Plisch 4th TV band TX as a EME QRO PA 432 MHz


EME PA 432 MHz Open part of PA where is cavity with tube
Original G1 - G2 power supply replaced by GM3SEK power supply boards

TH 293 datasheet

Existing stabilizer of G1 and G2 was replaced by GM3SEK tetrods boards. Toroidal transformers made by Czech republic company JK Eltra according request 580V / 50mA AC G2 and 150V / 10mA AC G1. Transformer for heating 5,8V/50A AC. 
Feed trough capacitors for heating lines. Due to connection with cathode is necessary build capacitors as showing here. Blue weirs are lambda/4 long lines 16mm2 flat. BCB capacitor has 157pf and extensions capacitors are 470pF/1kV ceramics. This solution protect very well PA for oscillating and leaking RF trough heating transformer and cathode power supply
Mechanical parts of PA 432 MHz - rebuild Plish cavity
Front panel - left down small power supply including G1 - G2 GM3SEK boards, left top measuring SWR - HF and Ua, Ug1 and Ug2. Measuring below left Ia, Ig1 and Ig2. Right cavity with TH347. Box top left including also control board, where are switching relays. There is also Kathrein directional coupler and board with LED diodes for indication. Schematics you can find in section Electric parts Rear panel
Left side - Ug1 - Ug2 power supply down. Right side, blower and heater transformer 5,8V/35A

Electrical parts

GM3SEK tetrods boards

Block diagram - connection between HV PS and GM3SEK G1-G2 PS 

Internal connection between GM3SEK boards and led and control boards

Connection between Led diodes and control boards trough 25 pin connector

Heating of TH 347 - 327 - 293 is requiring 30 second heating with half of value, in this case I have installed transformer with two primary coils and time delay switching relay with thermistor 2A/250V in primary coil.

PCB of LED diodes board


PCB of Control board


PCB of HV divider board


PCB of G1 and G2 divider board


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