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As far as Error 900, it is a common error for the Ricoh printers.
Error 990 indicates a dirty sensor, so either a maintenance unit is dirty or you have a clogged print head.
Instead of throwing a bunch of words at you, I'm going to provide you with a visual.
CLICK HERE TO VIEW A VIDEO on repairing this issue on your own.
Please let me know if this resolved it for you.
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