Victor 204R Calculator Checkup and Cleanup

The Victor 204R is dif­fer­ent, but very much the same cal­cu­la­tor as the Victor 204 Medalist orig­i­nal­ly pro­duced by Victor Comptometer Corporation. I picked up this cal­cu­la­tor at a bet­ter than bar­gain price, that was almost a giveaway.

The Victor 204R is a 12 dig­it cal­cu­la­tor with mem­o­ry and per­cent func­tion. This unit was made in Japan for Victor Technologies Inc. which had been recent­ly acquired by Sirius Systems Technology, Inc. in late 1982.
This unit has com­po­nents with date codes in the lat­ter half of 1985. The orig­i­nal Victor 204 was first built in 1976.
Except for the key­pad col­or scheme and name badge it looks to be iden­ti­cal to the lat­er mod­els of the Victor 204 Medalist cal­cu­la­tor, includ­ing the cir­cuit board.
I have seen two oth­er ver­sions of the 204R. One with beige numer­ic keys along with light and dark grey func­tion keys, and anoth­er with the typ­i­cal orange and red func­tion keys.

The 204R uses a Rockwell A4540EB cal­cu­la­tor on a chip IC along with a pair of Sharp IR1403 dri­ver IC’s. Display seg­ments are con­trolled by tran­sis­tors T4 thru T12.
The 204R uses a switch mode pow­er IC (OT1) oper­at­ing at 100 kHz to sup­ply mul­ti­ple volt­ages for the board. The pow­er trans­former sec­ondary volt­age is 13.8 VAC and is rec­ti­fied by diodes D23 thru D26, and then fil­tered by C18 a 1,000uF @ 25 V capac­i­tor to sup­ply 14.7 volts DC.
Other volt­ages on the board are ‑31 volts across C20, and ‑15.6 volts across C19.
The VFD fil­a­ment volt­age is 3.33 VAC across VFD pins 1 and 34.

The cir­cuit board is a sin­gle sided phe­no­lic type and has a 250 mA fuse in the AC sec­ondary input sec­tion before the diodes.

The dis­play is a Futaba 13-MT-37B1 vac­u­um flu­o­res­cent unit with 12 dig­its and minus sign, error, mem­o­ry 1 and 2 indi­ca­tors. The mem­o­ry 2 indi­ca­tor is not used on this model.

The cir­cuit board area behind the dis­play includes some resis­tor arrays, and ceram­ic capac­i­tors. There is also a diode with an elec­trolyt­ic capac­i­tor that is tied to the switch­ing pow­er sup­ply IC, with a mea­sure­ment of 4.9 volts across C21.

The key­pad cir­cuit board is home to 27 key switch­es, and two slide switch­es for the round­ing, and dec­i­mal point func­tions. It inter­faces with the main board via a 21 pin head­er. There are unused pads for three addi­tion­al key switch­es, pos­si­bly used in the mod­el 210R for addi­tion­al func­tions, and pads for an unpop­u­lat­ed slide switch .

Other than being a bit dirty with some yel­low­ing from sun­light expo­sure this unit was in very good con­di­tion. The capac­i­tors checked out in great con­di­tion, so all the orig­i­nal capac­i­tors will stay in this cal­cu­la­tor.
A quick retrobrite pro­ce­dure was all that was required to restore the case­work. The key­caps required sig­nif­i­cant­ly more effort to get into pre­sentable shape. A full 24 hours in the per­ox­ide solu­tion, along with pol­ish­ing each cap with Novus #2 plas­tic pol­ish was need­ed to get them look­ing good.

The AC pow­er cord is per­ma­nent­ly attached, which is a nice change from all the obso­lete pow­er cables that I have recent­ly worked with.
The Victor 204R seems to be an uncom­mon cal­cu­la­tor with very few images or infor­ma­tion avail­able on the inter­net. It is a great lit­tle desk­top cal­cu­la­tor with well spaced keys, and a pleas­ing look in my opinion.

This one was quick­ly adopt­ed by my wife for dai­ly use at her desk.