The SB-800, discontinued in 2008, was Nikon's premier flash for several years. It offered wireless capability as a master flash or as a slave that could be triggered by the on-camera flash of many Nikon DSLRs, a quick-recycling battery pack, and excellent integration with Nikon cameras. The SB-800 was replaced by the SB-900. Some issues have cropped up with the SB-800.
Basic Troubleshooting
Power issues often result from the batteries being installed incorrectly or wearing down quickly. Use lithium AA batteries or nickel metal hydride recyclables; the latter perform best. Standard AAs will wear down quickly. Weak batteries can cause the flash to power off or can keep the ready light from turning on.
Wireless
The wireless range depends on the SB-800 being able to sense the pre-flash from the main SLR. If the flash fires on the camera but you seem to have trouble triggering it in wireless mode, check that the sensor on the wireless flash is in position to receive the signal. The maximum range is 33 feet when the SB-800 faces the master flash, and 16 feet when off to the side.
Check also to make sure that under wireless settings the SB-800 is set to either Master or Remote. Press the SEL button and use the +/- buttons to scroll to Wireless under the Custom Settings menu.
Flash Out
If the SB-800 is dropped the bulb can break; if it's used extensively it can wear out. Then it will need to go to an authorized Nikon repair facility.
No Communication
Proper operation of the SB-800 depends on the contacts of the camera and the flash being clean and aligning. If the camera doesn't seem to read the flash when it's attached, try cleaning the contacts with a swab dipped lightly in isopropyl alcohol.
Tags: down quickly, feet when, master flash