Hp35 display problem. Opened without bending the sticker

[isanchez]

Hi,
I hate opening classic models because it is almost impossible to release the back sticker without causing a damage. Sometimes this damage is very small, but it is always there. Moreover, if this sticker and the calculator are in perfect state...this is the case of my HP35 (4th version). I would like to share with you my experience. Maybe can be of help.

I have to say that this HP35 looks absolutely new. I have a nice collection of HP35's, but none like this. Some weeks ago I realised that the display was failing. The middle bank of five led bubbles, did not displayed the upper segment, in all five digits of the mentioned bank... I wondered how to open it without ruining the sticker.

My solution was to drill two small holes inside the battery compartment, in order to cut the two screws under the sticker. I discovered that it is not necessary to measure the position of these two screws...there are two small marks in the plastic surface that show their position. The holes should be placed in the bottom half of the calculator, right over the mentioned "marks" in the plastic (this is important). I started first with a very thin drill (1.5mm), using a manual driller (see pictures). When I reached the metal screws, I changed to a Dremel with a thicker drill (3mm-3.5mm). As result, both screws got cut and the calculator was disassembled without affecting the sticker.

On the other hand, you get two small holes in the battery compartiment, but they are not visible at all and, if you want, they can be filled with black putty or black silicone.

As I said, I share some pictures of the process (and the dsiplay failure), available here: https://we.tl/t-HLQF1mHtCf

Following with the repair process, now I would request of your help: Where do you think it lies the problem: is it the display driver, a contact or more surely the full bank of leds? As I see that exactly all upper segments of the whole middle bank are missing, I got doubts of what is more probable, to start with ;-D.
Can I use the HP45 leds?

Well this is it, Thanks and kind regards!!

Ignacio