Commodore SR-37 calculator “repair” and review

Before Commodore made computers, they made typewriters, and later calculators. I scored one such calculator, one that was listed as “non-functional”. The repair itself was very quick, as I had expected.


Honestly, it was just the power adapter. And some gunk in the keys. I’ll spare you the details on the gunk for today. Let’s see what’s wrong with the plug. Here’s the picture from the listing:

昭和の頃 赤色表示電卓 コモドール Commodore SR-37 難有品(^00WH10A_画像1
The pic from the listing.

Why would you bother to take a picture with the AC adapter cord connected to the calculator but the AC adapter not plugged in? Well, while I didn’t really think too much of it when I saw the listing, I quickly found the answer after it arrived here: it’s damn impossible to get out of there!

Until I got out some pliers and turned it left and right while pulling a little bit for a while. The cable was really sticky, and I believe (though this is half a year ago already) pretty much glued the connector to the device.

So, did they use a bit of an unusual plug shape? Yes, they did! It looks a bit like a mono headphone connector, maybe a bit thicker? (That reminds me, the ZX81’s power connector probably uses something similar.) But anyway, my trusty 28 in 1 “28 in 3” plug set ( contained something that fit beautifully, and applying power at about 9V, the calculator sprang to life.

Original connector (top) and replacement connector
Glorious LED display
Device’s innards. I didn’t take it apart any further than this, but cleaned up the gunk. Apparently didn’t take an “after” picture though, so you’ll just have to trust me that it looked as clean as a whistle afterwards. Maybe.


So you are thinking of buying a calculator, and hey, you’ve always wanted to show off how cool retro tech can be. Someone nearby is selling a retro calculator with an LED display. It looks fantastic! But will it be useful?

The Commodore SR-37 does pack a lot of functions, maybe not quite as many as a modern scientific calculator, but it’s not far away. (For example, you can’t easily convert degrees to radians.)

So let’s see how useful this thing is. I’ve thought of some expectations the modern calculator user may have that aren’t quite fulfilled by this device:

Doesn’t use power when turned off using power switch on device.
Doesn’t use a lot of power. So for example not 1.4 W even when you make it display 8888888888888888888888.8.
Doesn’t turn off the display to conserve power after a short while.
Doesn’t take a long time to compute, e.g., exponentials or roots. Definitely not like 2 seconds!
Comes with a boring LCD rather than a beautiful LED display.
Table 1.1: table of broken expectations

The main problem in my opinion is that it uses a lot of power. Even if you turn it off, it’ll use some power (100 mA or so). At least my model didn’t come with a place to put in batteries so it’s external power only. The fact that this device is basically slightly on all the time (unless you unplug the cord or have a switch nearby), I’m a bit concerned for its longevity. So I don’t think I’ll use it much. :(

Besides, what I really need is a calculator that is really good at converting between bases, like kcalc. I’m not sure such a device even exists!

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