Dot matrix LED driver chips

While searching for something else, I came across a forum where a bunch of TIL305 dot-matrix vintage LED displays would be driven by a HT1632C chip. Neat, because it would avoid the abuse of bunch of ATtiny's and allow greater flexibility. Unfortunately the usual Far East sources don't stock a breakout board with the HT1632C already soldered and without a modern LED matrix.

DIY? HT1632C comes in 48/52-pin LQFP package that is too small for my soldering tools.

Well, digging a little further I found that Holtek produces also three versions of the HT16K33 driver, and it is commonly found on breakout boards on eBay, without LEDs attached. It is controlled via I2C and it features a matrix keyboard input too, just in case. Last but not least, its made in 20-28SOP that is manageable with a fine tip soldering iron if I ever want to make a PCB (not a bad idea since wiring is going to be a mess).

I ordered a few, so that all those TIL305 can finally spring to life.

Industria Macchine Elettroniche IME-141 - power up

A fuse holder inside IME-141

Industria Macchine Elettroniche IME-141 calculator was the one in the lot of four that wouldn't power up, so it was necessary to have a look inside. The first step was to remove three screws and I got a bit worried when I found all of them to be loose. At the first peek inside I noticed the dust (meaning not much has been done inside), the date code on a capacitor telling me (19)73 and a fuse holder: that's a synonym of hope!

Hidden into the fuse holder was this transparent component, showing to the world its inner workings and an obvious gap: the fuse had blown.

Blown old fuse

Its markings suggest it was 125V 1/16A: so large and so sensitive? Perhaps it wasn't even the original one, since there is no marking on the expected value. The closest I could find at home with the same size was 5A, borrowed from another appliance. Well, better 5A and a finger on the power switch than a fully bypassed fuse, isn't it?!

"Hello 2018 World" from IME-141.

All set: calculator switch in "ON" position, finger on the external switch ("OFF"), eyes closed in case something blows up. Click! No alarming sounds, no smells. So I did open my eyes to see the squared 0 staring at me. It works!! Fun is over. HA!

Actually I need to find a safer way to power up the beast without replacing the AC socket. Or forget the historical thingie and fit a standard one.