Swann MARK II - Advanced Operation and Maintenance; Alternate Tube Operation; Maintenance Overview; Operational Safety

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13.
also operate in the SSB mode, first tune the
transceiver and Mark II for SSB transmission,
just as described in previous instructions. Then
insert carrier in accordance with instructions
furnished with the exciter. With Swan Trans-
ceivers, this is explained in tuning instructions
under "AM operation."
If the exciter operates only in the AM mode, it is
recommended that an oscilloscope and an audio
oscillator be used for proper adjustment. Feed
an audio tone of about 1000 cycles intothe Mic.
Jack of the exciter and couple the vertical input
of the scope loosely to the output of the Mark II.,
Switch the exciter to Transmit mode and adjust
its modulation level to approximately 90%. Then
adjust P.A. Load and P.A. Tune Controls on the
Mark II for optimum output with minimum flat-
topping of the modulation envelope. Next,
remove modulation and check the total power
input with carrier only. It should not exceed the
legal 1000 watt limit. Reduce coupling from the
exciter as required to control input.
CAUTION: It is quite possible to run well in
excess of the legal power limit on CW as well
as SSB with the Mark II. The design of an
amplifier with excellent linear characteristics up
to the legal limit results in this capability. The
burden of operating within legal limits falls on
the operator and Swan Electronics Corporation
is not responsible for improper or illegal opera-
tion. Every well informed operator should be
familiar with measurement procedures, and with
mathematical calculations of power level. When-
ever possible, an oscilloscope should be used to
monitor peak power levels, since ordinary meters
are unable to do so.
RTTY Operation. The Mark II is rated at a
minimum of 800 watts continuous input power
for RTTY service. The full legal limit of 1000
watts may be run for periods up to 1 hour or
longer when ventilation is adequate. Tempera-
ture rise of the power transformer is the main
limiting factor, and it is limited to a maximum of
105° C
Tuning procedures when using FSK or AFSK
are essentially the same as when tuning for CW
operation. Care must be observed in order to
hold input power to the legal limit. For con-
tinuous operation, it is important that adequate
ventilation be provided. In a confined, relatively
warm environment, the equipment will natu-
rally run hotter, and additonal ventilation from
an auxiliary fan may be advisable. Normally,
however, this will not be required. Temperature
rise is the sole criterion.
Alternate Tube Types. Although the Mark IT is
now manufactured for use with the Eimac
3-500Z tubes, it may also be operated with the
type 3-400Z. Power ratings will be the same.
Either tube type will operate easily at the legal
power limit. The 3-500Z's are supplied with the
Mark II because of the added safety factor in the
higher dissipation rating. Two changes are re-
quired to use the 3-400Z's. First, the plate caps
must be changed, and since the type needed for
the 3-400Z is supplied by Eimac with the tubes,
this should present no problems. Second, the 4
diodes connected in series with the filament
center-tap circuit must be jumpered. These
diodes are the large stud mounted type located
on a terminal board under the amplifier chassis.
Their zener characteristic is used to supply
approx. 4 volts of bias required by the 3-500Z's.
Simply connect a jumper wire around them
if 3-400Z's are to be used.
MAINTENANCE
(a) The 3-500Z tubes will show little or no color,
due to the carbon plate and higher plate dissipa-
tion rating.
(b) The Amplifier Function Switch is no longer vul-
nerable to damage because it no longer switches
the H.V. directly, but switches the relay K3 in-
stead.
(c) K2 is now a highly reliable Mercury relay and
burnishing is no longer necessary or possible.
There will be litle maintenance required in the Mark
II amplifier. The 3-500Z tubes will provide thou-
sands of service hours when operated according to
instructions. Deterioration of a tube will generally
be indicated by a change in idling current or inabil-
ity to draw normal plate current, or both.
However, except for oc-
casional field problems which may occur with any
electronic device, the tubes may beexpected to operate
month after month and year after year withno prob-
lems. NOTICE — Ifwarranty replacement is required,
the tubes must be shipped to the tube manufacturer
with a comple!: failure report. Do not ship them to
your dealer or to Swan Electronics as this will only
delay warranty adjustments.
Other components are also operated conservatively,
and well within nominal ratings. The electrolytic
filter capacitors in the power supply are computor
grade, meaning that they have a much higher degree
of purity and quality control than conventional
types. Life expectancy of these filters is approxi-
mately 10 years. The silicon diodes used in the sup-
ply are hermetically sealed and are not likely to ever
fail or wear out. They are rated at 600 PIV, 1
ampere.
The blower motors are lifetime lubricated and like-
wise are not expected to require maintenance of any
kind.
CAUTION:
DUE TO THE USE OF A MERCURY RELAY
(K2), THE POWER SUPPLY MUST BE SITTING
IN A NORMAL UPRIGHT POSITION BEFORE
CONNECTING OR PLUGGING IN POWER
CORD. THE MERCURY RELAY MAY CLOSE
ACCIDENTALLY IN ANY OTHER POSITION.