Heathkit SW-7800 - Circuit Board

Page
114
Heathkit
CONTROLLER
CIRCUIT
BOARD
CONDITION
POSSIBLE
CAUSE
+
16-volt
source
missing
or
low
(about
8
volts).
304,
U305.
1308,
D209.
2322,
0323
6328.
pope
+
12-volt
source
missing,
A.
R609
(on
the
receiver
circuit
board).
*No
VFO
output
A
8.
G.
C3
(tuning
capacitor)
or
shielded cables.
*No
VCO
output
A.
Q316
through
0318.
B.
L301
©.
Output
cable.
Incorrect
input
bandpass
fier
selected
(on the
receiver
circuit
|
A.
$101 and
cable.
board)
B.
$203
and cable
©.
U301
through
U304.
D.
301
through
a315,
Main
tuning
cange
less
than
1
MHz.
A.
Check for +18 ls
at
P301
pin3,
*
You
may
use
the
RF
detector
on
the Controller
circult
board
10
verity
that the oscillator
is
operating.
Set
the
VTVM
to
the 1.5
VDC
range;
then
connect
the
common
test
lead
to
chassis
ground
and
the
test
probe
to
AG
(on
the
AF
detector).
Connect
a wire
from AF
to
the oscilator
output
terminal. You
should
measure
‘about
.25
volt
at the
output
terminal
for
both
the
VFO
and
VCO.