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HP-97 missing keys
10-06-2017, 07:23 PM
Post: #1
HP-97 missing keys
Hi All,

Recently I acquired a HP-97 in very good condition. Unfortunately two keys have broken off at some point. The previous owner did not have them. Is there anyone with a spare HP-97 that can serve as a donor for these keys? Second question: is it even possible to replace these keys? The white plastic remains that can be seen in the photo can be lifted up somewhat, but they cannot be taken out. So I am not sure how I could replace the keys, even if a donor can be found. Any help is much appreciated!

Kees Bouw.

[Image: missingkeys.jpg]


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10-07-2017, 06:19 AM
Post: #2
RE: HP-97 missing keys
To answer the question can they be replaced, yes they can. Open the case, and remove the keyboard from the top case assembly. There is a HP-97 service manual on the museum here which describes the procedure along with key replacement.

It is not difficult, have removed keys myself, but a certain amount of manual dexterity is needed. Especially when you get to the "foils" which comprise a portion of the keyboard contacts. You do not want to bend them and should avoid touching contact surfaces.

You can replace keys by simple observation when you disasemble the 97. The 1st few times I have done such service manuals were unavailable to me. However, check the service manual, having a clue beforehand always helps.

Basically you separate the parts of the keyboard. Keys are held in place by "hats"; a retaining disk. In your case, as the top of the key is broken off, once you separate the keyboard the broken key stems should fall out. Insert a replacement key, spring and install the retaining "hat".
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10-09-2017, 09:17 PM
Post: #3
RE: HP-97 missing keys
(10-07-2017 06:19 AM)Duane Hess Wrote:  To answer the question can they be replaced, yes they can. Open the case, and remove the keyboard from the top case assembly. There is a HP-97 service manual on the museum here which describes the procedure along with key replacement.

It is not difficult, have removed keys myself, but a certain amount of manual dexterity is needed. Especially when you get to the "foils" which comprise a portion of the keyboard contacts. You do not want to bend them and should avoid touching contact surfaces.

You can replace keys by simple observation when you disasemble the 97. The 1st few times I have done such service manuals were unavailable to me. However, check the service manual, having a clue beforehand always helps.

Basically you separate the parts of the keyboard. Keys are held in place by "hats"; a retaining disk. In your case, as the top of the key is broken off, once you separate the keyboard the broken key stems should fall out. Insert a replacement key, spring and install the retaining "hat".

Thank you for the good news! I am very glad that the keys can be replaced without too much trouble. Now I have to actually find these keys - or rather someone with a non-functioning / for parts HP-97 who is willing to sell the keys to me...
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10-23-2017, 08:52 AM
Post: #4
RE: HP-97 missing keys
Hi,

Having seen the keyboard I am wondering if the keys can be replaced without doing damage. There seems to be a heat steak kind of thing at the top of the hats, the plastic appears to be melted to keep the hat in place. Are you supposed to just break it? But then how do you put it together again? The service manual says: "To replace, align key and spring properly, then push the hat onto the key stem until it snaps into place." They seem to ignore the melted bit at the top. Pulling the hat off takes some force (I have tried but not with force) which makes me think something will break off. What I would really like to do is take all the keys out so they can be cleaned properly. Is this something that could or should be done, or is removing a key only done when absolutely necessary? One other remark: the scan of the service manual is of rather poor quality, especially the photo's. Maybe someone who has the original can make a new scan? I would be happy to do it but I do not have an original service manual.

Kees.
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10-23-2017, 12:17 PM
Post: #5
RE: HP-97 missing keys
Possible idea: what about printing them? (print as: 3d printing)

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10-23-2017, 12:51 PM
Post: #6
RE: HP-97 missing keys
The hats can be pulled directly from the key "stem".

I have either worked on or cleaned 3(4?) HP-9x keyboards. The hats snap over the little "blob" you refer to as a heat stake. I don't know how the retaining "nub" is formed. But the hats can be rotated likely no heat staking is involved. Simply pull straight up to remove the hat. A rather small angle might be OK. It does take some effort. Not sure how to describe it but definately a noticeable force.

