OK, so I've come back to this to try to solve the problem, after a bit of a break. No luck yet, but I've got some more information.
I cut the ribbon cable to the TFT shorter, so it's now about 15cm long. Result is that there is no more corruption / garbling of the display, so that's fixed. Except for the hot regulator issue below, the system seems to be working perfectly.
However, the hot linear voltage regulator problem remains. I've tried with a 20x4 LCD as an alternative to the TFT to get more information to try to diagnose the problem.
Results:
TFT backlight on: Pro2+ reg hot, Meduino reg hot
TFT backlight off: Pro2+ reg slightly warm, Meduino reg hot
TFT cable disconnected: Pro2+ reg slightly warm, Meduino reg slightly warm
20x4 LCD backlight on: Pro2+ reg slightly warm, Meduino reg hot
20x4 LCD backlight off: Pro2+ reg slightly warm, Meduino reg slightly warm
In all cases when the backlight is switched from on to off, the regulator cools down rapidly from hot to warm, within about 5 seconds.
I thought the heat issue could be related to the RTC battery charging / drawing too much current due to being faulty. So I unplugged the RTC board from the main Pro2+ board, but still both regs hot when the TFT is connected with backlight on.
Reading around on the web, hot to touch probably means it's in the range of 60-70 degrees celsius. I suppose that putting my finger on the regulator for a few seconds might contribute to the higher temperature by stopping convection.
Do the above results tell us anything? Are you 100% sure that the regulators on your boards are not hot to the touch when the backlights on the TFT and LCD are on?
I cut the ribbon cable to the TFT shorter, so it's now about 15cm long. Result is that there is no more corruption / garbling of the display, so that's fixed. Except for the hot regulator issue below, the system seems to be working perfectly.
However, the hot linear voltage regulator problem remains. I've tried with a 20x4 LCD as an alternative to the TFT to get more information to try to diagnose the problem.
Results:
TFT backlight on: Pro2+ reg hot, Meduino reg hot
TFT backlight off: Pro2+ reg slightly warm, Meduino reg hot
TFT cable disconnected: Pro2+ reg slightly warm, Meduino reg slightly warm
20x4 LCD backlight on: Pro2+ reg slightly warm, Meduino reg hot
20x4 LCD backlight off: Pro2+ reg slightly warm, Meduino reg slightly warm
In all cases when the backlight is switched from on to off, the regulator cools down rapidly from hot to warm, within about 5 seconds.
I thought the heat issue could be related to the RTC battery charging / drawing too much current due to being faulty. So I unplugged the RTC board from the main Pro2+ board, but still both regs hot when the TFT is connected with backlight on.
Reading around on the web, hot to touch probably means it's in the range of 60-70 degrees celsius. I suppose that putting my finger on the regulator for a few seconds might contribute to the higher temperature by stopping convection.
Do the above results tell us anything? Are you 100% sure that the regulators on your boards are not hot to the touch when the backlights on the TFT and LCD are on?