Thanks to John Novack for these.
Work In Progress
The Sage 930A is a handy piece of test equipment, which can be had for a fairly reasonable price on eBay. Being an 80's vintage piece of electronics, it is also very repairable, so even units being sold as non-working can be quite easily brought back to life. From a design standpoint, it was quite leading edge, containing two break-through devices: the first DSP (the TI TMS320) and the first FPGA (the Xilinx XC2064).
The supervisor brains of the system; a 4 MHz Z80 CPU and supporting logic.
There are two identical PCM cards in the system, the only difference between them being a jumper setting and their position in the chassis. The ROMs on these cards are part of the system address bus, and the set will fail its boot-up ROM tests if either of the PCM cards are removed.
Handles signal processing and tone generation functions.
In addition to the listed semiconductors, this board contains a number of relays and transformers, providing all the facilities required to simulate and terminate an analogue line interface.
Not documented yet. Largely dominated by VFD driver circuitry.
Not documented yet. Very little active electronics.
In both of my Sage 930As, the power supply is a custom Power-One unit. It appears to be a fairly standard +5v, +15v and -15v design, tweaked (by Power-One) to provide -52V, -48V and an opto-isolated 120Hz powerline-derived timing reference signal. The circuitry providing the -48V regulation and the 120Hz timing signal appears somewhat bodged on to the end of a standard power supply design. The diodes constituting the bridge rectifier for the timing signal are tucked in wherever there is free space on the PCB.
This power supply has a number of what appear to be custom semiconductors. Depending on the vintage there can be up to three: the main regulator IC, the main chopper transistor, and the feedback transistor. The desire to obscure the origins of the regulator IC seems to have abated in later power supplies, so I know that it is a LM723 regulator. The other two devices continue to have untraceable part numbers.