Background:
This TV has a weird fault where there is signal corruption on all the HDMI inputs, when running at 1080p 60Hz (which is a supported mode). I've tried many different cables and even different sources, with no difference. Running at lower resolution or refresh rate there is no problem at all.
The corruption presents itself as the signal occasionally going black, sometimes going all blocky, but sometimes is very subtle and presents itself as stray pixels flashing randomly on the image.
As the mainboard warms up, the corruption becomes less and less. If I hit the mainboard with a heat gun and get it to a nice toasty 70C, the problem eventually completely disappears (only to start progressively coming back as the board cools off). The cooler the board, the worst the problem becomes. In particular, the greatest effect seems to come when heating/cooling the main processor (IC8001).
Initial Troubleshooting:
All power supply voltages and on-board regulators checked to proper voltage and for the presence of any ripple. Nothing abnormal found.
All electrolytics on mainboard tested for capacitance and ESR, all checked out ok.
Replaced IC4503 (HDMI switch), absolutely no difference.
Basically I'm out of ideas what else to try, other than replacing IC8001 (Toshiba TC90413XBG) but this being a 456 pin BGA I don't like my chances.
The Hunt for a Replacement Board:
This TV uses board part number TNPH0786, suffix AM. I can't find this board anywhere at all. There are a lots of other TVs that used the same board but with a different suffix, they appear from pictures to be the same board hardware-wise.
Am I correct in my assumption that the difference between the different board suffixes would be the firmware configuration, since the hardware appears to be the same?
What are the potential pitfalls of dropping in a board from a TV of smaller size but same resolution? Could this potentially work?
As a last resort, could I swap the EEPROM chips over to the replacement board so it has the correct firmware?
Anyone even run into something like this before?
This TV has a weird fault where there is signal corruption on all the HDMI inputs, when running at 1080p 60Hz (which is a supported mode). I've tried many different cables and even different sources, with no difference. Running at lower resolution or refresh rate there is no problem at all.
The corruption presents itself as the signal occasionally going black, sometimes going all blocky, but sometimes is very subtle and presents itself as stray pixels flashing randomly on the image.
As the mainboard warms up, the corruption becomes less and less. If I hit the mainboard with a heat gun and get it to a nice toasty 70C, the problem eventually completely disappears (only to start progressively coming back as the board cools off). The cooler the board, the worst the problem becomes. In particular, the greatest effect seems to come when heating/cooling the main processor (IC8001).
Initial Troubleshooting:
All power supply voltages and on-board regulators checked to proper voltage and for the presence of any ripple. Nothing abnormal found.
All electrolytics on mainboard tested for capacitance and ESR, all checked out ok.
Replaced IC4503 (HDMI switch), absolutely no difference.
Basically I'm out of ideas what else to try, other than replacing IC8001 (Toshiba TC90413XBG) but this being a 456 pin BGA I don't like my chances.
The Hunt for a Replacement Board:
This TV uses board part number TNPH0786, suffix AM. I can't find this board anywhere at all. There are a lots of other TVs that used the same board but with a different suffix, they appear from pictures to be the same board hardware-wise.
Am I correct in my assumption that the difference between the different board suffixes would be the firmware configuration, since the hardware appears to be the same?
What are the potential pitfalls of dropping in a board from a TV of smaller size but same resolution? Could this potentially work?
As a last resort, could I swap the EEPROM chips over to the replacement board so it has the correct firmware?
Anyone even run into something like this before?
Comment