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Seems they are as I suspected, little photovoltaic cells encased in plastic. About 0.5V full sun, 0.25V in a natural lit room.

I've noticed that when you first hit the leads with the test clips, the voltage jumps up to almost 3.0V. It looks like even the high impedance of my meter is enough to drag them down to 0.5V. I have to wonder what they were using to read these in the 1970s.

Seems they are as I suspected, little photovoltaic cells encased in plastic. About 0.5V full sun, 0.25V in a natural lit room. I've noticed that when you first hit the leads with the test clips, the voltage jumps up to almost 3.0V. It looks like even the high impedance of my meter is enough to drag them down to 0.5V. I have to wonder what they were using to read these in the 1970s.

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[–] [deleted] • 1 pt

what is hFE top right button? i'm guessing transistor tester due to the labels on the buttons below?

[–] • 2 pts

Yes, this meter has a built-in transistor tester. It dates to the late 80s when something like that was kind of expensive.

[–] [deleted] • 1 pt

Neato

[–] • 2 pts

Radio Shack sold useful stuff, once upon a time.