My thoughts would be, was it a Sony OEM transformer or a generic type? If the latter, that is probably a likely suspect. Another thing would be misplaced wires or switches that could have been accidently moved while replacing the transformer. I have had some of these sets that had no high voltage, and all it turned out to be was a broken solder connection on one of the pins going to the flyback transformer. Usually, if the flyback is bad, the Horizontal output transistor would be also defective. It's also possible that in the process of removing the old flyback (fun job wasn't it?) you may have cracked one or more of the circuit traces in that area of the PC board.
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