Alcohol is fine. Just be aware that the CCD position is crucial for good focus. It's OK to remove the cover, and any plastic tunnel cover between the lens and the CCD. But do not remove any screws that are painted (precision adjustment). There are four screws that can be removed to change the CCD as an assembly but it's entirely unnecessary to remove them for cleaning. Especially NEVER TOUCH the screws that attach the CCD sensor board to the CCD frame. You'll never get it positioned properly again.
On most modern MFPs you can print PDFs directly from a USB stick. I do most of my image diagnostics that way. It's quick & easy. The files are attached below. That being said, you cannot print a PDF directly on a CS-2550. Those test patterns will work fine for you. I think you'll discover that you lose the first (8) of them in the first month. The remaining (2) test patterns will last you for many years, until they get quite ratty and tattered. (10) is a good amount. =^..^=
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