HP 67/97 card reader: O-rings vs. vinyl tubing

[Ed Sowell]

As I mentioned in an earlier post, O-rings work fine for me except for the noise. To hear it click here.. In trying to figure out what causes the buzzing I took it apart again. I notice that the tiny pinch roller works against the drive roller right in the middle, over the gap between the O-rings. To see this click here.. It's clear that there is no support in the middle and edges of the pinch roller are doing all the work. Moreover, the O-ring OD measures about 6.47 mm as opposed to the 6.15 mm that is mentioned by Bernd Schmeling. Perhaps the noise is due to flexing of the card under the stress?

I'm going to try the vinyl tubing approach and see how it works.

Comments appreciated

Edited: 7 Apr 2010, 3:17 p.m.

[Michael de Estrada]

The O-rings that I use only measure about 6.05mm uninstalled. Although they will expand somewhat once installed on the wheel, I can't imagine them expanding to the extent that you mention. I have used O-rings on 6 different card readers of all types (65/67/97/82104A), and never experienced any noise problems. Also, that noise may not be related to the card feed, but to the motor/coupling/gears.

[Ed Sowell]

Thanks, Michael.

You must have different O-rings than I do. The ones I have measure 0.250" (6.35mm) unmounted. Also, you can see in the photo that when mounted they are larger than the diameter of the shoulder which measures 0.242" (6.15mm). Where did you get your O-rings?

I don't think it's the clutch. I pulled the worm gear and clutch off the motor shaft and looked it over. The rubber in the clutch did not appear to have deteriorated; it was plyable but tough and required some force to push it back on. And the card reads in smartly as oppposed to the jerky motion I've read happens when the cluth is failing. In any event, I don't see how it could make the "ZZZZZ" sound I'm hearing. Were you able to hear it?

Perhaps the noise could be from the meshing of the worm and spur gears. In fact, with the O-rings being oversized as mine appear to be they no doubt press the gears together tighter than they should be.

By the way, when you reinstall the eccentric shaft how do you know when it's properly in place? IOW, do you just push really hard or do you look at the gap between the head and the reader frame?

thanks for your interest.

Ed

Ed

Edited: 7 Apr 2010, 4:55 p.m.

[Michael de Estrada]

Hi Ed,

I got my last set of O-rings from Mark Hoskins (Waterhosko) on TAS. He's the guy who makes replacement battery packs for Classic and Spice series calculators.

O-rings

The installed O-rings per your photo look much larger than mine, which extend less beyond the shoulder. Also, on my HP97 card reader, my O-rings barely clear the card reader frame, and I'm pretty certain yours would not, so maybe yours are rubbing, but I don't know if that would create a buzzing noise.

Yes I heard the noise and if the pressure from the oversized O-rings was sufficient to cause some slippage of the motor shaft inside the coupling (clutch), the end of the motor shaft could be rubbing against the worm gear. Or, like you said, maybe gear noise.

When I install the eccentric shaft, I use a flat blade screwdriver in the slot, and push and turn until it stops. There will be a small gap of ~1mm remaining between the shaft shoulder and the reader frame.

Hope this helps.

Regards,

Michael

[Ed Sowell]

Thanks, Michael. that helps a lot.

Ed

[Gerry Schultz]

Does the motor still make this noise when it's not connected to the drive roller? If you turn on the motor with no load, does it still make that ZZZZ sound? When I listened to the noisy motor sound you posted, I immediately thought it sounded like a bearing. So, does the motor still make the same noise if the motor shaft is unloaded?

[Katie Wasserman]

See this post from quite a while ago. In it I mention tubing from Small Parts that works perfectly and has held up well for 10 years in many card readers that I've repaired.

-Katie

[Michael de Estrada]

I've thought about the tubing method, but so far O-rings have worked well for me. Of course, I've only been doing this for about 3 years, so I don't yet know how well they will stand up long term. Right now I'm just starting to try some serious repairs on printers.

[Ed Sowell]

Good luck with the printer, Michael. I've recently finished refurbishing mine, so if I can be of help let me know.

Ed

[Ed Sowell]

Thanks, Katie. So, what did you do with the remaining 9' 11 3/4" ?

[Ed Sowell]

No. I ran the motor off a 1.5V battery before inserting the drive gear/roller. Could hardly hear it.