There are a few reasons you might not be able to read the main LCD screen on a Mastermind LT. The first possibility is that it needs its contrast adjusted. The LCD screen is sensitive to changes in temperature, and also changes as it ages, which can result in the screen being to light or too dark. To fix this, the Mastermind has the ability to adjust the LCD's contrast from its built in setup menu

To adjust contrast:

1). Hold the 1 and 3 buttons until you get to the setup screen (hold for about 3 seconds). If you can't read the main screen, you'll know you're in setup because the LEDs over each button will change colors.
2). Then, press the 1 / Down Arrow button repeatedly until you get to the Contrast item. If you can't read the screen, you'll know that you're there when the LED over the 1 / Down Arrow button turns off. The Contrast item is the last item in the list, and will take 20 or more button presses to get there.
3). Now, if the display is too light, press the Bank Down / Val + button repeatedly and see if the screen becomes visible. It could take 20-30 presses. If it's too dark, where the whole screen is black, press 3 / Val - repeatedly instead.
4). If that doesn't work, then a screen replacement is probably needed. You can buy a replacement screen here:

This page includes a video showing the replacement process. No soldering is required, but it does involve a lot of disassembly and reassembly.

If you don't want to do the work yourself, please contact us at, and we can set up an RMA and get it repaired. We also have a few international repair centers that we can recommend.