Error code U9

Question

Hi I have the error code U9 showing on my Olivetti Copia 9814. The book says switch it off for 5 secs then try again. Well, this works each time but only for 1 or 2 copies. I bought this machine while I was 'in the trade'I had a small office machinery company till 2001 when I sold up so if you can point me in the right direction I should be able to get spares or repair it myself.

many thanks
Chris