Heathkit SW-7800 - Page 27

Heathkit
Page
115
SYNTHESIZER
CIRCUIT
BOARD
CONDITION
POSSIBLE
CAUSE
No
RF
voltage
at
TP201
or
no
10 MHz oscillator
injection.
(You
|
A.
may
check this
by
using
the RF detector.
See
the
chart
for
the
|B.
Controller
circuit
board.
Connect
a wire
from AF to
the
un-
|
C.
L202,1203.
‘grounded end
of
R206. You
should
measure
2.5 volts
on
the
|
0.
Y20t
VIM,
No
RF
voltage
at
TP202,
‘A.
NoVFO
injection
B._NoVCO
injection,
©.
221,
u2t4
1.
0208,
a209,
a211
LED
D201
ist,
indicating
an
unlocked
PLL condition,
when band
|
A.
C272
through
C276,
Switch
SW4
is set
to
a frequency higher
than
25
MHz,
B.
L209,
L211,
L212.
Display
indicates
a frequency
that
is
455
MHz
too
high.
A.
Ground
jumper
plugged
in at
Display
indicates
000, but
Receiver
receives
okay.
‘A.
Jumper
wire
between
holes
D
and
E
is
missing
Receiver
receives
okay,
bul
random
frequencies
appear
in
the
display.
2216
through
2219,
vata,
U202,
U208
through
U2t2,
op>