Settings, batteries and the hot-shoe
Confirm the flash is switched on and fully charged with fresh batteries — weak batteries cause slow recycling and misfires. Check the camera isn't in a mode that suppresses flash, and that any high-speed-sync or second-curtain settings aren't causing confusion.
Clean the hot-shoe and the flash foot contacts. Seat the flash firmly and lock it. If TTL exposures are wrong but the flash fires, a contact or communication issue is a likely cause.
Slow recycling or no fire at all
Very slow recycling, a flash that won't recharge, or one that powers on but never fires usually points to an internal fault — the trigger circuit, capacitor or a burnt flash tube.
Important: flashes store high voltage in their capacitor even when switched off. They should not be opened at home. This is a repair to hand to a workshop.
Safe checks first:
- Fresh, fully charged batteries
- Flash switched on; camera not in a no-flash mode
- Hot-shoe and flash-foot contacts cleaned and locked
- Note whether it fires at all, or fires but misfires in TTL
- Do not open the flash — it holds high voltage