This looks to be a later model 500V Texas Star.......
The Texas Star amplifiers are not very complicated to work on...
Splitter and combiner failure definitely indicates a major failure.....
Minimum, its looks it will require a complete set (4) power transistors, new combiner, possibly new splitter.
Also 4 new 10 ohm bias resistors and the 1.8 ohm bias resistors......
A few capacitors will also need to be checked for proper value.......
I am not a certified technician, but I do all my own repairs on amplifiers and transceivers (except for the very small surface mount components).
I do not do any repairs for payment, only for cost of parts, plus shipping.
I also do all my testing on a Palstar 2.5KW dummy load, not on