What is likely to have "popped" on my SB21?

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Myszolow

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Hi guys,

I have a Nikon SB-21 macro flash that I bought second-hand. It worked a treat with my D100 when I got it, but last week I went to use it and on half-pressing the shutter release button to get autofocus, the flash made a popping/crackling sound and fired - without the shutter being fired.

After that, the AS14 controller unit won't take a charge (you know the high pitched whining sound you get when the flash is charging). But the focussing light still works and still switches off when the test button is pressed.

I'm pretty sure something in the controller has blown, but not sure what. Anyone know what this is likely to be and if it's likely to be fixable?

I might send it to Nikon if it's likely to be worth it. What do you guys think will have blown?

If it just "let go" like that, my hunch was it might be the main capacitor. But on opening up the unit the main cap is not swollen or anything. To my limited knowledge of these things it seems like it must be the main cap or something in the triggering circuit.

Any thoughts/suggestions?

TIA

Alex
 
whats an sb21 worth?
whats the repair cost with nikon likely to be?

if 2 > 1 then open it up yourself have a looksie (I agree with you sounds like a blown cap) make sure you discharge the caps properly (a resistor across the terminals works better than a wire or screwdriver) see if one has blown up read the numbers off it buy a new one and solder it in.

A multimeter than tests conductivity would be handy here as you can test each cap conducts so don't have to rely on visual clues
 
You can test caps but it is usually easier to test them out of circuit as other components still in the circuit can affect the result. For the cost of the item it is not worth paying out too much but replacing the caps should not be too expensive.
 
david1701 said:
if 2 > 1 then open it up yourself have a looksie (I agree with you sounds like a blown cap) make sure you discharge the caps properly (a resistor across the terminals works better than a wire or screwdriver) see if one has blown up read the numbers off it buy a new one and solder it in.

A multimeter than tests conductivity would be handy here as you can test each cap conducts so don't have to rely on visual clues
Click to expand...

Thanks David.

I have looked inside, but even though I have a multimeter which can do resistance measurement, I'm not quite sure how to test a capacitor. Also the main capacitor has a funny copper spiral at the base of it, which looks unlike any capacitor I've ever seen before. Would that be a separate component or part of the cap?

How much is it worth? Good question. I paid £64 for it, but it's really frustrating because the flashbulbs part of the unit looks pristine - like it's been out of the box only a couple of times since new. It worked beautifully for about 50 shots since I had it and then suddenly went pop. :'(

Nikon said they'd look at it and give me a quote (which if I turn down will only cost me £12). But still, if it's an easy fix I'd be happy to have a go myself. I've not sent it in yet as I didn't want it getting lost in the Christmas postal confusion.
 
Myszolow said:
How much is it worth? Good question. I paid £64 for it, but it's really frustrating because the flashbulbs part of the unit looks pristine - like it's been out of the box only a couple of times since new. It worked beautifully for about 50 shots since I had it and then suddenly went pop. :'(

Nikon said they'd look at it and give me a quote (which if I turn down will only cost me £12). But still, if it's an easy fix I'd be happy to have a go myself. I've not sent it in yet as I didn't want it getting lost in the Christmas postal confusion.
Click to expand...

In this situation, I'd think about cutting my losses since the Nikon quote is unlikely to be low. I'd list it on ebay as faulty with an accurate description and hope someone will buy it to fix it for profit (probably a Nikon repair employee!). Then I'd buy something new with a guarantee... Sorry, not much help. Hope you can get it fixed for cheap.
 
Myszolow said:
Thanks David.

I have looked inside, but even though I have a multimeter which can do resistance measurement, I'm not quite sure how to test a capacitor. Also the main capacitor has a funny copper spiral at the base of it, which looks unlike any capacitor I've ever seen before. Would that be a separate component or part of the cap?

