Heathkit GC-1005 - Troubleshooting Guide; Display Malfunctions; Setting and Alarm Issues

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Troubleshooting Chart
This chart lists the condition and possible cause of several
malfunctions. If a particular part or parts are mentioned
(Q107 for example) as a possible cause, check that part to
see that it was installed and/or wired correctly. It is also
possible, on rare occasions, for a part to be faulty and
require replacement.
Q105
Q102
ea.
CONDITION
POSSIBLE CAUSE
A digit or a segment of digit
does not light.
1.
Check pins of that display t
- - - ...e.
The same segment of all six
1.
Associated transistor i:Q101
digits remains lit or does
not turn on.
through Q107). See above.
One digit does not light or has
1.
Associated transistors (Q201
undesired segment glow.
through Q212) as follov.'s:
V101B - Q211, Q212.
V101A - Q209, Q210.
V102B - 0207, Q208.
V102A - Q205, Q206.
V103B - Q203, Q204.
•
V103A - Q201, Q202.
2.
Display tube. Interchange tins -.:
if tube is bad.
None of the digits light.
1.
Diode D201.
2.
Fuse F301.
3.
Check for +15 volts at BX on circa..:
board.
4. ZD201.
5. D202.
6.
IC201.
One digit lights up much brighter
1.
Associated transistor (Q201
than others.
through Q212).
Only one digit is turned on.
1. IC201.
Time or alarm cannot be set.
1.
Diodes D204 through D21 1.
2.
Switch S301 through S306.
3.
IC201.