Philips 37PFL5322D/37 Chirping from psu

[orgwood]

Re: Philips 37PFL5322D/37 Chirping from psu

I've got everything working again and am wanting to know if I have to load the 24VDC rail to make it work? I found a STP10NK60ZFP in another supply to replace the STP10NK80ZFP with but I think I can put it in the 12VDC rail and move the 80ZPF that there up into the 24VDC side. I'm doing all my testing with my voltmeter now and am able to measure the Hot AC/DC side to check out the booster as suggested by budm. So far there is no doubling of that voltage and the 24VDC rail only rises to around 11VDC when the Standby pin is brought high. Any thoughts?
Thanks, Dave

[orgwood]

Re: Philips 37PFL5322D/37 Chirping from psu

I swapped the FET from the 12VDC rail up into the 24VDC spot and am getting exactly the same ticking sound except when I bring the standby pin up to 12VDC through a 1k resistor and the ticking sound increases. The 24VDC rail comes up to around 11VDC with no load but this time I noticed the FET on the 12VDC side gets pretty darn hot to touch. When that pin is not brought high it decreases a lot in temperature and is easy to touch. So I need to find out how the "booster" action works and find the bad component. The ticking sound is definitely within the large transformer T905. I have replaced ZD902 & 904 but am not measuring much voltage across them when I try to activate the booster circuit so now I'm starting to wonder if I got some bad ones. I may have to pull them loose and put a supply across them to see if they're working. Any help?

[budm]

Re: Philips 37PFL5322D/37 Chirping from psu

You should be able to run the 24V power supply without load, but right now you need to get the PFC Voltage working.
The Power MOSEFT used for the standby 12V power supply is not the same as used for the 24V power supply so I would not just swap them.
When the STADBY pin is forced on, you need to find out if the PFC IC Vcc pin 8 is getting the Voltage to run which at this point you did not tell me yet if you do have >360VDC at the two legs of the main filter cap. I asked about it (post 26) before you had the accident and damaged the board.

[orgwood]

Re: Philips 37PFL5322D/37 Chirping from psu

Thanks so much for your reply. In my PS there are three FETs - the large one used on the main supply Q902 mounted on the heatsink with Q901 that I think is the booster 24VDC rail and Q904 that happens to be the same P/N as Q901 and has no Heat Sink but that's the one that is getting hot when the SBP in forced on...I thought it was the standby 12VDC one. I will check again today to see what voltage is appearing across the main filter cap when the SBP is forced on but I don't think it ever gets above ~160VDC (RMS value of 120VAC rectified). There is a small PFC SMT chip on the bottom that's different and 2 DIP PFCs on the top that are the same P/N. I thought the bottom one drove the main supply but I see now that Q914 drives the large FET through the SMT PFC and Q912 drive the VCC on IC904 together via the SBP so essentially they provide the boost of the "normal" high rectified rail upwards would be my guess. Swapping the same P/N FETs was easy and produced no changes in symptoms. I can put those same P/N PFCs in DIP sockets and swap them too to see if anything else changes. I'll get back to you soon. Thanks again.

[budm]

Re: Philips 37PFL5322D/37 Chirping from psu

I do not see Q904 in the diagram (provided by you on post 35), Q908 is for the 12VSTBY and it is not mounted on the heat sink.
IC 902 PFC IC, Q902 is the power MOSFET for the PFC Voltage booster.
There is only PFC IC 902, so n way you can swap it with other IC on the board.
IC 902 (SG6961) is PFC IC
IC 907 is the SMPS IC (TEA1507P) for 12VSTBY
IC 904 is the SMPS IC (TEA1507P) for the 24VDC.
So I hope the diagram you provided match your board.

[orgwood]

Re: Philips 37PFL5322D/37 Chirping from psu

My eyes have a hard time reading the schematic even with 2 cheaters on. Q904 is a 7G on my schematic. IC907 is my IC902 and I thank you for the clarifications The rest of it makes sense.

[budm]

Re: Philips 37PFL5322D/37 Chirping from psu

This is what I see on your diagram for the 37"

[orgwood]

Re: Philips 37PFL5322D/37 Chirping from psu

Yes...that's the one and I'll use your markup to go from here. I swapped Q901 & Q908 since they are the same on my assembly board with no changes in symptoms. I'm going to go see if IC902 & IC904 are getting their VCC. I know IC907 has to be getting it because the standby 12VDC is working. So you're saying that when the standby pin is forced high, the voltage across the main filter cap C907 goes from ~160VDC to upwards of ~360VDC? If that's so doesn't that affect Q908 too?

[budm]

Re: Philips 37PFL5322D/37 Chirping from psu

"So you're saying that when the standby pin is forced high, the voltage across the main filter cap C907 goes from ~160VDC to upwards of ~360VDC? " That is correct if the PFC Voltage booster is OK (unless there is overload in the 24V power supply section).
"If that's so doesn't that affect Q908 too? That should not affect the standby 12V power supply section unless something is drawing too much from the 12V section.

[orgwood]

Re: Philips 37PFL5322D/37 Chirping from psu

Those zeners to both sections, ZD904 & ZD906 are connected to that rail that goes up to ~360VDC. I'm going down to the workshop to check this out right now and see what I find. Thanks, Dave

[orgwood]

Re: Philips 37PFL5322D/37 Chirping from psu

Here's my lack of understanding coming from a linear PS era...the VCC on both those ICs seems to jump around 5-10VDC and is not steady even with a filter cap from VCC to GRD. Is that supposed to happen? Also, I'm wondering if I got 2 regular diodes from a kit supplier for the 2 ZDs in series...I'm pulling those and going back to my original ones. That might explain why that rail stays near the 160VDC instead of going up 200VDC to 360VDC.
I know the caps were bulging so that's why I bought a kit. Later I bought a diode kit for the 12VDC section and that started working. So maybe my problem started with the 12VDC section and I made the 24VDC worse by replacing not only the bad caps but also working zeners with regular diodes from that kit. I'm going to work on this some more and report back. Thanks, Dave

[budm]

Re: Philips 37PFL5322D/37 Chirping from psu

See attached PDF. I would check the caps for the VCC and those parts in the sync rectifying circuits of the 24V output section.

