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You might want to check on an antenna to see if your output VSWR is skyrocketing at the same time? If it is, chances are the amp is going into an oscillation at the higher drive power. Since the output transistors have already failed, that condition may have overloaded the DC chokes and bypass caps feeding the output transistors.

These are chokes L1 through L4 and caps C30 through C36. In particular, look for any discoloration of the chokes. If they shows signs of overheating, they have lost some of their ability to decouple the RF from the DC and could be a source of RF feedback at higher power. One common path for this to occur is when enough RF backs up into the DC line and finds it way into the bias circuit. VHF amps are more sensitive to these issues.

[QUOTE="Shockwave, post: 757411, member: 10882"] You might want to check on an antenna to see if your output VSWR is skyrocketing at the same time? If it is, chances are the amp is going into an oscillation at the higher drive power. Since the output transistors have already failed, that condition may have overloaded the DC chokes and bypass caps feeding the output transistors. These are chokes L1 through L4 and caps C30 through C36. In particular, look for any discoloration of the chokes. If they shows signs of overheating, they have lost some of their ability to decouple the RF from the DC and could be a source of RF feedback at higher power. One common path for this to occur is when enough RF backs up into the DC line and finds it way into the bias circuit. VHF amps are more sensitive to these issues. [/QUOTE]

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