Try lightly tapping the tube with a pencil eraser while it is on the tester, to make sure the tube doesn't have a marginal short circuit.
Also, it's possible that something else failed in the amp that caused the tube to flash. For instance if a coupling capacitor connected to the grid broke down, it might have put a large positive voltage on the grid, causing the tube to flash.
Regards,
-- Al
Also, it's possible that something else failed in the amp that caused the tube to flash. For instance if a coupling capacitor connected to the grid broke down, it might have put a large positive voltage on the grid, causing the tube to flash.
Regards,
-- Al