Philips LCD TV with Sound, No Picture (model 42PFL5322/10)

[retiredcaps]

Re: Philips LCD TV with Sound, No Picture (model 42PFL5322/10)

Usually a fuse blows in unexpected or out-of-spec conditions, and obviously, I haven't fixed anything besides the fuse.

I agree that fuses blow for a reason, but from what I have learned here with other cases, sometimes a fuse (like any other component) can just go bad on its own.

If I had to guess it would be one of those ICs (Nikos) that may have blown a fuse. However, since your TV works, that implies all the components on the inverter board are working fine.

[sagie]

Re: Philips LCD TV with Sound, No Picture (model 42PFL5322/10)

Great job of tracking that down. Ironically, a bad fuse is mentioned in the 2 seconds to black guide, but I haven't mentioned it as a possible cause for a while now.

Yes, I now see it... But it was really the CCFL test that helped me localize the faulty area.

Anyway, thanks for the following up and getting your TV working again.

No, thank you! What I am wondering about now is what made the original fuse blow. Usually a fuse blows in unexpected or out-of-spec conditions, and obviously, I haven't fixed anything besides the fuse.

[retiredcaps]

Re: Philips LCD TV with Sound, No Picture (model 42PFL5322/10)

I found out the 2 were sharing an SMT 3A fuse. I tested its resistance, and unsurprisingly, it wasn't conducting.

Great job of tracking that down. Ironically, a bad fuse is mentioned in the 2 seconds to black guide, but I haven't mentioned it as a possible cause for a while now.

Anyway, thanks for the following up and getting your TV working again.

[sagie]

Re: Philips LCD TV with Sound, No Picture (model 42PFL5322/10)

Try this, as explained by PlainBill, for testing the ccfls

https://www.badcaps.net/forum/showpo...78&postcount=3

Well, looks like I fixed it. It wasn't the CCFLs, but the ingenuously simple CCFL test helped me find the problem. From the CCFL test I detected what appeared to be two malfunctioning CCFLs. The two were next to each other, in one corner of the set.

It seemed to me too much of a coincidence that 2 adjacent CCFLs failed together. So I searched the power supply path of the 2 CCFLs for shared components that could've failed. I found out the 2 were sharing an SMT 3A fuse. I tested its resistance, and unsurprisingly, it wasn't conducting. I soldered a new 3A fuse, and the set now works.

Many thanks for your help, retiredcaps and PlainBill!

[retiredcaps]

Re: Philips LCD TV with Sound, No Picture (model 42PFL5322/10)

One of the transformer secondaries is 732 ohms, whereas the other 5 are 767 - 782 ohms. So there may be short circuit turns on this one. BUT even if I can prove it is the fault where could I get a replacement?

If there are any markings on the transformer, try

http://www.lcdparts.net/T.aspx

or ebay.com. We have helped people identify bad inverter transformers and they have found the correct replacement on ebay.

[Huttonfrank]

Re: Philips LCD TV with Sound, No Picture (model 42PFL5322/10)

I am trying to repair a LG 32LC56. It has a single inverter board very similar to this one. (mine is VIT71020.66 MODULE INVERTER V.32 LCD-TV REF : 19.31T03.001) There are only six CCFLs. I have established that Philips and LG have a lot of common parts.
Symptoms are the same. On the inverter board is an IC type OZ964. The data sheet is free on the net. It is a DC/AC CCFL generator and control IC.
The application circuit shown is only for 1 CCFL so in this case the circuitry is much more extensive. I found that pin 3 of the OZ964 which is the enable pin goes from 5V when the backlight is on to 0v when it goes off. the line from the pin goes to various other points on the board, so it seems that an over or under voltage or current detection circuit is driving this line low and shutting down the CCFLs.
One of the transformer secondaries is 732 ohms, whereas the other 5 are 767 - 782 ohms. So there may be short circuit turns on this one. BUT even if I can prove it is the fault where could I get a replacement?

[PlainBill]

Re: Philips LCD TV with Sound, No Picture (model 42PFL5322/10)

Thanks again for your help, retiredcaps.



I might save you some searching by telling you the service manual which is widely available on the Internet for this chassis (LC7.1E LA) has absolutely no information about neither the CCFLs, nor the PSU or the inverter boards, so there is no specification for spare CCFLs, etc. It appears to me as if Philips has no interest in having these parts being serviced.

It's not a matter of interest, it's a matter of ability. The following applies to both LCD and plasma, (and to a certain extent, even DLP) TVs.

