whenever turned on it displays randomly changing numbers, occasionally stopping on something but then continues randomly changing numbers.
I opened it up and was greeted by what i would classify as gore. I dont know where to start. the display tube has an odd black spot on one end, i suspect that to be a burn mark of sorts. (pic2)
The board at the bottom has an odd wire going seemingly randomly. i have no fucking clue what that is supped to be. (pic3)
wat do?
pic2
pic3
>an odd black spot on one end
That's a getter. It's not a problem.
I'd check the keypad and its wiring first and tried to clean it if it were filthy.
>>917501
Now when I actually checked your pics, I see plenty of track which have lifted from the PCB. Have fun.
Jesus fuck that's an old calculator OP, do want.
So you have two big problems here, dry joints fucking everywhere, and lifting tracks. The first will explain your glitchy operation but unless you have a good 5 years doing professional level repairs (reads; fault finding and diagnostic of analogue and digital electronics) with the soldering skills to match, you will likely do more harm than good trying to fix either i'm afraid. Throw it back together and throw it on a shelf as a neat example of tech gone by, find a collector who can use it for parts or repair it without killing it, or if you're ausfag, sell it to me (who is a collector that can use it for parts or repair it without killing it)
Thanks for the info, I might try finding a calculator with similar button functions and just put in the old casing.
>>917496
Wow, based on the IC package (ceramic) and it's lead layout, that's from the 1970's.
Touch up all solder joints. Replace any electrolytic capacitors. If that doesn't fix it then it's toast, everything is in the IC, and that's long since obsolete, and worse, it looks Russian.
Oh, and be damned sure you're wearing a grounding strap on your wrist working with it, you're working on a grounded mat, and your soldering iron is ESD safe as well, the IC is probably NMOS, won't have shit for ESD protection on it's pins, and will get blown if you even whisper the word 'static' in the same room with it.
I'll just leave this here.
>>917496
>>917497
>>917498
byeutiful
>>917659
How the fuck..?
>>917868
I'm assuming all the calculations are done in the chips to the top left (if this is a calculator). There's no math logic circuits in the schematic.
![a_d068fca9[1].jpg](https://i.imgur.com/qKBKq1x.jpg "a_d068fca9[1].jpg")
>>917868
Anonymous delivers.
what a beauty, please don't fuck this up
I see countless broken solderjoints which are the likely cause for your problems, but it seems like you haven't done something like this before so please let someone who knows what he or she is doing fix this
>>917497
that black spot is the getter you dumbass.
>>918072
Is that not just because it was soldered on the other side, and the "joints" are just what's spilled through the holes?
>>918079
for example those three diodes, the top left one seems to have a loose connection. it just happens over the years
>>918079
>>918080
Possibly, but there is at least one connector from the keypad that has lifted, given the mechanical stress those pins alone would have gone through after god knows how many years of furious number crunching its fair to assume there are fractured joints everywhere. I'm with >>917506 and >>918072. Without some specialist knowledge like >>917647 alludes to, it's just too easy to hamfist a permanent defect into the unit. There are collectors out there that will pay good money for dead/parts only units (as I discovered when I got my hands on a bunch of 30's era aircraft gauges that were mechanically ratshit, but still valuable for their good condition face plates and undamaged glass), if OP found the right forum he might make some decent cash.
>>918097
I kinda just want to desolder that ic and hang that bitch on my wall to look at from time to time.
>>918642
You can find unused Soviet ICs from eBay. No need to smash OP's calculator.
>>917659
I have a completely off-topic question, but I'm not going to create a separate thread for it so here goes.
Can anyone identify the title font? Is it maybe just technical writing in Cyrillic (I'm not too familiar with standard writing etc.) or a more commonly used type?
Pic: semi-related.
>>919064
Roughly:
Schematic of a mixer (FM) discriminator
I would resolder all the parts I marked in red. measure those trimpots because they might not work anymore due to contact oxidation. Clean the entire board would be a good idea too.
>>919138
>
Basically, resolder everything.
>>919163
With an esd safe soldering station, old chips are crazy susceptible to static
Could we have pictures of the case, and the display?
![0emVCR6[1].png](https://i.imgur.com/YFBRUH5.png "0emVCR6[1].png")
>>919673
>>918097
>>919138
some of the connections arent as bad as they look. im just a beginner and i dont have the knowledge repair this thing based on what you say. the most i could do is check some connections and resolder everything, with a piece of wire around my wrist connected to a psu.
what should i do with this thing? put it away for 30 years? find an expert to repair it? sell it?
>>918072
you like old calculators, huh
check this one.
