Fixed in a flash


Posting this as a work-in-progress.  I’ll get photos posted shortly.

[Insert photo of broken SB-800 LCD]

My Nikon SB-800 speedlight took a nosedive during a recent project, and the impact hit the LCD display squarely.  The outer LCD protective cover survived intact, but the shock shattered the fragile LCD panel inside, and most of the display became unreadable when the LCD fluid leaked.  Rather than ship this flash unit back to Nikon, I opted to buy a replacement LCD panel for about USD$50 and tackle the repair myself.

[Insert photo of the replacement LCD]

Fortunately for this project, I found Nikon’s SB-800 Repair Manual online (below).  This flash is another marvel of engineering with a rat’s nest of wiring inside; the repair manual looks very helpful in getting it pulled apart and re-assembled.  In particular, it describes how to safely discharge the high-voltage capacitor, safe handling of a fiber-optic sensor cable inside, and how all the connectors get unplugged.

Opening it up

The front cover of the SB-800 opens by removing four screws on the bottom and two on the top of the main body (after rotating the head 90° and pointing it up; don’t remove the rear two screws on either the top or bottom).  This lets the front cover come off, after which a total of 16 connectors must be unplugged to fully disconnect the cover, remove the front PCB (printed circuit board), remove the battery case, and reveal the rear PCB.  The repair manual details these steps.

[Insert photos of the opened SB-800]

A shortcut – I discovered that the rear PCB could be accessed without disconnecting any cables.  Gently lift the battery case and pivot it to lay on top of the front cover that’s been unscrewed.  Removing the remaining two screws near the hot shoe allows it to be moved out of the way as well.  Be very careful not to stress the cables, especially the blue/grey pair connected to the front cover – they’re the shortest of the bunch.  (No, it’s not possible to just remove the back cover instead.)

From here, it takes 6 screws to removed the rear PCB and access the LCD panel.  The brown flat cable at the top of the PCB is connected to the LCD panel, and also needs to be disconnected.  The connector has a brown clip that needs to be slid upward (but not removed) to release the LCD ribbon cable.

[Insert photo of the rear PCB]

Once the rear PCB is removed, the back cover is free, and the LCD panel just lifts out.  The white silicone button module may be stuck to it, but it’s not really attached.  In this case, while the LCD panel had broken, the LCD fluid had not leaked out of the panel itself.

[Insert photo of the back cover]

Replacing the LCD was as simple as dropping the new one in the opening.  Note that the replacement ships with a plastic film over the LCD display – this needs to be peeled off before installation.  When installed, the bottom edge of the LCD tucks under the lip of the silicone button panel, and there are a pair of foam bumpers that need to be attached to the top of the LCD back (ordered separately, p/n SS043-38).

[Insert photo of the damaged LCD]

Success… almost

I put the patient back together and loaded 5 freshly charged batteries.  It fired up normally, and the new LCD worked just dandy!  I exercised the zoom motor by pulling the wide-angle lens in a few times; the motor zoomed fine, and seems not to have been damaged by the impact.  I fired off a few flashes with the manual button, and it seems to be recycling just fine.

Then, I noticed a catch.  The LCD was dark.  Drat.  The electroluminescent panel that sits behind the LCD wasn’t working.  I pulled the SB-800 apart again to check it out, and I noticed these rubber bumpers on the back of the LCD were missing.  I hadn’t ordered them, and they didn’t come with the LCD panel.

[Insert photo of the back of the LCD]

I cut the bumpers off the old LCD and stuck them on the new LCD.  My hope was that perhaps they were necessary to apply pressure to the EL panel in the right places so the EL panel made electrical contact to the PCB behind it.

Re-assemble it and test one more time – bingo!  The LCD glows like it should.  I’ll run through a battery of test shots with it, but to all appearances the flash is fixed.

Resources

Note that the above sources for manuals aren’t “official”, so the links are likely to fail at some point.  (Although it’d be convenient, I won’t be hosting Nikon’s documents on my server.)  In case you need to go searching, here are Google searches for the parts list and the repair manual – note that a lot of the results will be sites offering to sell the PDFs; just keep digging to find a free one.

Warning!

All flash units contain high-voltage components that store a charge long after the power source has been disconnected.  Opening a flash unit exposes you to risk of electrical shock which can damage other components in the flash or cause serious personal injury in some cases.  (E.g., trigger an irregular heartbeat that could be life threatening.)  Proper safety techniques are beyond the scope of this posting – don’t open the case if you’re not trained.

Legal stuff

Yep, this content probably has errors and omissions – there are no warranties. This is an “over-the-shoulder” look at my work, notes, and opinions; it’s neither a how-to guide nor or a recommendation that you undertake a similar project. I wish you well, but if you attempt this project it’s at your own risk.

