ICOM IC-7600 : NO TX power - repairing, part 1
I lost TX power on Icom IC-7600 before ARRL SSX DX contest. Tube PA failured and than Icom did not have any TX power. Just Id bias current was shown on the LCD.
At first I looked at pre-driver, driver and PA voltages, all OK. Than I took R&S FSL-6 with small capacitor probe and measure RF power. There was only abt -60 dBm at the input of PA board. Than I connected generator on 14,1 MHz with 0 dBm and great, there is abot 70W at the output. PA board is alive! Than I looked at schematic again. There is small MMIC amp called BGA 616 with 18 dB of gain and some switching PIN diodes. I am affraid, this parts are under two another boards: Preamp board and Filter board. It was not easy to take it out, but I used CuAg wire and cleaned pins from the tin.
Than I measured RF power at PIN diode D604. Set TRX to 14,1 MHz, mode RTTY and press TX. There was about -13 dBm. On D601 was quite the same, so diode switching is right. Continued to D201 which is TX way switch diode, still the same. So all is clear. MMIC amp is dead. Instead of abt + 3 dBm at the MMIC output, there is -60 dBm.. not so bad for ATT, but for amp? :)
Preamp and BPF boards