Jonas,
It is very uncommon for IC501/IC502 to fail, but quite common for IC503 to fail with blown finals.
So I would first lift a leg of IC503 that connects to the output of IC501 or IC502, and make sure it is not some failure in IC503 that causes the IC501/IC502 outputs to look bad.? Failures in ICs can affect their inputs as well as their outputs.
Stan KC7XE
