Thorn 8500 Chassis
Model: Ultra 6713
Original List Price : £222.64 (exact price in 1971 unknown, this is the 1975 price )
Integrated Circuits: Yes
June 1971 saw the production of the first British colour chassis aimed at breaking through the £200 barrier – The Thorn 8000 series chassis. With a 17″ A44-271X shadow mask tube and all solid state circuit. Along with its successors, the 8000A, 8500 and 8800, proved to be very popular with the viewing public and more reliable than many engineers at first predicted.
Here we have the Ultra 6713 with the 8500 chassis, which was released in July 1972. It differs from the 8000 using a 19″ tube: the higher scan drive requirements led to a redesigned line output stage and focus circuit and the use of a choke instead of a dropper resistor in series with the live mains input line. This latter modification provides an HT rail of about 190V in place of the 170V used in the 8000 series. Line output is via a 1700V transistor the BDX32