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Model 256/PC Instruction Manual
TESTER FEATURES
Functions of the Model 256/PC are selected through function keys on the front panel (Figure 2).
The function keys are flush-mounted membrane switches that are activated by a gentle but
positive touch. Five functions are represented by their own keys, and fourteen others are
selected through a menu. The LCD display provides the user with test conditions, signature
codes, test point numbers or user labels, build sequences, and error information.
A rear panel (Figure 2) contains a Program Cartridge receptacle, power switch, fuse, enable
receptacle, connectors for footswitch and probe, a printer/PC interface port, and four 64-pin
connectors for interfacing to assemblies under test.
A wrist-strap kit provides the capability to locate wires during assembly and troubleshooting
through body conductance, using either a probe provided in the kit, or touch by fingers.
A foot switch is provided for advancing in assembly modes and restarting the test in TEST
mode.
An optional 80-column serial printer provides hard copies of Error Lists, Wire Lists, and User
Label Lists.
SIGNATURE CODES
Signature codes are used for program/harness traceability. They are produced as follows:
The first harness (usually a "known good") of a specific part number is run through the LEARN
KNOWN GOOD mode on the Model 256/PC, which calculates and then displays a six-digit
signature code unique to that wiring configuration. The signature is then used in identifying the
wire list program when selecting it for loading from memory. The signature code eliminates the
requirement of assigning program names to programs for identification.
If a printer is connected, the signature code is included on the wire list and error list printouts.
Whether in hard copy (printout) form or recorded manually, the signature code is paired up with
the part number for that harness, and kept on file to verify and identify programs.
USER LABELS
Six-character User Labels can be assigned to test points for each wire list program stored in the
Model 256/PC. Each User Label relates a harness connector/pin to a test point on the rear of the
tester. When User Labels are assigned to point numbers, all displays and printouts will show
User Labels in lieu of the point numbers. Therefore, when an open or short is displayed between
two points, the display will show the error for the exact connector and pin numbers on the
harness. This eliminates the need to have a separate translation chart cross referencing the test
points to the actual harness connector/pin numbers. The Model 256/PC does not have a built-in
wire list/user list editor. An optional PC DOS software program is available which provides
external control and data transfer between the tester and a PC.
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