My HP41CV just arrived. Cleaning tips?

[Trond]

Hi again everyone!
I just received my first 41C (of any kind) specifically HP 41CV. My feelings are a bit mixed about the condition: at first I thought I had to send it back because some of the keys (notably the Enter key) seemed to stick. The Enter key took a moment to come fully back out the first time I pressed it. BUT it seems to get better the more I press it. I wonder if the packaging materials were pressing the buttons down in shipping. On the other hand, there are no scratches or dents at all. It feels solid. It seems to work as it should. It also came with three books (Owner's manual, opersting manual, standard applications) plus calc pouch with zipper all for a little over $200.

I still think the unit feels a bit......dirty. Any cleaning tips here?

[rprosperi]

(12-03-2017 11:07 PM)Trond Wrote:  Hi again everyone!
I just received my first 41C (of any kind) specifically HP 41CV. My feelings are a bit mixed about the condition: at first I thought I had to send it back because some of the keys (notably the Enter key) seemed to stick. The Enter key took a moment to come fully back out the first time I pressed it. BUT it seems to get better the more I press it. I wonder if the packaging materials were pressing the buttons down in shipping. On the other hand, there are no scratches or dents at all. It feels solid. It seems to work as it should. It also came with three books (Owner's manual, opersting manual, standard applications) plus calc pouch with zipper all for a little over $200.

I still think the unit feels a bit......dirty. Any cleaning tips here?

Do not use alcohol, acetone or any strong cleaners or solvents on the keyboard, it will likely remove part of the labels on the bezel. Many folks recommend mild detergent/water solutions; use with moistened (not dripping!) toothbrush or I prefer (lots of) Q-tips.

If the machine was not used for a long period, the keyboard will likely work better as you use it more. While it's possible there was some kind of spill inside (e.g. soda or coffee) you can usually tell as there is sticky crud around the keys.

Once you have removed the serious dirt, you can also use small amounts of Armor All using a soft cloth; it cleans the plastic and leaves a nice finish.

The key is to just take your time cleaning it slowly and lovingly. Plan to spend an hour on it. It may not take that long, but the results will be much better than if you try to do it in 5 minutes.

[Trond]

(12-03-2017 11:40 PM)rprosperi Wrote:  Do not use alcohol, acetone or any strong cleaners or solvents on the keyboard, it will likely remove part of the labels on the bezel. Many folks recommend mild detergent/water solutions; use with moistened (not dripping!) toothbrush or I prefer (lots of) Q-tips.

If the machine was not used for a long period, the keyboard will likely work better as you use it more. While it's possible there was some kind of spill inside (e.g. soda or coffee) you can usually tell as there is sticky crud around the keys.

Once you have removed the serious dirt, you can also use small amounts of Armor All using a soft cloth; it cleans the plastic and leaves a nice finish.

The key is to just take your time cleaning it slowly and lovingly. Plan to spend an hour on it. It may not take that long, but the results will be much better than if you try to do it in 5 minutes.

OK! I was planning on using damp (not dripping) watercolor brushes, to see how far that takes me.

[Trond]

Thanks for the tip again. Brushes, q-tips and distilled water has been taking care of most of the dirt. Some of the keys are definitely better.

Next problem: the calculator feels a bit wobbly on straight hard surfaces. I think the rubber pad on the lower left side is a bit thin or something? Do you have any good fixes for this?

[hth]

(12-04-2017 04:32 AM)Trond Wrote:  Thanks for the tip again. Brushes, q-tips and distilled water has been taking care of most of the dirt. Some of the keys are definitely better.

Next problem: the calculator feels a bit wobbly on straight hard surfaces. I think the rubber pad on the lower left side is a bit thin or something? Do you have any good fixes for this?

Take a look at the rubber feet, they should have a smooth surface. When they wear a more pitted surface appears, like some erasers. This usually starts around the edges. It takes quite some use before this happens though.

