The Analog Control module controls all the function of the analog JUMA PA100 model. It is using rotary switches, moving coil meter and LEDs for user interface.
The right most rotary type BAND switch (SW4) has 6 positions for different bands. The switch is connecting +5V to the corresponding band signal which goes to the main board to activate the desired band low-pass filters by means of the relays. Bands 14/18 MHz and 21/24/28 MHz are using the same filters, thus 6 positions of the band switch handles all 9 HF bands.
The rotary type GAIN switch (SW3) is controlling the input attenuator of the PA100 amplifier in binary manner. There are 4 gain positions which will adjust the PA gain in 2 dB steps.
The rotary type MODE switch (SW2) has 3 positions OFF - STBY and OPER. The switch is supplying the +14V to the control board circuit and it handles the Standby/Operate states via the TX signal. The LED4 is lit when the OPER is selected and the LED3 will be lit during transmission. The LED5 is installed inside the moving coil meter and it is lit when the power is switched on, i.e MODE switch is in the STBY or OPER position. This LED will illuminate the meter scale.
The left most rotary type METER switch selects what is indicated in the moving coil meter, Current, Voltage, Temperature, relative Reverse power or relative Forward power. Each measured parameters are scaled with resistors R15-R21 to same voltage level. After the rotary switch the signal is fed to the peak detector (A2-A) and buffered for the moving coil meter. The peak detector has a fast rise time (1 ms) and a slow fall time (1s) to achieve good meter readability also during SSB transmission. The nominal voltage range to the moving coil meter is 0-2 VDC which can measured in the test point TP1. The trimmer R29 is used to calibrate the moving coil reading. See adjustment instructions in the separate Adjustment instruction.
The analog control board is monitoring the PA heatsink temperature. The comparator A1-B takes care of the over temperature protection. PA100 will be forced to the standby state and the corresponding LED2 will be lit if the temperature protection limit 80°C is exceeded.
The analog control board is also monitoring the over current signal coming from the main board. This signal is handled by the MOSFET TR3 which will force PA100 to standby state in case of over current (24 A) and the LED1 will be lit. The over current protection is latching type and it must be reset by user with the MODE switch.
Cooling fan control
The temperature signal 0-2V (0°C-100°C) is also used to control the cooling fan with the comparator A1-A. The starting temperature of the fan is adjusted by the trimmer resistor R2. Middle position of trimmer (default) corresponds 55°C and the adjustment range is 37°C-75°C.