Philips 47PFL3603D/27 scratchy weak audio

[DXseekerMO]

I got this TV for free earlier this year with a backlight problem the guy didn't want to have fixed again. The problem was very easy to find.....you all should have seen the light show behind the backlight transformer.....it literally looked like welding spatter!

At any rate the trace around one leg of the BLT went up in smoke right before my eyes and left a crater in the board. I solder bridged the leg to the remaining trace, tested it then buried the repair in epoxy to hold it solid. I also refreshed the ground pads and cleaned up the chassis where they were arcing. The screws were tight so maybe the last guy resoldered the BLT to the board without concern for the grounds?

Now the problem I'm having is scratchy weak and fluctuating audio on both speakers. The speakers look fine. I pulled the main board and saw nothing obvious. While the MB was out I refreshed the grounds, board and chassis.

So has anyone seen weak scratchy audio with this particular TV or have any troubleshooting steps? On this one I am at a loss where to start. I'm pretty sure the zoomed in picture on the main board is the audio section.

Pictures attached. Thanks everyone!

[DXseekerMO]

Re: Philips 47PFL3603D/27 scratchy weak audio

I see a very high view to reply ratio on a few posts tonight, but mine is stuck at 3 views and no replies. Did I miss the mark somewhere?

[DXseekerMO]

Re: Philips 47PFL3603D/27 scratchy weak audio

Bump

[TechGeek]

Re: Philips 47PFL3603D/27 scratchy weak audio

Can you post clear pictures of the main board? (The board that your inputs connect to)

[budm]

Re: Philips 47PFL3603D/27 scratchy weak audio

Does the main board have:
1) RCA Line level audio output that you can verify to see if it also has bad sound on those RCA audio line out jacks.
2) Headphone output jack that you can verify if it also has bad sound or not.
If one of the BTL is tied to GND then more likely the output stage of that Class D amp chip is damaged.
Disconnect the speaker connector and measure the Voltage between chassis GND against each pin of the speaker connector on the main board.
BTW, what is the P/N of that Class D amp chip?

[DXseekerMO]

Re: Philips 47PFL3603D/27 scratchy weak audio

I'll get that chip number and see if I can find a datasheet for it too.

[DXseekerMO]

Re: Philips 47PFL3603D/27 scratchy weak audio

Can you post clear pictures of the main board? (The board that your inputs connect to)

Thank you, here are the pictures below.

Does the main board have:
1) RCA Line level audio output that you can verify to see if it also has bad sound on those RCA audio line out jacks.
2) Headphone output jack that you can verify if it also has bad sound or not.
If one of the BTL is tied to GND then more likely the output stage of that Class D amp chip is damaged.
Disconnect the speaker connector and measure the Voltage between chassis GND against each pin of the speaker connector on the main board.
BTW, what is the P/N of that Class D amp chip?

The P/N of the Class D amp chip is TDA8932B. I posted the datasheet for it. Also what is BTL, never heard that.

Voltages:

Speaker connector (4-wire):

Terminal 1 full volume: -.18 to -.22 Half volume: -.020
Terminal 2 full volume: 0V Half volume: 0V
Terminal 3 full volume: 0V Half volume: 0V
Terminal 4 full volume: .001 to .010 Half volume: .003

Cap 2304: top lug 0V, bottom lug 13.03V
Cap 2308: Top lug -13.03V bottom lug 0V
Cap 5301: 13V both lugs
Cap 5302: -13V both lugs
Cap 5303: .03V top lug, 0V bottom
Cap 5304: -.03V top lug, 0V bottom

[tvtimmy]

Re: Philips 47PFL3603D/27 scratchy weak audio

You can also use a main board from these models.

[DXseekerMO]

Re: Philips 47PFL3603D/27 scratchy weak audio

Thanks for posting that! I've yet to see another TV with that kind of main board interchangeability. I will consider replacing it if this one can't be fixed...or I mess up on the repair. The chip is about $2.50 from Digikey and its available.

[DXseekerMO]

Re: Philips 47PFL3603D/27 scratchy weak audio

bump

[DXseekerMO]

Re: Philips 47PFL3603D/27 scratchy weak audio

I guess I'll just order the class D audio IC, toss it in there and hope for the best.

