Nikon SB-24 Flashtube replacement and zoom motor access February 2011 Rex Peterson lenstracks@inebraska.com http://www.lenstracks.com
Disclaimer: The procedure outlined in this document worked for me, on my Nikon SB-24. Please be advised it may not work for you. Dangerous voltages are present inside this flash unit. If you dont know what you are doing and how to deal with these voltages, dont open your flash unit. If you turn your flash into a non-working piece of junk, dont blame me. The procedure outlined below will certainly void your warranty.
This document will guide you to remove and replace the flashtube in the Nikon SB-24 flash, as well as to access the zoom mechanism. What you will need 1. Nikon SB-24 flash, preferably yours. 2. Small screwdriver - philips & flat, small needle nose pliers. 3. Small soldering iron & solder (if you are even THINKING about using acid core solder, quit now while you are ahead). Solder wick will help as well. You only need to solder if you are replacing the flashtube.

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Nikon SB-24 Flashtube replacement and zoom motor access Here are the flashtube measurements.
The best choice for a replacement flashtube that I have been able to find is through these guys: http://www.xenonflashtubes.com/tubes.html Their part number is FT-4045
If anyone tries one, please send me a note and let me know how it works out.

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Nikon SB-24 Flashtube replacement and zoom motor access
Before beginning to disassemble the flash, turn on the SB-24 and set the zoom to the widest setting (24mm). Then remove the batteries and point the flash in the straight up position. Using a small screwdriver, pry up the rubber cover on each side and remove them.
There are six screws to remove.

two near the end

and two on each side. NOTE Only remove the two screws towards the front on each side.

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NOTICE these screws on the sides are flat head philips. These are the only flat head screws you will be removing. All the rest of the screws are what I would consider a "cheese head".
This is the flat head screw You should now be able to separate the cover. Be aware that there is a retention clip on each side which makes the cover a little difficult to pry apart.
!!! DO NOT TOUCH ANYTHING INSIDE YET !!! THIS IS WHERE YOU CAN GET SHOCKED

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WARNING
most of the parts on the PWB carry a dangerous voltage. Before proceeding you must drain the voltage. Measure using a volt meter to ensure the voltage is safe.

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Nikon SB-24 Flashtube replacement and zoom motor access The yellow capacitor is a good place to measure.
To discharge the capacitor, you will need to connect a resistor across the flashtube. The resistor must be sized to match the resistor power to the voltage on the capacitor. You have two choices 1. Measure the voltage and calculate the proper resistor using R=V^2/P 2. Use a worst case resistor and wait a long time. I started with a 470K 1/4W resistor. After the voltage dropped to about 100V I changed to a 27K resistor. I left it to discharge & had some cookies. An hour later the voltage was below 1V.
You are on your own here be safe and dont blow up a resistor or get shocked. Be aware that if you discharge a capacitor quickly and remove the load resistor, the capacitor voltage can start to rise.

Be careful.

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You should be able to lift the board out and swing it down to reveal what's inside.
Remove the three screws holding the shroud in place.
Before you start pulling out the shroud, pull this wire up and over the screw boss.

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With a little wiggling and persuasion the shroud should pull out. Be careful handling the flash as it is easy to break a wire.

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If your problem is with the zoom motor hunting back and forth, I would start by removing the small square PWB and look underneath at the contacts.
The board will require a little prying to get it up off of the standoffs, and I found it easiest to lift the right end and push the board right, then lift the left side up and clear of the flash tube housing. Underneath are a couple of contact fingers. It they are not touching the board, or if there is a piece of crud between them and the board the zoom motor will not work properly.

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To remove the flash tube requires more work. I started by removing the metal cover holding the window in front of the flash tube, but I think it would be easier to leave this until later your choice (although if you remove the window now and find out the flash tube is not broken you might be better off looking for a different problem).
Remove the 2 screws holding the little square board and the 4 screws holding the motor mechanism. This photo is from a later stage in the disassembly but the view is better.
After removing these screws, parts really start to come loose.
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Be very careful, because with all these parts connected by wires it becomes quite easy to break a wire, or bend the delicate fingers which indicate zoom position.
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To get the flash tube housing away from the motor mechanism takes a little prying. !! THIS WAS NOT DESIGNED TO BE DISASSEMBLED !! BE AWARE of the little metal clip. It shouldn't come off now, but if it does there is a spring underneath which will launch the clip across the room. Don't loose the clip or spring!
I used a very small screwdriver to pry the black piece of plastic out of the clear plastic housing. The clear part needs to be moved only enough to let the latch on the black piece to clear. There are two, one on each end.
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When they are finally apart you will see the latches and hopefully the little metal clip will still be in place.
If you didn't do it earlier, you can pry off the metal bezel holding the glass window in place and remove the window.
Next unsolder the small bare wire from the transformer (this is the trigger). You can now unsolder the wire from one end of the flash tube, and remove the PWB from the other. The board has a slot instead of just a hole for the electrode from the flash tube which makes removal very easy.
After you have these unsoldered, you can remove the tube by sliding it out one end. The white rubber thingy slides off easily.
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Before installing a new flash tube, clean the reflector housing with a q-tip or soft tissue. The flash tube must be CLEAN with no fingerprints. Hold it using needle nose pliers by one electrode to re-install. The end of the flash tube with the trigger wire must be on the end of the reflector housing which has the slot for the PWB.