©2009 Richard Hornbaker. All rights reserved.
http://richard.hornbaker.org

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23 Responses to “Fixed in a flash”

  1. Hi, I am planning on taking my apart to replace the fresnel lens and flash tube. My only question – what is the wattage of the resistor used to discharge the capacitor. In the manual it say 200ohm – 1Kohm however not the wattage.

    Thanks.

  2. Hi, Surya. That’s an excellent question. The underlying question is what does the resistor actually do? Looking at the photos and schematic, those holes lead directly to the contacts on the main high-voltage capacitor. The wattage requirement could be quite high for such a low resistance.

    Caveat: This is “high voltage” stuff and it can be dangerous. I wouldn’t hesitate to attempt this myself, but I wouldn’t recommend you try it.

    That said, I’d use an Ohm’s Law calculator like the one here: http://www.the12volt.com/ohm/page2.asp – assuming 325 volts (which I’ve read elsewhere and may not be accurate), a 1k-Ohm resistor would try to pass 0.33A of current, which translates to 8.1 Watts of power. That’s a super chunky resistor that wouldn’t be cheap and probably requires a heat sink. An alternative might be 16x 1W resistors in parallel, but at 16k- to 20k-Ohms apiece. Or discharging with a much higher resistance over a longer period to reduce the current and power rating. And I’d be sure not to hold the resistor with my fingers during discharge. 🙂

    I also notice that the discharge holes and capacitor contacts internally don’t seem to line up for discharge unless the head is rotated straight up.

  3. Surya Says:

    Hi Richard,

    Thank you for your response. Lots of resistors 2K Ohm 5-10 Watt for few bucks, so I am going to order one of those and attempt to replace the burnt flash tube. Understanding what I am doing well is a must here I know 🙂 and I plan to do that and take all preventive measures.

  4. Surya Says:

    Hi Richard,

    So, I discharged the cap and took things apart and took out the flash tube. When I look at the new tube the trigger wire attached to it is naked and my old tube trigger wire is insulated. Do I just solder the naked wire or do I cut that and attach the old one?

    http://picasaweb.google.com/chatautphotography/SB800#5479738285630324178

    Also on page 17 (A1) of the repair manual it talks about soldering the trigger wire to the reflector and also talks about soldering to another point later on.

    Would appreciate prompt your help, since I got this thing opened up 🙂

    Thanks.

  5. Surya Says:

    Hi Richard,

    I got my answer to the 2nd question (one wire is already attached to the reflector) so I guess I do not need to worry about that. Now the only lingering question is the naked wire.

    Thanks,

    Surya

    • Hi, Surya.
      Looking at your photo, I would solder the loose end of the bare wire wherever the original wire was soldered. A marginally-educated guess is that it probably discharges any electrical field around the flash tube when it fires (i.e., like a ground wire). If you’re concerned about the bare wire shorting against something it shouldn’t, you could certainly slip a small-diameter piece of heat-shrink tubing over the exposed portion. Apparently Nikon isn’t concerned about the replacement part causing a short, but clearly insulation was also OK on the original version…
      HTH,
      Richard

  6. Hi Richard,

    I used a 100K OHM 1Watt resistor. I inserted my voltmeter tip into the hold and then used the resistor to though the ends of the voltmeter tip so I could see the voltage being drained. It worked like a chard. I could see the voltage going down to zero (peace of mind).

    SB-800 – replacing the tube was a pain. I got it replaced but still not firing, so I am assuming there is more issues than just the tube (the tube did look dark at one end – thus I assumed burnt).

    Another thing I noticed is – when capacitor is fully charged it only has about 68 volts. So not sure the capacitor is bad thus not able to hold enough change.

    Not sure if I should get it repaired or just junk it. I do have another SB-800 for use; a friend of mine gave me this SB-800 because of the burnt front element, and I was mostly using this for studio work. I might be better of getting Vivitar 85 for $80 dollars a piece.

    What would you do 🙂

    • Hi, Surya.

      68 volts seems way too low to me. If you have another SB-800, take a reading off that capacitor for comparison. I’m thinking it should be closer to 300v when the ready light is on. Also, did you find the flash head needed to be pointed straight up to discharge the capacitor?

      I would spend the ~$10 shipping to send it to Nikon and have them give me an assessment of the damage and a repair quote. That’ll give you a little more info to decide whether to scrap it, try to fix it yourself, or pay Nikon to repair it – regardless, they’ll pay to ship it back. I’ll warn you that their descriptions are really vague – nothing you could perform a repair from, but it’d give you a rough idea where the problem is and you can always ask them for more details. But they might also make an estimate based on a quick look, and not an internal inspection – this would only be useful to decide whether or not to have Nikon do the repair.

