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01-16-2016, 01:16 PM   #1
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Anyone know how to disassemble a Sunpak DX-12r ring flash?

Hi,

I went to use my ring flash today (I haven't in quite awhile) and it just wouldn't turn on. A couple of times I thought I heard a tiny "pop" when I turned it on. Brand new batteries installed. I suspect that the cap may need to be replaced. I have some experience with fixing electronics, but for the life of me, I can't figure out how to get this thing apart, and don't want to break it. There was no service manual, or schematics on the internet that I could find after scouring for quite a while.

If anyone has ever cracked one of these open, please help me!

Thanks,

George

01-18-2016, 01:39 PM   #2
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Remove hotshoe adaptor, then remove 4 screws as in pic below, lift out the cover plate then loosely refit the 2 screws of the back moulding, this will prevent 2 plates falling out when you eventually get it apart.



Remove 3 screws in top moulding as shown in next 2 pics





The top moulding is now held on with 2 plastic clips which are part of the moulding, if you try to lever the top off then you have a very good chance of breaking them.
The easiest way is to carefully drill 2 small holes (about 1.5 mm) in the casing, making sure that you only go through the casing and do not drill the plastic clip inside,
you can then insert a small screwdriver and carefully push on the clip while you prise the top off, it helps if you've got 3 hands !

Position of holes in pics below:






Once the top is open then you will find another 4 screws which again fix into 2 plates so follow the same practice as you carried out on the base.
After that the bottom section will come apart.

DO NOT ASSUME THE MAIN CAPACITOR IS DISCHARGED JUST BECAUSE THE FLASH ISN'T FIRING, DISCHARGE IT CAREFULLY, IT CAN GIVE YOU A VERY NASTY & POSSIBLY LETHAL SHOCK.

The fault you describe may not be the main capacitor faulty, it sounds more like the large yellow 3.9uF is shorted. (A common fault, this can be replaced with a similar but more common 4uF type)

Good Luck, and let us know how you get on.

Ray
01-19-2016, 08:14 AM   #3
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QuoteOriginally posted by Ray-uk Quote
Good Luck, and let us know how you get on.
Wow... your the man when it comes to great disassembly instructions, if I had this flash, not the two left hands made up of banana fingers and I understood electronics, I'd give it a go based on your reply.
01-19-2016, 08:27 AM   #4
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Well, perhaps if you didn't spend all your time chasing after all those female lenses

01-19-2016, 11:52 AM   #5
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QuoteOriginally posted by Ray-uk Quote
if you didn't spend all your time chasing after all those female lenses
Really? classy female glass wins hands down every time in my book...
01-19-2016, 06:33 PM   #6
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Wow Ray! Awesome pics and desription, thanks! How did you know where to drill the holes to access the clips that hold everything together?

I will attempt the repair probably Saturday, and will report back.

Thanks again!

George
01-20-2016, 04:10 AM   #7
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QuoteOriginally posted by gsrokmix Quote
How did you know where to drill the holes to access the clips that hold everything together?
After a bit of fruitless levering I could feel where it was holding on, then it was just down to luck.
The plastic clips are quite wide so it didn't have to be that accurate.

Another thing worth knowing is that most of the electronics are fixed to the rear panel, so lay it on it's back and lift the front off once you get to that stage (and watch out for the spring in the battery lid)

Although it's a different model the circuit diagram below is very similar, may be of some help.




Ray

01-23-2016, 02:33 PM   #8
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OMG what a f***ng nightmare trying to work on this thing!

The disassembly was fine thanks to Ray's instructions, but I can't figure out what is wrong, & I don't think I'll ever get it back together again . I don't know how they assemble these things at the factory. It's impossible to get all the parts lined up so the 2 halves fit back together.

All the caps tested fine.

Ray, the 3.9uF cap you were referring to was the one piggy-back on the main cap? The one in my unit is grey, not yellow. Nothing visibly wrong with any of the components. I'm gonna have to shelf it for now & have a go at it some other time.

Thanks for all the help!

George
01-24-2016, 05:24 AM   #9
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QuoteOriginally posted by gsrokmix Quote
OMG what a f***ng nightmare trying to work on this thing!


Ray, the 3.9uF cap you were referring to was the one piggy-back on the main cap? The one in my unit is grey, not yellow. Nothing visibly wrong with any of the components. I'm gonna have to shelf it for now & have a go at it some other time.

Thanks for all the help!

George
I could have told you they are a pig to put back together, but you sounded so capable
With a bit of fiddling they do all click back together easily once you get everthing aligned.

Yes the cap may well be grey and yes it is leaning against the main cap although not connected directly across it.
The 3.9 cap only breaks down at high voltage and will not show the fault with an ordinary ohmmeter or a visual inspection.
You either need an insulation tester or simply substitute it for another, the same cap will be found in almost any auto flashgun of the same era, e.g. Vivitar, Hanimex, Starblitz and many more.

It is possible that for test purposes the flash will work with the 3.9 removed because although it's across the main supply it only comes into use when using the flash in auto, low power or TTL modes, but I haven't tried this.

Don't give up .... you've got this far.

Ray

Last edited by Ray-uk; 01-24-2016 at 05:39 AM.
01-24-2016, 08:09 AM   #10
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Ray,

I should've remembered from taking apart a few 285's that these things are tricky little puzzles.

I checked the 3.9 with an ESR meter & it looked ok. I think I have a parts 285 laying around, I'll see if there is a substitute in that one to try.

The flash wasn't powering up at all in either of the modes. I only ever use it in manual mode.

While inspecting the boards it did look a little funny where the 2 tabs on the horizontally mounted board in the front half touches the main board. I'll have to look closer at that as well.

Thanks for help, I really appreciate it, and will let you know of my progress, or lack thereof!

Thanks again,

George
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