These devices have been used in a high power amplifier for a
radar system and 19 out of 24 have suffered damage(see attachments).
The main suspect is lightning strike on the antenna or
somewhere nearby. The radar is located in Singapore and has been operating
during the rainy season, when a lot of lightning occurs.
High reflected power has been ruled out by rigorous testing
of the transistors SWR protection circuit. The transistors are able to operate
into an infinite mismatch at all angles and at full output power for
approximately 4us, before the SWR protection triggers.
I would like to know if it is possible to analyse the device
and gain some insight on how the damage occurred?
All the devices have a low resistance reading on the gates
and drains when measured with a multimeter.
Can any clues be revealed if only the gate or only drain is
If only the gate is damaged, that would suggest too much
input power and the drain should remain undamaged. Is this correct?
I have never seen this amount of damage on these devices so
something with a large amount of energy must have caused this.
Any insight is welcome.