Pretty sure that one uses RF transistors that mount by a threaded stud that pokes out the underside of the heat sink, each secured by a nut on the outside.
That one is famously prone to fail from excess drive wattage, or high antenna SWR. Clobbers the two RF power transistors.
Finding replacements for the stud-mount transistors is doable, but expensive. The opening in the circuit board is too small to substitute more-modern flange-mount RF transistors.
The problem could have another cause, but the odds don't favor it.
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