This poor transceiver had been accidently left connected to the antenna array during a thunderstorm. Whilst not having had a direct hit, it would seem that a local striation must have hit the antenna. The fault being no RF transmission – no power output and quite deaf on certain bands in receive mode.
Upon investigation, it was found that there was no RF drive into the final PA stage on any band. The fault was traced to a short circuit RF driver transistor and associated components which feed the final stage board. A new 2SC5415A, couple of resistors and a diode got set working in transmit mode.
The RF input comes via a selection of filters etc, coupled with pin diodes. A number of these were open circuit, so had to be changed. The little ISV271s were a bit hard to come by, as was the transistor itself. The signal generator was hooked up and reception on all bands checked. All seems to be in order. Bit fiddly but not as bad as changing a dial cord on a 1940s Philips radio!
