OT - Opening an Alesis ModFX (?)

[scott@dreamstate.to]

While unpacking my beloved Alesis Bitrman after a New Years jam
I noticed something rattling inside. There is one screw on the bottom
which I have now removed (and I can't spot any others) but the top
is still reluctant to be removed so that I can see what's what inside.

Has anyone here successfully/safely opened up a ModFX
and can you give me clues as how to proceed next?

I've pushed down gentley on the knobs (with no useful result yet)
but I'm wary of crunching something inside by pushing too hard.

Thanks in advance,
Scott M2

http://www.dreamSTATE.to
ambientelectronicsoundscapes
http://www.THEAMBiENTPiNG.com