CFAG320240 Intermittent Blanking


New member
I've been using the CFAG320240 for several months now, and it runs great except for an intermittent blanking of the display accompanied (sometimes) with a lockup of the S1D controller.

The screen will go blank except for a single horizontal line just below the center of the display. The S1D controller stops responding at this point. If I tell my uC to reset and re-init the display, everything comes back and runs just fine - for a while.

When frame ground is connected to signal ground, this problem occurs every time the unit is powered up. With frame ground left open, this problem occurs maybe four or five times over the course of an 8-hour day. If at any time I touch signal ground to any part of the frame, the display will blank out as described.

All of the data and control lines are run directly from uC pins. The contrast is being run by an external pot, though this problem still occurs when the external pot is disconnected.

I've measured 5Vac between the frame and the signal ground.

The LCD is mounted to a grounded metal panel. I've tried isolating the frame from the panel with insulated mounting posts, nylon screws, and covering every metal part of the frame with electrical tape. The problem persists. This has been tested across 5 different CFAG320240 units.

Can you offer any explanations or suggestions for further diagnostics?
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CF Tech

How long and what type is the cable between the microcontroller board and the LCD?

If there is 5Vac measured between grounds, then there might be some kind of noise problem in the system.

Can you attach a photo of the setup?