Lots of use can also cause some to become stretched longer and they reside inside a raised frame in the bottom case. When they stretch they may no longer fit inside this frame, making some crawl up on the frame edge and that can cause it to be become uneven and wobbly. At this stage they are usually quite worn like described above.

It can also be so simple that a foot is misplaced slightly, examine them and how they are positioned in their frames.

Håkan

[Trond]

The wobblyness is a bit odd, as I can't see any problem with any of the rubber feet. I am thinking of applying a couple of thin layer of black acrylic paint on top of the rubber, to increase the thickness just a little (I have fixed plastic things with acrylic paint before, never rubber though). Alternatively I could try to tear the rubber off and reapply it with a thicker layer of glue. What do you think?

[hth]

(12-04-2017 05:50 PM)Trond Wrote:  The wobblyness is a bit odd, as I can't see any problem with any of the rubber feet. I am thinking of applying a couple of thin layer of black acrylic paint on top of the rubber, to increase the thickness just a little (I have fixed plastic things with acrylic paint before, never rubber though). Alternatively I could try to tear the rubber off and reapply it with a thicker layer of glue. What do you think?

I have no idea really, I have not encountered a truly wobbly HP-41. Well, the few times it did wobble, most time it was solved by moving it to a different part of the table. The other situation was caused by the enlarging foot pad I described above.

I have an HP-41 here without feet here and it does not wobble, so if you truly want to go to the bottom with the problem, you may need to take the feet off and try it on truly flat surfaces to see if it is caused by the case or the feet.

If memory serves me, the feet are made of rubber with some kind of sheet material at top and bottom. This sheet is what gives the smooth surface and it lasts for a long time.

I doubt thicker glue is the solution, a shim is probably better in that case. Your paint idea may be good too.

Just be careful with what you expose the foot pads to, some chemicals may cause a reaction so that the sheet material separates from the rubber (a low tack replacement glue I used had this effect).

Håkan

[BruceH]

If only someone with experience of this kind of cleaning / restoration work would write a book about it!

;-)

[mfleming]

Snark!

You can buy a set of replacement feet on TAS for around five or six bucks. A extra is usually included and there is a strong adhesive on the bottom to attach the rubber foot to the case. They are a fairly close match to the originals. That may seem a bit expensive for a few rubber rectangles, but I've used them and they work well. Beats scrounging around with various bits of rubber sheet and double-sided tape.

~Mark

[rprosperi]

(12-05-2017 01:19 AM)mfleming Wrote:  Snark!

You can buy a set of replacement feet on TAS for around five or six bucks. A extra is usually included and there is a strong adhesive on the bottom to attach the rubber foot to the case. They are a fairly close match to the originals. That may seem a bit expensive for a few rubber rectangles, but I've used them and they work well. Beats scrounging around with various bits of rubber sheet and double-sided tape.

~Mark

I got some of them too; they are not inexpensive as Mark says, but I agree they are good quality. But be careful when installing them. Often, when you peel off the paper that comes on the back side (covering the adhesive), the adhesive layer can easily come off and stay with the paper (rather than staying with the rubber pad) depending on how you peel it back. Its easy to do it right (I suggest using an X-Acto knife or micro-tipped tweezers) if you are aware to watch out for it, so now you know.

[Dave Frederickson]

(12-05-2017 01:19 AM)mfleming Wrote:  A extra is usually included ...

which is for the card reader. The 41 feet fit the 71 and there are larger feet for the 75 and smaller ones for the Voyagers. Samson Cables sells some, too.

[Trond]

Dang The calculator seems to eat batteries too fast. I bought new batteries on Friday, and they are already gone (calculator turns itself off after less than a minute).

[Dieter]

(12-10-2017 06:43 PM)Trond Wrote:  Dang The calculator seems to eat batteries too fast. I bought new batteries on Friday, and they are already gone (calculator turns itself off after less than a minute).

If you are still tallking about an HP-41, two questions come to mind:

(1.) Are you sure the batteries were really fresh? Where did you buy them?

