Philips 37" LCD 37pfl7662d/05

[tom66]

Been eyeing this one up, has sound but no picture, panel itself is good according to seller. Is it worth me getting it? First full HD set I've ever considered repairing. Any opinions? Is there a common fault with Philips LCDs of this series?

[tom66]

Re: Philips 37" LCD 37pfl7662d/05

I am getting the TV tomorrow. I was looking on eBay and I noticed I have the exact same main board for that TV (according to several pics from ebay), except mine was ripped from a Philips 32" 720p with a broken LCD panel. I believe the board is okay but can't be 100% certain. However it will help in eliminating faults.

I doubt the board will just work on a 1080p display, but maybe it'll auto-detect it? That would be nice, although I see it as being unlikely.

I might have to reprogram the 24C64 to get it to work with a 1080p LCD, which will be fun, as it is SMD.

It might be possible to transplant the EEPROMs.

What might happen with a 720p board and a 1080p display? Will the picture be completely screwed (like no hsync) or will it just sit a small image in the corner of the display?

[PlainBill]

Re: Philips 37" LCD 37pfl7662d/05

1. Don't get ahead of yourself. The chances are the problem is NOT the main board.

2. I don't know what the result would be for using the wrong main board. The odds are it will NOT auto-detect it. On other Philips sets the display type is saved in one of the EEPROMS. There is a procedure for correcting the display type if it is incorrect; this procedure does not require anything more complex that a remote and a working brain.

PlainBill

[tom66]

Re: Philips 37" LCD 37pfl7662d/05

1. Don't get ahead of yourself. The chances are the problem is NOT the main board.

2. I don't know what the result would be for using the wrong main board. The odds are it will NOT auto-detect it. On other Philips sets the display type is saved in one of the EEPROMS. There is a procedure for correcting the display type if it is incorrect; this procedure does not require anything more complex that a remote and a working brain.

PlainBill

Great to hear. I have the Tcon too from that 32" set, but it doesn't match the eBay pictures. I hope it's just a main board, but it could be a Tcon or even an inverter problem (got an inverter too, but again might not be the right size), the seller is unclear.

[tom66]

Re: Philips 37" LCD 37pfl7662d/05

Just got it in. Plugged it in, display lit up for half a second (with "EXT1" in the corner), then switched off. Looks like 2 seconds to black, I'll test the transformers and see if any need replacing. LCD panel is intact, although a bit dirty, and the video processor itself seems to be working, so the main board may well be unnecessary.

[tom66]

Re: Philips 37" LCD 37pfl7662d/05

Bam! Transformer 3 is failed. All others measure 5.2kohm; this one is just open. I will try sourcing a replacement and see if that works.

Edit: My error, it is #4 counting from the top.

I have found a replacement on eBay.

[tom66]

Re: Philips 37" LCD 37pfl7662d/05

Okay, so I ordered the replacement transformer and removed the old one. Well it is very clearly failed; there is a black mark in one side of the secondary winding, which has also burned the PCB silkscreen. It's in the top right corner.

What causes these transformers to fail? I thought transformers were generally quite reliable.

[ipman]

Re: Philips 37" LCD 37pfl7662d/05

High tempeature or current. Or both at the same time. Isolation will melt under those conditions.

[PlainBill]

Re: Philips 37" LCD 37pfl7662d/05

Okay, so I ordered the replacement transformer and removed the old one. Well it is very clearly failed; there is a black mark in one side of the secondary winding, which has also burned the PCB silkscreen. It's in the top right corner.

What causes these transformers to fail? I thought transformers were generally quite reliable.

This particular failure is the result of poor winding technique. The problem is the ultra fine gauge wire used. When ending the winding the worker is supposed to leave a tiny bit of slack to allow for expansion and contraction. If they aren't careful, the wire will be under tension, and break from vibration or thermal contraction. Once there is a break, an arc forms.

PlainBill

[tom66]

Re: Philips 37" LCD 37pfl7662d/05

This particular failure is the result of poor winding technique. The problem is the ultra fine gauge wire used. When ending the winding the worker is supposed to leave a tiny bit of slack to allow for expansion and contraction. If they aren't careful, the wire will be under tension, and break from vibration or thermal contraction. Once there is a break, an arc forms.

PlainBill

Thanks for the explaination PlainBill, that makes a lot of sense and would explain why only one has failed. Out of curiosity is it possible to rewind these transformers? I had to pay £16 for the part, which isn't bad for a 1080p 37" (which I got for £40), but I'm a cheapskate .

[PlainBill]

Re: Philips 37" LCD 37pfl7662d/05

Thanks for the explaination PlainBill, that makes a lot of sense and would explain why only one has failed. Out of curiosity is it possible to rewind these transformers? I had to pay £16 for the part, which isn't bad for a 1080p 37" (which I got for £40), but I'm a cheapskate .

