Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

[DrOetker]

I'm trying to fix my grandpa's TV - Philips 42PFL3606H/58 (TPM6.1E). It was working normally up until now, he said that while he was watching the TV at first the display went off, and after around 30 minutes, he lost the sound also. He tried to turn it on, but it wouldn't turn on anymore.

While plugged in it draws 9.7W, there is no red and green lights. While pressing the remote (power button, prog +-, etc.) or the buttons located on the device, it reacts and the red light blinks after the keypress. After pressing the power button, total power consumption falls to 0.1W, and after pressing it once again, it raises again to 9.7W.

I checked the voltages on CN903 (both before and after pressing pwr button and then after disconnecting mainboard) they are as following:

MB plugged in(9.7W) /// after pressing pwr btn(0.1W) /// MB disconnected (0.1W)
ENA -- 5.10V /// 0.05V /// 0.00V
DIM -- 2.68V /// 0.08V /// 0.00V
12V -- 0.28V /// 0.00V /// 0.00V
24V -- 0.00V /// 0.00V /// 0.00V
S/B -- 3.26V /// 0.08V /// 0.00V
5V -- 5.19V /// 4.71V /// 4.70V

PSU: 715G4802-P01-H20-003H
MB: 715G4609-M3A-000-005X

I noticed a few things... While plugging in the power cable, i can see a tiny spark on SG902 for a moment. No clicking sounds, blue LED on the back of the PSU doesn't turn on at all. Diode D910 is shorted. Voltage on C946 is 8.19V, and on C907 315V. There is no excessive heat generated anywhere on the MB, processor is mildly warm on the touch.

I'm trying to narrow down the fault.
Any help would be greatly appreciated.

[dick_barton]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

Are you certain the diode is shorted. Have you measured it out of circuit?
With the mainboard disconnected from the power supply use a 1K resistor between +5V and S/B then check the voltages again

[DrOetker]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

Are you certain the diode is shorted. Have you measured it out of circuit?
With the mainboard disconnected from the power supply use a 1K resistor between +5V and S/B then check the voltages again

I measured it in the circuit. I'll do that, thanks for the help!

[dick_barton]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

Is the top of Q902 blown off?
C922 looks odd in your photo but it could just be a distortion in the photo.

[DrOetker]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

Q902 looks fine. All caps look OK, there in no visible damage on any of the components.

Top of C922 is also looking good.

[budm]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

Check the DCV between the two legs of the main filter cap when TV is turned on to see if you do have 380 ~ 400VDC PFC Boosted Voltage or not.
If not then you need to find out if the PFC IC has the switched VCC for it to run or not.

[DrOetker]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

Okay, so I connected +5V and S/B wire (PSon) via 1k resistor, and the voltage readings on CN903 connector are:

Still no voltage on +12V and +24V rails.
S/B voltage fluctuates; +4.7V and then gradually falls to +2.1V in 3-4 seconds, then rises back to +4.7V, stays still at +4.7V for a second or two, and then cycles again.
+5V voltage fluctuates as S/B voltage, of course.

I also connected +5V and ENA (BLon) with another 1k resistor, nothing changed.

It seems to me that I wasn't able to start this PSU alone by simply connecting the standby voltage back to the S/B.

Anyway, voltage on main filter cap (C907) is 312V.
I also measured VCC on IC901 (NCP1271D65R2G), VCC on IC902 (FAN6961SZ), voltage on pin 4 IC905 (TNY277PN-TL).

VCC on pin 6 IC901 = 4.26V (MB connected), 0.38V (MB disconnected), 1.54V (5V-S/B bridge).
VCC on pin 8 IC902 = 4.22V (mb connected), 0.38V (MB disconnected), 1.53V (5V-S/B bridge).
Pin 4 IC905 = 289V (MB connected), 312V (5v-S/B bridge).

Voltages on IC904 (EL817MA):
pin 1 = 4.07V
pin 2 = 5.20V
pin 4 = 0.08-0.12V.

D910 diode is fine, I desoldered and tested it.
I also tested motherboard, both U7003 and u7005 give stable 3V3SB all the time MB is connected, so I don't think MB is an issue here.

Please do note that I attached the diagram of PSU, I apologize for not doing it immediately.

Diagram od MB: https://datasheetspdf.com/pdf-file/1...lips/TPM6.1E/1

[dick_barton]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

So is +5VSB fluctuating or holding fast when disconnected from the mainboard and no jumper resistors in place?
What voltage do you have on the 3 legs of Q907

Voltages on IC904 (EL817MA):
pin 1 = 4.07V
pin 2 = 5.20V
pin 4 = 0.08-0.12V.

Do you have pins 1 & 2 crossed. I would expect pin 1 voltage to be higher than pin 2

[DrOetker]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

So is +5VSB fluctuating or holding fast when disconnected from the mainboard and no jumper resistors in place?
What voltage do you have on the 3 legs of Q907

+5VSB is holding fast and steady at +5.1V when MB is connectet, it's also holding fast at +4.7V when the MB is disconnected and no +5V-S/B jumper in place. It is fluctuating only when I plug in +5V-S/B jumper.

