Philips 47PFL4606 No Power Fuse Keeps Blowing

[budm]

Re: Philips 47PFL4606 No Power Fuse Keeps Blowing

I just read the thread below about the board used in the 37" which is what you say it is the good board?
https://www.badcaps.net/forum/showth...695#post977695

[budm]

Re: Philips 47PFL4606 No Power Fuse Keeps Blowing

1. i did place an part from an other donor board.
2. i did not put back R947 and R966,Q906
3. Yes iam going to leave it out.
4. Q907 = 9,8 to 10.5V on all the legs to hot ground

1) We still want to leave R966, Q906 for the Brownout protection circuit out for now. R947 is not part of the brownout circuit, I had you removed to isolate the standby power supply from the PFC and the 12V/24V circuit.

2) R947 (4.7 Ohms) is for supplying Voltage to the PFC IC and the 12V/24V SMPS IC, so without having it in place you will have switched 15V Vcc to run those two IC's. You will leave it out for now until we finish checking the parts in the PFC section.

3) Q907 is used as a switch to provide the switched 15V to run the PFC and 12V/24V SMPS IC'c. It is turned on when 1K pull up resistor is connected. Did you replace Q907 since the old one was shorted?

4) You need to check R929 (47K) which is connected between Gate and Source pin of PFC MOSFET Q902, we want to make sure it is not damaged.

5) Did you verify if R916 is 4R7 or not on the good board? That is important, you must verify that.

[trunks81]

Re: Philips 47PFL4606 No Power Fuse Keeps Blowing

1. i did place an part from an other donor board.
2. i did not put back R947 and R966,Q906
3. Yes iam going to leave it out.
4. Q907 = 9,8 to 10.5V on all the legs to hot ground

[budm]

Re: Philips 47PFL4606 No Power Fuse Keeps Blowing

I wish you did not put in all those parts in yet since I am not done verifying more parts.

1) Remember that Q907 is shorted out. Your post #64 "On Q907 between C/B i am getting 1ohm in both ways". Did you put in the new one in?

2) Did you put R947 (4.7 Ohms) back in place. My post #59 "2) Remove R947 (4.7R)"

3) At this point if you did not put R947 back in place, you need to leave it out.

4) Put in new Q907, then check the Voltage on all 3 pins with 1K and with 1K, the Voltage needs to be about 15V when 1K is connected (that is what you get on the good board and the other board that we repaired).

[trunks81]

Re: Philips 47PFL4606 No Power Fuse Keeps Blowing

Ive got on the next voltages on C922,C915 and C920 = 0.83V
Also seeing this back on both VCC pins of IC901/902 = 0.83V

PFC D901 = Measure on both boards the same ! no low ohm
Q907 = 9,8 to 10.5V on all the legs to hot ground

On the + of D915 to hot ground = 411V
On the + of C946 to hot ground = 10.52V

ZD908 = 7.67V
R959 = 4,7ohm (4R7 on schematic
D916 is working measure 0.5V and reverse OL
12V1 to ground is 340 ohm
12V2 to ground is 1K ohm
24V to ground is 2.47K ohm

C946 When 1K resistor in place iam getting 10.52V and removed 7.8V

[trunks81]

Re: Philips 47PFL4606 No Power Fuse Keeps Blowing

Replaced the next parts.

IC902 = FAN6961
IC901 = NCP1271D65R2G
R917 = 47ohm
R916 = 4,7ohm
D910 = 1N4148
C920 = 1U 25V
C915 = 1U 25V

After replacing these parts got no 24/12V

[trunks81]

Re: Philips 47PFL4606 No Power Fuse Keeps Blowing

Strange tested R916 on the good board and soldered that one out of circuit and it tested OL

[budm]

Re: Philips 47PFL4606 No Power Fuse Keeps Blowing

Hello

R917 soldered out of circuit and that resistor is 47ohms
D910 soldered out of circuit and tested very low in both ways
R916 soldered out of circuit and tested OL

So you have more damaged parts.

"R916 = OL and on the good board 133kohm tested in circuit"
What does R916 of the good board show? It cannot be 133K as you reported, it is supposed to be 4R7 Ohms.

