Hgb lamp failure

Replace the HGB lamp module – this fixes it 90% of the time. They’re consumables and don’t last long.

Check the lamp connector – make sure it’s fully seated; loose connection = flicker = inconsistent results.

Clean the optical path – dust or cuvette residue can also mimic a weak lamp.

Run a full optical calibration after replacing the lamp.

If the error stays after a new lamp and calibration, the HGB photodiode board is your next suspect, but that’s far less common.