Troubleshoot display board

[Skwerl77]

Hi Rob,

The third display board decided to quit on me about an hour after hooking it up. 
I got it in the mail today, hooked it up, and everything looked fine. I reset some of my configurations no problem. I wanted to change the lighting setup but it told me to wait until the mode finished changing. I went back about an hour later, pressed a button, the display locked up like the other times, and wouldn't come back up (reset power).

Whether the SD card is installed or not, the display powers up but does not display anything. No static, no lines, just all black but is lit up. The LED's on the display light up, as do the LED's on the display board and Arduino. I used a new arduino with a fresh sketch installed, and a new display, so I'm pretty sure the issue is on the board. Any advice on where to start looking? 

Thanks!

[Rob F]

Hi Skwerl77, that doesn't sound good, are you sure water didn't get on it again? :) I'm sorry for this trouble, honestly I don't think I've ever had a problem with the display board, the design of that hasn't changed since I started. Those other display boards going out was a surprised even with a little salt water as there's nothing on the board to cause that however the first time you got grey bars like it was SD card related so the water could have caused that. On the other board you mentioned there was a lot of corrosion around the headers so that seemed obvious but if this was only connected for an hour I don't corrosion can build that quick. Did you put that conformal coating on this board as you were going to? The only thing I can really think of testing is the 5v pin on the Arduino, this is where the board powers up the Arduino and display, maybe it's not putting out a full 5v but that doesn't sound like the issue as you see lights on it. I don't know what could cause it, I think I'll have to send you another board.

[Skwerl77]

It is weird, like I said it did work at first. Let me check the 5v..
5.0 and 3.3 to the arduino ground..

----

Well, for grins I plugged a wall cord into the arduino (without the ethernet cord, so just the arduino, display board, and display screen), and nothing. Then I plugged it into the display board. Half the splash screen. Back into the arduino: nothing. Back into the display board: nothing. Pulled it out and then back into the display board a few times, nothing. Then about the fourth time, full splash screen. Yay! Pulled it out and back in again: nothing. Then again, full splash. Plugged into the arduino: splash screen.
So now basically it works. I have no idea what happened. In the navy we used to call that PFM: Pure F'ing Magic.

I didn't apply the coating yet, I wanted to wait until I could compare the other boards at work. I cleaned the other two out reeeeeally good, with electrowash and isopropyl, I wonder if they'll work now too? I'll let you know monday?

Thanks again!

[Rob F]

Hmm, that is strange. I put the DC power jack on the display board in case the display is located a long way from controller and the line lose in the ethernet cord is to great. You shouldn't power the display using the DC jack on Arduino though, it works but doing that the regulator on the Arduino is handling the load and will heat up as the display draws quite a bit.

I was just wondering if the coating maybe caused the DC regulator to heat up and lose it's output. With those other boards cleaned I do think they should work as most of it is traces directly to Arduino however there could be corrosion still inside the female header for display that you can't access. If it powers up the regulator works and the only other issues would be no communication to controller, no SD card working or no eeprom. The display should still turn on though and without SD card you would still see some text. I'm interested to know if they do.

[Skwerl77]

Hi Rob,

I had a few minutes during lunch to look at the display boards, I believe the problem is somehow related to the 3.3V on the board? Not very informative, I know, let me see if I can explain further..

Starting with a known good screen and arduino, swapping through the three display boards I have, one of them working (lets call that one orange, because, well, it's orange and the others are blue) intermittently.
When Orange does work, I see 5v and 3.3v on the screen (through pins 38 and 40 on the display board). When Orange or Blue1 or Blue2 don't turn on, there is not 3.3v on those pins. (Blue1 did work for a second, but had grey lines which makes me think there is ALSO an SD card issue, or at least the SD socket as I haven't been using an SD card for this troubleshooting, I'll tackle that next).

So, I can trace the screen 3.3v pin to the SDA pin on the arduino through R7 (as well as Vcc for the EEPROM IC3). Does this pin on the arduino get turned on by anything or should it always have 3.3 on it?
Is there something else that would enable/inhibit this 3.3v? Am I even barking up the right tree?

Thanks,
Jared

[Rob F]

Hey Jared, it could be power related. The display has 3.3v and 5v going to it, the 3.3v powers up the chips on display and 5v feeds the actual display. Pin 40 is a GND, pin 38 is 3.3v and pin 6 is 5v. The 3.3v comes from the Arduino as little current is required and the 5v comes from the regulator on the board. The Arduino is powered up using 5v but the Due operates at 3.3v so all the output pins including SCL and SDA have 3.3v but that's different from the 3.3v on pin 38 which should always have 3.3v, nothing switches this.

I'm a little confused how you see 5v and 3.3v through pins 38 and 40, you should only get 3.3v?

If you have 3.3v on pin 38 sometimes it could be a bad connection in the headers where Arduino or display plugs in. If you solder a wire directly to the 3.3v pin on Arduino and solder other end to pin 38 that possible issue will be gone.

[Skwerl77]

Sorry, I wrote that kind of confusingly.. I should have said, I see 5v on pin 6, and 3.3v on the screen (through pins 38 and 40 on the display board)

I went to throw a wire from the arduino 3.3v and just now saw the actual trace from 3.3v to that pin.. I got confused before! I thought the 3.3v was somehow being supplied by the SCL/SDA?? Duh.

Anyway, in doing so, I measured the 3.3v pin on the arduino just by itself: 3.3v. When attached to the board, I get about 1.5v.

When I plug in 12v to the board all by itself, with nothing else attached, on the pin labeled 5v (near C4) I measure 4.41v. On the pin right next to it labeled 3v, I measure 4.14v. On the other two boards in this same configuration (nothing else attached), I measure 5.0v and 0.0v.
I'm thinking voltage regulator? I'd dig into it further but I gotta drive home. I'll trace it out tomorrow but any guidance would be appreciated! :-)

Thanks!

[Rob F]

It sounds like the one board is definitely bad, I believe I've seen the same thing once, it baffled me and I never got a reason why/how it happened. With the board disconnected from power use the continuity meter and I bet the 5v and 3.3v pin on display board are shorted with no Arduino plugged in. When I saw that I slowly removed all the components on the board and the short remained so it was internal, I believe I even removed all the headers. Because of the pullup resistors on the 3.3v line the main 5v is being pulled down that's why the odd readings, it's not the regulator.

When you power the board with no Arduino you should get 5.0v and 0v but with Arduino mounted you should have 5.0v and 3.3v.