I found it easiest to place the white rubber thingy on the end of the flash tube with the trigger wire and then slide the flash tube into the reflector housing.
Then with the trigger wire pointing straight away from the reflector housing stretch the white rubber thingy to the other end and over the flash tube. You can wiggle the ends and slide the tube back and forth to get the rubber thingy situated.
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Nikon SB-24 Flashtube replacement and zoom motor access After the flash tube is installed, reconnect the wire, PWB and trigger wire.
Double check the flash tube and reflector to insure there are no fingerprints on anything. If there are, now is the time to get them cleaned off. Clean the glass window and put it in place over the flash tube. Clip on the metal retaining piece (I waited until later, but it would have been easier to do it now). Now put the motor assembly and PWB back in place. There are 5 screws holding things in place.
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Make sure to place the red and black motor wires behind the little retaining post. (the photo shows the reflector housing in place, which it really isn't quite yet, but I only had this one photo showing the post.)
OK here is where I managed to knock off the little retaining clip, and yes, it did fly off the bench. Luckily the spring stayed in the hole.
Reinstalling the reflector housing onto the motor mechanism is a little tricky, but much easier for you folks 'cause you know ahead of time the pitfalls of knocking off this clip.
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Basically, you push the reflector housing back onto the black plastic mount from which you pried it from earlier HOWEVER, you need to keep a screwdriver pressing down on the little metal clip to prevent it from being caught on the reflector and pushed off by the housing.

push here

Here you can see how the reflector housing has four ridges, two of which ride over the clip to hold it in place. The problem occurs when the center two ridges catch on the clip as you are pushing the black piece into the reflector housing. The force pushes the clip back, and shears off some of the black plastic holding it in place. This makes reinstalling it a real bitch.
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After the reflector housing is back in place, tuck the wires into the slot along the top edge of the reflector housing. Slide the black shroud back in place and secure with 3 screws. Also be sure to tuck the sensor wire into the slot and route around the boss.

Make sure the sensor wire is routed to the outside of the shroud, otherwise it will interfere when the zoom moves all the way back. Now you can place the main board back in the slots. As you rotate the board into position, be sure the bundle of wires pass through the slot on the board to prevent any of the wires from being smashed.
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Clean the lens and re-install. The side with the grooves goes towards the flash tube. The outside surface of the lens is smooth. Don't forget to put the thin plastic sheet between the backside of the main board and the plastic housing.
When you install the cover, be sure the main board slides into the slots on the cover. With the cover on, you will have to press the front together to insure the clips on the sides snap together. Make sure the lens is properly seated before you start hammering on the cover.
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Reinstall the two flathead screws on each side, and the two screws on top. Put in some batteries and give it a go. Be sure to cycle the zoom motor through all positions. If all is well, glue the rubber covers in place using a contact adhesive, preferably a water based type to prevent the adhesive from softening the plastic. One thing which often is asked regards "calibration" after installing a new flash tube into an electronic flash unit. If the flash is used in "manual" mode, this isn't much of a problem, especially with digital cameras where you can easily evaluate the lighting. For use with a camera where the camera is measuring the light output of the flash to determine exposure, calibration isn't really necessary as the camera doesn't care if the flash is calibrated. The one place where calibration is important is where the flash unit is in "aperture priority" mode where the aperture setting and film speed (ASA) is set on the flash. In this case the flash is expected to output the light necessary to give accurate exposure for these settings on a camera, and uses an internal sensor to measure the light. Since the amount of light from a "calibrated" flash can vary wildly depending on the scene (black horse in a barn vs. a white horse in the snow) I don't get consistent results anyway when using this mode. I chimp on my camera. All of the photos in this document were taken in manual mode, using flash units set to manual power levels, triggered using CyberSync modules. OK some of them are overexposed, but to get good images of black plastic require some artistic license. I didn't calibrate the flash. If you know how, let me know and I can add the procedure to this document.
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Good luck, I hope this procedure helps you if you should decide to work on your flash. And if by chance you find this helpful and it saves you some time, please consider a small donation to keep me interested in writing these things. You will find a donation link at: www.lenstracks.com If you have any suggestions for another modification project or repair, please send me a note.

Thanks, Rex Peterson

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