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As was mentioned previously,
crowding the band edges is not recommended unless a positive
and constant check upon frequency is maintained.
Particularly with a phone transmitter where
the sidebands may run three or more kc over and under the base frequency.
Even a single side-
When plugging the VFO output into a crystal socket,
be sure that the "hot" lead or center
wire
of the VFO plug is connected tothe grid side of the crystal socket.
If the VF-1 tends to overdrive
the crystal stage, swamping resistance can be connected across the crystal socket.
IN CASE
OF DIFFICULTY
'
Mistakes in wiring are the most common cause of difficulty.
Consequently,
the first step is to
recheck
all wiring against the pictorials and the schematic diagrams.
Often having a friend
check the wiring will locate an error consistently overlooked.
Also, with miniature sockets there is a possibility of shorts between adjacent socket terminals
due tothe close spacing.
This should be checked and if any doubt exists, the terminal should be
pried apart until obvious spacing can be seen between them.
Sometimes apparently good solder connections will have an insulating coating of rosin between the
wire, terminalandsolder.
This is oftenthe case when insufficient heat was applied in soldering.
An ohmmeter check of connections,
WITH ALL VOLTAGES
OFF, will test this condition.
A voltage check at tube socket terminals will often indicate the reason
for faulty operation.
A
table of voltages is shown
below.
These voltages were measured
with a 20,000 chm
per volt
multimeter,
during VF-1 operation with the Heathkit AT-1 Transmitter.
Range Switch
40-20-15-10
NOTE:
A VTVM
should not be used to measure voltage asthe presence of RF will invalidate the
reading obtained.
If a different source of power supplies the VF-1, the voltages in columns 1,
5 and 7 of socket A (6AU6) will change accordingly.
Page 18
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