There are only a few companies making flat panels. When Philips wants to build an LCD TV, they purchase LCD assemblies from one of the LCD panel manufacturers. The LCD assembly consists of the LCD panel, the inverter(s), the CCFLs, and the tcon. The power supply may be a similar situation - they purchase them from a manufacturer. In the case of a plasma panel, the panel, sustains, buffers, main control card, and often the power supply are sold as a unit.

Philips is quite good about providing schematics where possible, but if the subassembly is built by another firm, they are usually unable to provide schematics.

PlainBill

[retiredcaps]

Re: Philips LCD TV with Sound, No Picture (model 42PFL5322/10)

Try this, as explained by PlainBill, for testing the ccfls

https://www.badcaps.net/forum/showpo...78&postcount=3

[sagie]

Re: Philips LCD TV with Sound, No Picture (model 42PFL5322/10)

Thanks again for your help, retiredcaps.

I'm not sure how to test the 20 ccfls. I'll have to think and do some searching.

I might save you some searching by telling you the service manual which is widely available on the Internet for this chassis (LC7.1E LA) has absolutely no information about neither the CCFLs, nor the PSU or the inverter boards, so there is no specification for spare CCFLs, etc. It appears to me as if Philips has no interest in having these parts being serviced.

[retiredcaps]

Re: Philips LCD TV with Sound, No Picture (model 42PFL5322/10)

This time, they were all in the range of 1300-1333 Ohms, which makes the max reading still within 3% from the min reading.

Those readings suggest the inverter transformers are likely good.

Yes, each of the 2 boards carries 5 medium sized caps and a small cap.

The Mercedes Benz vent and the brown color suggest they are United Chemi-con caps. UCC is a reliable manufacturer, but they have a problematic series with the KZG caps.

Assuming the caps are good on the inverter board and power board, that leaves the ccfls and/or wiring to check.

I'm not sure how to test the 20 ccfls. I'll have to think and do some searching.

[sagie]

Re: Philips LCD TV with Sound, No Picture (model 42PFL5322/10)

Can you actually list all 40 readings? It matters because if 39 of them measure between 1350-1360 Ohm and 1 reads 1310 Ohm, then

1360 * 0.97 = 1319 Ohm. OR 1310 * 1.03 = 1349 Ohm.

How the 3% guideline came about by PlainBill.

https://www.badcaps.net/forum/showpo...7&postcount=18

edit: We have had cases where the measurement was off by as little as 5 Ohms to cause "2 seconds to black".

OK, as I checked the resistances a second time to write them down, I got much more consolidated readouts for some reason. This time, they were all in the range of 1300-1333 Ohms, which makes the max reading still within 3% from the min reading. I wrote all of the readings in the bottom of this message.

Are there any caps on the inverter board? If yes, what brand and series are they?

Yes, each of the 2 boards carries 5 medium sized caps and a small cap. They all appear to be in good shape visually (at least in my eyes).

I couldn't really make a brand, but here are the markings on them:
* Medium sized - 1st type

(M)105°C
7(7)
1W

* Medium sized - 2nd type

(M)105°C
7(7)
3W

* Small sized - 3rd type

(M)105°C

One of the boards carries 5 caps of the 1st type and 1 of the 3rd. The other board carries 3 caps of the 1st type, 2 of the 2nd and 1 of the 3rd.
I think the manufacturer simply uses the 1st and 2nd types interchangeably.

I've also attached some photos to show the one of the boards and a few of the caps.


Transformer secondary windings readouts
1st board

1.1: 1312
1.2: 1306
2.1: 1327
2.2: 1317
3.1: 1319
3.2: 1316
4.1: 1311
4.2: 1308
5.1: 1317
5.2: 1318
6.1: 1332
6.2: 1326
7.1: 1310
7.2: 1306
8.1: 1307
8.2: 1300
9.1: 1317
9.2: 1312
10.1: 1306
10.2: 1300

2nd board

1.1: 1333
1.2: 1327
2.1: 1325
2.2: 1317
3.1: 1317
3.2: 1311
4.1: 1312
4.2: 1306
5.1: 1324
5.2: 1318
6.1: 1334
6.2: 1329
7.1: 1330
7.2: 1328
8.1: 1330
8.2: 1326
9.1: 1327
9.2: 1321
10.1: 1331
10.2: 1333

[retiredcaps]

Re: Philips LCD TV with Sound, No Picture (model 42PFL5322/10)

Are there any caps on the inverter board? If yes, what brand and series are they?

[retiredcaps]

Re: Philips LCD TV with Sound, No Picture (model 42PFL5322/10)

I tested all 40 secondary winding pairs, they all measure in the range of 1310-1360 Ohm.

