The Museum of HP Calculators

HP Forum Archive 10

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41 display cleaning
Message #1 Posted by Randy Sloyer on 5 Feb 2003, 10:33 p.m.

I have a CV full-nut that I'm trying to clean up. It's down to a very annoying black dirt chunk stuck right in the middle of the display. It appears to be on the lens, not the LCD, and no matter how I blast the duster in there, it will not move. Any suggestions welcome.

If I get desperate, can the LCD assembly be removed with the desoldering of the 16 leads? Any dangers/cautions for doing this?

      
Re: 41 display cleaning
Message #2 Posted by Vieira, Luiz C. (Brazil) on 6 Feb 2003, 12:15 a.m.,
in response to message #1 by Randy Sloyer

Hi, Randy;

a few weeks ago, I sent a large PDF file to David Hicks with scanned images Actual view) showing how to remove the fullnuts' LCD in a step-by-step procedure.

I'll upload it in a site but I personaly preffer sending an e-mail with the downaloading address to those who want the file. The site is not my own, so I must be care.

Gimme a couple of minutes and I'm sending you an e-mail, O.K.?

Anyonwe else? (I'll send e-mails with this address to regular MoHPC contributors and visitors only; sorry, folks)

Cheers.

            
Re: 41 display cleaning
Message #3 Posted by Christof on 6 Feb 2003, 2:11 a.m.,
in response to message #2 by Vieira, Luiz C. (Brazil)

Luiz- I can put the pics and any notes up on my webserver.

the bandwidth isn't really great, but I don't figure more than a few dozen people really care about this level of interaction, so I won't get /.'d offline :)

                  
Re: 41 display cleaning
Message #4 Posted by Vieira, Luiz C. (Brazil) on 6 Feb 2003, 3:39 a.m.,
in response to message #3 by Christof

Hello, Christof;

I'm sending you an e-mail with the file's location. Would you, please, download it and have a look? I believe some procedures always involve risks to the equipment or even to the technician, and we must be aware of those who will attempt to do what is suggested without following the safety precautions. The procedure contained in the PDF doc does not contain the descrition of necessary precautions and measures to be taken. I think they must be added prior to allow the document to be released.

Would you check for this possibility, please? I'll add the necessary recomendations and upload the final version so you can "holst" it for as long as you wish; deal?

Thank you very much for your offer. (sometimes I think we should give David Hicks a resting time and offer a bit of our own space for some experiments, like this one; David has been doing a lot for us, don't you think?)

Best regards.

            
Re: 41 display cleaning
Message #5 Posted by Chris(FLA) on 6 Feb 2003, 11:30 a.m.,
in response to message #2 by Vieira, Luiz C. (Brazil)

Vieira,

Can you send me this info also. I have a 41C and a donor display that I would like to use to fix the 41 but have been worried about doing this without experience in this procedure.

I don't want to kill my 41 :)

Thanks,

Chris

      
Re: 41 display cleaning
Message #6 Posted by Dave Shaffer on 6 Feb 2003, 1:28 a.m.,
in response to message #1 by Randy Sloyer

Randy,

Check out this old discussion (from archive 6): http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv006.cgi?read=10212

where Tony Duell and I exchange ideas and results.

Good luck - and be carefull!

      
I read the posts mentioned by Dave Shaffer and..
Message #7 Posted by Vieira, Luiz C. (Brazil) on 6 Feb 2003, 1:44 a.m.,
in response to message #1 by Randy Sloyer

... I must agree it is a lot safer than removing the LCD assy (dessoldering).

I have successfuly removed fullnuts LCD's for three times in order to replace dammaged units. But it was in specific conditions: everything (soldering iron, my wrist, calcualtor's contacts) electrically connected to the same condutive grounded reference.

Hope you have success!

Thanks, Dave.

      
Re: 41 display cleaning
Message #8 Posted by Randy Sloyer on 6 Feb 2003, 9:14 a.m.,
in response to message #1 by Randy Sloyer

Thanks to all for the responses. Once again, many great nuggets of knowledge buried in the archives. I was hoping someone could point me in the right direction!

Thanks, Luiz for the pdf file.

Now, if there was some way to index the archives and strap a search engine on the resulting database...

            
Ooops...
Message #9 Posted by Vieira. Luiz C. on 6 Feb 2003, 10:30 a.m.,
in response to message #8 by Randy Sloyer

I heard it before...

      
Re: 41 display cleaning
Message #10 Posted by David Smith on 6 Feb 2003, 6:03 p.m.,
in response to message #1 by Randy Sloyer

You might want to try feeding a slip of paper undr the display and trying to knock off the dirt. I try this before I resort to the desoldering station. Sometimes you need to feed it from the side, others from the top. Sometimes helps to fold the end you insert over to give you some better brushing action. Works around 90 percent of the time for me. I also have a thin piece of plastic (teflon, I think) that works even better.

If you have to unsolder the display only unsolder the conenctions to the keyboard. Avoid melting the top screw posts. Be careful of the connections to the back of the LCD cricuit board. Many times these are just barely making contact (and are often open circuits in "dead" machines. When working on machines I always go down the row of display pins with a metal probe and gently tug on each one looking for bad connections.

Finally, make sure you remove all the solder flux. Displays that only display when a key is held down are often caused by residual solder flux. Keep alcohol off the clear display window, otherwise you will be removing the display again to polish off the white stain it causes.

            
Re: 41 display cleaning
Message #11 Posted by Randy Sloyer on 6 Feb 2003, 7:25 p.m.,
in response to message #10 by David Smith

Thank you David! I was about 10 minutes away from heating up the Pace station and taking the plunge.

I used a piece of brown paper that had a little backbone to it and it worked like magic.

The older I get, the more I realize patience is truly underrated. Of course it helps to have Dave hosting this site to put us all in touch with the collective brain trust of HP calculator restoration.

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