Philips 32pfs4132/12 LCD TV repair

[pepona]

It´s just the marking code. "PF" means Power Forest.

[nForce]

Hello, I have one beginner's question.

Why do I have to remove the diode from the circuit to test if it's OK?

Thanks.

[lok]

Hello, I would like to know, what is wrong with my LCD Philips TV. When I turned it on, I heard a bang, and now I can't turn it on. The red indicator light is not showing. So because I heard a bang I thought to myself it must be a capacitor which blew up. So I opened it up and looked at the power supply board.  See for yourself this power supply board:



Here you can see that all capacitors are OK. I have measured all capacitors with the multimeter, and all capacitors are not conducting. So I have measured the resistors and one of them (marked with a green rectangle) which I think it's a 0.27-ohm resistor has a resistance of a few megaohms. So is this the problem? Why I can't see a black or brown spots on the resistor indicating that it blew up?

With the visual inspection of the board, I can't see anything which blew up, because I heard a bang. Does anyone see a problem on the board (I am not an electronics engineer)?

Thanks for the help.

Hey, nForce did you fix your power supply?
It seems I have that same resistor problem, but only I can see black marks of it, so it seems more likely thats the problem.

[nForce]

Hello, I did not saw your post before. Did you fix it? So you only change the resistor, or you had changed some other components?

[Dacke]

Hey, nForce did you fix your power supply?
It seems I have that same resistor problem, but only I can see black marks of it, so it seems more likely thats the problem.

On your board with the burned resistor if you look closely at the mosfet above it there is a burn spot between the source and drain pins,  this is likely where it arced or shorted,  possibly from dust buildup/debris on the bottom of the mosfet package.  This, in turn,  blew out the current sense resistor (the one that is burned) which is a low value and just acted as a fuse at that point.  Newer TVs will generally have RTV over the legs of switching fets and PFC fets in an attempt to prevent this, but cheaper TVs may not.  There's possibly other damage as well (blown gate resistor, oscillator, safety caps nearby, etc.).  It can be a bit of work but it's usually not very expensive to repair.

[waltham1]

Apologies if bumping old threads is not correct on this forum.

Just wanted to share that I appear to have had the exact same issue with my Philips 4132.

See photos attached. I believe it is to do with this resistor as previous, mine is showing obvious wear signs after the small bang and death of the screen.

Unsure whether to get it repaired, or whether money is better spent on a new unit. Experience or advice is much appreciated. I am no TV technician or electrician, so would be paying someone to fix it. Wonder if that would make sense financially? Is it an easy/cheap job?

Many thanks.

[Scooby]

Hi there,
Sorry for digging this old topic, but I ran into the same problem.

I changed all components: Q9101, R9101, C9126, U9101 (which I upgraded to PF6003AG according to Pepona's recommendation), D9104, R9109, R9110, R9111 and R9113.
The TV worked fine again ... but only for a couple of hours, and then it happened again: a BANG, and a black screen again.

Meanwhile I noticed that the Q9101 MOSFET ran very hot ... too hot because it burnt again.
So there must be an excessive current draw somewhere, but I am unable to locate it.

I changed again the whole bunch of components and did a quick test: I works again, but still Q9101 is getting very hot.

Someone could give me a hint please ?

I checked other components on the PSU (the electrolytic capacitors and the blue film capacitor). Their values seem ok, except for the big 82µF capacitor wich only has 76µF, but that's probably acceptable ?

Thanks for you help.

[Scooby]

Hi again,

I finally found out why my MOSFET was overheating.

The problem was that I installed a counterfeit TK6A65D MOSFET, which I bought from AliExpress.
On a genuine TK6A65D the RDS(on) restance is about 1 Ohm.
On the counterfeit one, I measured 11.6 Ohm@100mA, 16.8 Ohm@500mA and even 40.8 Ohm@640mA !!

After installing a genuine one, bought from a trusted seller, there's no heating issue anymore.
The MOSFET temperature is stable at 53°C during operation

[peterpepo]

Hi,

I came across this thread, when searching for same problem. The power indicator is dead, no light.

