it would be too beautiful and simple if you could solve it as you suggested ....... a bit of optimism comes from the fact that the radio has 2 HF + V-UHF power amps and it seems impossible to me that both are burned at the same time. it is much more likely that the pre drive driving both power amplifiers has burned out.
So I appeal to all owners of this radio who know of this rare problem.
HB9IRB