HP-97 repair questions (a lot of)

[Paul Berger (Canada)]

(07-18-2016 07:25 AM)x34 Wrote:  Got a giant lot of HP-97 and paraphernalia on local auction, including boxes, bag, papers, program listings (one with author's autograph, sic!), HPCC membership card, sealed original HP paper 6-pack, original and working (rebuilt) battery packs, etc. Lucky me!

But, easily predictable for 1979 item, there are two problems:

1. mag card reader, which I know how to repair.
2. printer does not advance paper properly - guess, feed mechanism should be fixed.

So, please, help me with fixing printer. The feed mechanism advances paper a bit,
one side better than other. Does it have two rubber rings on single shaft to do it?
May be, replacing the rubbers would fix it?

The most common problem is the "rubber" tires on the paper feed shaft get hard and smooth, I have successfully replaced them with a slice of silicon tubing, but unfortunately you need to partially disassemble the printer to get to them. Another thing that can go wrong the rubber rolls are advanced using a cam and ratchet and I have seen cases where the teeth of the ratchet don't engage properly causing the paper to not feed properly. If the feed rolls are just slipping, if you put some slack in the paper on the input side so that it is not pulling the paper off the roll it will probably feed ok until it takes up the slack.

When putting the printer back together, the advance cam fits into a slot in the print head carrier if it is not in that slot the paper will not feed.

Paul.