Texas TI-34 solar scientific calculator from 1987

[jebem]

Four elements 2.2V solar panel from National. Two zebra strips used to connect it to the PCB.



General parts view.



Power supply details.
The solar panel generates 2.2V unloaded (off-circuit) under strong light conditions, and 1.75V under load (in-circuit), due to the tiny axial 1.75V LED installed in parallel acting as a limiter/regulator.
The 22uF capacitor gives about 10 to 20 seconds memory contents retention under zero light conditions.



The tiny axial 1.75V LED can be seen here being tested off-circuit.
Check the bright red light at 3 seconds mark.