This is the back side of the main PCB in a Canon PowerShot G9. When assembled, the mystery chip is facing the shielding over the battery compartment. The chip is mounted in a clear QFN package, and there's a big black area that looks suspiciously like a light sensor. Which doesn't make any sense given the ICs location.
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Any guesses?
Expensive looking package. Someone thought whatever it does, was important enough to spend extra money.
My guess would be that it's a crypto chip, with an 'erase keys if camera opened' tripwire. In which case that black square is not a light sensor; rather a solar cell, that gives enough power under room light to drive the erase circuit.
Now, why would there be a secret-key crypto chip in a consumer camera?
I have a much simpler question.
The tag strip of custom wire-wound resistors are from an old Shimadzu QV-50 Spectrophotometer. One of them has been replaced with a multi-turn pot, presumably because the original resistor failed.
I have two of these instruments, from the same source; on the other unit these resistors are all original.
The question: These wire resistors (1st pic) use a wire with low temperature coefficient, yes?
So, how would I go about constructing a proper replacement, with the right temp coefficient?
The trimmer is set to 980 ohms, and I could measure the hopefully still good resistor on the other unit.
Oddly enough, only some of these have anything written on the little slips of protective paper, and there's only loose correspondence between the written numbers and actual values. For instance one marked "10" is 8.9K.
Incidentally, I've had zero luck finding any kind or user or service manual for the QV-50. Shimadzu didn't reply to a query.
All I found were a few advertisements in old magazines from the 1960s.