Display replacement on a 41CV/X halfnut

[Johnboy]

Has anyone attempted to do this ? and succeeded ?? I've done a few fullnut display replacements but never a halfnut.

I realise I need to take the keyboard out, but I don't know how hard it would be to remove the display from the PCB.

Any pointers would be appreciated.

Thanks
John

[Diego Diaz]

Hi John,

If you mean to replace the display board, first thing to consider is that the display in the HNs is mounted on a board that also contains the ROMs 0, 1 & 2; as well as the power supply, etc.

So, if the unit to recover is a CX you'll need a CX display board, and vice-versa.

Of course, if you install a CV display board on a CX and remove the "bridge" Timer PCB you'll end up with just a CV.

Apart from that, once the keyboard PCB has been removed by cutting the 36 plastic (mushrooms) rivets, there are just 14 solder joints to be undone. Fairly easy with a good soldering iron and extractor.

In case you're just meaning to replace the LCD, then there's no need to desolder the board. Undo the aluminium frame tabs and make sure that the pads, the zebra connector strips and the donor LCD are perfectly clean before reassembly.

Reassembling the keyboard PCB is where things become harder.

You can go the "cheap" way and place a small drop of superglue on every rivet, but it won't likely recover the tight feeling of the keyboard.

Drilling (by hand) a 0.8mm hole in every small post and replacing all the rivets with self tapping M1x2.5mm is a perfect solution; but it takes a lot of patience and a *very* steady hand.

Hope you find this information useful.

Really interested in how it goes for you.

Cheers from the Caribbean.

Diego.

PS: Just to clarify, I have just made th disassembly, but have not made the display replacement.
   

[Johnboy]

Thanks Diego, it's just the LCD I wish to replace. I was given a halfnut CV with broken LCD and clear plastic window.

it's good to know I can replace the LCD without any soldering, thank you so much for that information.

I have removed the heat stakes on full nut CV/CX machines previously, and had good success using hot glue on each stake when reassembling. I am careful when dissassembling to only remove the surround of each heat stake, making a donut shaped piece of plastic being removed. That way I keep all of the heat stake "post", for the glue to bind to.

The drill and screw idea is interesting, I have never thought of that ! Do you have a photo of the M1 x 2.5 screws ? I'd like to see how big the screw head is.

Also, do you have a good method for removing a 41 calculator plastic display window ?

Thanks
John

[rprosperi]

(09-27-2023 03:04 AM)Johnboy Wrote:  Thanks Diego, it's just the LCD I wish to replace. I was given a halfnut CV with broken LCD and clear plastic window.

it's good to know I can replace the LCD without any soldering, thank you so much for that information.

I have removed the heat stakes on full nut CV/CX machines previously, and had good success using hot glue on each stake when reassembling. I am careful when dissassembling to only remove the surround of each heat stake, making a donut shaped piece of plastic being removed. That way I keep all of the heat stake "post", for the glue to bind to.

The drill and screw idea is interesting, I have never thought of that ! Do you have a photo of the M1 x 2.5 screws ? I'd like to see how big the screw head is.

Also, do you have a good method for removing a 41 calculator plastic display window ?

Thanks
John

It would be interesting, and help to future folks undertaking similar repairs, your technique of cutting the heat stakes as you describe - accomplishing that is the key to simpler reassembly so a "how-to" would be appreciated.

[Diego Diaz]

Hi all,

I'm also interested in this "donut" technique. :-)

Regarding the screws, here is an example link. (I have no connection with the seller whatsoever.)

I think that the plastic clear window is ultrasonic welded, hence there are chances to break it. Polishing the acrylate seems a more safe approach. Sorry about the bad news on that.

Cheers.

Diego.

[Johnboy]

Thanks Diego, I did a successful hn display swap last night !

I will write up the "donut method" with pictures.

Cheers,
John