Philips 40PFL4707 SMPS fuse blown.

[genuineguy]

Hello Experts
Need your help with SMPS repair for my LCD. The details as below.

1. Philips 40PFL4707/F7 Manufactured March 2012
2. SMPS Board BA21P6F01 01 1
3. SMPS board has a sticker that says A21P6MPW C 7219720
4. This is a 110v Mains Supply TV sold in USA
5. I imported this from USA into my country where we have 230V.
6. I have a simple winding transformer that converts 230v to 110v

For last few months, the TV was not in use and last week when I wanted to use it,I found it not powering up.

Primary suspect
1. Something went wrong inside the TV OR
2. Someone messed up the Main supply point and by mistake connected it to the 230V supply directly

I opened up the TV and found the fuse was blown. DMM test of Q601 ( K10A50D Toshiba MosFet) revealed that its Drain Source is shorted.

I did following tests
1. Desoldered one leg of all the HOT side diodes and all are Ok.
2. Did DMM continuity test of all the primary suspects on the HOT side and all are ok
3. No component is burnt
4. I had a spare IRF840 Mosfet. Its rated 500V and 8.5A. I replaced it for Q601 and the fuse got blown again. The MosFet was shorted again.

I looked at the shopjimmy.com repair kit for this TV model. All those components that he sells are perfect tested on my board.

Need help in various areas like

1. Any one has the schematic and service manual accessible for this model ?
2. Should I just insert a K10A50D and try once ? I feel it will blow up. I used IRF840 as its cheaper and easily available locally.
3. Do not solder Q601 and insert fuse and see if it blows up again ? That will show something else is wrong in Hot side.
4. Should I suspect the Gate circuitry ?

I am still not sure the root case of this issue. If its indeed supply of 230V then some component is blown up that appears hard to find.

I am attaching some images

[genuineguy]

Re: Philips 40PFL4707 SMPS fuse blown.

Hello Experts
Any tips please ?

[ReeceyBurger123]

Re: Philips 40PFL4707 SMPS fuse blown.

If the Fet fails it will probably kill the gate circuit. Take pictures of the underside of the board buddy.

[genuineguy]

Re: Philips 40PFL4707 SMPS fuse blown.

Hello ReeceyBurger123
Thanks for your response buddy.
I am attaching the pic

[ReeceyBurger123]

Re: Philips 40PFL4707 SMPS fuse blown.

Ok checked the resistors and Ic showing in my pic for S/C. If there aren't any other shorts on the board after that probably safe to put a new fet in and fuse and test.

[genuineguy]

Re: Philips 40PFL4707 SMPS fuse blown.

Is there a particular resistor you want me to check for shorts ? Or you want me to check for all the resistors short in this circuit in your picture ?

Can you please elaborate how to check short circuit in the IC ? Any particular pin pair I need to check ?

Right now, I have desoldered one leg of all the diodes on the entire board and none of them are short and they pass the DMM diode test nicely.

I was thinking to do this for all the resistors and then repeat the one leg desolder test for all capacitors.

However I will follow your expert instructions if there is a definite way to zero in on the problem.

Do you know the IC no ? Do you the schematic or service manual ? I am not able to read the IC no even with a magnifying glass.

[fzabkar]

Re: Philips 40PFL4707 SMPS fuse blown.

Here is a better photo of the top side:
http://assets.shopjimmy.com/media/ca...pw-001-top.jpg

Can you tell us the markings on the PWM IC and Q651?

[genuineguy]

Re: Philips 40PFL4707 SMPS fuse blown.

The above link gives me below errorAccess Denied

You don't have permission to access "http://assets.shopjimmy.com/media/catalog/product/cache/1/image/f8f28dc4a19c21aeb55ee5774693fb5d/s/h/shopjimmy-a21p6mpw-001-top.jpg" on this server.
Reference #18.6b3ff63d.1442986354.41689fd

[budm]

Re: Philips 40PFL4707 SMPS fuse blown.

Pictures provided by SHOPJIMMY.
Look at the repair kit and then inspect those parts on the list.

[genuineguy]

Re: Philips 40PFL4707 SMPS fuse blown.

Hello Budm
Thanks for your advise. Really appreciate your time. Its exciting to get attention of an expert like you.

