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New-to-me HP-65: card reader troubles
07-26-2020, 11:28 AM (This post was last modified: 07-26-2020 11:32 AM by teenix.)
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RE: New-to-me HP-65: card reader troubles
(07-26-2020 01:52 AM)0culus Wrote:  Hey all,

Longtime lover, collector, and USER of HP calculators. I added two in the last week...another HP-15C and a beautiful, complete HP-65. The 65 might as well be has everything and apparently only one owner before me. Meticulously cared for.

However, it seems to have the common issues with the card reader. The motor starts but will not engage a card. There was a little bit of squealing at first but this quieted down. Guessing this was the clutch. So based on reading the stuff in the MoHPC knowledge base area, this is most likely the gummy wheel problem.

I'm a bit nervous about tearing into it without doing my research thoroughly, so I thought I'd ask around if there is any updated knowledge on this repair beyond what's already out there.



It is not too difficult to repair the card reader "gummy" wheel problem and there are plenty of ideas and notes available in posts available on this Forum and on the web.

Once the calculator back is off, there has only been a few issues I've come across.

Be careful removing the plastic covers over the 2 screws at the top end of the calculator. Being a bit forceful here can leave unsightly marks on the plastic.

The rubber feet covering the two bottom case screws may have hardened over the years, and when bent over to access the screws, they may split.

Don't force the circuit boards apart from the edge connectors. Try to handle the boards only by their edges to avoid static damage to the components and avoid contaminating the circuit board traces with all the liquid goodies that tend to ooze from skin.

When disassembling the card reader it is possible to fracture or completely break the wiring between the circuit boards near the point of soldering.

Be mindful with small parts magically disappearing from the card reader if they fall out or are being cleaned.

Don't bend the gold contact fingers for the card sensing unless necessary. It is hard to put them back to the original shape and tension.

The overall design is good for servicing but also be careful of reassembly, especially the power and Run/Prgm switch contacts. Sometimes they can unknowingly fall out during assembly and short the circuit board traces causing chip damage. Try the switches first before inserting the batteries.

When the keyboard and backing plate are put back in place, they should sit in place without any rocking. Otherwise they are not seated properly on the plastic locating pins and may warp when the calculator cases are screwed back together.

Be gentle and try not to "scrub" the front panel if you want to clean it up. The printed characters may come off the plastic and if you then go look in the mirror you probably won't like the look you see.

During reassembly, maybe leave out the 2 screws under the back label, so that if another repair is required, the label can stay in place and suffer less damage.

Good luck, have fun :-)


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RE: New-to-me HP-65: card reader troubles - teenix - 07-26-2020 11:28 AM

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