I prefer to call it 'judicious use of monetary resources'.

It's not really practical. The manufacturing process involves winding a precise number of turns on a plastic bobbin, inserting the ferrite core, then impregnating the assembly with varnish. If you have access to the proper bobbin, cores, and wires it could be done, but otherwise - no way.

If the windings are not damaged it is sometimes possible to bridge the gap with a very fine wire.

PlainBill

[tom66]

Re: Philips 37" LCD 37pfl7662d/05

I prefer to call it 'judicious use of monetary resources'.

It's not really practical. The manufacturing process involves winding a precise number of turns on a plastic bobbin, inserting the ferrite core, then impregnating the assembly with varnish. If you have access to the proper bobbin, cores, and wires it could be done, but otherwise - no way.

If the windings are not damaged it is sometimes possible to bridge the gap with a very fine wire.

PlainBill

Thanks. I've been eyeing up a faulty inverter board on fleabay (for cheap), might be worth salvaging the transformers from that for future repairs or to resell as parts. There are 10 on one board. Presumably only one is failed.

I hope the transformer is here tonight so I can try it out .

I've gotta decide if I want to swap this for my (also) trashpicked 42" 720p LCD, I mean the extra resolution would be great, but the 5" less diagonally would probably kill it. Would make for a killer computer monitor, though... just got to find the space for it... or wall mount it...

[tom66]

Re: Philips 37" LCD 37pfl7662d/05

Oh, and something interesting I noticed...

Inside the TV, there is a second T-con... well, I'm not sure you could call it that, but it's a shielded board, about half the size of the main T-con, and connects between the main board and the T-con using the LVDS cable. In fact it is labeled "1080p BOLT-ON MODULE", so I'm guessing this somehow upgrades it to 1080p, along with the higher-resolution LCD panel, but I'm not exactly sure how it does that. It also has an auxillary 4-pin connector going to the power supply, could be for extra power or maybe inverter synchronisation(?).

[PlainBill]

Re: Philips 37" LCD 37pfl7662d/05

Oh, and something interesting I noticed...

Inside the TV, there is a second T-con... well, I'm not sure you could call it that, but it's a shielded board, about half the size of the main T-con, and connects between the main board and the T-con using the LVDS cable. In fact it is labeled "1080p BOLT-ON MODULE", so I'm guessing this somehow upgrades it to 1080p, along with the higher-resolution LCD panel, but I'm not exactly sure how it does that. It also has an auxillary 4-pin connector going to the power supply, could be for extra power or maybe inverter synchronisation(?).

Information on that might be available in the service manual. If nothing else, reading the service manual is useful on the nights you can't sleep.

PlainBill

[tom66]

Re: Philips 37" LCD 37pfl7662d/05

Information on that might be available in the service manual. If nothing else, reading the service manual is useful on the nights you can't sleep.

PlainBill

No luck finding one... Searched elektrotanya and eserviceinfo. Although I might have some luck if I look for main board part numbers, or similar xxPFL7662D series LCDs. (32, 37, 42, 47...)

Edit: Spoke too soon, found one for the 42PFL7662D: http://www.eserviceinfo.com/download.php?fileid=61885

That might be close enough. Can't open it yet as I am at college (during a break period), and the computers are locked down.

[tom66]

Re: Philips 37" LCD 37pfl7662d/05

Good news. I replaced the transformer and it works perfectly now...

Well, it works... but there is one minor glitch. When first switched on, the right hand side of the display starts off dark, then flickers to life. Within 3 seconds of the left side being on, the right side is stable. I'll upload a video of this later, but does anyone know what might cause this problem?

Once powered on and the right side has stopped flickering, the picture is perfect for a long time. (I haven't tested it for longer than 10 minutes though, I'm going to leave it on for a few hours and see if it's still okay.)

I hope it's something simple, like bad capacitors, but it is full of Rubycon and Chemicon, mostly 6000 hour caps, so it would seem unlikely. Sad though, as I'm seeing newer Philips sets full of Ltec.

[tom66]

Re: Philips 37" LCD 37pfl7662d/05

Video: http://www.youtube.com/watch?v=HIAYwDKwT0Y

[Dgtech]

Re: Philips 37" LCD 37pfl7662d/05

Thats a strange one there. Me personally, I'd be happy with that but I would wonder how long would it last before it does that all the time. Sell it quick!!! LOL

[Andy56]

Re: Philips 37" LCD 37pfl7662d/05

I have the same TV with the same problem, have you fixed it yet?

[tom66]

Re: Philips 37" LCD 37pfl7662d/05

I have the same TV with the same problem, have you fixed it yet?

Yep fixed.

The problem was a failed inverter transformer, you can either replace the transformer or the whole inverter.