New-to-me HP-65: card reader troubles

[0culus]

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 new...it 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.

Thanks!

Sean

[teenix]

(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 new...it 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.

Thanks!

Sean

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 :-)

cheers

Tony

[rprosperi]

Nice collection of notes Tony, really convenient and useful to have them all in one place.

[BOOKMARKED] !

[0culus]

Thanks for the writeup, Tony! Very good info. One further question...are there any close up detailed photographs available of these potential small parts footguns inside the machine when assembling/disassembling? [edit] I was also going to say that this specimen is in as-new condition, so no cleaning needed! =)

Sean

[0culus]

Here's some pics!

[teenix]

(07-26-2020 04:51 PM)0culus Wrote:  Thanks for the writeup, Tony! Very good info. One further question...are there any close up detailed photographs available of these potential small parts footguns inside the machine when assembling/disassembling? [edit] I was also going to say that this specimen is in as-new condition, so no cleaning needed! =)

Sean

https://www.hpmuseum.org/cgi-sys/cgiwrap...i?read=179

cheers

[Dave Britten]

(07-26-2020 11:28 AM)teenix Wrote:  Be mindful with small parts magically disappearing from the card reader if they fall out or are being cleaned.

This is especially important. I find that it's best to work over a plastic restaurant tray, and don't hold the items unnecessarily high up. The raised edge will catch any pieces that might attempt to roll to freedom, and it also prevents you from brushing small parts off the table with your arm/sleeve.

You still have to be mindful of any parts that might launch themselves across the room due to spring tension (I don't think there's much risk of this in a 65).

[0culus]

(07-27-2020 12:05 AM)teenix Wrote:  

(07-26-2020 04:51 PM)0culus Wrote:  Thanks for the writeup, Tony! Very good info. One further question...are there any close up detailed photographs available of these potential small parts footguns inside the machine when assembling/disassembling? [edit] I was also going to say that this specimen is in as-new condition, so no cleaning needed! =)

Sean

https://www.hpmuseum.org/cgi-sys/cgiwrap...i?read=179

cheers

Perfect! Bookmarked. I have gathered from reading that the internal construction of the 65 and 67 is largely identical. Is this correct?

[0culus]

(07-27-2020 02:10 AM)Dave Britten Wrote:  

(07-26-2020 11:28 AM)teenix Wrote:  Be mindful with small parts magically disappearing from the card reader if they fall out or are being cleaned.

This is especially important. I find that it's best to work over a plastic restaurant tray, and don't hold the items unnecessarily high up. The raised edge will catch any pieces that might attempt to roll to freedom, and it also prevents you from brushing small parts off the table with your arm/sleeve.

You still have to be mindful of any parts that might launch themselves across the room due to spring tension (I don't think there's much risk of this in a 65).

And I have the added challenge of two furry little monsters that love helping me in the electronics lab...I think I might have just the thing for working on top of though. And keep the cats locked out while I do it. =)

[teenix]

(07-27-2020 02:25 AM)0culus Wrote:  Perfect! Bookmarked. I have gathered from reading that the internal construction of the 65 and 67 is largely identical. Is this correct?

Pretty much, except for the CPU boards and display driving method.

cheers

Tony

[0culus]

I can happily report a successful repair thanks to waterhosko's kit, and some patience. The old wheel had totally disintegrated and the pieces were all over inside the calculator. I cleaned it up, put two o-rings on the freshly cleaned wheel, and reassembled. Machine passes both self test programs in the standard pac.

The label got slightly creased, but I am leaving out the two screws and putting them in a baggie in the calculator's box.

Anyone happen to have any NOS ones laying about they are willing to sell? :o)