How much is it worth? Good question. I paid £64 for it, but it's really frustrating because the flashbulbs part of the unit looks pristine - like it's been out of the box only a couple of times since new. It worked beautifully for about 50 shots since I had it and then suddenly went pop. :'(

Nikon said they'd look at it and give me a quote (which if I turn down will only cost me £12). But still, if it's an easy fix I'd be happy to have a go myself. I've not sent it in yet as I didn't want it getting lost in the Christmas postal confusion.
Click to expand...

does it have the mode where if you touch the probes together it beeps?
if so touch both ends of each cap a quick and dirty way to tell you if one of them has properly gone (they can be gone but still conduct but it means more involved testing - taking out ect) but it tells you if any have separated inside
 
PhotoTalk said:
In this situation, I'd think about cutting my losses since the Nikon quote is unlikely to be low. I'd list it on ebay as faulty with an accurate description and hope someone will buy it to fix it for profit (probably a Nikon repair employee!). Then I'd buy something new with a guarantee... Sorry, not much help. Hope you can get it fixed for cheap.
Click to expand...

Yeah, cutting losses is certainly an option, but I don't have the budget for a new one at the moment or I would have splashed out £280 on the Sigma macro flash in the first place. I think I'd be better off trying to fix it than let it go for a pittance.
 
david1701 said:
does it have the mode where if you touch the probes together it beeps?
if so touch both ends of each cap a quick and dirty way to tell you if one of them has properly gone (they can be gone but still conduct but it means more involved testing - taking out ect) but it tells you if any have separated inside
Click to expand...

No, doesn't have that mode, but I found a site that showed what to do and it looks as if the main cap is faulty as it starts off with low resistance and only climbs up to about 86 k and won't go any higher. Seems to be leaky.

This is what it looks like (sorry, embedding didn't work)

http://www.flickr.com/photos/46184416@N04/4248010416/

What's a good source for capacitors? Farnell doesn't seem to have a 330v in the right capacity.
 
rapidonline, rs and maplins are all good shouts espesh if there is a local maplins (tend to be dear but no postage costs so cheaper for short runs)
 
Myszolow said:
No, doesn't have that mode, but I found a site that showed what to do and it looks as if the main cap is faulty as it starts off with low resistance and only climbs up to about 86 k and won't go any higher. Seems to be leaky.

This is what it looks like (sorry, embedding didn't work)

http://www.flickr.com/photos/46184416@N04/4248010416/

What's a good source for capacitors? Farnell doesn't seem to have a 330v in the right capacity.
Click to expand...

To properly check the cap you need to remove it from the rest of the circuit, so you need to desolder and then lift one leg from the board before testing. If you don't remove it from the rest of the board, the other parts of the circuit will skew your test.

A capacitor should show a swing to a lowish resistance then back to infinity. If it retains a resistance, it's broken.

Transformer could also have gone, particularly since that's the part that is used to charge the Cap converting 6V to 330V and lots of tiny fine wires to burn out or snap.
 
it looks like the main cap has blown going by those pics?
 
JasonRS said:
To properly check the cap you need to remove it from the rest of the circuit, so you need to desolder and then lift one leg from the board before testing. If you don't remove it from the rest of the board, the other parts of the circuit will skew your test.
Click to expand...

OK - thanks I'll do that and test again.

JasonRS said:
Transformer could also have gone, particularly since that's the part that is used to charge the Cap converting 6V to 330V and lots of tiny fine wires to burn out or snap.
Click to expand...

The reason I think it's the cap is the way it let go in the first place. If it was the transformer, would the flash have flashed when I hadn't told it to? (on half press for focussing - no exposure).
 
Myszolow said:
If it was the transformer, would the flash have flashed when I hadn't told it to? (on half press for focussing - no exposure).
Click to expand...

No idea, but I'd expect the cap to fail over time not in one go, unless it had gone pop, which you'd definitely see, and smell.

If it flashed, then the cap was holding charge and the control circuit failed, probably a smaller failure like a short, which has subsequently caused other component damage.
 
Well I desoldered the capacitor and put it on the multimeter to measure resistance. It climbed gradually over a period of about 4 minutes, reached infinity and stayed there. So I guess it's not the cap. That's bad news really because we're getting past the extent of my electronics skills now. :'(
 
Look at the photos on teh manufacturers website for the same model of caps, there's nothing exposed at the bottom of the cap but the black film wrapping around the bottom.


JasonRS said:
How can you tell that from the photo?
Click to expand...
 
Hairyduck said:
Look at the photos on teh manufacturers website for the same model of caps, there's nothing exposed at the bottom of the cap but the black film wrapping around the bottom.
Click to expand...

The copper spiral is a different component. After I desoldered the cap it looks fine. I'm all confused now and think it's almost time to give up.
 
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