Sharp EL-5800 Scientific Calculator: sturdy built and reliable machine

[jebem]

Got this machine since a long time ago, in dismantled state and waiting to be repaired.
Today morning I decided it was time to start emptying the dismantled machines drawer, so I picked the one at the top of the pile. I have another model with similar build documented here.

The only issue with this 1976 machine was the battery compartment that had oxidation in the power switch/battery terminal assembly. The machine was sold as non working.

According to the Instruction Manual, this calculator takes two AA dry batteries, or the optional Ni-Cd battery pack EA-18B and the Ni-Cd Recharger model EA-17E.
Look to Katie Wasserman site for the manual.

After cleaning all the parts to remove the battery electrolytes products, it was time to repair, test and assemble it.




Single chip machine: Hitachi HD36125
Display Futaba 9-ST-12




Keyboard assemblage.
Note the metal spring interconnecting the front metal face plate with the keyboard metal frame assembly.



The keyboard PCA snaps over the keyboard membrane and two screws fix it securely in place.




Heavy battery corrosion has damaged the positive terminal in the battery compartment.
I have these miniature battery terminals at hand, so have trimmed one of them and soldered it to the original remaining terminal.
Could not do a clean job though, as the plastic assembly is soft and started to melt when soldering.
I was too lazy to dismantle the whole set in order to be able to do a cleaner job.
Still it is mechanically and electrically working fine now, despite the ugly looks.



(continued)

[jebem]

After power on. Current consumption = 62mA
All digits lit. Current consumption = 80mA



Main PCA folded and in place.




Cover installed. It snaps at 10 different points (latches). It takes just one screw.




Forensics test - asin(acos(atan(tan(cos(sin(9))))))result:
10.7508





Error condition on display: SQRT(-2):
All zeros and all decimal points lit.




Despite being boxy, it is still a nice looking machine.




This is the package I got.