Specifications

Page 11
Copyright 2006 Robert A. Larson, KC9ICH
CHART I
TROUBLESHOOTING GUIDE
Symptom
Probable Cause / Cure
Unit is totally inoperative.
Check fuses.
Unit operates on 117VAC but not on 13.8VDC.
Check fuse and diodes CR1 through CR4.
Operates on DC. Will not operate on AC.
Check for defective fuse, F2, defective transformer
Ti and bridge rectifier diodes CR5 through CR8.
All digits in display light but unit is inoperative.
See Chart II for troubleshooting procedure for this
symptom.
Unit operative but with small error.
Requires calibration. See paragraph 5-3.
Only least significant number in display changes
with changed input.
Defective counter A9.
Only least and next significant number in display
changes with changed input.
Defective counter A8.
First three digits change with input change, others do
not.
Defective counter A7.
One display (other than most significant figure) does
not change with change in input.
If second most significant figure, defective counter
A7 or decoder/driver. If other digit, defective
decoder/driver.
Most significant figure (permanent ―2‖) is only
lighted display.
5 Volt regulator defective.
Display reads 25. 500 even with input.
Defective input amplifier Q1, defective sampling
gate A6-B. Timing system defect. See Chart II for
timing system troubleshooting.
One segment in one digit of display does not light.
Defective display unit. Defective decoder, driver.