This Henry 3KA has been converted to a 5K. It uses two 8877’s. The amp will deliver about 5000 watts out into a coaxial dynamic peak reading meter, while being pulsed with a 3898 pecker pulsar, this pulsar uses audio peaks  during tuning is the SSB mode. Out put into Nye Viking meters measure just under 5000 watts with about 140 watts drive.   All watt meters read differently.   Coaxial Dynamic meters are compared closely to Bird Watt meters.

The input circuit of the Henry 3KA was designed when radios use tubes for finals and did not require a perfect input SWR, so when using a radio with solid state finals, as most radios now have, your radio's internal antenna tuner should be used for maximum output of the radio/amp.

The 3KA has a manual soft start switch from the factory, which is called the PRE OP, there is the CW mode which is close to 3000 volts, then SSB mode which delivers ~3900 volts un keyed.  There is also a reset button inside the front spring loaded access panel, if it pulls to much current will trip, resetting this reset can be done while without shutting down the amplifier, just open the cover and depress the switch, a buzzing will notify you it has been rest.

The blower in the 3KA is much quieter than most Henry amplifier’s, the blower is mounted on a rubber grommet, which helps keep it quieter.

I have added a relay switch to enable the amplifier to be put in standby, two LED’s indicate whether the amplifier is in standby or ready to operate.

8877’s require 3-5, minutes of warm up time before using the amp, this 3-5 minutes  is a manual wait before applying any drive.

The Amplifiers weighs approximately 160 lbs, it operates only on 230 volts,  not  110 V.

Henry amplifiers were designed when most amateur radios were tube type. Theses tube type radios did not require almost a perfect input swr, like modern transmitter do. Current radios have circuits designed so the radios swr must be very low or it will cut back on the out put power to stop any damage tot he solid state final transitors. Most tube type transmitters did not have these protective circuits and could operate fine with higher input swr transeivers made today. You must use your radios built in antenna tuner to provide your radio with a low swr input to enable maximum output from your radio to the amplifier. With out this, the amp will not deliver expected output.

Many Henry Radio Amplifiers were made years ago and continue to operate with little trouble. These amplifiers can fail from time to time, and some maintenance work may be required.