[Amps] malfunctioning Harris RF-355 500 Watt Amp

[pa3fun at amsat.org (Christiaan Roselaar)]

Hi,
My Harris AM-7223 Amp fails BITE with code 2-6, meaning "band switch error".
I notice that, neither in manual or in automatic mode, I hear any motor 
or switch when changing from band to band as I expected.
Is there anyone out there who can give me a clue?
I know american-milspec is offering manuals, but which one do I need, 
the "user manual" or the "depot level manual" (or maybe both???)
Any help appreciated,
Chris PA3FUN