Lelit Bianca: Testing the CPU (LCC not turning on)

If your Lelit Bianca is powering on, but the LCC display is dark, these instructions will help you determine if the LCC or the CPU needs to be replaced.

Tools Needed:
- Phillips screwdriver
- Multimeter

NOTE: Use caution when working with live voltage. If you have limited or no experience with 120V AC electrical systems, consider having your machine evaluated by a qualified technician.

1. Start by removing the panels from the machine.

2. Plug the machine in and power it on. The machine's power indicator ring will be illuminated and the LCC display will be dark.


3. Identify the ribbon cable attached to the back of the LCC display. Make sure that it's plugged in securely and then check the LCC display.  Sometimes this condition is caused by a loose ribbon cable. If the LCC display remains off, continue to the next steps.


4. Unplug the ribbon cable from the back of the LCC display. The next steps will involve testing the LCC display's low voltage circuit.


5. Set your multimeter to read Volts DC in the 20V range. Insert one multimeter probe into the ribbon cable's red wire port. Ground the other multimeter probe out on a bare metal part of the machine's frame as shown. The power being supplied to the LCC should read ~3V DC.


6. Plug the ribbon cable back into the rear of the LCC display.

7. Trace the ribbon cable back to where it plugs into the machine's CPU. This time leave the ribbon cable in place.


8. Set your multimeter to read Volts DC in the 20V range. Without unplugging the ribbon cable, backprobe the ribbon cable's red wire port as shown. Ground the other multimeter probe out on a bare metal part of the machine's frame again. The power exiting the CPU here should read ~3V DC. 


If both tests above indicate that the CPU is delivering ~3V DC to the machine's LCC display, but the LCC display remains blank, that's a good indication that the LCC display is faulty and will need to be replaced. You can stop here.

If those tests do not show ~3V DC at either end of the red wire on the ribbon cable, the next steps will require testing the machine's high voltage circuit to verify that the CPU is receiving power. 

9. Now power the machine off temporarily.

10. Identify the single Phillip's head screw holding the machine's CPU in place, then remove it.


11. With the CPU free, identify the main power wire attached to the back of the CPU, then unplug it.



12. Insert the red probe into the CPU power wire connector as shown. Make sure that the probe is securely in place and touching metal on metal inside the connector.


13. Power the machine back on. The machine's power indicator ring should be illuminated, while the LCC display is still dark. The next steps will involve testing the machine's high voltage circuit.

14. Set your multimeter to read Volts AC in the 200V range. The red probe should already be plugged into the CPU power wire. Then ground the other multimeter probe out on a bare metal part of the machine's frame again. The power on that wire should read ~120V AC. 


15. Power the machine off, then reconnect anything that you have disconnected.

If you have confirmed that the machine is sending ~120V AC to the CPU, that's a good indication that the CPU is faulty and will need to be replaced.