[trunks81]

Re: Philips 47PFL4606 No Power Fuse Keeps Blowing

Hello

R917 soldered out of circuit and that resistor is 47ohms
D910 soldered out of circuit and tested very low in both ways
R916 soldered out of circuit and tested OL

[budm]

Re: Philips 47PFL4606 No Power Fuse Keeps Blowing

Hello

Orginal PFC is indeed FAN6961 !
Q902 = checked out good.. all high ohmages
R919 = is 0.33ohm
R917 = 9,90ohm on the good board 47.07ohm tested in circuit
R916 = OL and on the good board 133kohm tested in circuit

1) R917 is 47 Ohms as shown in the schematic, it is connected in parallel with the diode, so your reading shows 990 Ohms, that means it is bad and possible the Diode D910 may be damaged too, check that.

2) R916 is 4R7 (4.7 Ohms) as shown in the schematic, you need to recheck it again and both boards.

BTW, you must look at the schematic to see what the values are shown in the schematic then look at the value as printed on the body of the resistors so we do not have to go back and forth re-verify your readings.

[trunks81]

Re: Philips 47PFL4606 No Power Fuse Keeps Blowing

Hello

Orginal PFC is indeed FAN6961 !
Q902 = checked out good.. all high ohmages
R919 = is 0.33ohm
R917 = 9,90ohm on the good board 47.07ohm tested in circuit
R916 = OL and on the good board 133kohm tested in circuit

[budm]

Re: Philips 47PFL4606 No Power Fuse Keeps Blowing

removed ic902, and now the resistance on C922 is 104kohm.. the same as on the working board

So the PFC IC902 is bad then.
Be sure to recheck PFC MOSFET Q902, R919, R917, R916.
Something caused the IC that you said you replace to go bad.
The original PFC IC is FAN6961 as shown in the schematic, correct?

[trunks81]

Re: Philips 47PFL4606 No Power Fuse Keeps Blowing

removed ic902, and now the resistance on C922 is 104kohm.. the same as on the working board

[budm]

Re: Philips 47PFL4606 No Power Fuse Keeps Blowing

Sorry.. C915 and C920 on the defective board measure around 260ohm,
Also i removed them and they measure OL

OK, that means the caps on the bad board is good, so it can be bad PFC IC902 or the SMPS IC901 for the 12v/24V, remove one of them and see if the resistance will go up.

[trunks81]

Re: Philips 47PFL4606 No Power Fuse Keeps Blowing

Sorry.. C915 and C920 on the defective board measure around 260ohm,
Also i removed them and they measure OL

[budm]

Re: Philips 47PFL4606 No Power Fuse Keeps Blowing

the resistance on the working board on C922 is 105Kohm
Both caps C915 and C920 measure around the 260ohm

That cannot be right. You are measuring the caps on the working board, correct?
C915, C920, C922 are connected in parallel so the reading should be all the same.

[trunks81]

Re: Philips 47PFL4606 No Power Fuse Keeps Blowing

the resistance on the working board on C922 is 105Kohm
Both caps C915 and C920 measure around the 260ohm on the defective board
I removed C915/C920 and IC902 and now the short is gone

[budm]

Re: Philips 47PFL4606 No Power Fuse Keeps Blowing

Hello

On Q907 between C/B iam getting 1ohm in both ways..
On caps C922 iam getting 266ohm

So Q907 is damaged when you had that blown up episode, the circuit is loading down the AUX Voltage (C946) so the TOP SMPS was in shutdown/restart mode, that is why you were only seeing about 2V on the 5V STBY output.
Now we have to find out which circuit is causing 266 Ohms reading on C922, it can be the PFC IC902 of the 12v/24V SMPS IC901, MLCC C920, MLCC C915.
I would try removing one MLCC cap at a time first, if the resistance still reading low on C922, if it still stay low then I would remove IC902, then IC901.
BTW, check the resistance of C922 on the working board to see what you get.

[trunks81]

Re: Philips 47PFL4606 No Power Fuse Keeps Blowing

Hello

On Q907 between C/B iam getting 1ohm in both ways..
On caps C922 iam getting 266ohm

[budm]

Re: Philips 47PFL4606 No Power Fuse Keeps Blowing

Indeed when 1K in place iam getting the 5V

Great!
1) So leave those parts I had you removed out for now then check Q907 in diode mode and in resistance mode on all 3 legs combination.
2) Check the resistance between two leg of cap C922.