As I have posted in my first description, I have already completed the step you have suggested. I looked at the part numbers on the shop jimmy repair kit and all are fine except the MosFET.

I will go n check again just to be sure I do it twice.

Any other tips ?

Any links or source to get the schematic or service manual for this TV ?

[CapLeaker]

Re: Philips 40PFL4707 SMPS fuse blown.

Look at the gate drive circuit of the Mosfet. Check for blown diodes, resistor that changed value (more resistance that it sez, or totally open).

[genuineguy]

Re: Philips 40PFL4707 SMPS fuse blown.

Did some troubleshooting. Here are the updates

1. All diodes are good on the board. DMM test passed after desoldering one leg
2. All small and big resistors are good. DMM test passed after desoldering one leg. I am yet to test the SMD resistors and there are very few very very small ones.
3. Tested DMM test of capacitors and they appear good. I dont have ESR meter.

Please find attached image of the SOP-8 chip. I need some help. Is it a buck converter IC ? Is really a G5640 2.5A buck converter ? How do I test if its good or bad

[CapLeaker]

Re: Philips 40PFL4707 SMPS fuse blown.

Make yourself a new jig. Google something like Light Bulb Trick for power supplies. I think budm also has it on his site somewhere.

I wouldn't bother testing the small resistors...
Just make sure all the Mosfets and diodes, caps are good and the gate drive circuit on the Mosfet. Then try the PSU on the Light Bulb protection trick and see what the PSU does. The light bulb protects the PSU from blowing out again.

[genuineguy]

Re: Philips 40PFL4707 SMPS fuse blown.

I suspect the FA5640 SMD PWM chip. All other components are tested and they are working properly.

I am not able to buy this chip locally. I am thinking to replace it with TL494 which is readily available in my local stores.

I know replacing a IC with a totally different IC is crazy idea ( as I will have to create an additional circuit for it) but I am not a professional repair person who has to finish the task in limited time. I am a hobbyist.

[Andrew F. Ali]

Re: Philips 40PFL4707 SMPS fuse blown.

Compare the spec sheet data for both chips and see if they can be interchanged. Did you try the 'light bulb' trick.....OOPS...I see this is since 2015 almost 2yrs have gone.

[genuineguy]

Re: Philips 40PFL4707 SMPS fuse blown.

Yes, 2 years have gone . I left it aside and forgot about it. Now got some time and remembered this incomplete project. ( The TV lies in the storage still open).

Will the light bulb trick too.

Today, I removed the main transistor and found that the expected voltages across the SMPS chip is not showing up. Luckily found the service manual for this TV and have uploaded it

[genuineguy]

Re: Philips 40PFL4707 SMPS fuse blown.

Hello Dear Experts

Have spent quite some time and has made *some progress in my debugging. Here are the results.
Please refer to the circuit on page 42 on the attached service manual. This manual is a great help and am able to make progress due to it.

1. Desoldered the Transformer. Connected two 24v Truck brake bulbs across the secondary. (Bulb1 pin15 and pin 13, Bulb2 pin 10 and 12). Connected one more bulb across primary winding pin 6 and ping 7. This is the auxiliary winding that is used for ZCD and also creating power supply for the chip FA5640. Connected pin 2,4 back to the board by wires.

2. Fuse does not blow during power on. The bulbs light alternately almost every two seconds. This continued properly. I did not run it too long as after a min or so, the Q601 is warm to hot ( can touch by finger).

3. I tend to conclude that FA5640 is still functioning. Since there is no feedback from the opto isolator and also pin 6 gets no power supply, I think it goes into some kind of a standby mode where it does limited switching ( As per the training manual, the power supply works in a limited mode and generates 3.3v and only when P-ON-H1 and P-ON-H2 is connected to 3.3v, the power supply works in full power mode). If I temporarily short pin 4 and 3 of optoisolator IC601, the lights stop blinking. They start as soon as the short is removed.

4. So far so good... now if I remove the bulb on transformer primary auxiliary and connect pin 6,7,8 back to the board the secondary side bulbs do not light up. Voltage at pin 6 of the chip is 10v ( manual says it must be 16v)

I could not get 2SK3498 so I replaced it with IRF840 ( some what similar specifications)

Any advise from the experts here ? Also help me understand the role of Q602. Is it running in a switching or analog mode here ?

