How do I replace the ribbon on an Underwood typewriter?
Really? An Underwood typewriter?
First, do you have a replacement ribbon that is not dried out? Does the ribbon come on one spool or two?
If the typewriter already has a ribbon installed, it is a simple matter of noting the path the current ribbon follows, and which way the ribbon winds onto the spools. Then install the new ribbon following exactly the same threading path. If there is not already a ribbon installed, then it is a little more complicated, and it will depend on your spatial relationship visualization skills.
1. Type a few letters on the typewriter, and take note of which way the spools turn.
2. Mount the two new spools containing the new ribbon so that the full spool will supply (unwind), and the empty spool will take-up (wind) the ribbon.
3. Thread the ribbon through all of the guides in the threading path - there are probably about 6-8 guides that the ribbon has to go through. The most important guides are the ones that carry the ribbon in front of the typeface elements as they strike the paper. But equally important are the guides that monitor the tension of the ribbon - they will cause the spool advance mechanism to reverse the ribbon take-up direction when the ribbon reaches the end of travel.