Sharp Compet CS-2115 Calculator

Another nice cal­cu­la­tor find for the col­lec­tion is my CS-2115. It is a 12 dig­it cal­cu­la­tor with a vac­u­um flu­o­res­cent dis­play, mem­o­ry, and sev­er­al extra functions.

Sharp Compet CS-2115 after clean­ing and some maintenance

The Sharp CS-2115 was intro­duced in 1979 and had anoth­er vari­a­tion out­side of the US and Canada, which includ­ed a 000 entry key. The cal­cu­la­tor is a sin­gle chip design with a few sup­port­ing com­po­nents main­ly for the pow­er sup­ply. The CS-1115 is a 10 dig­it ver­sion of this cal­cu­la­tor with the only dif­fer­ence being two less digits.

The unit is AC line pow­ered with 120 VAC at 60 Hz with a 2.3 Watt pow­er con­sump­tion. The pow­er trans­former only has a sin­gle pri­ma­ry wind­ing, so no oth­er volt­age options are avail­able inter­nal­ly. The sin­gle sec­ondary out­put of the trans­former is 7.2 VAC.

The case bot­tom has two bat­tery com­part­ment doors, which are unused on this mod­el. The same case is used for sev­er­al oth­er Sharp cal­cu­la­tor models.

The top case is eas­i­ly remov­able with 5 screws and a plas­tic snap on each side. There are no com­po­nents attached to the case top which includes a green fil­ter bezel for the dis­play which is attached by three melt­ed plas­tic posts.

The unit was ful­ly func­tion­al when I received it, but I want­ed to change out the 40+ year old elec­trolyt­ic capac­i­tors as part of the gen­er­al main­te­nance, Overall the unit was in great shape with a scratch free dis­play bezel, and only required gen­er­al cleaning.

The main board is a very sim­ple sin­gle sided phe­no­lic cir­cuit board with a sin­gle 36 pin IC. The cal­cu­la­tor on a chip IC is a SC38402 used in many dif­fer­ent Sharp cal­cu­la­tor mod­els.
There are five elec­trolyt­ic capac­i­tors with four small­er capac­i­tors close to the trans­former, and a larg­er unit sol­dered behind the VFD dis­play. The larg­er round com­po­nent seems to be a 10 pin TO-100 pack­age TDK switch­ing volt­age reg­u­la­tor. A quick check showed a switch­ing fre­quen­cy of 144 KHz, and sev­er­al volt­ages includ­ing 26 volts for the VFD.

The key­pad, switch­es and Futaba 13MT54S VFD dis­play are also attached direct­ly to the main cir­cuit board.

Overall the CS-2115 is a great cal­cu­la­tor with a sharp easy to read green tint­ed dis­play, the keys are laid out nice­ly with a good spac­ing and a pos­i­tive key­press feel­ing with a qui­et but notice­able sound pro­duced at the ends of key trav­el.
Personally I like the over­all style and look of this cal­cu­la­tor. The put­ty col­ored plas­tic has a non-shiny mat­te fin­ish, which is accent­ed by the met­al band placed across the upper row of switch­es. This cal­cu­la­tor cur­rent­ly resides on my main com­put­er desk and is used daily.

The extra func­tions on this cal­cu­la­tor include: Item Count, Right shift, Square root, Register swap, Percent, Change sign, Multiple Use markup, Accumulation selec­tor, Constant select, Rounding selec­tor, Decimal/Add mode selec­tor, and mem­o­ry functions.

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