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SB-400 broken?


stephen_doldric

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<p>I wasn't sure if I should put this in with Nikon SLR's or under Speedlights, but chose Nikon SLR's since I think its more specific to Nikon. So sorry if I have it in the wrong spot. Also I found plenty of comparisons of the SB400 vs... But did not find anyone who has had this problem.<br>

I have a D40 and SB400. My SB-400 just started acting up. It produces a flash, but its too dim to light up the shot, even straight on. I did get a random shot where the SB400 was bright enough, but that was the exception. I tried it with the D40 flash in the exact same shot and it produces plenty of light. To me it sounds like the flash info from the camera to the flash is not getting there properly. My first try was to clean the contacts with an alcohol wipe and q-tip, but that made no difference. Has anyone else seen this? I don't have a second flash so I don't know if its the camera shoe or the flash. Thanks in advance.</p>

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<p>Put your camera on the fully automatic GREEN mode and see if it works. Make sure you have fresh batteries in the flash and that the red light indicating the flash is fully charged is on prior to taking a shot. Also, make sure you flash is pushed in all the way on the flash mount and locked in place. If it still doesn't work, your flash may need service. </p>
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<p>It is a bit of a long shot ;-) but you could just make sure that item 14 in the custom setting menu is set to TTL. It could possibly be set to manual though Elliot's experiment should confirm this since manual flash is probably only available in P,S,A and M modes. Also I don't know if this item controls the SB400 independently of the built-in flash.</p>

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<p>That was an awesome suggestion to try full auto (green mode). However that did not help it. It really seems like a communication / metering problem. Since the flash was only $110 (import) over a year ago I chose not to send it in for repair since I'm not even sure they would fix it and if they did I can't see it being less then $110. Instead, I opted to take it apart and see if I could clean up the springy internal part of the contacts. Since I've been around electronics for years I had no issue doing this (see my warning below about high voltage). I'll add a few details in here so that at a later date if someone wants to try the same there is some info. BTW - cutting to the chase, I was not able to fix it. As a matter of fact it won't even fire at all now, but it still charges up and the ready light comes on. As much as I love my SB400, I'm going to upgrade to a SB600 now. Can't justify the SB900 right now for the commander mode, but I'll at least get something that will work with the SB900 later on.<br /> <br /> <br /> Now for the details. <strong>WARNING</strong> : Don't try this unless you know what you are doing. There is a 800mfd capacitor fully charged with about 300volts sitting in this thing. So if you don't know what that means or how to deal with it, don't go any further. You can seriously shock yourself. It doesn't have a bleed resistor on it either, so it will stay fully charged for a very long time. I chose the brute force discharge method with a screwdriver across the leads along with safety glasses - it's that much arc and puts a puts a melted dimple in the screwdriver.<br /> <br /> <br /> The assembly of this flash is really complicated and tight. There are two screws holding it together in the bottom, and then it's pressure fit together. Two circuit boards (top and bottom - bottom is power, top appears to be logic, along with two flex circuits between the two. The battery compartment sits between the two circuit boards. The main capacitor sits right behind the flash head. Then just some flex circuits heading down to the shoe assembly.<br /> <br /> Dis-assembly is complicated in that if you don't know how to pry it apart (ie where the release clips are) you end up having to pry extra. That's what I did, and I'm still not sure what the factory method is to pry it apart. It really seems like the top housing is supposed to separate from the whole bottom section, leaving the circuit board and battery compartment, but there is actually a screw that I have yet to figure out how it's put together. I broke the small plastic tab for the screw, but seems optional (at least mechanically). So basically the guts come out leaving the bottom section and one of the flex circuits connectors disconnected in the process. So if that's not clear, the top section comes apart along with the circuit board assembly and battery compartment all on one, leaving the bottom section and some wires interconnecting and a dangling flex circuit cable. BTW reassembly is actually a lot easier once you get the top housing off.<br /> <br /> Once pried apart (wearing gloves so I wouldn't get shocked), I was able to work a screwdriver into the capacitor and discharge it. Followed by a second discharge (much smaller) several seconds later.<br /> <br /> All the parts still remain interconnected through various wires through the entire dis-assembly so each section of the housing is always connected to the others in some way. Now here is the most interesting part. The shoe assembly is a real PIA to disassemble and reassemble. It's part electric and part mechanical due to the lever. So avoid taking that apart if you can. If you choose to disassemble it it's going to be a pain to put back together. Also note there is little value taking it apart. I envisioned the contacts spring loaded and free floating needing cleaning internally. In reality the pins are bound/welded directly to springs, and the springs are soldered directly into a flexible circuit board that goes all the way to a circuit board. So each pin that touches the camera is very well electrically connected to the electronics in the flash. So as long as the pins are okay, there is very little failure possibilities. Very nice job Nikon!<br /> <br /> So in summation, there is very little that can be done inside the flash (as you would expect). If I had it to do all over again, I would never have taken apart the shoe assembly. The only real things you can do inside are: 1. Reseat the flex connector. 2. Examine for anything obvious like a loose wire. 3. Possibly if you had a couple of blow SB-400's you could shift around the circuit boards to make a working unit. 4. Look for any obvious fried parts (ie like the main capacitor or flash tube.<br /> <br /> Anyway, that's if for posterity. I was unsuccessful, but did get it back together mechanically, but made matters worse. So unless you are like me, I would not attempt to take apart an SB-400. That and I would be extremely hesitant to take it apart and put it on a camera body. In my case I have a D40 thats a few years old, so I was willing to accept that level of risk, but if my camera were newer and better it really isn't worth the risk to the camera body.</p>
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<blockquote>

<p>That brute force discharge also causes arc over inside the cap.</p>

 

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<p>Does it? Is that only endemic to electrolytic caps or all of them? I'm an EE myself but just a youngin' and haven't heard of this before.</p>

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