repair or replacement of 41c clear display cover

[dmh]

Hi, I have searched the forums but have been unable to find anything about repairing or replacing the clear display cover on top of the screen (the external bit you can touch).

I'm looking for tips/advice on removing, cleaning/polishing, but probably more likely, replacing and exactly what will work (specs etc).

I've had the back off a few but not ventured to the front or display of the 41c series.

The one I have that needs work is a fullnut if it makes a difference. The clear display part is dirty and very dark in one spot and I think fixing this will help (although the display does look a bit dimmer than usual too).

TIA, dmh

[Dave Frederickson]

Is it the clear cover or the LCD that has discolored? It's unlikely the clear cover has discolored and possibly the reflective layer in the LCD that has.

[Raymond Del Tondo]

Could you send a photo of it?

This way it may be easier for other people to get an idea where the problem actually is;-)

[GreyUser]

The window is made of crystal polystyrene and is ultrasonically welded into the case. It is an injection molded part and it would not be easy to replicate and even if you made one, getting the old one out and a new one in is not a simple task as removal usually results in breakage of the thinner border edge which then prevents a replacement from being installed. It is far easier to replace the entire keyboard assembly with the window being part of that assembly.

You can remove the lcd assembly in a fullnut which makes cleaning and polishing the window possible but it’s not without risk. Sometimes removal of the lcd is required for access to the inside of the window but that should be avoided unless absolutely necessary.

Removal of the lcd assembly in a fullnut requires good soldering skills, a proper desoldering station helps but isn’t an absolute necessity. Heat the pins, one at a time and slide a small straight bladed screwdriver under the connection pin and hold away from the motherboard until the solder cools. You lift and disconnect all the lcd assembly pins, remove and then clean up the board with desoldering braid. Bend the pins of the lcd pack into place, remove any excess solder if needed. Place a piece of masking tape over the lcd display or carefully set aside, the polarizer is quite soft and very easy to scratch.

In extreme cases, scratches other dings can be sanded out of the window with progressively finer sandpaper, 1000 to 4000 grit is range I’ve used and then polish for a like new surface. Once the surface is restored, a trip through an ultrasonic cleaner will remove the residue in the gaps between the display window and the case. Then dry in a warm area with small fan. The keyboard needs at least a day or two of drying time to remove all traces of moisture.

PS: agree with Dave that a dark spot is likely not the window but is unfortunately more likely to be a bad area in the lcd. If it’s grayish black, it’s a failing lcd and easy to identify in a photo.

[dmh]

Thank you for your replies.

I've taken a few photos and quickly linked below.

The unit is as I recently received it and quite dirty and although the LCD has seen better days it looks like the main mark is on the back of the window (actually looks like it's on the outside in one of the pictures but I can't feel it/wipe it off).

From the responses so far it doesn't sound easy (for me, at least) or promising.

Let me know what you think of the after reviewing the photos.

https://www.dropbox.com/s/57z8mv4jjdpyhc...1.jpg?dl=0

https://www.dropbox.com/s/lcedyh8evlb3wd...2.jpg?dl=0

https://www.dropbox.com/s/9upwa82bycb7ma...3.jpg?dl=0

[Hans Brueggemann]

the protective window seems to be mold-infested from the inside.
if your soldering skills and your soldering equipment are up to it, it's not that difficult to desolder the LCD from the main board. desolder the mainboard side of the contact strips only, not the LCD side, because the brown LCD circuit board is made of thermally inferior material and notorious for "losing pads".
once the LCD assembly is out, a couple of cotton swaps and acrylic polish on the protective window in the calculator top frame will do the trick.
the LCD assembly itself shouldn't be polished. use isopropanol (IPA) and a cotton swap to wipe its display surface clean. use sparingly, don't let the IPA trickle into the contact stripe area.

[Raymond Del Tondo]

Thank you for the pics.
As Hans wrote, it can be cleaned, if you are able to desolder the LCD unit.

However I've rarely seen a unit with that much dust particles between the LCD and the protective acryl.

That brings up another question:
Does the HP zipper case for the unit spread black sticky dust particles?

[Divasson]

Regarding the polishing of screen to remove scratches, it has worked wonders for me this product plus a soft cloth and a lot of rubbing:



Pay attention because there are two types: for glass and for plastic. We want the latter!

It can be found in Amazon and it really works well.

[Note: I have used also a Dremel with the cotton tool and it heats the plastic, leading to micro-cracks that render the screen unusable. Hand-rubbing remains the only way]