I recently found, and purchased, a broken Nikon SB-400 Speedlight off eBay for $35. Knowing I’d been looking for one for years, I figured worst case the tube was bad, and I’d be able to replace that for less than $15. The seller was great to work with, and got the unit shipped out immediately. The unit arrived, and I had a small hope it just worked, since the seller indicated they didn’t have a camera to actually test it with (and interestingly, the SB-400 has no “test” button (you can’t press the ready light and get it to fire like pretty much every other camera flash that has ever existed)). But, sadly, it didn’t work. Okay then, time to take her apart (WARNING: Camera flashes contain a high voltage (and relatively high capacity) capacitor. In most cases, these can hurt you. It SOME cases, they could probably kill you. If you don’t know how to properly discharge these capacitors, DO NOT attempt flash repairs yourself!).
The unit has (I know this in hind sight) 3 screws that hold it together. Two are obvious on the bottom side by the flash head itself, and one is in the battery compartment, under a small stick on plastic “cover”. After these three are removed, the flash opens relatively easily, and you are greeted by the top board (which houses the micro controller) the capacitor, and the flash head. In my case, I discharged the capacitor using a multimeter with a “Lo-Z” adapter on it (Fluke calls theses a Stray Voltage Adapter, but basically, it’s a MOV in a box that makes the multimeter have about a 3k ohm input impedance, so discharging the capacitor and watching it discharge is easy).
Visual inspection showed the unit had been opened before, but I’m guessing very little done, as I couldn’t see any obvious signs of work being done. What I did find, however, is the “brown” wire that runs to the head position switch, was crushed, and severed by one of the case screws1. Obviously it had not been put back in the correct spot last time it was opened, so when the case was closed, it was caught in the screw pathway, and then the screw severed the wire. I’m guessing, though, that the screw allowed intermittent contact, which probably confused the micro on the flash, and prevented it from working. Once I removed the broken wire, I carefully put batteries back in the unit, put it on my D90 (better to have it get fried than the D7100), and tested it. It fired! Well, shit. And I was expecting the flash tube to be bad (and was upset there was no good way to actually test if the tube was good or not). I pulled the batteries and re-discharged the cap (again, careful!). Not having any 28AWG brown wire at hand, I grabbed some 30AWG wire (it’s only a sensor, so there’s not really any current going through the wires), and replaced the broken wire. Not too hard to solder, but always annoying to strip wire that thin. Then carefully tucked it into the proper “raceway” for the sensor wires. Putting the unit back together is easy. Careful putting the cap back in since you can break the wires I just fixed. Then drop the top back on, and re-screw on. Throw some batteries in, and re-test. FLASH! Not bad for a flash that sells used on eBay for $120-150 regularly. =)
- Sorry for the lack of pictures on this repair. I never think to take them at the time figuring a repair can’t be this easy. Maybe I need to start taking video. [↩]