How does the HP-97 printer paper feed work?

[Harald]

I have started repairing the HP-97 I mentioned a bit further down. I have a problem with the printer. The paper feed does need a little help by pulling the paper manually. I have taken it appart and all the gears (at least all three I can see) are ok. And the head moves as it should. But I do not understand how the paperfeed works? Can anyone help?

Also, I have replaced the gumy wheel and the cardreader pulls the card through fine. But I get an error when trying to read a card. Not sure if it is the reading or the writing that is the problem. Should it be able to read cards written by an HP-67? In that case, I suspect reading doesn't work. Any thoughts on what to check?

Cheers,
Harald

[Harald]

OK, I have worked out how it is supposed to work. I think it is just the rubber wheels that have hardened. How do I replace them? And what with? Has anyone done this yet?

Edited: 30 Mar 2012, 7:49 p.m.

[Ignazio Cara (Italy)]

Hi Harald,

I have did the job in this mode, take a look at the following.
slideshow.

The silicon o-ring are 8x2 mm (OD=8;ID=4).

Let me know if it's quite understandable.

Regards

Ignazio

Edited: 31 Mar 2012, 3:33 a.m.

[Harald]

Thanks for that! Seems like a good solution. However I wasn't prepared to take drastic measures yet. Insted I tried to scrape the hardened surface off the rubber wheels, and had a bit of succes. The paper is beeing pulled through now, but not quite straight. Maybe I can improve on that. If not, I'll try your approach.

Cheers,
Harald

[aurelio]

For what regards the card reader issue I remember that I read with a 97 a card written by a 67!
Regards

[Harald]

Thank you! I just found that out myself,^too. The cardreader is now working! Somebody had messed about with the adjustment of the spring contacts and then used a bit of tape to jack up the PCB. I had removed that tape when doing the repair, but not re-adjusted the contacts. Now that I have done that, it is working!