Messed up my first project (HP-97)

[jgbackes]

Well it was bound to happen. I got cocky. I was just getting started by cleaning up the outside of the 97 while the battery charged in the other room.

There was some sharpie on the outside case, I got out some swabs & alcohol and it came off with just a little elbow grease. The keyboard looked a little gunked-up so I thought what the heck I've already got the swabs and alcohol out I'll just use that.

BIG MISTAKE. As soon as the alcohol evaporated the plastic turned milky. I tried cleaning it with soap and water but no luck, I've done some kind of damage to the plastic itself. I feel like such a dork I should have known to try it on a small area first.

A little Googleing says that a low temp heat gun is probably my best bet if I want to keep all of the lettering in tact.

Is there a general consensus from the group on the proper way to fix this?


jeff

[teenix]

Is it just residue, or has it soaked into the plastic?

Does it clean off with a swap in water/mild detergent mix?

cheers

Tony

[Hans Brueggemann]

imho, your calculator doesn't look that bad. it just seems that the IPA treatment has partially dissolved the top matte varnish of the keyboard, hence the white residue.
the objective now is to remove all the remaining varnish and residue without deteriorating the imprints. remove all keys from the keyboard and clean it. then, protect the surrounding from overspray with tape. give it a couple of very thin fresh coats of matte varnish from a spray can (or airbrush). if a layer of varnish gets glossy while spraying, you are overdoing it. test your spraying technique on some black scrap plastic first. let the varnish thoroughly dry between coats. if done properly, the keyboard faceplate will look like new.
Don't use a heatgun, it will just ruin your calculator as the plastic might warp sooner than you would expect.

[jgbackes]

(08-04-2024 12:10 PM)teenix Wrote:  Is it just residue, or has it soaked into the plastic?

Does it clean off with a swap in water/mild detergent mix?

cheers

Tony

Tony,

It's not residue, I've scrubbed and scrubbed with water and a drop of dawn soap.

I have to take everything apart to fix the gummy card reader and hardened pinch rollers so while I have it apart I'll try hitting it with some clear and see if that fixes it (yes, I've learned my lesson, little test area first).

jeff

[jgbackes]

(08-04-2024 12:55 PM)Hans Brueggemann Wrote:  imho, your calculator doesn't look that bad. it just seems that the IPA treatment has partially dissolved the top matte varnish of the keyboard, hence the white residue.
the objective now is to remove all the remaining varnish and residue without deteriorating the imprints. remove all keys from the keyboard and clean it. then, protect the surrounding from overspray with tape. give it a couple of very thin fresh coats of matte varnish from a spray can (or airbrush). if a layer of varnish gets glossy while spraying, you are overdoing it. test your spraying technique on some black scrap plastic first. let the varnish thoroughly dry between coats. if done properly, the keyboard faceplate will look like new.
Don't use a heatgun, it will just ruin your calculator as the plastic might warp sooner than you would expect.

Hans,

Thanks, I'll give that a try and report back.

jeff

[aj04062]

If that fails, I have several keyboards with a few missing keys. Unlikely I’ll ever get another working 97 out of the lot of bad units as the cases are pretty toast.

Message me if you want to arrange a swap as I’d like to keep the keys in case I need for future repairs.

[John Garza (3665)]

Try a tiny amount of oil (like WD-40) on a swab (damp not wet). Then blot (don't rub) off the excess with a dry shop towel.

[BobVA]

It might be worth trying something like 303 Aerospace Protectant or STP "Son Of A Gun" protectant. They can do a nice job on dried out plastic.

[jgbackes]

(08-05-2024 08:02 AM)John Garza (3665) Wrote:  Try a tiny amount of oil (like WD-40) on a swab (damp not wet). Then blot (don't rub) off the excess with a dry shop towel.

I'll try this on a small part and report back.

[jgbackes]

(08-05-2024 09:28 PM)BobVA Wrote:  It might be worth trying something like 303 Aerospace Protectant or STP "Son Of A Gun" protectant. They can do a nice job on dried out plastic.

Thanks I’ll try this as well. I'm pretty sure I have some 303 in the garage.

[jgbackes]

(08-05-2024 08:02 AM)John Garza (3665) Wrote:  Try a tiny amount of oil (like WD-40) on a swab (damp not wet). Then blot (don't rub) off the excess with a dry shop towel.

(08-05-2024 09:28 PM)BobVA Wrote:  It might be worth trying something like 303 Aerospace Protectant or STP "Son Of A Gun" protectant. They can do a nice job on dried out plastic.

Reporting Back:

I tried this on a small portion of WD-40 and it worked like magic.

I've Also tried 303. No luck, as soon as I buff it it comes back to a very dull "green" color.

thanks so much for all the support! What a wonderful group!

jeff