Laney LC30 blowing HT fuse

[Psabin8951]

I have a Laney LC30 Mk1 which blows its HT fuse as soon as it comes off standby.
I have tried with all valves removed and it still happens.
Fuse stays intact with output transformer unplugged however. Is this likely to be the culprit?
+/- 15V present from Regs to all ICs.
No damaged tracks on the boards.
I can only find a mk2 Schematic online which makes things more tricky.
Any pointers appreciated.

[Jazz P Bass]

It does appear that the OT is bad.

[Psabin8951]

Confirmation. New output transformer and all good ty!