Princeton Gamma Tech "System 4"

This page Last updated Dec 26 2009 See this linked page for other DEC systems I have.

A few years ago I acquired a Princeton Gamma Tech "System 4", which includes an LSI-11 board and other QBus cards, in a "small" rack system with color monitor and keyboard. It powers up and boots their operating software, which does chemical analysis. Recently I disassembled this system to save space. The parts are available as of April 2009.

assembled system

The purpose of these systems were to acquire & analyze signals and control a liquid nitrogen cooled SiLi (silicon-lithium) x-ray detector that was mounted in a SEM (scanning electron microscope) port, also interfacing the electronics and providing analysis of microscopic features provided by the microscope. They were superseded by the PGT System 4+ that had non-joined monitors and keyboards, although the bottom cabinets were similar. One System 4 was featured on the forensic MD TV show, "Quincy" with Jack Klugman. Forensic labs are still a big customer base.

The included items are in the rack. There is the LSI-11 chassis ; two 8-inch floppy drives (look like Shugart 851's) driven by a single board controller (probably SASI to floppy); and a number of PGT modules for analog processing and high voltage. (No hard drives.) When booted, the color monitor displays the opening message and requests date and time. The system is not Y2K, it complains about a two-digit year past 00! After this dialog it displayed a graph and waits for function key or typed commands in the PGT application language. Most commands seem to require access to the floppy drive.

Disassembled system

The cards in the QBus computer chassis are, right to left:
upper card, DEC M7270, KD11-HA LSI-11/2 CPU; lower card, memory, 304-0225-001 rev G, looks like 64 Kbytes
PGT board, TVC-449 TV-3 card, for plotter and video RGB monitor
PGT board, ADCC-622 or ADC-4E, an I/O card
SMS (Scientific Micro Systems) brand L/E-HIP, model 57050 ASSY 3614-0001 or 3616-0001, disk adapter card; by 34-pin cable to external SMS floppy board
upper card, PGT-61-963-C, an I/O card; lower card, Sigma brand assy 400200, 4 port serial card

externally there is a Sigma brand SMS FD0-107I, ASSY 3451-0001-L, floppy "formatter" data/control card, between the SMS Qbus board and the floppy drives.

The PGT modules below the computer rack are:
316 HIgh Voltage module
331B S.A. ADC analog to digital module
347 amplifier
310-10 DC supply and display and A/C power switch.

pgt7.jpg, image of back of unit showing drives, formatter board, PDP-11 chassis
pgt8.jpg, power supply
pgt10.jpg, SMS FD0-107I floppy data/control or "formatter" board
pgt11.jpg, rack of I/O modules
pgt12.jpg, PDP-11 internal chassis with fans
pgt13.jpg, PDP-11 backplane power cabling
pgt14.jpg, monitor CRT
pgt15.jpg, probably Shugart 851 drive

To show cabling connections,
pgt1.jpg, image of back of unit
pgt2.jpg, image of back of unit
pgt3.jpg, image of back of unit
pgt4.jpg, image of back of unit
pgt5.jpg, image of back of unit
pgt6.jpg, image of back of unit