Grundig 48 VLX 8582 BP, Possible T-CON issue?

[Gjackson]

Hi all, I have a 48" LED Grundig with video artifacts (see images), half of the screen is black while the other is filled with lines. I tried to disconnect half of the display from the T-CON and turn it on and vice versa but both times resulted in a fully black screen with only the backlight on. To me this does not seem like a problem with one half of the LCD screen. Could this be a T-CON fault, the weird thing about this tv is that it has an extra board (circled in red, see pics) in between the MAIN board and the T-CON, could this be bad too?

[Diah]

Re: Grundig 48 VLX 8582 BP, Possible T-CON issue?

this board are PFG scale for UHD, later on they put this circuit on main boards together. so i don't think its fault.
did you have sound? and when you play signal from HDMI did the white half screen changed color or lines..?

i would do first downgrade firmware... as this process will pass any fault at PFG when it display the upgrade screen-

this is the service manual for yours TV chassis KP.

[Gjackson]

Re: Grundig 48 VLX 8582 BP, Possible T-CON issue?

When plugging in HDMI, the only response I saw was the backlight getting brighter, no change in the actual LCD. I wasn't able to get audio to work however that's probably because I am on a bad source, as for downgrading firmware, How do I go about that? I can't access the correct menu since I can't see anything on screen. The Tv does show signs of life, the backlight brightness changes upon pressing certain keys on the remote so there is definitely activity. The heatsink on the PFG board does get pretty warm, more than the cpu on the main board, not sure if that's normal.

[Diah]

Re: Grundig 48 VLX 8582 BP, Possible T-CON issue?

first you need to be sure you have sound via HDMI signal with RC one by one step down by source.
about downgrade.. after you download the firmware and extract the rar file you will have folder in name Target_KP if it was Target_KR rename it to Target_KP ( KP & KR use same firmware ) copy the folder on USB formated with fat32. while the TV turnoff from the wall insert the USB to any USB Port on the side of the TV. on joustic behind the tv press the middle straigt not for up or down.. keep pressing while you plug the TV in wall.. the front LED Indicator will blink 5-6 time then release your finger.

[Gjackson]

Re: Grundig 48 VLX 8582 BP, Possible T-CON issue?

I'm going to try the firmware downgrade soon, before that I took some random measurements on the T-CON test points:

0.972 Hvin_12v
11.7 vin_12v
0.565 vcln
0.942 FB_RD
0.939 VRD
-7.58 Voff
0.008 Von_o
1.77 Sfc1
0.052 Avddb
0.038 havddb
1.8 Vcca_1.8
1.8 Vccb_1.8
3.3 Cs
1.88 Sck
0.533 vcs3
0.533 vcs4
3.3 Vcs2

The Test points marked in red in the picture I attached all show either roughly 0.56-0.58 volts or 0v. Most of them are 0.56v.

The main fuse is good as there is 11.7v present there.

I couldn't locate the Usual VGH and VGL on this board.

[Gjackson]

Re: Grundig 48 VLX 8582 BP, Possible T-CON issue?

I did the firmware downgrade, it blinks for a couple of minutes after I power on while holding and then stops, I'm assuming it completed successfully. There is no change in the state of the display.

[dskall]

Re: Grundig 48 VLX 8582 BP, Possible T-CON issue?

I'm going to try the firmware downgrade soon, before that I took some random measurements on the T-CON test points:

0.972 Hvin_12v
11.7 vin_12v
0.565 vcln
0.942 FB_RD
0.939 VRD
-7.58 Voff
0.008 Von_o
1.77 Sfc1
0.052 Avddb
0.038 havddb
1.8 Vcca_1.8
1.8 Vccb_1.8
3.3 Cs
1.88 Sck
0.533 vcs3
0.533 vcs4
3.3 Vcs2

The Test points marked in red in the picture I attached all show either roughly 0.56-0.58 volts or 0v. Most of them are 0.56v.

The main fuse is good as there is 11.7v present there.

I couldn't locate the Usual VGH and VGL on this board.

So you are missing voltages. Voff and Von are VGL and VGH

[Gjackson]

Re: Grundig 48 VLX 8582 BP, Possible T-CON issue?

Missing voltages are indicative of a bad DC-DC converter on the T-CON?

