Troubleshooting; Before You Start-Safety Summary - Wyse WY-99GT Maintenance Manual

4
Troubleshooting
Before You Start-Safety Summary .................. 4-1
Tools Required ..................................... 4-2
Primary Troubleshooting Procedures ................ 4-2
Preparing the Terminal for Troubleshooting ............ 4-2
Power-On Self-Test .............................. . .. 4-2
Diagnostic Self-Test ................................ 4-3
Troubleshooting Quick Reference Guide ........... . .. 4-4
Troubleshooting Flowchart ......................... 4-5
Problem Symptoms and Troubleshooting Procedures .... 4-8
Symptom 1: No Video . . . . . . . . . . . . . . . . . . . . . . . . .. 4-8
Symptom 2: Dim Video ........................ 4-9
Symptom 3: A Single Line of Video on the Screen .. 4-10
Symptom 4: Vertical Roll ....................... 4-11
Symptom 5: Video Brighter on the Left Side,
Characters Compressed .......... . .. 4-11
Symptom 6: Raster; No Video .................. 4-11
Symptom 7: Letter on Screen Before or After
Diagnostic Self-Test . . . . . . . . . . . . . . . .. 4-12
Symptom 8: Poor Display Quality ................. 4-14
Symptom 9: Keyboard Not Operating ............ 4-15
Symptom 10: Communications Problems ........... 4-1 5
Symptom 11: Characters Scrambled or Degraded,
Dots Missing .. . . . . . . . . . . . . . . . . . . . .. 4-1 5
Symptom 12: Characters Don't Appear on the Screen 4-1 5
Symptom 13: Graphics Doesn't Work ............. 4-15
Symptom 14: Atrributes Don't Work .............. 4-15
Symptom 15: 80/132-Column Mode Doesn't Work 4-15
Additional Troubleshooting Procedures .............. 4-15
Installation Checklist ................................ 4-1 5
Checking for Continuity ............................. 4-1 6
Power Supply Check from the Logic PCB .............. 4-1 6
Checking Horizontal Synchronization .................. 4-18
Checking Attributes and 80/132-Column Mode .......... 4-18
BEFORE YOU START-SAFETY SUMMARY
A
Warning This terminal contains high voltage. Don't attempt to
service the terminal without taking all precautions needed when
working with high voltage.
• If you must open the terminal for any reason, first turn off the
power and unplug the terminal.
• Remove any jewelry, especially any on your hands and wrists.
Also remove jewelry from your neck if it is long enough to
hang in the machinery. Avoid wearing clothing that carries
static charges.
• Use only insulated or non conductive tools.