MITS 941M Calculator
I’m not really a calculator collector other than some early HP computers that might be considered calculators by some. I saw a MITS 941M metric converting calculator on eBay and just had to get it. I don’t collect calculators but I do collect MITS Altairs so I was curious.
Here’s a few pictures from the auction:
It was advertised as not tested which means it doesn’t work. When it arrived, I tested it and lo and behold, it didn’t work. I was just praying the batteries didn’t corrode and kill the circuit board. A small leaflet indicated that this calculator had rechargeable ni-cad batteries. That didn’t sound too good. A small prayer and a few screws later, this was what I discovered.
Clearly the batteries are now garbage so I removed them promptly. The construction of the calculator included a clear plastic sheet between the batteries and the circuit board and this was the savior or the circuit board would have been
Disassembling it a little further, I could see the circuit board looked very “Altair-like” with a light colored board and tin traces. To my surprise, a white ceramic chip was visible so I had to pry it open a little. Enclosed was a MOS MCS 2521 integrated circuit. Unfortunately, the way the display was attached, I couldn’t take a complete picture of the calculator motherboard.
At some point, I’ll try to put in 6 AA batteries and see if it fires up. I don’t think it will be a problem but all-in-all, I think this is pretty cool and is an excellent example of the lineage of Micro Instrumentation and Telemetry Systems.