|Re: Classic Series Enter Key|
Message #6 Posted by Gerson W. Barbosa on 18 Dec 2012, 12:59 p.m.,
in response to message #3 by Dan Lewis
Only the first picture is linked, but you get the idea.
You might want to take a look at the following, in case you haven't done it yet:
P.S.: I only was able to see your pictures because my wife has a FB account.
Pictures and captions below by Dan Lewis:
The HP-35 (One of the first versions)
The legends on the keys are formed using an expensive, but very effective, double-shot mold process. The legends are cast all the way through the key, ensuring they can never wear off!
The workstation, showing the all important anti static mat and hairdryer (Thanks Mom!) The black coil in the lower left corner is the static suppression cord that connects the mat to the bracelet I'm wearing on my right wrist.
The back label of the calculator (before I got my hands on it), It even shows you how to "work" RPN!
Working very slowly with the hair dryer and razor blade, I pulled the corners up just enough to get to the screws. The calculator was TOASTY!
Here's goes nothing (everything)! I lifted the back off to peek at the inside. Now I was wondering If the static kit would work. I don't know what that white chip is, but apparently, it's OK!
A closer view of the big chip. Sorry, my hands were a tad shaky. The number 300 can be seen in the lower right corner. Your guess is as good as mine.
October 1972, a good year! See that black IC there, can't get that at RadioShack!
Time to dig myself deeper into the hole I'm in! The screws are backed out, releasing the circuit from the calculator's kung-fu grip. Those three silver canisters are the calculator's ROMs. It uses these, like an instruction manual, referring to them for every calculation.
Here can be seen the front half of the calculator separated from its "guts". the backsides of the keys can be seen on the left. More on these later.
This was really the only part I was concerned with, the on/off switch.
Flipping the calculator's innards over, we can see the surfaces that the keys press upon. These are Beryllium Copper strips...plated in gold! The key design has not been changed to this day. Start at the lower left hand corner and go right 4, up one. See it? One looks like it hasn't been pressed right? That's because the ENTER key is double the size of the other keys, but only has one pressing surface. The plastic sheet is for spill proofing. I wouldn't try a "whole" cup of coffee though.
Here's a close up of the ENTER key. See? I told you. Only one does anything, the other is just for show.
Here can be seen a close-up of the LEDs that make up the display. Each one of the 15 LEDs has eight individual segments. HP was the first company to produce LEDs such as these. LEDs of the time used too much power, so HP made their own, better ones. The two chips below the LED matrix also have the hp logo on them. Won't find these at "The Shack". Or nearly anywhere for that matter. You can imagine why I was so scared of static discharge.
Another close-up of the LEDs. The grime on the switch contacts can be seen on the right, between the chips and the key surfaces.
A close up of the four little black lines that had been causing all of my problems.
A little abrasion took care of the problem. Notice that most of the parts on this calculator are either gold or gold plated. Copper would've worn away long ago.
Here's the back of the enter key. I still don't know why they decided to make it that way.
Altough you may not be able to see it, before leaving, so to speak, I penciled in my initials and the date.
A closer look at those contacts on the bottom of the circuit reveals that they are actually snap-like in form. That way, the sides can be assembled separately and then snapped together.
Imagine there are two buttons, push one, you die, the other, you live. I'm exaggerating of course, but that's how I felt flipping that switch. I saw the 0, so I tried the famous 8888888888 CHS EEX CHS 88 that lights all segments of the display. To my delight, it works!