Q907 (BC857C) voltages:
1 pin (base) = +7.43V when MB is disconnected, when I place the jumper it fluctuates from +1.45V to +1.7V.
2 pin (emitter) = +7.43V when MB is disconnected, after placing the jumper it fluctuates from +2.09V to +2.40V.
3 pin (collector) = +0.39V (MB disconnected), after plugging jumper it's +1.56V.

Do you have pins 1 & 2 crossed. I would expect pin 1 voltage to be higher than pin 2

You are right, I made a mistake. Voltage on pin 1 is higher, I made a mistake regarding the pin order.

[dick_barton]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

You are using a 1K resistor (or close to that value) when you jump +5VSB to S/B
So you have the +5VSB so it looks like IC905 is working so it should be providing a decent voltage to the emitter of Q907 whicj currently is not the case

I would initially check R959, D916, C946, C915, C922

[DrOetker]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

You are using a 1K resistor (or close to that value) when you jump +5VSB to S/B
So you have the +5VSB so it looks like IC905 is working so it should be providing a decent voltage to the emitter of Q907 whicj currently is not the case

I would initially check R959, D916, C946, C915, C922

I am using 1k resistor when i jump +5VSB to S/B and this is when voltage start to fluctuate. I also tried to jump +5VSB to ENA (BLon?) via another 1k resistor, but this doesn't change anything.


Thank you for your suggestion, i tested those components.

R959 resistance is 22 ohms, tested in the circuit.
D916 diode - I tested it in diode mode in the circuit, readings are 0.52V and 2.98V. Then I desoldered it, tested it in diode mode agan, and this time values are 0.52V and OL, which should be fine I guess.
C946 cap - desoldered it and tested it, capacity is 50.8 uF.
C915 - in circuit when measuring resistance the values are 60k ohm on one side and 223k ohm on another. Voltage between pins is +1.53V. When checking continuity it isn't shorted. I haven't tested it outside the circuit, that would require heating gun which I don't have, but I can borrow one if it is required.
C922 - desoldered and tested it, measured capacity is 2.3 uF.

I also desoldered MOSFET Q802 (AOTF10N60) because when in circuit in continuity mode it beeps between drain and source in both directions. But out of the circuit, the readings both in diode and continuity mode were fine.

[dick_barton]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

Do a search for Trunks81 (using the search box at the top of the page) who was recently working on two power supplies similar if not identical to yours where you may find some useful information. If memories serves me, I think the problem may have been in the brown out circuit but I would have to read through the posts to be certain.

[trunks81]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

Hello

You can see these topics

https://www.badcaps.net/forum/showthread.php?t=86564

https://www.badcaps.net/forum/showthread.php?t=85509

https://www.badcaps.net/forum/showthread.php?t=86061

Ive have still the working board for the 47 inch so i can measure allong ?

To disable the brown out you most remove R966 and Q906

[DrOetker]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

Thank you for your input trunks 81 and dick barton.

I have indeed just read your threads and imho it seems that we have similar problems with our boards, although please do note that our boards are not the same (yours is chassis TPM7.1E for Phillips 37'' and 47'', mine is TPM6.1E for 32'' and 42''). There are components that are not the same, for example IC905 is a totally different chip (TOP264VG vs TNY277PN-TL).

I was reading about IC905 (TNY277PN-TL) and looking at the diagram, I'm very curious about BP/M pin and Zener (ZD907) attached to it. ZD908 should be connected with Q907. I will test these components tomorrow.


In order to work properly, higher voltage on C946 is needed. But there aren’t a lot of components in that part of the diagram, so it’s really not clear to me why the current is so weak, could it really be brown out circuit?

While moving the motherboard, a positive leg of C946 got loose, I was curious what would happen and I've done the measurments. When MB was disconnected (without 1k resistor jump +5VSB to S/B) the +5V current was stable at +4.7V. When I inserted 1k +5VSB to S/B jump, the current was stable at +2.16-.17V with very little fluctuation (+- 0.01V). As soon as I put the leg of C946 back to place (with 1k jump), it starts to constantly fluctuate as described earlier (from +2.1V to +4.7V). When desoldered, capacitance of C946 is 50.8 uF, unfortunately I do not possess an ESR meter to test it further.

More testing will be done tomorrow.

[R_J]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

Q907 (BC857C) voltages:
1 pin (base) = +7.43V when MB is disconnected, when I place the jumper it fluctuates from +1.45V to +1.7V.
2 pin (emitter) = +7.43V when MB is disconnected, after placing the jumper it fluctuates from +2.09V to +2.40V.
3 pin (collector) = +0.39V (MB disconnected), after plugging jumper it's +1.56V.