[R_J]

Re: Philips 47PFL3603D/27 scratchy weak audio

Also what is BTL, never heard that.

bridge-tied load (BTL)
That is where they connect the load (speaker) from one amp output to the other amp output for more power, the input phase needs to be 180° from one amp to the other.
If a trace burnt up on the output ic it is very likely it burnt due to a shoted ic
Do you have +12 (8,20,29) and -12 on (9,23,26) also -12 on (1,16,17,32) voltage supplies for the ic?

[petehall347]

Re: Philips 47PFL3603D/27 scratchy weak audio

have a Philips tv but not same model . audio chip was cooked and it put out dc to the speakers and cooked them . i removed the chip and tested with headphones and was fine so replaced chip and speakers and that fixed it . the caps next to the chip were running hot with faulty chip but run fine with new chip .

[DXseekerMO]

Re: Philips 47PFL3603D/27 scratchy weak audio

bridge-tied load (BTL)
That is where they connect the load (speaker) from one amp output to the other amp output for more power, the input phase needs to be 180° from one amp to the other.
If a trace burnt up on the output ic it is very likely it burnt due to a shoted ic
Do you have +12 (8,20,29) and -12 on (9,23,26) also -12 on (1,16,17,32) voltage supplies for the ic?

Are those the pin numbers to check on the IC? If so I will check them tomorrow.

The trace that burnt up was on the power supply board, the backlight transformer leg had a bad solder joint and had been repaired previously.

have a Philips tv but not same model . audio chip was cooked and it put out dc to the speakers and cooked them . i removed the chip and tested with headphones and was fine so replaced chip and speakers and that fixed it . the caps next to the chip were running hot with faulty chip but run fine with new chip .

When I check those pins tomorrow as suggested by R_J I'll see if those caps feel hot. Will an ohms check on the speakers tell me if they are cooked?

[petehall347]

Re: Philips 47PFL3603D/27 scratchy weak audio

yes check on ohms . you will see if shorted .

[DXseekerMO]

Re: Philips 47PFL3603D/27 scratchy weak audio

Unfortunately another problem has occurred after accidentally shorting pins 20 (Vddp2) and 21 (boot2) while checking for voltage. Now the TV turns on by itself then turns off about 4 seconds later. Once again I tried probing voltage with the TV on the stand, on the floor and while I was in an uncomfortable position. Stupid mistake.

I'm guessing BOOT2 signals the processor that the high driver circuit is OK upon start-up? If so could the TV be shutting down because this circuit is now shorted in the chip?

[R_J]

Re: Philips 47PFL3603D/27 scratchy weak audio

See if this manual will help, page 44 has a schematic of the TDA8932 audio ic.
It could be totally different but you never know.
Whenever I need to probe fine pitch ic's I either use my needle probe (made with a sewing needle and a piece of wire connected to meter) or find a component that is connected to the pin, ie res. cap. etc. and put yor probe on it.

Find a point to check if you still have +12 volts going to pin 20

[DXseekerMO]

Re: Philips 47PFL3603D/27 scratchy weak audio

I was probing the wire with the lead from my LED tester which has a very sharp fine point, but I never thought about tracing and probing elsewhere instead of at the chip.

On the diagram I didn't see anything tied in to the circuits I shorted across that explains turns on by itself and shuts down 4 seconds later. I only checked pins 8 and 20 so maybe I unknowingly shorted pin 8. If I read that right this is the supply voltage for that IC? This pin is right next to CGND, chassis ground?

[R_J]

Re: Philips 47PFL3603D/27 scratchy weak audio

In this model, the ic has two supply voltages, one +12 and one - 12v. Yours could be different and only have one +20 volt supply.
Does your ic have pins 16,17,1 & 32 going to chassis ground?
There are some small pico fuses on that power supply, F200, F201, F202 You may have blown one of them.
By looking at your pictures it seems your power supply, supplies both plus and minus 12 volts for the audio, both lines have fuses, F200 & F201
If one of those fuses was open before, that may have been the cause of the poor audio??