Heathkit IM-4100 - Page 50

in A (eegrearearry HEATHEKIT®
IN CASE OF DIFFICULTY
This three-part section gives suggestions for locating and
resolving difficulties.
The first part, ‘‘“General Troubleshooting Information,”
deals with problems that exist when you have just
completed the assembly of your kit. This information
primarily covers soldering and assembly problems.
The second part consists of a ‘“Troubleshooting Chart,”
which gives difficulties and likely causes.
The third part, “Important Wave Shapes,’’ contains
significant waveforms.
If the checks under these three headings do not help you
locate the problem, the difficulty may be a component.
Read the ‘Circuit Description’’ (Pages 50 and 51) and refer
to the Schematic Diagram in the Illustration Booklet to help
you determine where the trouble is.
NOTE: In an extreme case where you are unable to resolve a
difficulty, refer to the “‘Customer Service’ information
inside the rear cover of the Manual. Your Warranty is
located inside the front cover.
GENERAL TROUBLESHOOTING INFORMATION
th Make sure you have power at the transformer primary.
2. Make sure switch SW1 (120-240) is properly set.
3. Recheck the wiring. Trace each wire in colored pencil
on the Pictorial as it is checked. It is frequently
helpful to have a friend check your work. Someone
who is not familiar with the unit may notice
something consistently overlooked by the kit builder.
4. Most problems result from poor connections and
soldering. Use a magnifying glass and check all solder
connections to be sure they are soldered as described
in the “Soldering” section of the “Kit Builders
Guide.’ Also check for bits of solder, wire ends, or
other foreign matter which may be lodged in the
wiring. Look for solder bridges between circuit board
foils. Compare your foil pattern with the ‘’X-Ray
Views’”’ on Page 51 and 52. Many troubles can be
eliminated by reheating all connections to make sure
they are soldered as described in the “Soldering’”’
section of the “Kit Builders Guide.”
5. Make sure that the proper transistor has been installed
at each location and that each lead is in the proper
hole.
6. Press each integrated circuit into its socket so that
each pin will make a secure connection. Be sure that
each IC pin is properly installed in its socket and not
bent out or under the IC.
hs Check each IC to make sure its index mark matches
the half-circle on the circuit board.
8. Check the values of the parts. Make sure the proper
part has been wired into the circuit at each location.
For example, a 150 Q (brown-green-brown) resistor
could easily be installed in place of a 510 Q
(green-brown-brown) resistor.
9. Check the continuity of the circuit board foils. If you
find an open foil, bridge it through the circuit board
with a jumper wire.
10. Areview of the “Circuit Description” may help you to
determine where the trouble is.
Substitution
Corresponding components of the circuitry for each display
can be interchanged with the components of another, IC’s 3
through 7 can be interchanged, for example.
If one display unit shows a digit incorrectly, interchange it
with one of the other units to determine if the display or the
circuit is faulty. If the circuit is faulty and there are no
solder bridges on the associated foil, interchange the
decoder/driver IC with one of the others. This method can
be used with other single digit problems and can be
extended to interchanging the decade counter integrated cir-'
cuits.
Clock Circuit
Verify that the clock oscillator and divider circuits are
operating properly by checking the voltage at pin 12 of
1C19. The meter should alternately indicate less than 0.4
volt for one-half second and then greater than 2.4 volts for
one-half second.