached Images
File Type: jpg all-led working.jpg (599.4 KB, 6 views)
File Type: jpg voltages.jpg (589.2 KB, 7 views)
File Type: jpg led connector and board number.jpg (547.3 KB, 9 views)
File Type: jpg PSU.jpg (655.6 KB, 10 views)
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Old 07-12-2021, 04:49 PM   #4
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Default Re: Philips PUS6501 - no picture

Check the voltage ACROSS the main filter C9802. What is this voltage in standby and when the tv is turned ON.
Q8101 is for the PFC circuit. You can also check the VCC voltage across C9809 and post the voltage. Also check the voltage across C9304. It could be that C9304, C9305 or CC9313 are weak.
If the main B+ voltage is not boosted by the pfc voltage, the led voltage will also be low and likely not light the led's.
I assume 230vac line, so B+ will be 325VDC in standby but should rise to around 395vdc when the tv is on and the pfc circuit is working.
Note: the led ic U8101 (Vsen) senses the main B+ and likely will not turn on until the B+ voltage is at 395vdc.

Last edited by R_J; 07-12-2021 at 05:03 PM..
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Old 07-12-2021, 04:50 PM   #5
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Default Re: Philips PUS6501 - no picture

Did you measure each led string vled+ to the corresponding vled- for each string?
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Old 07-13-2021, 01:56 AM   #6
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Default Re: Philips PUS6501 - no picture

Quote:
Originally Posted by CapLeaker View Post
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.
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Old 07-13-2021, 02:24 PM   #7
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Default 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.....
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Old 07-14-2021, 12:02 PM   #8
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Default 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?
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Old 07-14-2021, 07:27 PM   #9
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Default 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.

Last edited by R_J; 07-14-2021 at 07:57 PM..
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Old 07-15-2021, 04:58 AM   #10
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Default 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.
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Old 07-17-2021, 01:20 PM   #11
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Default 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?
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Old 07-18-2021, 12:22 PM   #12
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Default 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?
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Old 07-18-2021, 01:41 PM   #13
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Default Re: Philips PUS6501 - no picture

If Q8102 struck, then the U8101 SSC9522S PWM controller and its strapping could have suffered
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Old 07-18-2021, 04:33 PM   #14
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Default Re: Philips PUS6501 - no picture

Quote:
Originally Posted by betmen View Post
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
Quote:
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.

Last edited by R_J; 07-18-2021 at 04:37 PM..
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Old 07-19-2021, 12:59 PM   #15
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Default 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....
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Old 07-19-2021, 06:05 PM   #16
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Default 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.

Last edited by R_J; 07-19-2021 at 06:17 PM..
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Old 07-20-2021, 12:46 PM   #17
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Default Re: Philips PUS6501 - no picture

Quote:
Originally Posted by R_J View Post
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.
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File Type: pdf power supply 43PUS6501.pdf (347.3 KB, 3 views)
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