If everything moves, that's a good sign. Here are some more things to check:
* Ensure the rollers are in good shape. On many machines, they have become bloated, with bumps along the way. While the machine may still work Ok as it is, at some point, the rollers will need to be replaced or refurbished.
* The racks should be clean and free of any dirt or rust.
* Check if the white bracket that holds the rack drive couplers in place is present, and if the little red rack drive couplers are also present. These are visible parallel to the drive shaft if you take off the lid to access the racks.
* Check if the thermostat functions correctly. This is a mechanical thermostat just like in a typical refrigerator and they sometimes malfunction. You can check correct operation by filling the developer and blix tanks with water, set the thermostat to the desired temperature and then monitor using a thermometer if the water temperature comes up to the right temperature and stays there.
* Check if the circulation pump works well. Same as above; fill the baths with water and check if it starts pumping.
* Check transport speed; with the tanks filled etc., run a piece of RC paper (doesn't matter if it's black and white or color; any reject print will do) through the machine and observe how long it takes. It should be around 45 seconds each for the developer and the blix baths if the machine is geared for RA4. It'll be several minutes per bath if it's an older, unmodified machine.
Any idea on where I can find how to modify in case I need it?
I'm planning to do a blog on this, but the essential information is still present here:
https://www.vogelstimmen-wehr.de/rcp20.htm
The actual parts listed on that web page are surprisingly still available from Conrad as of now.
You will need to enlarge a hole on one of the gears you need to buy, machine the drive axel down by a millimeter if memory serves, you'll need to reposition the motor (and enlarge the mounting slots for it) to tension the drive belt and you'll need to install a new fan because the original fan (which isn't very effective anyway) is in the way of one of the new gears. I printed a new fan for my machine (which turns out to work much better than the original) and also installed a little CPU fan that blows across the coil of the motor. Keep in mind that due to the higher turning speed of the machine, the motor runs hotter than it does originally, so adequate cooling is a good idea. This is probably also the reason why Durst & Thermaphot didn't give any warranty on the modified machines and didn't recommend modifying them.
If your machine has badly damaged rollers, keep in mind that this creates additional friction, making the racks much harder to turn for the motor. Do not modify the machine unless the racks run smoothly, otherwise you might burn out the motor and it'll be a chore to find a replacement for it.
Again, I'm planning to do a blog with a couple of photos that show the essential elements that I found missing or incomplete on the website linked to above. I'll try to remember to post back here once I get that post up.