[genuineguy]

Re: Philips 40PFL4707 SMPS fuse blown.

Here is some update on my experiements

1. Removing the transformer and connecting bulbs helped me to get readings that showed that the IC is actually working and not dead

2. However, removing the transformer and connecting it with wires was a super bad idea. The stray things blew my primary mosfet multiple times and I have a pile of dead mosfets already on the table.

3. Instead of bulbs, I connected 5W 270ohms as resistors. I desoldered the cathode of all secondary diodes and connected resistors at the cathode and gnd points. This again proved suicidal and killed few more primary mosfets to add to the dead pile

4. Finally, I have connected the 5W resistors directly to the secondary windings. I have three of them as there are 3 taps to the secondary winding. This has given me some stable results. The voltages actually swings from 52v-0v-32v-0v-48v-9v with each reading having about 1sec or less and every high goes back to 0v. if I turn mains power for about 10 to 15 seconds. The primary mosfet does not blow, however it get super hot. I can touch it but it is hot...
This is the most stable state I have reached after lots of experimentation without blowing mosfet

My current conclusions
1. The IC FA5640 is not totally dead. Atleast it appears its resonating in the burst mode and kicking the transformer. As per the service manual, the supply board is supposed to only generate 3.3v and would kick in full power mode only if P-ON is shorted to 3.3 which as per the circuit would feed about 2.1v to the feedback pin3 of ICFA5640 ( photo transistor of opto isolator)

2. There appears something wrong at the secondary. I have tested all components using my DMM but could not find any fault. So there is some interesting fault out there. However I will focus on it after I have confirmed that the primary is really working neatly.

3. I am still struggling why the primary mosfet gets hot. Its in a switching mode and K10A60D has 0.5ohms on resistance... also the IC is switching in burst mode with on and off period separated by 1 to 2 seconds.


My next plan is to use a resistor voltage divider across the primary capacitor that is holding 162v and feed about 2v to the pin3 feeback point of IC ( this is the photo transistor point)... This is to simulate nomal secondary voltage and finish testing of the primary section. still thinking

any tips ?

[Andrew F. Ali]

Re: Philips 40PFL4707 SMPS fuse blown.

I think you have totally messed up all the directions/instructions of the experts...yes experts...I don't think the light bulb test jig can be replaced with a resistor...you have to follow the directions precisely or you'll end up spending more on this TV than it's worth.

[genuineguy]

Re: Philips 40PFL4707 SMPS fuse blown.

@Andrew
My apologies if I don't sound like a good student at this forum. I am doing electronics as my hobby and while I do this TV repair, I like to experiment a bit more to learn (and that may cost me few more fried mosfets which is okay)

The light bulb jig is ready on my table and I have been using it but could not go really far with it.

Here are my results

1. This is a quasi -resonant IC based supply so looks like its pretty complex and not a simple TL494 type PWM situation.
2. Since I am not sure of the secondary faults, I have connected three 5W resistors to the three secondary windings to give standard load and avoid any induced voltages on primary. I will debug the secondary later as could not see any obvious faults yet.
3. I have checked each and every primary component and found nothing is faulty as of now on the board
4. Connect a 200W (thats what I have) bulb and a 3A fuse. On power on, the bulb turns on and off ( almost 1 to 2 sec gap). The ouput 5w load resistors show voltages climbing and falling 0v-6v-0v-5v-0v-6v-0v-5v. The Q601 gets really hot but I can touch it. This is correct behaviour as the IC is in power on burst mode as there is no voltage applied at pin2.
5. Now I applied 1.7v, 1.8v, 1.9v, 2.0v to the pin2 (feedback) of IC and I noticed that the bulb now turned on more bright with flickering
6. An interesting fact was that on power on, without external voltage at pin2, the bulb turns on and off ( 1 sec) and then when I apply 2v to the pin2, the bulb is flickering very fast and mostly on... This flickering continues even if I remove the pin2 external voltage. This I tend to conclude that that the IC does not go back to the power on burst mode and that is a wrong behaviour. If there is no voltage at pin2, it should go back to the power on burst mode.
7. If I remove the bulb, and keep the 2v applied at pin2 and power on,, the fuse blows and Q601 is fried. If I replace a new Q601 the entire cycle above repeats