Driving a Sharp TCON/panel with a universal main board

[advant]

This thread is about trying to get an Universal Main Board to work with a Sharp TCON and panel.

I have a Sharp LC-46D85UN TV that has had a main board issue. Since this model is from 2009, I am not able to find an exact replacement of the main board. Instead, I decided to see if I can future proof this tv by getting a Universal Main Board (T53U21.2) from China to work with the Sharp TCON (CPWBX4291TPZA) and panel. The universal main board supports a 8 bit dual channel LVDS interface whereas the TCON requires a 10 bit dual channel LVDS input. I have modded the LVDS connector to match 8 bits of LVDS data exactly to the TCON pinout and left the remaining 2 bits floating. I believe this is okay as this should only a cause a minor color issue in my opinion especially with the JEIDA LVDS standard that Sharp TCONs typically use. In this case it is the LSB's that get missed and not the MSBs if the 5th bit from each channel is not connected.

I have been able to test and program the universal main board by connecting it to an LCD panel that I removed from a laptop. The board works fine in this case. The board itself can be configured to support a 6 bit, 8 bit or 10 bit LVDS interface through the software (although it's pinout does not allow 10 bits)

I get no picture when I connect the universal main board to the Sharp TCON/Panel. I have been able to work around the backlight issue by driving the inverter board of this TV from a backlight enable signal of this main board. So the backlight is up and running correctly. But no picture whatsover.

Thinking that the TCON board may have an issue, I ordered a second TCON board from Ebay and tried it with the universal main board. Same result-- no picture. I don't believe both TCON's have the same issue. So it is clearly something that the Sharp main board would have output that I am missing with the universal main board.

On the Sharp TCON, there is a 15 pin LP connector that is connected to the main board. This has the following signals.

Pin # 15 : DET (output from TCON)
Pin # 14 : LCD_EN (input to TCON)
Pin # 13: VCOM_SDA (bidi to TCON)
Pin # 12: VCOM_SCL (bidi to TCON)
Pin # 11: VCOM_WP (input to TCON)
Pin # 10: COND_DET (output from TCON)
Pin # 9: TEST_MODE (input from TCON)

The rest of the signals are not connected.

Does anybody know the function of the signals LCD_EN, VCOM_SDA, VCOM_SCL and VCOM_WP? I suspect I am missing some kind of an I2C command to get the TCON working. All analog voltages (3.3 V supply, VCOM etc) all check out okay in the TCON. Like I said earlier, I don't suspect a TCON issue as two TCONs are showing the same no picture symptom.

How do I kick start the TCON board to start receiving the LVDS signals? Can somebody please who has a Sharp TV respond back if the TV powers up and works normally with a disconnected LP connector? If the LP connector needs to be connected to get a normal picture, I am probably missing some commands from the main board. If I knew what they are, I can possibly try to reproduce the signals using an Arduino based I2C interface.

I have been under the impression that the LP connector above is needed only for VCOM gamma programming.

Appreciate any pointers on what the issue is. Also, does anybody know how to get the TCON to produce a test pattern without any inputs from the main board? Do the Sharp TCONs have such a feature?

[advant]

Re: Driving a Sharp TCON/panel with a universal main board

To add to the above, I am also looking for some basic tests that might confirm that the panel is good. I only have back light currently. There is no difference if I disconnect the ribbon cables from the TCON to the panel. I can never see any pixel turn on. Should one half of the panel display white when the ribbon cable for that half is disconnected? I am not seeing that. Could it be that the panel is the culprit?

[moltensolderlabs]

Re: Driving a Sharp TCON/panel with a universal main board

Hi. This might be late, and you probably have a new TV by now, but my Sharp LC-52E77UN is on its last legs, motherboard wise--it gets a communication error randomly and shuts off and the OPC and power LEDs start blinking.

I am also planning on getting a V29 universal LCD board wired to the LCD, because I am for sure not paying $200+ for a replacement motherboard when you can get a new 50" LCD TV for $250 these days...

I probed the the LP connector with continuity mode, and found that TEST_MODE and COND_DET pins unpopulated and unused.

According to my research, if the vcom signal is not present, nothing will display on screen. See the following:

https://www.microchip.com/forums/m542278.aspx
https://gist.github.com/mozbugbox/2f...377c367fb61098
https://cdn.badcaps-static.com/pdfs/...fbdd095014.pdf

[moltensolderlabs]

Re: Driving a Sharp TCON/panel with a universal main board

I ordered the v29 board, which I expect should arrive in a month from China. And I also ordered a 24MHz USB logic analyzer from Amazon, which should arrive in a week--I will use this to decipher the i2c signals that must be present to activate the TCON board. I will be using Sigrok Pulseview.

My hope is that I can use an Arduino (Attiny85) to play back the same waveform to activate the board. I'll keep this thread updated if I succeed in deciphering the i2c commands.

[vverve]

Re: Driving a Sharp TCON/panel with a universal main board

That's an interesting project!!
Could it revived an lc-52e77un that was on its way to RIP(rest in parts..) ?

[vverve]

Re: Driving a Sharp TCON/panel with a universal main board

https://www.panelook.com/modelcompare.php?ids=9308,9307
If ever,found this looking for sharp panels info.