2015's calculator anniversary - the SR-52

[jebem]

Reassembling the keyboard PCA takes a steady hand and lots of patience.

I had to remove the metal domes from the original auto adhesive plastic film.
Then drop and align the domes one at a time, row by row, on the KB PCA.

To fix the domes in place, have just used regular (1.5cm wide) transparent adhesive tape.
After finishing with the 5 rows, have cut the excess tape around the lateral sides and applied a second layer of a wider (5cm) adhesive tape to seal the keyboard contacts.

A brief electrical test confirmed that all rows and columns were isolated between them.
Testing a couple of key presses confirmed good electrical contact as well.




After soldering back the KB PCA, did some more testing.
I'm using an external regulated power supply at 3.7V.

The initial random issues are gone, probably due to the cleaning and re-soldering.

After powering on from a cold state, this is what the SR52 can correctly calculate:
- All single X register functions (lnX, logX, x!, 1/x, √x, x2, sin, cos, tan, asin, acos, atan);
- D.MS and D/R both ways (using INV key);
- Degrees and Radians switch afects the calculations accordingly;
- P/R (polar/rectangular) works as well - in this machine it takes Memory Register 00 in addition to Register X;
- The four basic arithmetic operations are fine when using the PROD (x and /) and SUM (+ and -) functions for direct register arithmetic on any of the Memory Registers 00-19.
- Storing and recalling numbers to/from Memory Registers 00 to 19 and 98 and 99.

However, two issues remains to be fixed:
1.- The machine stops responding to keystrokes about 15 minutes after power on.
2.- After powering on from cold, this is what the SR52 is failing to do:
- All operations requiring more than the single X register (˟√y, y˟ , x, /, +, -);
- In LRN mode (programming), any key-codes appears as "00";
- Trying to store numbers in the Memory Registers 60 and 70 will just recall "00" as well.

The usual forensics test: 9 sin cos tan atan acos asin returned: 9.000004661




69! testing:



Degrees selected. 45 sin looks to be OK.
(I also tried sin (Pi/2) in Radians mode and the result was 1)




Idle current consumption around 160mA @ 3.7V.