Power Amplifier on GU-43B Manual


Connect AC cable of the Remote Control Unit (RCU) to 230VAC mains (white socket). Connect the 3-phase socket of the Power Amplifier (PA) to corresponding 3-phase AC outlet.

It is not necessary to push any buttons or activate any switches in the PA itself. Don’t touch the Amplifier, please – it might cause damage!


This is RCU  (remote control unit on the table):

On the RCU you may choose one of four modes:

1 OFF Activate OFF mode
2 FAN In the Bypass mode the fan is working, bias voltage feed is switched ON, there is no screen voltage on the tube and no relay switching voltage. This mode is used for cooling of the tube during switching OFF while there is no filament voltage.
3 STB Standby mode. Filament voltage is fed to the tube. Otherwise everything is just the same as in point 2. In this mode PA continues to work in Bypass mode.
4 ON

Operate mode

Switching ON

Before switching the PA «ON» the tube must be heated minimum for two (2) minutes in the STB mode.

Switching OFF

Like a diesel turbine - PA should work after the engine stops :

  1. Switch the PA to the mode STB for two (2) minutes
  2. Switch the PA to the mode FAN to cool the tube for min. two (2) minutes
  3. After two (2) minutes switch the PA to the OFF mode.

Led “АВАРИЯ” is switched ON

In case of High Voltage (HV) or Screen Current (SCREEN) protection the light emitting diode (Led) «Авария» (ALARM) on the RCU is switched ON.

To switch the protection off you have to go to the mode STB and then back again to the mode ON. If the protection is activated once more, you must find the reason for this and solve it. The reason may be a mismatch of the antenna or excess HF drive power from the exciter (radio).


HF Drive power from exciter to the PA must be no more than 25 W (25% at Icom 7300)  on the 80, 40, 20 meter bands and no more than 15W (15% at Icom 7300)   on the 15 and 10 meter bands:

Band switching

All bands are pretuned to the corresponding antennas. To switch to the desired band you must manually choose the band and momentarily push the black button on the RCU:

Switching is automatic. When the STB led switches OFF, switching to an other band is done and the PA is ready for operation.

If during antenna switching or earlier than 10 seconds of starting last band switching the chosen band was changed, you need to pay attention to the STB led having been switched OFF. If STB led is not switched OFF, you must push the switch the black button one more time.

Please take your account to following points:

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