HP 67 Circuit Board

[metawops]

(07-11-2022 10:51 PM)teenix Wrote:  Stay on this thread or start a new one, it's all good

cheers

Tony

Thanks, Tony! I'll stay here, then.

HUGE thanks to AndiGer who supported me by sending a few magentic cards and silicon two fuel tube snippets. ??
I installed one on the gear axle and reassembled the reader and the HP-67 up to the point where I could do a first test. (I didn't change any capacitor, yet; should I?)
I connected the HP-67 to a lab power supply, set that to 3,7V and switched the HP-67 on.
The display is fine, the keys are fine, it calculates correctly.

Now, first question: am I allowed to use the card reader under this (lab power supply, no batteries) circumstances? I hope so, because I did insert a magnetic card. ?

Result: the card could hardly be moved through the calculator. It went in veeeery slowly, the motor made a low sound (slow rotation) and the card almost got stuck completely inside the reader. I was lucky that, after a while, it came out on the other side so I could pull it to help the motor. (The result in the display was, of course, "Error".)

Maybe the silicon tube is too thick? I measured an outer diameter to be 6.57mm which should be fine, right? (I have another tube that has an OD of 6.08mm – both measured when applied onto the axle.)

HOWEVER ... When I took everything apart again I noticed that one of the two tiiiny screws that fix the motor to the plastic chassis is missing!! ?

Here's a photo:
   

Now ... is there a chance I can get hold of one such screw? What are the exact specifications for this screw? Any hint? Is it even a real problem? Will the reader only work with the 2nd screw properly installed?

In another attempt (before I saw that the screw was missing) I connected the motor directly to the lab power supply (card reader fully assembled) and set the power supply to app. 1.8V – can I supply more voltage here?. The motor made "uneven" sounds but the card was transported quite nicely. I made a video that you can download (>80MB) here.

Off to bed now, eyes going bad, too many tiny things ... ?

Thanks a lot for any help!

Stefan.