User's Manual

Page 6 of 17
WARNING! Before opening the upper lid of the amplifier make sure that power supply
has been disconnected AT LEAST 5 minutes, allowing the electrolytic capacitors to
discharge fully. Disconnect power cord from the outlet!
WARNING! OM4000 HF amplifier can be operated ONLY if both of supply cables are
connected!
WARNING! Make sure that all screws holding the case together are properly in place
and tightened before carrying the amplifier with the handles!
CAUTION! The amplifier must be installed in such a way that free flow of hot air from
the tube is allowed. The amplifier must not be installed in a constrained surrounding
(i.e. tight shelves etc.). During long operation the upper lid and the vent grid can reach
high temperature!
CAUTION! The amplifier must be properly grounded during operation.
CAUTION! During operation the amplifier must be installed in such a way that the
back of the amplifier remains accessible.
CAUTION! The amplifier is an A category product. In a household it can influence
other electric appliances. In such cases the user is responsible to take proper actions to
mitigate this disturbance.
CAUTION! Read this manual carefully. Fallow all of instructions during installation
and operation to avoid damage to the amplifier not covered by manufacturer´s
warranty! Do not attempt to perform any change of hardware or software!
3.
GENERAL DESCRIPTION
3.1. HF part
his amplifier is using two pieces of ceramic tetrode FU728F in a grounded-cathode
circuit (input into control grids). OM4000 HF achieves excellent linearity by the
voltage stabilization of the control grid bias and the screen voltage. The power input is
given to the control grid, using a broadband input circuit with an input impedance of 50
Ohms. This adaptable input circuitry ensures a good input SWR (better than 1.5:1) on all
amateur bands.
The output of the amplifier is a Pi-L circuit. The ceramic capacitor for TUNE and LOAD are
divided. This enables the amplifier to be tuned exactly and makes it possible to easily return
to the previously set positions after band changes.
T
WARNING! The installation of this device must be compliant with CFR 47, 1.1310 of
the Federal Communications Commission rules. Refer to guidance in OET Bulletin 65,
Supplement B for more information on evaluation of the installation.