Heathkit IG-18 User Manual

Page 58
TROUBLESHOOTING CHART
DIFFICUL TY
Pilot lamp lights.
No sine or square
wa ve output.
B+ voltage low or
no B+ voltage.
No sine wave output.
Square wave output ok.
No square wave output.
Sine wave output ok.
Bottom of
square wave
goes below zero.
POSSIBLE CAUSE AND SUGGESTED CURE
1. All controls set at zero.
2. Measure the B+ voltage at point A on the
generator circuit board. If the voltage is
low or there is no voltage, refer to the next
Difficulty on
this Chart.
3. Feedback control not setproperly. (Refer to
Adjustments section on Page 41.)
4. Check transistors Ql, Q2, Q5, Q4, and
Q3 in that order.
5. Open filam ent in lamp Ll.
6. Wrong part value, improper connection,
or faulty part in notch filter circuits
(units and tens switches). checks at
other frequency settings to test this pos-
sibility.)
Measure the resistance of the &"U"""~V" circuit
board at TPI as described step under
"Tests" on Page 39. If '" less
than 1500 (2, apply the the previous
page to the generator '-'u ""..... If the re-
sistance is 1500 n '" check the fol-
lowing:
1.
Transistor
2. Diodes D5 and
3. Zener diode
4.
CapaCitors Cl C2, C3, and C4.
5. Transformer primary windings.
1.
Short circuit or excessive load at sine
wave output terminals.
2. Check control RI06.
3. Check capacitor C6.
1. Short circuit or excessive load at square
wave output terminals.
2. Symmetry trimmer not adjusted properly.
3. Check transistors Q6, Q7, and Qa.
4.
Check control RI0l.
5. Check capacitor ca.
6. Frequency set too low.
1. D8 open .•

Heathkit IG-18 Specifications

General

Brand	Heathkit
Model	IG-18
Category	Test Equipment
Language	English