IC-820H repair

Suddenly a day my IC-820H display 'disappeared' (only few dots etc.) no frequencies - no sound - no transmit possibility :-(

I found this link:

Service questions

This page shows the reason could be PLL unlock and therefor I looked after the central 30,2 MHz oscillator X1 and found it at PLL PCB below the Main Board.

No RF out of the oscillator - low 5 V supply (1.2 V) for the oscillator unit and low voltage was the reason.

The oscillator supply a TA7805F was fed via 3 parallel coupled 27 ohms resistors R175, R201 and R202 from 13 V.

At 5 V regulator input the DC-level was 6-7 V (too low). When I touched the three 27 ohm resistors one was completely loose and another had a cracked solder at one end so a soldering iron was warmed up.

The 3 resistors were resoldered and the oscillator started up when I turned the power on.
A short test showed the transceiver and display were normal again.

Good luck.

IC-820H partial diagram of PLL near X1 TCXO

IC-820H partial PCB layout of PLL near X1 TCXO

IC-820H Service Manual

mail link

Updated 15.12.2012