The VCC voltage for the PFC IC is generated from the AUX winding of the 12VSTBY power transformer T905 PIN 5&6.
It is rectified by D929 (BAV103) and filter cap C958 (47uf 25V, need to be checked for ESR and capacitance),the Voltage on this cap should be aorund 20VDC or so.
The + Voltage of C958 is fed through switched transistor Q914 which is turned on by the PS-ON sinal, the output at the
Collector of Q914 is fed to VCC pin 8 of the PFC IC902.
The 24V SMPS IC904 (TEA1507) VCC PIN 1 also get the small kick start Voltage from Q912, C921 (100uf 25V, need to be checked for ESR and capacitance) is startup/running cap.
One the 24V SMPS IC starts runninb then the AUX winding pin8 & 9 of the transformer T907 will generate the running Voltage, the Voltage is rectified by D907 (RGP100) and filtered
by C921.
So that is how the VCC for the two ICs are generated.
SMPS IC TEA1507 Vcc start is about 11VDC.
PFC IC SG6961 Vcc start is 12VDC.

[orgwood]

Re: Philips 37PFL5322D/37 Chirping from psu

Golly, that's a lot of information to digest...I'll look at it in detail tonight before bed.

Here's what I've managed to do...
I put in 8 pin DIP sockets for both those ICs and found that one of them doesn't work in the 12VDC section. I also managed to blow the FET in the 24VDC section somehow maybe by running it without the IC in that section - live and learn. So now I'm off to find another TEA1507. I've got many SMPSs but they don't seem to have that particular IC. I might as well ask - does it cross to another manufacturer's part as several have 8 pin DIPs with different markings? So I think I found what was keeping the 24VDC rail down. Also, I replaced all the caps with kit parts from someone who seemed to know what they were doing so I hope they had the ones with low ESRs. If you find my solution for the Westinghouse 42/47" LCD set, you'll know I understand the importance of low ESR caps in switchers. That cap keeps the set from booting. I've helped several people fix their dead sets. I found that one using a hair dryer heating up the caps to find the culprit. Thanks again, Dave

[jetadm123]

Re: Philips 37PFL5322D/37 Chirping from psu

No sub for the TEA1507. However, readily available on eBay.

[orgwood]

Re: Philips 37PFL5322D/37 Chirping from psu

I just ordered 5 TEA1507s and 6 FETs STP10NK80ZFP so if anyone's looking for them, send me a PM and we'll work something out. I hope I won't be needing them all.

[orgwood]

Re: Philips 37PFL5322D/37 Chirping from psu

See attached PDF. I would check the caps for the VCC and those parts in the sync rectifying circuits of the 24V output section.

The VCC voltage for the PFC IC is generated from the AUX winding of the 12VSTBY power transformer T905 PIN 5&6.
It is rectified by D929 (BAV103) and filter cap C958 (47uf 25V, need to be checked for ESR and capacitance),the Voltage on this cap should be aorund 20VDC or so.
The + Voltage of C958 is fed through switched transistor Q914 which is turned on by the PS-ON sinal, the output at the
Collector of Q914 is fed to VCC pin 8 of the PFC IC902.
The 24V SMPS IC904 (TEA1507) VCC PIN 1 also get the small kick start Voltage from Q912, C921 (100uf 25V, need to be checked for ESR and capacitance) is startup/running cap.
One the 24V SMPS IC starts runninb then the AUX winding pin8 & 9 of the transformer T907 will generate the running Voltage, the Voltage is rectified by D907 (RGP100) and filtered
by C921.
So that is how the VCC for the two ICs are generated.
SMPS IC TEA1507 Vcc start is about 11VDC.
PFC IC SG6961 Vcc start is 12VDC.

I get it now. Even though you used the 47" schematic, it is so similar in those stages that I can understand it now...those diodes were really messing me up until you pointed out how things got running. I had already pulled and tested all the components on the cold side of the 24VDC and 12VDC side. Once I get my TEA1507s I should be back in business. You really have helped me on this board and I have learned so much about SMPS circuitry from this. Thanks again.

[budm]

Re: Philips 37PFL5322D/37 Chirping from psu

I just notice that now I extracted out the wrong page!

[orgwood]

Re: Philips 37PFL5322D/37 Chirping from psu

I just notice that now I extracted out the wrong page!

It doesn't matter since I now understand how things get started up thanks to your explanation and diagrams. Thanks so much! Dave

[orgwood]

Re: Philips 37PFL5322D/37 Chirping from psu

As a follow up post, I received my parts FETs and ICs...installed them and everything works as it should now. My son will install this PS and give it the final test. Thanks to BUDM for sticking with me through my education and providing copious information about how everything works in the circuit diagram. I have already repaired 2 other SMPSs using my new knowledge. It's strange that this design has so many failures compared to linear but then again, most of the failures in linear are semiconductor related too. Here though, the caps seem the weakest link most of the time probably because of the HF beating they take. Thanks again, Dave

[budm]

Re: Philips 37PFL5322D/37 Chirping from psu

Thanks for good news.