UNIVAC Solid State

The UNIVAC Solid State was a 2-address, bi-quinary coded decimal computer, with memory on a rotating drum with 5000 signed 10 digit words, spinning at 17,667 RPM in a helium atmosphere. It was announced by Sperry Rand in December 1958, as a response to the IBM 650. It came in two versions: the Solid State 80 (IBM-style 80 column cards) and the Solid State 90 (Remington-Rand 90 column cards).

With 20 vacuum tubes, 700 transistors, and 3000 FERRACTOR amplifiers in its CPU, the Solid State was one of the first computers to use solid state components.

The system used a clock derived from a timing band recorded on the main storage drum. This signal was read and amplified, processed and sent to the driver tubes, a pair of 6146 power pentode output tubes. The output from these 6146 tubes then fed the main clock power amplifier consisting of six 4CX250B metal/ceramic power tetrode tubes running in push-pull/parallel, yielding an output of a kilowatt. The SS80/90 computer could be heard quite clearly in the AM broadcast band at 707kHz and 1414kHz. The 4CX250B Tetrodes used a grounded plate (anode) due to forced aircooling requirements. Interestingly, this tube is still in demand by amateur radio operators. The power supply output was -1.6KV for cathode supply and -800V screen grid supply at 1.8A capacity. The supply weighed nearly 100 pounds and was mounted at the very top of the power supply stack.

The Line Printer ran at 600 lines per minute, using a continuously rotating print drum technology, with letters, figures and punctuation marks distributed around the drum at each column. 132 solenoid-operated flat-faced print hammers comprised a print line. pinched at ten to the inch. As a desired character arrived at the printing position, as indicated by timing marks on the end of the drum, a thyratron would fire and energize a print column solenoid, propelling its hammer to the back face of the printing paper. The paper would be bounced against a wide inked ribbon and against the drum, printing the desired character. The hammer would then rebound with a spring to await the next thyraton firing and the process would repeat on the next line down the sheet. Drum printers, when not adjusted properly, or due to component wear would mis-register the character vertically The Card punch had a maximum rate of 150 cards per minute. Timing was quite critical throughout the operation of the card punch, the card reader and the printer, all being based on electromechanical principles. The basic card punch mechanism was manufactured by Bull, a French company with license to manufacture and market sell an 80 column punch. The machine came in two versions, the P147 and the P67, the main difference being electromagnetic clutch or a solenoid operated mechanical "dog" clutch to initiate a punch cycle. Since many gears, electrical contact cams were affixed to the main shaft with taper pins, the P 67 with it's severe stopping dog clutch would cause timing loss more frequently than the P 147. Most emergency maintenance time was spent replacing worn and damaged taper pins and retiming the machine. The card punch had a preread station, a punch station and a checkread station. The machine could be quite difficult to maintain and required much skill to troubleshoot and maintain. The machine cycle was oddly divided into 420 "points" or "Bull degrees".

See also

• List of UNIVAC products
• History of computing hardware

External links

• Unisys History Newsletter. Volume 1, Number 2, December 1992 (revised 1999) - The UNIVAC Solid State Computer
• Univac Solid State Manuals and documentation