Users may need to check their 390/391 lamp to see if needs to be replaced. A bad lamp will typically produce reading or calibration errors.
Typically, an X-Rite 390/391 densitometer will begin to experience reading failures after the lamp is below 93% of its original use. Replacement lamps can be purchased from X-Rite Customer Service. The X-Rite part number for the lamp is: 880-07. Please use the following steps to check the lamp on these densitometers:
Go to the "MAIN MENU" by selecting the two [MENU] keys (the two buttons on the right).
Press [p1] and then [p2].
Tap the two middle buttons to access the "BIT MENU" and then select [lamp].
If the stated lamp life is less than 93%, then it would be wise to replace that lamp.
Press the [exit] button to exit to the "BIT MENU" and then tap both [MENU] buttons to return to the "MAIN MENU"