PanelDue 2 7" dead screen

mhackney

I have the PanelDue 2 (7") in a portable case with the CF card exposed through a slot. As I was putting it down a screwdriver on my desk inadvertently poked into the CF port and the screen went dark. The screen is dimly lit or at least if I put it in the dark it gives off an even low light (no buttons are distinguishable). If I press on areas where buttons like Home are located, the printer homes. Is this display dead or can it be repaired?

dc42

My best guess is that you shorted out the 3.3v supply on the CF card pins. Perhaps this blew the 3.3v regulator on the PanelDue controller. So I suggest you start by measuring the voltage between the 3.3V and ground test pads on the back of the PanelDue controller board.

Another check you can do it to connect a PC running YAT or Pronterface to the Duet via USB. Check that the connection is working, then send M111 S1 P3. This will cause all GCode commands to be echoed to USB as they are processed. If the Duet is receiving from PanelDue, you should see a continuous stream of "aux: M408" commands. If not, this is another indication that the 3.3V regulator may be dead, and you can repeat the test with the display disconnected from the PanelDue controller to see if the display is causing the problem.

mhackney

Thank you David.

I see 3.3v on the back of the PanelDue controller board. I then connected Duet to USB and enabled g-code logging. I see a stream of M408s

And as I mentioned, if I click on the PanelDue where, say, the home button should appear, the printer indeed homes.

So would this indicate that the PandelDue controller is likely fine and the TFT is damaged? If so, I'd actually prefer a 5" display on this machine (the E3D Tool Changer beta) so I can simply source the proper display using the part # from your blog. Does this make sense?

dc42

Yes, it's likely (but not 100% certain) that the PanelDue controller is OK and the display is faulty.

Is the display backlight lighting up at all? Does the PanelDue controller still beep if you touch the screen where there should be a button? The most common problem with these displays is that the backlight inverter chip fails. The part number of that chip is listed on the Connectors & Spare Parts wiki page.

mhackney

@dc42 When I first plug it in the backlight lights brightly and then dims. If in a dark room I can see that it is lit dimly. The controller does beep where there should be a button and sends that command to Duet properly.

dc42

There is usually a 3-position "jumper block" on the back of 7" displays labelled Backlight Control with a 0R resistor in the middle "LED_A" position. It's worth checking the voltage on that resistor. If the PanelDue controller is commanding full brightness, it should be at +3.3V. At lower brightness levels it is PWM'd so it will read lower.

mhackney

One advantage of having 10+ printers running Duet and PanelDues is that I can swap parts. I moved the PanelDue controller to a known good display and it works fine.

I checked the voltage and it is commanding +3.3V. I'll order the backlight inverter and see if I can resurrect this panel.

dc42

You could also check that you are getting 5V across the smaller of the 2 tantalum capacitors in the backlight inverter circuit, and whether either the backlight inverter chip or the larger tantalum capacitor is getting hot. The larger tantalum capacitor is the smoothing capacitor for the output from the backlight inverter.

mhackney

The smaller capacitor is reading 5V. The other and inverter don't seem to be hot. I might just by the panel and be done with it. I have more than

dc42

@mhackney said in PanelDue 2 7" dead screen:

The smaller capacitor is reading 5V. The other and inverter don't seem to be hot. I might just by the panel and be done with it. I have more than

That sounds like a good plan then.