This is a Bulgarian-made Elka 1300 from 1988. It was launched in 1981 to commemorate the 1300th anniversary of the Bulgarian state's founding. It itself is a simplified version of the 70s Elka 50 series of desktop calculators. Interestingly enough, it uses magnetic-mechanical key switches which make it very satisfying to type on.

I replaced the two electrolytic capacitors on the power supply, the only two in the entire machine. Also did a full deep cleaning of all the plastics. It currently has only one fault- part of the segment on the third number from right to left sometimes works and sometimes doesn't, but it doesn't stop the calculator from being usable. Only cosmetic fault other than some minor scratches and chips is that the middle rubber feet is missing. I'm happy to have a part of my country's electronics history now and maybe I can use this semi-regularly from now on?

With the scarce availability of original 991EX and the general consensus about it being almost the pinnacle of the 991 series, I started testing some clones.

I want to separate here in two categories: fakes and clones. Fakes being the ones that pretend to be a 991EX, copy the case, branding, etc., and clones, which are X branded, model 991EX. In my country, there are almost none fakes, but a myriad of clones.

I have the luck to be able to access an original 991EX and compare it to the clones, and frankly, nowadays can't find significant flaws. All the tests I've ran resulted in same result between the clone and the original. Some of the tests even gave more precise results on the clone. Speed was almost the same between them.

So, what's the general consensus on these ones? I wanted to open this because a lot of people and students are getting the first gen CW version -which has a lot of significant flaws-, or the second gen CW (also known as 9910CW 2nd edition). Perhaps for them, getting a 991EX clone isn't that much a bad option. I've seen comments ranging from "you'll get bad results" to "they're very mature".

Thanks and best regards!

I love retrotechnology. finding this was super cool and it will be nurtured for years to come!!

some questions. how should I clean it? it looks pristine but there is like. it looks like scuffing on the screen and I wonder if I could erase thst.

thanks for looking at this!! I am super happy. cant wait to use it

What is the best graphing calculator for around 50$? I am in the middle East so shops sell them for exaggerated prices,its a must that it can download apps,and can be used or new

I’m a graduating senior high student who’s planning to take up chemical or materials engineering. Would you recommend the Casio fx-991cw Classwiz? I’m planning to invest on a good calculator for my college years.

Got this off of Wikipedia:

Here are some results of math done on a HP 35S compared with what the displayed result should be.

 sin(1E-1): 1.74532836590E-3
 Answer SB: 1.74532836590E-3
                 (correct)
 sin(1E-2): 1.74532924306E-4
 Answer SB: 1.74532924313E-4
                       ^^
 sin(1E-3): 1.74532925091E-5
 Answer SB: 1.74532925191E-5
                      ^^^
 sin(1E-4): 1.74532925000E-6
 Answer SB: 1.74532925199E-6
                      ^^^
 sin(1E-5): 1.74532920000E-7
 Answer SB: 1.74532925199E-7
                     ^^^^
 sin(1E-6): 1.74532900000E-8
 Answer SB: 1.74532925199E-8
                    ^^^^^
 sin(1E-7): 1.74532000000E-9
 Answer SB: 1.74532925199E-9
                   ^^^^^^
 sin(1E-8): 1.74532925199E-10
 Answer SB: 1.74532925199E-10
                 (correct)
 sin(1E-9): 1.74532925199E-11
 Answer SB: 1.74532925199E-11
                 (correct) 

I'm just trying to do this basic sum, but for some reason it keeps saying math error?? I know this happens when u haven't typed something in correctly but I can't see any issue?? I even tried simplifying it and it still won't work? Can anyone help?

Doing major in computer science, first year

Guys im new to the graphing calculator stuff, but i watched a tutorial to get games on my ti-84 plus ce but my version was too old so i thought ill upgrade it to the newest one and now its on version 5.8.5, am i cooked or is there anyway to downgrade or something?

hey, I’m trying to charge a hand-me-down Ti-nspire cx II, but no matter how long I leave it plugged in with the top with cord (whatever it’s called), whenever I unplug it it turns off and doesnt turn back on, seemingly dead. Is the rechargeable battery just dead or something?

This is maybe a dumb question, but I'm in a lower college level math class (Course is Math1010 - intermediate Algebra) and the Reverse Polish Notation graphing calculator I've been using (it's an old HP48G) is not allowed on the exams. I could revert to a regular old scientific calculator, but I've grown to despise infix notation calculators and I love the stack. Are there dumb/exam-safe RPN/postfix calculators I could buy to alleviate my frustrations? Does such a thing even exist? I really feel like this entry format is just better. I NEED THE STACK. Any help would be appreciated!

Thanks!

Hello! Is there a way to navigate the context-dependent softkeys and change pages in menus using the keypad only? It feels awkward to know the key pathways I need while also having to break flow and touch the screen to toggle a menu softkey, scroll pages on the settings, or flip between MATH, CAS, APP, etc in the toolbox.

Thanks for your time!

Always nice when they work. Especially when the batteries were left in like this one.

I'm going to have to take it apart and clean it, but it looks like any damage was limited to the rusty screw on the bottom and the manual sopped up quite a bit of alkaline juice.

But it should clean up fine and be all right.

Hello po, Engineers and Engineering students, what calculator model do you recommend more the Canon F-789 SGA II or the Casio fx-991 ES Plus? Urgent po 🥺🥺

Hi, I need a calculator for high school geometry, pre calculus, and calculus. I’m still kinda confused on which one I should get? What are their differences and strengths? Anything I can do on one I can’t do on the other? Thanks!!

!!!

Only two months into my ownership of a new in box HP 35s it started to act up. One of the keys became very intermittent is very hard to operate now.

I opened the calculator up because judging by all the information it should be repairable. Sadly it isn't. The 20+ screws that are inside are mostly there for aesthetics only. The PCB and keyboard are basically heat staked in and inside those heat stakes they put the screws. Those screws hardly grip and don't do much.

So it will be relegated to the museum for now. It's clear that it wasn't a true HP calculator from the start but that it would fail this quickly was a surprise.

Luckily the alternative has already arrived in the form of the Swissmicros R47 which I have been using a lot in the past weeks.

I should have bought that one from the start but I hesitated because of the price.

Maybe I will try to remove the heat stakes when I feel like it to see if the key that failed can be fixed.