Samsung LE37B650T2P bright screen issue

[mycroes]

Hi board,

I have a Samsung LE37B650T2P showing everything very bright (but it does seem to show everything). The TV has the following T-CON: T370HW02 VE (37T04-C0J).

I measured the VG* points and got the following results:

VG1: 17.17-17.18V
VG2: 17.06V
VG4: 14.43V
VG6: 12.37V
VG8: 11.49V
VG10: 8.74V
VG11: 8.59V
VG12: 0.34V
VG13: 0.36V
VG15: 0.36V
VG17: 0.34V
VG19: 0.32V
VG21: 0.33V
VG22: 0.32V

Is this a clear failure of the AS15-HF? Or should I perform some other checks before getting the AS15-HF replaced?

I'm not able to do the replacement myself, but someone in the family is willing to try it. However that takes some scheduling, so if I could check more to be sure that it's the AF15, that'd be great. Also this is my first ever TV repair (or diagnosis), so any help is greatly appreciated!

Regards,

Michael

[ReeceyBurger123]

Re: Samsung LE37B650T2P bright screen issue

Hmm I have had an issue like this on a le32r88bd where there was a failed voltage regulator have you checked all of them ?

[mycroes]

Re: Samsung LE37B650T2P bright screen issue

No I only checked the VG's listed above. Honestly I had to search for a picture of a voltage regulator to know what I should be looking for (but it's no unfamiliar sight, luckily). Should I only be checking the voltage regulators on the T-CON?

Also one detail I forgot to mention; if I leave the TV on, then after a while (say 10 minutes) it will show normal picture for like half a second, sometimes it will blink between normal and bright for a bit and then go back to bright for a while again, but every now and then there will be slight moments of normal picture.

[CapLeaker]

Re: Samsung LE37B650T2P bright screen issue

here is a spread sheet that tom66 made to determent a bad AS-15
https://www.badcaps.net/forum/showthread.php?t=35301
your AS-15 looks bad.

[budm]

Re: Samsung LE37B650T2P bright screen issue

Bad AS15, just another failed AUOPTO T-CON board.

[ReeceyBurger123]

Re: Samsung LE37B650T2P bright screen issue

Ahh yes I misread that, my bets then on bad AS15 ic.

[mycroes]

Re: Samsung LE37B650T2P bright screen issue

Thanks a lot guys, will order replacements and see if I can get it fixed.
Regards,

Michael

[mycroes]

Re: Samsung LE37B650T2P bright screen issue

I'm at two failed attempts now. First my uncle tried to replace the AS15, but he destroyed one of the leads on the board and didn't bother to try to put the replacement AS15 on. So I ordered a replacement T-con board. I actually ordered one which was from some 46 " TV (didn't pay any atention to anything but the 'T370HW02 VE 37T04-C0J'), however it never reached me, so when the seller was going to send me another board he actually referred to the 55.37T04.C34 which I had, so supposedly that's what I have now (but the serial number label is missing).

However, with this new T-con board even the backlight doesn't turn on. The power led blinks red, about once per second. Is this a defective T-con board?
Regards,

Michael

[mycroes]

Re: Samsung LE37B650T2P bright screen issue

Also, with the replacement T-con board there's no startup sound, which is there with the old T-con board and without T-con board.

[saddle_au]

Re: Samsung LE37B650T2P bright screen issue

Only one or more leads broken on the TCON board from the AS15 means the TCON can be salvaged. You are probably talking about something like a pad lifted with the chip when it came off.

Lift the leg of the chip where the missing pad was, up to horizontal before soldering the AS15 back on, Test all other pads first for shorts then solder a wirewrap wire from the first cap/res/via the line used to go to, then solder the other end to the raised leg.

I've did this about 4 times before I figured out a bulk solder, cut pin removal method and later Chip Quik. Chip Quik works great except when the part has a bottom pad soldered to the board.

[mycroes]

Re: Samsung LE37B650T2P bright screen issue

Thanks for the advice saddle_au. A colleague offered to solder the replacement chip, and I was quite impressed with what I saw when he was done. He also said that the lead that was missing was not connected to anything, which was probably the reason it came off in the first place. He mentioned he did the replacement with a hot air gun (for paint removal?) and

So far so good, however when I put the board back in it was not entirely what I hoped for. The colours where really dark and there seemed to be too much red. I have exactly the same TV (exact same model number) in the living room, so I good do a reasonable comparison. Since this was going to be the bedroom TV it didn't have to be perfect, so it was good enough.

Soon I noticed that there was some distortion horizontally. It's not so easy to explain, but the photos clearly show that where horizontal lines are these 'wear out' horizontally over the entire width of the screen. Also, there was some ghosting, which is not really noticeable during moving scenes, but for instance when I would exit a movie to a menu it would be very visible. I captured it in the photos as well, it stays around for a while, after 10s or so it's still very visible (as in the picture).

However, now a short while later (have been using the TV for less than a week, think it has been turned on for about 3.5 hours) the brightness starts appearing again. After having the TV turned on for 10 minutes or so, the screen starts 'blinking' with extreme bright image (the issue it all started with anyway). This goes from low frequency bright blinking to full bright a few minutes later (without returning to normal picture).

So I'm now wondering if it's even worth the effort to do another AS15 replacement (I actually bought 2 AS15's, so at least that part is covered) or if there's something else I should be looking at. I didn't measure the voltages on the AS15 test leads yet. Is a bad AS15 also an explanation for the horizontal distortions that can be seen in the pictures?

I've put some pictures up on Google Photos: https://photos.google.com/album/AF1Q...rJT4xlQ9NcUYmI.

I'm very happy with all the support I've already gotten here, I hope you guys have yet some more answers to the questions here...
Regards,

Michael

[ReeceyBurger123]

Re: Samsung LE37B650T2P bright screen issue

I would say put another AS15 on, your mate cant solder thats for sure you DO NOT use hot air to solder such an Ic you need an iron. Try and find someone who can properly replace it if not try a new Tcon.

[mycroes]

Re: Samsung LE37B650T2P bright screen issue

Hi ReeceyBurger,

Thanks for your advice. I understand what you're saying, though I do believe my colleague has some soldering capabilities (from memory it was also looking way better when it was just soldered, seems like something's gotten out from underneath the chip and onto the leads). From what I understood he used a hot air gun and flux because of the heating pad on the backside of the chip. He had used this technique before to solder an Arduino print. I don't want to defend my colleague for how he did this, but this was his explanation of the how and why as far as I remember it.

Can you point me to a guide on the process of soldering a chip like this? I know there's a subforum for equipment and soldering, but unfortunately there's not a lot of stickies there (should I post this a separate thread in there?). From what I understand you also can't use an SMD hot air rework station for this?

Also, the removal of the original chip was done with a Dremel cutting tool, do you have any advice on removing this chip?

Again, thanks a lot for the help!
Regards,

Michael

[michael dranfield]

Re: Samsung LE37B650T2P bright screen issue

To remove the chip with hot air you first need to pre heat the board to around 120-130 degrees c then use the hot air and the chip will come off in a couple of seconds, it sounds to me like you chip does not have all the pins soldered correctly or you have not used a "no clean flux" and you need hot air to replace the chip as the ground plane and heatsink is underneath the chip where it cant be soldered with an iron.
I find the easy way to diagnose a failed gamma IC it to run the set for 5 mins, if the chip is hot its faulty , they should not get hot after only 5 mins.