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Turning an MLA-2500B into a
GS-35B HF RF Deck
The remote Power supply is 0-5000 VDC @ 2
AMP, CCS. Running at 3500VDC no load, it pulls down to 3300VDC
under full load. Plate current is 600-700 mA and grid current
runs about 200 mA with 100 watts drive. Idle grid current is 100
mA with a single 50 volt, 50 watt zener for bias. This PA is capable
of between 1700-1900W output on most bands, using the stock MLA-2500B
tank circuit. Input is untuned, as a properly tuned GS-35B presents
an input impedance which "looks" enough like 50 ohms to please
any transceiver/driver!
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Click
on picture for zoom .
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MLA-2500 with original tubes removed, power supply removed, and
GS-35 socket installed in
former power supply compartment.
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As above, side view, also with additional bracing for
GS-35 socket installed.
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As above, view from front.
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Bottom view, showing blower and holes in former power supply chassis taped over with
packing tape to insure all air will pass through the GS-35 cooling radiator.
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Top view showing tape on TOP of power supply chassis floor as well. The
GS-35 socket enclosure has been installed,
and wiring of control interface has begun in rear left corner of tank circuit
compartment.
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As above, with additional cabling and T/R relay circuitry added.
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As above, showing more cabling added in tube / metering compartment. The big black
cables are actually split flexible cable sheathing.
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MLA-2500 with meter switches removed and meter swapped out; 1.5A for plate current,
1.0A for grid current - probably could use 0.5A for the grid. Note nifty name plate
to cover holes left when switches were removed.
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MLA-2500 GS-35B RF deck in-line. The
power supply is under the table. Belden 40 KV
HV cable and millen HV conecters are used for HV connections.
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