All parts being plastic sooner or later you will wear it out. But I have pulled a cap off & reinstalled 2-3 times with no noticeable deterioration (off & on is 1 time). In my opinion, you would wear the hat first. Most likely enlarging the hole (you'll notice the hat is the softer material). Even so, if it still stays on the stem I doubt any noticeable change in key action is likely.

At this point you should have 2 key stems/hats to practice on. The ones that were broken to begin with.
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10-23-2017, 01:12 PM (This post was last modified: 10-23-2017 01:16 PM by Duane Hess.)
Post: #7
RE: HP-97 missing keys
I have removed all keys simply to clean them.

The cautious part of keyboard cleaning is the "backplate". I have been told the yellow markings is a type of ink. Depending on age (?) it can start to wipe off very quickly. Often I use dilute dishwashing liquid; i.e. same strength to wash dishes. 2-3 drops in 1/2 cup water. Or 50% Windex.

I rub on the keyboard but not on top of the yellow nomenclature. Rolling a Q-Tip over that area then rinse with clear water. I use the water faucet with a small stream. Then blot dry with paper towel or dish towel.

The entire backplate is coated after the yellow markings, which does wear off leaving that washed-out white appearance. If it is loose I rub it off & live with the results. If wear is light and doesn't come off I don't mess with it further.

Depending on dirtyness I have scrubbed with full strength Formula 409, Mean Green or dishwasing liquid (always with few drops water) with a toothbrush. But NEVER on top of the yellow markings. And avoid letting the liquids stand on the yellow markings. (or contact)

EDIT: I assume there are more fastidous folks than me and are much more cautious. And hopefully more knowledgeable. Sometimes living with the dirt seems the more likely alternative when considering longevity; maybe that's wrong.
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10-23-2017, 05:35 PM (This post was last modified: 10-23-2017 05:35 PM by BobVA.)
Post: #8
RE: HP-97 missing keys
Regarding 3D printing, Geoff Quickfall had good results fabricating new buttons for an electronic marine chronometer a while back.
If you don't find original keys for the replacement this thread on that repair might give you some ideas.
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10-23-2017, 06:12 PM
Post: #9
RE: HP-97 missing keys
Also note that if one goes for professional plastic molds, there are some types of plastics that are super sturdy that may be used.

For example rackstuds (if someone works with stuff for racks: https://rackstuds.com/ ) that is plastic plus glass.

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10-24-2017, 07:03 PM
Post: #10
RE: HP-97 missing keys
(10-06-2017 07:23 PM)Bouw Wrote:  Is there anyone with a spare HP-97 that can serve as a donor for these keys?

Dear Kees Bouw,

I may have some spare HP-97 keys hiding somewhere in my infamous basement. But it takes me a while to look for things and to respond. Don't do anything drastic or expensive to replace these before checking with me again, I will do some searching as time permits. I probably can find some keys for you, but cannot guarantee it. If I don't have a junker HP-97 on hand, I don't want to create one from good parts.

Best regards

Dan M.
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10-24-2017, 08:37 PM (This post was last modified: 10-24-2017 08:39 PM by Bouw.)
Post: #11
RE: HP-97 missing keys
(10-24-2017 07:03 PM)DanM Wrote:  
(10-06-2017 07:23 PM)Bouw Wrote:  Is there anyone with a spare HP-97 that can serve as a donor for these keys?

Dear Kees Bouw,

I may have some spare HP-97 keys hiding somewhere in my infamous basement. But it takes me a while to look for things and to respond. Don't do anything drastic or expensive to replace these before checking with me again, I will do some searching as time permits. I probably can find some keys for you, but cannot guarantee it. If I don't have a junker HP-97 on hand, I don't want to create one from good parts.

Best regards

Dan M.

Hi Dan,

Thank you for this very kind offer. Through my ad in the Classifieds section I found another member offering these keys. We reached an agreement on the cost and he sent them to me, but I have not yet received them. If I may, I will keep you as a backup option if it does not work out for any reason.

Best regards,

Kees.
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