HP 25C calculator in action!

This is a very hard to find HP 25C. Because their electronics is very fragile, most of them are not in working condition. The main killer is the power supply. Then the battery terminals are not connected to PCB properly, the supply killes the memory chips. Here you can see that it is running the forensic test! The result of the following calculation "arcsin(arccos(arctan(tan(cos(sin(9))))))"

Category:

Science & Technology

Tags:

• HP
• 25C
• Calculator
• Programmable
• Vintage

[superblackser]

@marybob321 - no, this was 1976+, almost 10 years later. Moon landings the first time? Try slide rule, lots of paper, lots of books, and very, very limited computing power. No "calculators".

[superblackser]

I still have mine, purchased new ~1976-77. I replaced the battery pack once in the 1980's. Still works fine. Admittedly my HP-41CV pretty much replaced this so it wasn't used for a long time, but it really is amazing for what I could do with it. It really forced you to be creative within its limits, you could still do amazing stuff.

[senorMiguelCoconut]

wow. great.

... i got this one from my grandma. (really.) :)

[marybob321]

this is the stuff the had to go to the moon with (first time)

[paulellis55]

One of the marvels of the time. Simple, elegant & powerful. Way better for learning and doing high school and college math than the overstuffed TI-8x series that the business development guys in Texas have brilliantly baked into school math curriculum everywhere.

[mixxmexx]

run the moonlander..

[HifiCentret]

Just a little comment. I wanted to power up my HP-25 the other day and grabbed two random batteries (alkaline without thinking). The display lit up wierd. Chocked I though it now was dead too. I then tried two NiMH which has same voltage as NiCd (which they were originally). Thank Heaven it now as it should. So wonder how many of those units are really dead and how many where the owner don't realize voltage can be too high with alkaline / don't have any NiMH/NiCd.

[HifiCentret]

I've got two. Both works electronically but the display on one have segments partly dead (positively the display). Wonder it should be pretty easy to secure the electronics. Perhaps I should experiment on one. If my guesses are right it should be as simple as putting in a few polyester capacitors the right places to kill transients. And while at it you might as well change the important electrolytic for modern polyesters too. (Electrolytics has a bad habit of drying out and cease functioning)

[DrBPhD]

Nice machine but I need more memory for both variables and programs. The quality of these machines was great though. It's a shame they don't make 'm like this anymore (with modern state of the art electronics inside it would be quite useful). Still regularly use a 41CV and a 48G myself.

[fpspapasito]

wow, its freaking awesome, i personally prefer the hp calculators to the ti ones, but if you dont mind, do you collect calculators?