TECH GURU's out there, how to clean Circuit Board?


Looks like something has spilled onto the Circuit board. Older Rotel amp, there some greasy stuff and cat hair all over the internal board, very dirty and grimy.....

How do I clean this up, works perfectly but I believe its not a healthy thing, I am a tech oriented guy so I need instructions, like what can I use to clean, solution or anything? brush and what should I avoid doing.

Thanks for your help
rapogee
Thank you everyone, Bombaywalla and all of you out there!
Very knowledgeble people and this is why I like forums such as these, very educational and helpful.

I used all your advise, paid $10 for the unlta wash from Radio Shack, $4 for brushes from the dollar store, cut the brshes up to enhance the stiffness and control .5 inch sprayed over the brush and cleaned process, never sprayed directly to the board only on some empty areas than needed.
Used a little alcohol or some areas with cotton swab and too my time and cleaned it up good. WORKED!
Images enclosed:

Believe me the board was originally brown in colour with dirt all over.... like the lable shown with the serial board #####, NOW ITS GREEN as original... Thank you very much. First 2 images shows cleaned board, last shows the cleaner I used, I also used rubbing alcohol or certain stuborn areas very little and with caution.

http://img.photobucket.com/albums/v430/rainbowrav/closer2.jpg

http://img.photobucket.com/albums/v430/rainbowrav/closer.jpg

http://img.photobucket.com/albums/v430/rainbowrav/worked.jpg
thanks again on the feedback, Rapogee. looks like a job well done by yourself!
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