A lot of four calculators

This acquisition has been a very lucky find: four devices in the same lot, and three of them from early 1970's! I've had to wait a couple of months before getting my hands on them, but I think it was worth it! Let me briefly introduce them and their display technology (let's not forget I got into calculators because of their displays!):

• Casio CL-200 co-branded Lagomarsino (Nixie)
• Industria Macchine Elettroniche IME-141 (Single-digit VFDs)
• Industria Macchine Elettroniche IME-401 (Panaplex)
• Canon P34-D (VFD tube)

These devices should provide me with some entertainment, beginning with finding a way to power them up! Only IME-401 has a now-standard AC socket, while larger and older machines need a plug probably called "oval". Nevertheless I have been able to power up three of them with mixed results.

Three 1970's and one 1980's desktop calculators.

The real bounty of this acquisition could be the bunch of apparently unrelated power cords, plugs and sockets that came in the box.

RD-160: lower part of the tuning range

Before returning the chassis into the Radiomarelli RD-160 case I had to fix the lower tuning range. If it mutes then something stops oscillating. So I probed the variable capacitor with an ohmmeter and found out that the plates shorted in the first third of the range.

A closer look revealed that the outermost plate, that is made of three petals, was bent. And the middle petal was bent inwards, shorting the capacitor.

Last I cleaned up the plates blowing a bit of air and passing a strip of plain paper through all blades.

RD-160: capacitors replaced

Just a quick visual update now that I have replaced the 5 capacitors. I read an advice of buying axial capacitors as replacements and now I see why.

"All American 5" circuit of RD-160, with new capacitors.

Next step is powering it up!

Inside the Radiomarelli RD-160

My journey into the wornderful world of valves (tubes) has taken me in front of a 5-tubes radio receiver from 1955: components looked different back then!

Without a wiring diagram I've had to reverse engineer the circuit starting from the tubes. Large-ish cylinders are the possibly leaky capacitors. Two of them have like "melted" their caps: I will replace all five. I am in doubt about the large dual electrolytic, and it will stay for now.

Inside RD-160 - original!

In order to reconstruct the wiring diagram I took a picture of the circuit, cut it on the computer to show only relevant parts, increased brightness and printed it out on A4 paper. This way I can add notes on paper while I understand which component is which. I wanted to print it in B/W, just borders, but it wouldn't be easy to distinguish between components on different layers.

Three out of five "suspect" capacitors have lost their markings. I will chop them off so that their leads will be used as support for replacements. The capacitance meter confirms their expected values, within 20%. Still, I don't trust them.

Now waiting for the order to arrive. I chose replacements rated for 630V and I bought packs of 10, just in case I will step into another valve radio to restore (I want one with the wooden case!).

Canon Palmtronic 8 (LD-84)

Yes, another calculator showed up at home. This time it is a pocket device called Canon Palmtronic 8, also known as LD-84. It works off 2xAA batteries and has 8 digits shown on a VFD display. It also accepts an external 3Vdc power source.

This one did not need any restoration, except for some light cleaning of the plastic case.

The rightmost digit is slightly fainter than others because obviously it has been "on" longer than other segments.

What else? The weight is just fine, and those two batteries account for lots of it!