Friden 1160 Circuit Board #5

Circuit Board #5 is unique to the 1160, providing various control functions. Board #4 and Board #5 in the 1160 contain most of the control and sequencing logic for the calculator.

Board #5 in the exhibited Friden 1160 has a total of 16 integrated circuits, of which three are 7400-series TTL devices made by Signetics, with the remainder being DTL devices made by Texas Instruments. Along with the IC's, the board contains five transistors, 38 diodes, 61 resistors, and 17 capacitors.

An earlier version of this board was manufactured and made its way into very early production 1160 calculators, as a Revision 1 board is mentioned in the first version of the Service Manual for the 1160, which was published in early January of 1969. An update to the Service Manual, published in March of 1969, shows the Revision 2 board replacing the Revision 1 board. The Revision 1 Board #5 uses one fewer integrated circuit than the Revision 2 board, and the layout of the board is significantly different. If you have a Friden 1160 with a REV-1 Board #5, the museum would love to hear from you. You can click the EMail button on the navigation bar at the top of this page to contact the museum.

The Service Manual, along with other training materials for factory and field service technicians had to be prepared well in advance of release of the calculators for sale, to allow the service force to have proper reference materials for training and service of this new series of calculators, especially since the 116x-series were Friden's first calculators that utilized integrated circuit technology. Along with the field force, the sales force also has to have been trained the features of the machines, and best how to sell these new calculators versus the competition. Along with training, a batch of production calculators needs to be sent out to all of the sales offices and any authorized distributors so that they have machines that they can demonstrate. This is why the Service Manual was published well before the May introduction date of the 1160/1162, and actual trial production of the calculators likely commenced at the very beginning of 1969, with prototype and pre-production machines likely built in the latter part of 1968.

Board #5 in the exhibited calculator has a date of April 1, 1969 stamped onto the upper right-hand edge of the circuit board. Another 1160 Board #5 has been observed with a date stamp of February 13, 1969. Most likely this date was stamped on the circuit board at the point when it had been completely assembled and passed production test procedures and was placed into finished board inventory for installation in a calculator. Some 116x-series circuit boards have been observed that have no discernible date stamped on them. Why some boards have the date stamp and others do not is a mystery.

This board, based on the April 1, '69 date stamp, has the roll pins inserted into the holes at the upper left and right corners of the board to aid in removal of the board from the card cage. After a June 12, 1969, production change order, the roll pins were no longer installed, leaving just the holes. Friden created a special tool that field and factory service people could use to easily remove the circuit boards, making the roll pins no longer needed.

Any Revision 1 boards had to be installed in 1160 calculators built within a few weeks or so after February 13, 1969, as there is certainly time that elapses between the date a circuit board is completed, and the date at which it becomes a part of a completed and tested calculator, which is when the serial number is assigned. This is further indication that the changeover from the Revision 1 board to the Revision 2 board likely occurred sometime in January of 1969.

The bare circuit board in the exhibited calculator carries Friden Part # 7002189 Revision 2, and the complete board assembly has Part # 7002188. The Revision 1 board carries the same part number, and specifically has "REV-1" etched into the circuit board after the circuit board part number.