Samsung LN37A550P3F with bad Gamma AS15 AUOPTO T-CON

[budm]

Another one of failed AUOPTO T-CON board with bad GAMMA Vref IC AS15.

[tom66]

Re: Samsung LN37A550P3F with bad Gamma AS15 AUOPTO T-CON

Did you check gamma curve or just replace IC? You can try the spreadsheet I made which helps determine bad gamma IC for sure.

https://www.badcaps.net/forum/showthread.php?t=35301

[budm]

Re: Samsung LN37A550P3F with bad Gamma AS15 AUOPTO T-CON

I already installed the new IC, the TV is already donated today. I will keep that spreadheet in the future, but so far all the AUOPTO T-CON that I have replaced the AS15 solved the problem, I did 5 so far, need to get more IC.

[tom66]

Re: Samsung LN37A550P3F with bad Gamma AS15 AUOPTO T-CON

It seems to be a common fault, you can almost always see it from the picture. The nearest was one which just had overly contrasted image, I believe same Samsung model but Taiwanese, which is also where AUO panels are from.

I'm a data hoarder, I like numbers and certainty. Unfortunately haven't had a single bad gamma IC myself yet.

[tibimakai]

Re: Samsung LN37A550P3F with bad Gamma AS15 AUOPTO T-CON

Last two weeks, I have done the same thing on the same TV, and a 46A630(AS15G).
I have the same TV now, but it needs a new mainboard.

[marcmum]

Re: Samsung LN37A550P3F with bad Gamma AS15 AUOPTO T-CON

I have this exact same model with the T-CON Gamma IC problem (screen too bright/white). My question is how do I get access to the T-CON board? I've removed the 5 screws holding the metal cover and it's loose, but it won't come free. It looks like the T-CON board is moving with the cover. I didn't want to force it too much for fear of doing any damage to the two connectors on the other end of the board. Can someone tell what I'm doing wrong?
I was hoping to take some voltage measurements to confirm the bad Gamma IC (I downloaded the spreadsheet) before sending it off to get repaired.
Thanks.

[tom66]

Re: Samsung LN37A550P3F with bad Gamma AS15 AUOPTO T-CON

There's sometimes a thermal pad which is lightly glued to the case. You just need to lever it slightly, maybe best to remove board completely from set.

[mmartell]

Re: Samsung LN37A550P3F with bad Gamma AS15 AUOPTO T-CON

Try rotating it back and forth in a cirxular motion that should break the seal.

[Dang]

Re: Samsung LN37A550P3F with bad Gamma AS15 AUOPTO T-CON

The above works, seat the whole thing properly, there's sometimes some lugs to hold the T-con in place, gently hold it down where the LVDS cable enters and twist clockwise then anticlockwise, after a few turns it should come free, just make sure the T-con board can't move, a little bit of heat from a hair dryer can help here.

[marcmum]

Re: Samsung LN37A550P3F with bad Gamma AS15 AUOPTO T-CON

Thanks for all the suggestions. I used a small screwdriver and a little force and the cover popped free. It took a little more dis-assembly to remove the cover, but I eventually got it out. I took the VGMA voltage measurements and tried the above spreadsheet. I think the gamma IC is bad, but a number of the cells in the spreadsheet didn't translate over when using Microsoft Excel.
One more question on removing the T-CON board, how do the two ribbon cables that go to the screen connect to the board? Do they push in from the side or the top of the board? It wasn't obvious to me and I don't want to do any damage when disconnecting.
Thanks.

[tom66]

Re: Samsung LN37A550P3F with bad Gamma AS15 AUOPTO T-CON

Can you try posting your listing of voltages? I developed the spreadsheet in OO.org Calc so have not been able to fully test it in Excel.

[budm]

Re: Samsung LN37A550P3F with bad Gamma AS15 AUOPTO T-CON

@marcmum:"One more question on removing the T-CON board, how do the two ribbon cables that go to the screen connect to the board? Do they push in from the side or the top of the board? It wasn't obvious to me and I don't want to do any damage when disconnecting." The brown plastic bar flips up to release the cable, see picture #6 you can see the right one is flipped up. One thing is that it not very easy inserting those two flat cables back in place.

[marcmum]

Re: Samsung LN37A550P3F with bad Gamma AS15 AUOPTO T-CON

Here are my T-CON Voltage Measurements:
VGMA1: 15.4
VGMA2: 15.33
VGMA3: 15.18
VGMA4: 12.34
VGMA5: 11.54
VGMA6: 10.59
VGMA7: 10.05
VGMA8: 9.79
VGMA9: 8.27
VGMA10: 7.92
VGMA11: 7.88
VGMA12: 0.206
VGMA13: 0.206
VGMA14: 0.206
VGMA15: 0.214
VGMA16: 0.224
VGMA17: 0.244
VGMA18: 0.251
VGMA19: 0.257
VGMA20: 0.291
VGMA21: 0.292
VGMA22: 0.297
VCOM: 6.37
AVDD: 15.61
VGH: 17.3 mV AC (out of limits on DC)
VGL: 16.2 mV AC (out of limits on DC)

[tom66]

Re: Samsung LN37A550P3F with bad Gamma AS15 AUOPTO T-CON

I've never seen half of the readings at near zero, wow. Double check those last readings but if so, the gamma IC is definitely bad.

For VGH/VGL, generally not an issue on these, but you might have to use next highest DC range.

[splitcrete]

Re: Samsung LN37A550P3F with bad Gamma AS15 AUOPTO T-CON

What are the readings supposed to be for 12-22 my meter is on auto and I'm getting almost the same readings.

[tom66]

Re: Samsung LN37A550P3F with bad Gamma AS15 AUOPTO T-CON

Either slow increase our decrease. But it has to be consistent. Ie only increasing or only decreasing.

[splitcrete]

Re: Samsung LN37A550P3F with bad Gamma AS15 AUOPTO T-CON

I soldered a new as15-f in this morning . Do you think I missed a pin or two . Should I have another go at it ? That is only the second chip I have ever changed.

[splitcrete]

Re: Samsung LN37A550P3F with bad Gamma AS15 AUOPTO T-CON

Pin one was 15.09 and slowly went down till it got to pin 13 and it dropped to 2.336 and went down from there a little at a time pin 22 000.1

[tom66]

Re: Samsung LN37A550P3F with bad Gamma AS15 AUOPTO T-CON

The full readings would help.
Soldering looks OK.
Tibimaki replaced IC, and found new IC to be bad. So do not rule out chance you got a bad IC.

[splitcrete]

Re: Samsung LN37A550P3F with bad Gamma AS15 AUOPTO T-CON

Sorry pin 22 was 1.244