P&H Electronics LA-400B Manual

P&H Electronics

INTRODUCTION

This manual has been reproduced by James Lawrence, NA5RC, a LA-400B owner. There
are some notes on page 6 not associated with the manual. Where liberties are taken, they
are so noted.

GENERAL DESCRIPTION

The Model LA-400B Linear Amplifier is a grounded grid amplifier employing pentodes
connected as high mu triodes. This circuit design makes possible a compact, medium power
amplifier.
When used with a suitable exciter, this amplifier will deliver a high quality signal whether used
for single sideband, amplitude modulation, frequency modulation, or CW.
A variety of output impedances may be matched by the pi network output circuit; however, a
low impedance load is recommended. The low impedance input circuit is untuned. This
feature simplifies multiband operation. A well-filtered power supply incorporating full wave
mercury vapor rectifiers is employed. The cabinet housing this amplifier matches many
popular exciters. High quality components are used throughout.

SPECIFICATIONS

Power Rating
Drive Requirement
Driver Impedance
Frequency Range
Output Impedance
Metering Circuit
Tubes

OPERATING INSTRUCTIONS

Preliminary
1. Connect the driver to the coax fitting at the rear of the unit marked RF Input using a
short length of coax.
WARNING: Do not apply plate power without a suitable driver connection.
2. Connect a 52-72 Ω antenna or load to the coax connector marked RF Output located
near the center of the rear deck.
3. Provision for blocking bias from exciter on Rear Deck if desired (See Figure 1).
4. Plug the line cord into any 105-125 volt 50/60 cycle A.C. source.
5. Apply filament voltage and wait at least 60 seconds before any attempt is made to
apply plate voltage.
Manual Update by NA5RC
Model LA-400B
400 Watts P.E.P. Input
20 Watts for maximum output
52-72 Ω (The driver should employ link coupling or other
means for DC return.)
75 thru 10 Meters
50-75 Ω on all bands
Indicates RF Voltage Input, Plate Current, and RF Amperes
Output
2 ea Type 816 Rectifiers
4 ea Type 1625 (modified)
Linear Amplifier
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