Can you actually list all 40 readings? It matters because if 39 of them measure between 1350-1360 Ohm and 1 reads 1310 Ohm, then

1360 * 0.97 = 1319 Ohm. OR 1310 * 1.03 = 1349 Ohm.

How the 3% guideline came about by PlainBill.

https://www.badcaps.net/forum/showpo...7&postcount=18

edit: We have had cases where the measurement was off by as little as 5 Ohms to cause "2 seconds to black".

[sagie]

Re: Philips LCD TV with Sound, No Picture (model 42PFL5322/10)

c) Let's focus here first. There seems to be 10 inverter transformers on either side of the TV. You will have to measure the resistance of secondary pins for each of the 20 inverters. If there is a part number, report it.

All 20 should read within 3% of each other. If not, you have a bad inverter transformer. If you need help identifying which are the correct pins, take a clear close up picture of a couple of them (just 2 is the picture).

OK, the transformers are all 4004Qs. I tested all 40 secondary winding pairs, they all measure in the range of 1310-1360 Ohm. Went ahead and tested the 20 primary winding pairs, they all measure in the range of 1.1 - 1.6 Ohm.

I'm assuming my readings indicate the transformers are OK. Can anybody offer some more advice?

Many thanks!

[sagie]

Re: Philips LCD TV with Sound, No Picture (model 42PFL5322/10)

You can measure them "in circuit". List all your measurements for all inverter transformers.



Sometimes the flashlight trick doesn't work because of the screen, material, angle, etc. If you look in a dark room, you may have better luck?

It just takes one of the 20 inverter transformers to fail and the whole thing will shut down.

I tried to look in various lighting conditions, but I'll give the transformers a shot. Will update with my results.
Thanks!

[sagie]

Re: Philips LCD TV with Sound, No Picture (model 42PFL5322/10)

Do I have to take the transformers out of the circuit to measure the resistance, or may I measure it in-circuit?

OK, I've just read in the article you've linked I can measure it in-circuit.

Only one question remains -

I wasn't sure whether this was applicable to my situation since I can't see any picture when I shine a light on the screen. Does this makes any difference?

Thanks again!

[retiredcaps]

Re: Philips LCD TV with Sound, No Picture (model 42PFL5322/10)

Do I have to take the transformers out of the circuit to measure the resistance, or may I measure it in-circuit?

You can measure them "in circuit". List all your measurements for all inverter transformers.

I've read some similar text here at the forum, but I wasn't sure whether this was applicable to my situation since I can't see any picture when I shine a light on the screen. Does this makes any difference?

Sometimes the flashlight trick doesn't work because of the screen, material, angle, etc. If you look in a dark room, you may have better luck?

It just takes one of the 20 inverter transformers to fail and the whole thing will shut down.

[sagie]

Re: Philips LCD TV with Sound, No Picture (model 42PFL5322/10)

Many thanks for the prompt response, retiredcaps!

You will have to measure the resistance of secondary pins for each of the 20 inverters. If there is a part number, report it.

Do I have to take the transformers out of the circuit to measure the resistance, or may I measure it in-circuit?

2 seconds to black is discussed in more detail at (starting with posts #13 and #14)

https://www.badcaps.net/forum/showthread.php?t=10419

I've read some similar text here at the forum, but I wasn't sure whether this was applicable to my situation since I can't see any picture when I shine a light on the screen. Does this makes any difference?

Thanks again!

[retiredcaps]

Re: Philips LCD TV with Sound, No Picture (model 42PFL5322/10)

more c). This picture gives you an idea what the secondary pins.

http://lcdparts.net/TransformerDetai...ProductID=2749

[retiredcaps]

Re: Philips LCD TV with Sound, No Picture (model 42PFL5322/10)

I can order a replacement PSU on eBay, but I'm not sure if this is where the problem's at. From the control line behaviour I tend to believe the fault might be with the inverters.

2 seconds to black can be

a) bad caps
b) bad ccfls and/or wiring
c) bad inverter transformer

a) It looks like all Rubycon caps and Rubycon has a good reputation for reliability so we will assume they are good for now.

b) A single bad ccfl or wiring can cause the inverter circuitry to go into protection mode and shut down all the ccfls.

c) Let's focus here first. There seems to be 10 inverter transformers on either side of the TV. You will have to measure the resistance of secondary pins for each of the 20 inverters. If there is a part number, report it.

All 20 should read within 3% of each other. If not, you have a bad inverter transformer. If you need help identifying which are the correct pins, take a clear close up picture of a couple of them (just 2 is the picture).

2 seconds to black is discussed in more detail at (starting with posts #13 and #14)

https://www.badcaps.net/forum/showthread.php?t=10419