I guess most of y’all know by now that I’m a photographer. I use off camera flash shoe cords to extend the hot shoe to my flash bracket, which holds the flash unit. My main camera has been giving me erratic flash behaviour and recently pretty much quit working.
So I did what any self respecting modder would do. I cracked it open to see what the problem is. And found this…
This pin is the primary center pin in a set of 5 pins in the hot shoe on top of the camera. When tested with my DMM all the other pins showed continuity. The plate showed a ground. But this center wire at first showed nada, zip, zero, zilch. I tried cleaning it and got a 575 reading on the DMM! Scraped it and got a 550 reading and nothing else I did would change it. So when I cracked it open I saw this component busted open like it pooped itself.
What’s up with this part? Is this age or excessive flash use? I use flash in weddings almost exclusively, 1000 shots in a day. Sometimes more. As a photographer of course I ordered a new one. But as a modder I want to fix this one, use it as a back-up in case my other one want’s to join in, or the new one does, whatever.
Google-fu? What’s that? I’d like to find a diagram on it but Canon is notorious for keeping everything close to their chests, in house and proprietary and all that stuff. Simple little cord, 2 plastic boxes with about 9’ of wire in a coil costs $70.
Ok, backtracking to what might have caused this. Is it normal for a part like this to do what you see in the picture over a period of time? Or would an event have caused this? I ask because I don’t want to think everything’s all hunky dory just because I soldered a nickel piece back in and find out there’s a bigger picture.
The flash that I use on top of this is over $500, the camera on the other end is an $8000 rig. Granted, it’s now a dinosaur but that’s what it cost new and it’s current replacement is $7000. So it’s looking like the thing to do is scrap the cord and go with the new one.
Really appreciate the help though, both of you, at least I now have a sense of direction.
No Bort, not really. Semi-small town an hour or more away from the larger cities that might have a repair shop. I know Austin would, but they’d probably want half or more of the cost of a new one to solder that nickel part on. Liability, ya know?
If it says Canon on it, it’s several times more in cost than seems reasonable.
Before you replace it, lets see if it is bad. I think it is more likely that a wire is broken in the cable somewhere.
The pictured part is most certainly a rectifier diode - but the markings m2 73 don't make any sense to me, yet. Nice picture by the way!
I don't like the crappy way the diode is soldered, they've cut the leads so short there is no way for them to flex without putting stress on the diode junction inside the case.
You have a DMM right? Turn it to diode check position, usually marked with a diode symbol kind of like this |>|
If no diode check then try continuity. In either case the DMM will read something like OL with the leads open and 0 with them touching, (and may also beep).
Don't press the leads too hard on the connections or you may break the diode in half! Maybe use alligator clips if you have them.
A diode will have continuity in one direction and none in the opposite. Touch the black lead to the blue wire side of the diode, and the red wire to the other. You should get a reading greater than 0 (perhaps 100 to 500) and a beep. Now reverse the leads and you should get the OL reading and no beep.
If you get the same response in both directions, either OL reading or 0 reading then the diode is open or shorted respectively.
Personally I don't think there is high enough voltage or current in the hot shoe connections to damage that diode, so I would check continuity of the cable from one end to the other wire by wire. And flex the wires about while testing them. Cables will only take so much flexing before they break, and the "eratic" behavior you described sounds like the wire is broken inside the insulation, probably at the flex point where it enters the housing.
Good luck troubleshooting the unit, let me know if i can help.
That part is a simple diode. And, it doesn't look like it's failed. The brownish gunk appears to be RMA flux. You can test the theory with some Alcohol - it should clean right up. You can see the same residue in smaller amounts on all of the solder joints. I'm not sure what blew up, but I don't think it's that diode.
Does your DMM have a diode check function? You should see a value if you place the red lead at the end of the diode soldered to the pin and the black lead at the end of the diode soldered to the wire. Place the leads the other way, and you should get no value. That would indicate a 'good' diode.
I don’t think that diode’s the problem. Your MM showing resistance because the diode absorbs some voltage. Reverse your polarity and if your MM shows no connection, the diode’s doing its part.
Erratic behavior is more likely to originate from some broken internal wires, though still being held barely on contact by the insulation.
Thanks, I’ll see if I can get that reading. The part pictured is inside a plastic case, with molded stops keeping tension from pulling on the wires inside. I don’t flex the cord, almost never, as it sit’s on a bracket above my camera the vast majority of the time. I have held it overhead on a few occasions though.
Quick snap with the G1X, easier than setting up the 5DMkII with dedicated Macro lens. Lit up by my Nichia 219 Triple Hyperion at some 40% level. Gotta love a good light, right?
Thanks too for the direction on the DMM wheel, never used that before, didn’t know what it was. Only been soldering for a few months with any success. I used to butcher speaker wire, now I’m soldering stacks of resistors and 7135s, go figure.
These readings show the diode is 'good'. 0.630V is the forward voltage drop - spot on where I'd expect it. And the 1 when reversed show it blocks current in that direction.
I'm sorry to say that the problem is likely elsewhere. Could the contacts be worn, loose, bent? Otherwise maybe something internal to the flash itself?
The flash works fine on the camera, and it works fine with another shoe cord. But we use 2 camera’s in a wedding and I need this working. Well, I want this working, already dropped the $70 for a new one as weddings are unforgiving. Which is why I want to fix this one to have a back up.
I held continuity probes on each point consecutively while moving the cord around, stretching it out, shaking it, and it maintained the beep throughout. I have no idea now what could be wrong. But this cord is definitely giving problems on my 1DsMkII where the other cord works.
I can check this cord on the 5DMkII and see if there’s some kind of compatibility issue? It’s a two way communication with the camera, controlling flash power dependent on camera settings and distance, with distance information provided by the electronics in the lens.
Gotta love a good light, right?