MC1494 Ring Modulator

This PCB pretty much follows the test circuit given in the datasheet, although I'd like to know where it came from. Please add a comment if you know - thanks.
It has not been tested yet. If the chip is okay, the components will get a makeover. If the chip is dead, the board will be replaced by an early Serge RM, as 1494s are a bit rare now.
see below for updates

Dave Jones of http://www.jonesvideo.com/ kindly gave me a bit of info on these - "The chips are dated late 1971 and early 1972. Allowing for time in the supply chain the board is still probably from the early 70s (1972/73).

The op amp might be an industrial part numbered UA741. (metal can pin numbers are the same as MC1456, but the marking contains 741 in it)

The board is virtually identical to the "typical" diagram from the data sheet. Right down to the trimpot I crossed out (board was laid out for it, but it was jumpered out).

The board has a spot for a pair of zeners that are independent of the rest of the circuit, except for one leg going to ground. But those parts aren't installed."