If you are getting +7.43v on the E and next to nothing on the collector, you likely have either a shorted vcc on ic902, or ic901. D916/C946 are the vcc supply, Q907 is the vcc switch for the pfc and main ic's
If you were to isolate pin 6 on ic901 and the voltage on Q907-C comes up the ic901 is bad, Or you could isolate pin 8 on ic902 and see if the voltage comes up on Q907-C.
If ic901 is the problem, the pfc circuit should work giving +965 volts across C907
If ic902 is the problem, the main circuit should operate and give some voltage on the +24 & +12 volt lines. (likely +12v & +6v) but could be full 24&12 if not loaded

[DrOetker]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

If you are getting +7.43v on the E and next to nothing on the collector, you likely have either a shorted vcc on ic902, or ic901. D916/C946 are the vcc supply, Q907 is the vcc switch for the pfc and main ic's
If you were to isolate pin 6 on ic901 and the voltage on Q907-C comes up the ic901 is bad, Or you could isolate pin 8 on ic902 and see if the voltage comes up on Q907-C.
If ic901 is the problem, the pfc circuit should work giving +965 volts across C907
If ic902 is the problem, the main circuit should operate and give some voltage on the +24 & +12 volt lines. (likely +12v & +6v) but could be full 24&12 if not loaded

Thank you R_J for clarifying this.

I was searching for more information on some russian sites (since these Philips TVs were popular in eastern Europe) and found this video:
https://www.youtube.com/watch?v=OR-zpuNYXZ0

It was a 32pfl3606H/60 that won't turn on, with good +5VSB voltage and no current on +12V and +24V, exactly like mine. Turns out that IC801 (control chip for CCFL backlight) was defective, he said there was a short between pin 15 and 22, if I understood correctly (I don't speak Russian). After replacing IC801 the unit worked normally, it seems that functional IC801 is also vital in order to get the current on +12V and +24V rails.

That made me wonder about my CCFL control chip (IC801 - UBA2071AT) and I found out that there was very little resistance between pins 17 and 22 (only 3.6 ohms in both direction). Now I'm thinking that on my board a failed IC801 is the culprit and should be changed. I also desoldered and checked polymer capacitor C802, it's capacitance is 332 nF, this should be okay.

I zoomed in on IC801 part of the circuit and attached a picture below.

[dick_barton]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

If you lift Q802 and see if
1) the low resistance is gone between the two pins, 17 & 22
2) check the mosfet while out of circuit.

[R_J]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

Having a defective ic801 could kill the vcc coming from Q907's collector but if you want to be sure, isolate the emitter of Q806 which supplies ic801's vcc, Q806 is a 13v regulator for ic801 and is fed from Q907's collector

[trunks81]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

when measuring between 17 and 22 iam getting high ohmage of ic801

[DrOetker]

Re: Philips 42PFL3606H/58 Not powering on, no power indicator - PSU problem?

If you lift Q802 and see if
1) the low resistance is gone between the two pins, 17 & 22
2) check the mosfet while out of circuit.

When I remove MOSFET Q802, low resistance across pins 17 and 22 remains the same (3.6 ohms), nothing changes. Q802 was indeed my first suspect so I tested it before, it is fine and working properly. I tested it again, just to make sure, and it is working properly both in off and on state.

I realised that I did not test switch Q907 while the PSU is connected to the motherboard so I tested that now. I also tested IC901 and IC902 (while doing all the testing I used C907 leg as an negative; motherboard was plugged in and it was in working mode).

Q907
PIN 1 (Base) = +7.52V
PIN 2 (Emmiter) = +8.18V
PIN 3 (Collector) = +4.68V


IC901
PIN 1 +0.18V
PIN 2 +2.69V
PIN 3 0.00V
PIN 4 0.00V
PIN 5 0.00V
PIN 6 +4.22
PIN 7 N/A
PIN 8 fluctuates, most of the time it's slowly climbing from +3.5V to +4.1V, it can raise up to +5.05V (rarely), but also I've seen it drop to 0.5V for a second.


Pin function according to the datasheet: https://www.onsemi.com/pub/Collateral/NCP1271-D.PDF

Pin No. Symbol Function Description

1 Skip/latch Skip Adjust or Latchoff
A resistor to ground provides the adjustable standby skip level. Additionally, if this pin is
pulled higher than 8.0 V (typical), the controller latches off the drive.

2 FB Feedback An optocoupler collector pulls this pin low during regulation. If this voltage is less than
the Skip pin voltage, then the driver is pulled low and Soft−Skip mode is activated. If this
pin is open (>3 V) for more than 130 ms, then the controller is placed in a fault mode.

3 CS Current Sense This pin senses the primary current for PWM regulation. The maximum primary current
is limited to 1.0 V / RCS where RCS is the current sense resistor. Additionally, a ramp
resistor Rramp between the current sense node and this pin sets the compensation ramp
for improved stability.

4 Gnd IC Ground −

5 Drv Driver Output The NCP1271's powerful output is capable of driving the gates of large Qg MOSFETs.

6 VCC Supply Voltage This is the positive supply of the device. The operating range is between 10 V (min) and
20 V (max) with a UVLO start threshold 12.6 V (typ).

8 HV High Voltage This pin provides (1) Lossless startup sequence (2) Double hiccup fault mode (3)
Memory for latch−off shutdown and (4) Device protection if VCC is shorted to GND.


IC902
PIN 1 +0.92V
PIN 2 0.00V
PIN 3 +0.01V
PIN 4 0.00V
PIN 5 0.00V
PIN 6 0.00V
PIN 7 0.00V
PIN 8 +4.23V (stable)