[dskall]

Re: Grundig 48 VLX 8582 BP, Possible T-CON issue?

Yes, or short on one of the power rails. I would check pads with missing voltages for shorts.

[Diah]

Re: Grundig 48 VLX 8582 BP, Possible T-CON issue?

I did the firmware downgrade, it blinks for a couple of minutes after I power on while holding and then stops, I'm assuming it completed successfully. There is no change in the state of the display.

OK. next step you need to take out the bezel round the screen and inspect all around the panel glass if there unusual visible matter

[Gjackson]

Re: Grundig 48 VLX 8582 BP, Possible T-CON issue?

before I take out the bezel (because that sounds like a pain) I tried checking for shorts on the T-CON and here is what I found:

keep in mind this is with all LVDS and LCD cables disconnected from it.

1. AVDDB test point has 2ohm short to GND
2. PORT(?) test point has 0ohm short to GND
3. VCC_1.1v test point 255ohm to GND but that is probably normal

I'm not sure if the PORT test point is actually called PORT, I'll send a photo of it.

I turned the board over and started to test at random all the capacitors on the back and I found 3 caps that were shorted along with 2 others on the front side of the board, after tracing the tracks from the capacitors I found that all of them were connected to ICD3, after probing the AVDDB test point and the pin on the IC which connects to the capacitors I find a 0 ohm connection. To me it seems like either the IC or one of the caps went bad and is shorting AVDDB to GND or am I being stupid ? What is the voltage on AVDDB supposed to be? You can see 4 vias that go directly from the shorted cap to the pin on the IC in the photos I sent and I marked the shorted caps with black marker.

I'm not too good at SMD repair but I'm willing to try taking the chip out to see if the short goes away or I could try voltage injection, Also what is the weird 3 pin component next to the coil in the top capacitor picture?

Thanks for the help!

[dskall]

Re: Grundig 48 VLX 8582 BP, Possible T-CON issue?

I believe AVDD should be about 15v. Those ceramic caps are the usual suspects for shorts.

[Gjackson]

Re: Grundig 48 VLX 8582 BP, Possible T-CON issue?

Awesome news! Removed the 5 caps one by one and found one that was shorted, I'll try plugging the tv back in in a couple of mins and let you know if it works fingers crossed

[Gjackson]

Re: Grundig 48 VLX 8582 BP, Possible T-CON issue?

So.. Good and bad news, We have an image now! but a weird haze still fades in after a while of operation, after closing out of a menu the text that was previously on screen takes a while to go away and fades out slowly, it fades on only one part of the screen, on the side which before repair had lines. might be because of the now missing cap since I didn't replace it I just removed it.. doesn't make much sense why it would be on one side only but we have progress at least

[Gjackson]

Re: Grundig 48 VLX 8582 BP, Possible T-CON issue?

Hmm, removing the other caps which were previously suspected did help a bit even tough I tested them and they have very high resistance across them, but it is still very visible, I'll try to find a replacement capacitor for the one that was dead, it seems to have been a 10uf cap judging by the cap that was next to it.

[Gjackson]

Re: Grundig 48 VLX 8582 BP, Possible T-CON issue?

I replaced the bad cap and no change After rechecking the board the only irregularity I found was VCC_1.2v being 0.987v, no idea what could cause this as my meter says that it isn't shorted to gnd. PORT is still shorted to Gnd not sure if that's normal however I didn't find any more shorted caps. Both VRD and FB_RD test points are at approx 10v which seems good

[nomoresonys]

Re: Grundig 48 VLX 8582 BP, Possible T-CON issue?

so you have all the caps back in place? maybe recheck your work.

[Gjackson]

Re: Grundig 48 VLX 8582 BP, Possible T-CON issue?

Yeah everything is back in place and looks like they're all connected well

[nomoresonys]

Re: Grundig 48 VLX 8582 BP, Possible T-CON issue?

good that you fixed the shorted cap, could still have a tcon issue, I would try a replacement, might be able to fix at component level but in a lot of cases a replacement tcon is cheaper than buying the component/s plus shipping, plus headache of putting them in without messing something else up.

[dskall]

Re: Grundig 48 VLX 8582 BP, Possible T-CON issue?

VCC_1.2v being low could cause a problem. Maybe just bad regulator.