Electronics Gurus, I have a question!

I'm wondering what would cause a flash unit (specifically a Sunpak 383) to stop firing via both the hot shoe mount and the test button, despite powering up, charging the capacitor, and lighting the test button. I was dorkin' around with mine the other day and it worked great. No problems. I power it back on (the same day) to take a few shots and nada. Neither the shoe nor the test button work and it wasn't dropped. Batteries are absolutely fresh...I tried several sets, charged them up, recharged them, etc. Nothing.

Any ideas?

Blown flash tube, perhaps?

Could be the syne port is messed up somehow. If the port's contacts are shorted to ground, neither the shoe or test button will work. Try plug in the sync cable few times to see if will free things up, or take apart bottom of the flash (4 screws) to see if anything funny inside.

The cap is definitely charging? Those can go, as can the aforementioned flash tube.

The mini-jack sync port does have a switch of sorts in it that disables the hotshoe capability when the cable is plugged into it, although this does not disable the test button to fire it. As Lotto said try inserting and removing the plug a couple of times to see if it may clean up its contact. If you happen to have a voltmeter handy the shoe should have between 6-7 vdc between the pin and the side connection. If it's there it's no guarantee the flash will fire, but at least shows it could if all else is OK. Have you tried firing it both on and off the camera? You didn't mention whether the PC cord would fire it or not, but I'd guess it wouldn't.

I've got a 383 that randomly every once in awhile kind of does the same thing, but somehow restores itself and it's OK for a long period.

I don't use that wimpy cord. It's not firing at the shoe or the test button. I've tried firing it via PC Sync (PC to hot shoe adapter - a quality one) as well as on-camera and off by shorting it. It's definitely charging because I can hear it wind up. I'm betting it's the flash tube. I can't see it well enough through the fresnel to tell if it's burned out but the shoe looks fine inside as far as I could tell when I took it off. I've let it sit for a couple days and it still doesn't work.

I bet it's the tube too. I wonder if you can replace it, but they're cheap, just buy a new one.

I dunno tim. I looked at it and I can't see any way to get the head apart. I've got velcro on mine that's pretty hard to pull off. I saw in another thread that you just bought a couple...can you check 'em out and see if there are any screws around the head?

If you do get into it just keep in mind the cap has a charge of somewhere about 300-400 volts and it'll give you a real good belt if you get across it. Best to drain it down with a high value resistor if you have one.

On the sides of the flash you might try peeling back the two circular disks on the up and down swivel ends to see if there are screws that hold the head together. It's been this way on a couple flashes I've taken apart.

You said that you can hear it whining. Are you referring to the occassional whines one hears when the caps are being topped off. Or have you had instances when the cap were fully discharged and it had to be recharged again? And, if so, when and how did the discharge to occur?

BTW, although you called for electronics gurus, I'm not one of them. However, I did stay at the Holiday Express last week.

Thanks Mark. I might give that a go. I have to find out if I can even get a tube reasonably priced first. If not, there's no point in ripping it apart.

Leo, it whines for a full recycle. I can only assume it's self-discharging upon powering it off and letting it sit for a while.

I had hacked one of these into an old Kako flash years ago. Worked, but the power wasn't what it used to be.
http://www.radioshack.​com …sh+tube&parentP​age=search

Also ebay you might find something
http://search.ebay.com …aprchi=&fsop=1%​26fsoo%3D1

Also noticed there is a small philips screw on the underside of the head near the front

Mark makes a good point; drain the cap if possible, but at least don't poke your fingers at the leads otherwise.

I was fixing a plasma display (monochrome, A/C only) laptop years and years ago and ran across a bad cap; just brushing the metal can top gave me a nice hot cup of WAKE UP!

I'm guessing an exact replacement flash tube may be hard to find. I think if it were me and couldn't find a tube, I might think about modding it.

Always wanted a 120J....

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Yeah I'm not sure what I'm gonna do with this unit, but I've got a bid on a Viv 283 and am watching a few other listings. In the meantime I'll use the Viv 5600 but it's a big sucker that eats batteries like a Clinton on an intern.