(2.) Are you sure it's a low battery that shuts down the calculator? In this case the BAT annunciator in the lower left corner of the display should come on, then the display should fade out slowly. If the device instantly turns off without BAT signal, it's probably the Auto-Off feature which does not work properly, maybe because of a hardware issue. Usually the HP-41 turns off after about 11 minutes of inactivity. This can be disabled with the ON command.

Dieter

[Massimo Gnerucci]

(12-10-2017 06:43 PM)Trond Wrote:  Dang The calculator seems to eat batteries too fast. I bought new batteries on Friday, and they are already gone (calculator turns itself off after less than a minute).

A faulty capacitor, or, if you're lucky, an intermittent contact.

See here and here.

[Trond]

(12-10-2017 07:24 PM)Massimo Gnerucci Wrote:  

(12-10-2017 06:43 PM)Trond Wrote:  Dang The calculator seems to eat batteries too fast. I bought new batteries on Friday, and they are already gone (calculator turns itself off after less than a minute).

A faulty capacitor, or, if you're lucky, an intermittent contact.

See here and here.

Thanks!
I should emphasize that it stays on for much longer when the batteries are fresh. The problem is that it went back to turning off too quickly after just two days (or less) indicating to me that the batteries are being drained. Would this indicate an intermittent fault?

[Massimo Gnerucci]

(12-10-2017 07:39 PM)Trond Wrote:  

(12-10-2017 07:24 PM)Massimo Gnerucci Wrote:  A faulty capacitor, or, if you're lucky, an intermittent contact.

See here and here.

Thanks!
I should emphasize that it stays on for much longer when the batteries are fresh. The problem is that it went back to turning off too quickly after just two days (or less) indicating to me that the batteries are being drained. Would this indicate an intermittent fault?

I'd start by opening it and clening all contacts thoroughly with IPA. Check if there is some green/blue oxydation and try to get rid of it, if found.
If it still drains batteries so fast try to send it back and get a refund, there are so many 41 out there... Or, if you're comfortable with electronics try to replace the capacitors mentioned in the threads I attached before.

[Trond]

The seller has offered to send me a new and better 41CV when I send this one back. I am crossing my fingers that the next one will have less issues, but I have to admit I am a bit hooked to the 41C series.

[Massimo Gnerucci]

(12-11-2017 02:51 AM)Trond Wrote:  I am crossing my fingers that the next one will have less issues

Let's hope so! Good luck.

[Trond]

I received the new 41CV calculator. It seems to work fine, and is nearly mint-looking. There is one annoying thing though: the buttons 1 and 2 are considerably less sensitive than the others. The other buttons go in with a loud "click" very easily, while 1 and 2 sometimes don't register, I feel more resistance, and there is less of a click. Is there an easy fix to this? Am I being overly picky here?

[mfleming]

I haven't tried either method, but I've seen two approaches to cleaning the key contacts posted in the forums. The first involves swirling some DeoxIT contact cleaner around using a thin wire or bristle from a brush. There are plated thru holes in the main PCB behind each key where you can insert the wire or bristle. See this link for where you can buy the contact cleaner (highly recommended if you plan on doing any restoration).

http://store.caig.com/s.nl/it.A/id.2914/...ategory=20

Another method involves placing the bottom keyboard assembly in an ultrasonic tank with clean water. There was a long discussion somewhere on the inadvisability of using distilled water (do a search using the site:hpmuseum.org qualifier with you favorite search engine). The keys should be immersed but the display should remain dry. leave the keyboard & case to air dry a few days before reassembly. This method would dislodge any stray material that might have been lodged in the key contact dome.

Both methods do involve disassembling the HP-41 and removing the CPU daughter card and its contacts. With a calculator this old, you introduce the chance of a broken post, bad contact after reassembly, ESD damage and all sorts of problems. Don't be discouraged, just be careful! There are any number of posts detailing the process and maybe an article or two. Dig in and read up before opening the case.

~Mark