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INSTRUCTIONS FOR OPERTION OF
115675
;iMPLIFIER
General Description
The M5675 amplifier covers a frequency range of 88 to 108 nc.
This is done without the addition or removal of any padding
components in either grid or plete circuits.
Power gain of
this amplifier is approximately 10.
Vhen used as a final
output stage, maximum power output is in the vicinity of 50
to 60 watts.
The 115675 may also be used to drive following
amplifier stages.
The series type of circuit is used in the grid and a conven-
tional parallel type of circuit is used in the plate.
This
tends to make for less susceptibility of parasitics at higher
frequencies than the amplifier is used.
Screens of the 6146
amplifier tubes
are isolated by chokes rather than El' groun-
ded.
This has proven to be more effective at VET frequencies
and eliminates the need for neutralizing.
The reader should
refer to schematic B-65555 for a better understanding of the
circuit.
o
Tune-up
This particular amplifier should be tuned up for best effi-
ciency and coupled for best transfer of power even if consi-
derably less than full output power is desired.
The screen
control may then be turned down to reduce output power to the
desired level.
To tune the grid circuit, place the negative probe of a volt-
meter,
into TP401 and ground the positive lead.
With drive
connected to input receptJcle J401,
tune 0401 ( grid tunin)
for maximum negative reading on the voltmeter.
This voltage
may vary all the way from - 15 to - 45 volts depending on the
amount of drive.
This reading will drop as soon as screen
-.nd plate voltage are applied to the amplifier.
fter the grid circuit has been Properly tuned,
coupling
between 1401 and 1402, 1403 should be varied to obtain the
maximum negative voltage at TP401 with a minimum of drive.
C401 must be retuned each tine coupling is changed.
When the input circuit has been properly tuned, plate and
screen voltage nay be applied to the amplifier and the plate
circuit tuned.
It is recommended thlt this be done with the
amplifier coupled into a 51 ohm non- reactive load.
If plate
current is being metered,
tune
the plate tune control C407
for a dip.
Otherwise,
tune C407 for maximum power output.
Now vary coupling between L404 and 1405.
Turn amplifier
back on and tune C406 for maximull pc-Jer output along with
C407.
Several trys may be needed to find the best point of
coupling between L404 and 1405.
Each time the coupling be-
tween L404 and L405 is varied,
the plate must be retuned
along with output coupling capacitor C406.
4/21/60
-1-
115675 Arp.
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