      FYI, a common failing point with the SB-800 is burning out the circuit board by shooting too rapidly without cooling time. (I’m not sure if it’s a trace or a component that fries, but I understand it’s visually obvious.) This happens more easily when using batteries with low internal resistance (e.g., Powerex 2700, my favorites) that cycle the flash faster because they’re dumping power into the flash at a much higher current than it’s designed for. I’ve read that flashes generally don’t have current-limiting circuitry on their input, instead relying on the batteries’ natural internal resistance to limit the current. Too much current current = heat; rapid fire = no cooling time = burned or melted traces or components.

      Nikon fixed this in the SB-900 by adding a thermal cutoff circuit that shuts down the flash if its cycled too fast. People universally hated this feature, because the flash would shutdown completely at inopportune times – the circuit could be disabled, but not until after the flash had cooled down and re-activated.

      Anyway… if you’re just using it as an optically-triggered slave in-studio, an SB-800 is probably overkill – it’s certainly more feature-rich and probably more powerful than you require, and you can probably meet your need with a cheap non-TTL flash for less money than it’ll cost to repair.

      If you decide to scrap it, I’d be willing to cover the postage if you want to send it my direction.

      Cheers,
      Richard

      • Surya Says:

        Hi Richard,

        I will try to check the voltage on my good 800.

        I will chat with Nikon and if I decide not to get it fixed sure I can send it to you. Will let you know.

        Thanks for all your help and response.

        Surya

  7. Surya Says:

    Hi Richard,

    You know what, my battery was bad thus I was not getting enough juice (though the tube was burnt out). Now I can get it fired – feels great to have it fixed. Fully charge it was over 200 volts and when I used my resistor to discharge it smoked 🙂 but worked just fine.

    I did not pay attention to the motor when I got it from my friend. But the motor only moves 14mm or 17mm as if wide angle switch has been pushed (but its not). I have the whole thing opened up and I see the motor move 1/4 way up/down. Any idea what is going on here? Is the motor bad or any thing I could have messed up. I looked around and there is not much that could have messed with.

    • D’oh! Well, at least you discovered that before mailing it off to me – darn! 🙂 Reminds me of a project I built once and installed all the switches upside down.

      So, you probably realize this, but… the extra step to 14mm happens only when the wide-angle filter has been pulled out. In the event that filter breaks off, the SB-800 has a setting to disable the sensor. Otherwise, you should be able to manually change the zoom setting to 105mm using the left/right selector arrows, then exercise the full range of 14mm-105mm by moving the wide-angle filter in/out.

  8. Surya Says:

    Hi Richard,

    Yes it was due to the glass diffuser missing. I guess it was like that all along just that I did not notice it. I jammed a piece of plastic in there and now I can manually zoom in/put .. yaaay 🙂

    The only thing missing … I only ordered fresnel lens and after I took it apart found out that there is an acrylic panel in front of it. Not sure what the purpose of that is … but I might just order it.

    Finally, thank you millions for all your response .. now I can easily take an SB-800 apart and fix it 🙂 – without getting a ZaP 🙂

    Surya

    • Ah… there is a sensor switch on the SB-800 that gets pressed when the Nikon diffuser is attached and zooms to wide angle. (It’s a small oval hole, I recall on the bottom of the flash near the lens.) I bet not having the acrylic plate in place was somehow messing with the sensor’s operation.

  9. Surya Says:

    It was not the switch that gets trigger when you attached the stofen diffuser (outside of the flash). It was due to the missing flash wide angle diffuser (glass that you pull in/out). Since the diffuser is missing the switch in on position. I just put a piece of broken fresnel lens in there and now its working 🙂

    • Hi, Surya. If the piece of plastic jammed in there doesn’t stay put, there is an option in the SB-800 menu to disable the wide-angle diffuser sensor – precisely to work around the diffuser getting broken off.

      I’m glad you got it all working – it’s awesome to breathe new life back into a good piece of gear (and for a cheap price, too)!

      Cheers,
      Richard

  10. Lee Taylor Says:

    Will you be posting the pictures of your LCD replacement project. I’m about to attempt the same thing on my unit.

  11. Darren Casey Says:

    Hi Richard, i don’t suppose you have an updated link to the SB-800 repair manual and the parts list do you? My Sb-800 has just blown a PCB (B) and i was quoted £200 to fix, er i don’t think so!!
    regards
    Darren

  12. Rich Reiter Says:

    Thank you for this most informative web page. One of the Eveready AA batteries leaked in my SB-800 and after cleaning up the battery compartment and installing fresh batteries, my SB-800 worked again for a while then quit. Unfortunately, I had thrown away the batteries, and without the batteries, Eveready will not cover the cost of the repair. I figure the battery contents leaked through and caused corrosion, so I’m going to have to open the unit up and see what’s damaged. Thanks to your excellent web page, I have the information and courage to tackle the job. (About 10 years ago I opened a Honeywell Strobonar to modify it to work with a Nikon N70. But the Strobonar had thru-hole parts; I expect dealing with the SB-800 to be a lot tougher.)

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