I've measured all the parts, as mentioned in this thread as follows:

I don't know:
Q9101 - no short between S and D

Seems broken:
R9101 - 9,13kR instead of 0,27R
R9109 - 12MR instead of 10R
C9126 - split in half

Seems fine:
R9104 - 36KR (probably fine, since there are two in series), same for R9106, R9105, R9107
R9110 - 46,7R (should be 47 - ok)
R9113 - 0,998KR (should be 1K - ok)
R9111 - 10KR

Didn't measure:
U9101 since I don't have a scope. Don't know D9105, D9106 - Do I need to desolder them?


Do you think it is enough to swap what I am pretty sure is broken - R9101, R9109, C9126?
Do i need to swap Q9101 even though there doesn't seem to be short between S and D? Do I need to swap U9101?
Is there anything else I should measure to identify the issue?
Are there any alternatives for TK6A65D and PF6005AS? There is no carrier for PF6005AS (except one, selling for 17€) and TK6A65D are pretty difficult to find too.

I'm trying my best to diagnose before ordering anyting, parts are not very accessible here, and I have to order everything from internet.

[bemipefe]

Hello guys,

I experienced the same power failure for this LCD TV. The impacted components in was the same and I replaced as suggested these components:

Q9101 (replaced with TK6A65D), R9101, C9126, U9101 (replaced with PF6003AG), D9104, R9109, R9110, R9111 and R9113

However i have no output DC current in the external connector where I should measure 12 V.
The Q9101 is not shorted and when the board is powered source and drain are connected.
From the ground and R9146 I read  10-16 V but the value is not stable and it changes with the same sequence.

What can I check to figure out what component is failing ?
(NOTE: I don't have the complete schema but only what was posted as image in this thread)

[justElectronicx]

Philips TV PSU 715G7734-P02-005-002H – PF6005AG & MOSFET Keep Failing After Replacement

Hello everyone, 

I've been troubleshooting a Philips TV power supply (Model: 715G7734-P02-005-002H), and after checking multiple forum posts and analyzing my circuit, I found that many others have faced the same issue. 

By referring to the PSU datasheet (Page 44) and inspecting my board, I identified the blown components and ordered replacements from AliExpress. However, after replacing everything, the MOSFET (Q9101) and 0.27Ω / 2W resistor (R9101) keep failing on power-up. 

Components Replaced (Defective & Preventive Maintenance) 
After the first failure, I replaced the shorted components: 
✅ U9101 (PF6005AG PWM IC)
✅ Q9101 (K6A65D MOSFET)
✅ F9901 (Fuse, though it was fine on the second attempt) 
✅ D9104 (Diode)
✅ R9101 (0.27Ω / 2W Source resistor, keeps failing) 
✅ R9109, R9110, R9111, R1113 (Other critical resistors in the circuit)
✅ C9126 (100pf Capacitor between Source to drain)

Since the VCC voltage was fluctuating, I also replaced the following as a precaution: 
✅C9105 (10µF capacitor at startup circuit) 
✅ D9106 (1N4148W Diode, between startup caps) 

Debugging & Voltage Measurements
1️⃣ Checked the startup resistors (R9101, R9102, R9103 - all 510KΩ).
   - Measured ~480KΩ on each, looks within tolerance. 

2️⃣ Checked the entire startup circuit, all resistors & components tested OK.

3️⃣ Measured VCC voltage:
   - Without IC soldered: 47V (seems normal).
   - With IC soldered: Drops to 7.4V (suggesting an issue with startup or excess current draw).
   - Expected vcc voltage between 12V - 18V.

4️⃣ Soldered all other resistors and diodes again, but VCC remains 7.4V. 

5️⃣ Tried soldering the MOSFET again, but it blew instantly (this time the main fuse remained intact).

6️⃣ Measured Auxiliary Power: 
   - Got ~350V DC, which is correct.


What Could Be Causing This?
- IC not powering up correctly (VCC too low, could be internal failure or incorrect feedback loop). 
- Excessive current draw somewhere in the circuit (but no visible shorts apart from MOSFET failures). 
- Faulty transformer or snubber circuit (possible high-voltage spikes causing repeated MOSFET failures). 
- Incorrect gate drive signal (I don’t have proper tools to measure output frequency, so I can’t verify this). 


 Next Steps / Need Advice
- Could the transformer be damaged and causing overcurrent issues?
- Should I try a different brand of PF6005AG / MOSFET in case of a bad batch? 
- What other components should I check before attempting another replacement? 


Any suggestions or insights would be greatly appreciated! Thanks in advance.