Model 7002Switch System Instruction Manual - Advanced Test ...

MaintenanceTrigger 8 (STI8) is set up as input. The 9914 (U106) is thenprogrammed to generate a GET signal. A failure may indicatea problem with the ASIC or with the 9914.Tests 105.11-105.18 ⎯ Trigger Shorts testsFailure of Tests 105.11-105.18 suggests a digital board error.In Test 105.11, STI1 is programmed as the trigger input.Each of the other triggers (STI2-STI7 and GET) is programmedto toggle in turn. If a trigger is detected at STI1, ashort is indicated and the test fails. The test is repeated forSTI2-STI8 in Tests 105.12-105.18.Ordinarily, built-in-tests should be run with no external connections,however, the Trigger Shorts tests may be used toverify proper operation at the external TRIGGER LINK connectors(J1004, J1005). For example, by shorting pins 1 and2, and selecting BIT 105, faults 105.11 and 105.12 shouldoccur indicating that a short was detected between systemtrigger 1 and system trigger 2.the digital board (or at minimum, the microprocessor, RAM,EPROM, and EEPROM) is functional.Raw power supply voltages can be measured at the pointwhere they are cabled to the digital board from the powersupplies. Regulators on the digital board reduce the powersupply +6VDC level to +5VDC. This voltage can be measuredon regulators U116 and U117. The +60VDC used topower the vacuum fluorescent display is provided by U118(OUT+). The lithium battery should measure 3-3.25VDCbetween the case (+) terminal and chassis ground.Most connections between the digital board and other boardsare made through mass termination connectors, so there is aminimal chance of problems due to broken wires.Symptom ⎯ Diagnostics do not run:• Suspect a faulty digital board, display board, or powersupply.7.9 TroubleshootingThe following information is designed to help you troubleshootthe Model 7002 if a problem develops which resists diagnosisby the built-in tests. The BIT does not test to a 100%confidence level, but will detect and identify a majority ofproblems.WARNINGTroubleshooting procedures may requireyou to apply power and operatethe Model 7002 while it is partially disassembled,thus exposing you to lethalvoltages. To avoid risk of personal injury,refer any such procedures and testingto qualified personnel.7.9.1 Digital boardThe digital board contains most of the logic in the Model7002, and is tested extensively by the BIT. If the BIT runs,Symptom ⎯ A “No Comm Link” error indicates that the digitaland display boards are not communicating. If this erroroccurs, check for:• Defective battery.• Bad cable between digital board and display board.• Defective digital board.• Defective display board.7.9.2 Display boardsThe display test verifies individual characters, annunciatorsand LEDs on the display boards. If the instrument powers upand executes this test, the display boards and digital boardlogic are most likely operating properly. Problems with individualcharacters, annunciators or LEDs, should be easilyidentified. If a display is dead, check the condition of the ribboncable connecting the digital and display board. Serialcommunication and power for the display boards (including60VDC) are transmitted over the display cables.7-16