cooked 580 ex

Chris&jess wrote in post #7796935
My unit now has a full charge but I have no way to discharge it. Is there another way to discharge outside of purchasing a fancy tester?
Chris

The fancy tester is there to make sure the cap is fully discharged and is now safe to handle. You can get a cheap meter at Radio Shack or Sears. I've seen them for as little as $10.

Chris&jess wrote in post #7796921
were you able to repair the circuitry?

Yep, still works to this day!

Thanks guys!
Chris

JackProton wrote in post #7797475
The fancy tester is there to make sure the cap is fully discharged and is now safe to handle. You can get a cheap meter at Radio Shack or Sears. I've seen them for as little as $10.

Agree 100%. You shouldn't go poking into the circuit w/o some means of verifying the cap has been discharged. As noted, a reliable multimeter can be had at relatively low cost & is a good, virtually essential, investment. Make sure it has a range that can cover the max voltage you expect to measure, in this case 350V DC. It's pretty common to find meters w/ a 1000V DC range.

One possibility is a RS digital multimeter (DMM) for $20:
http://www.radioshack.​com …ctId=2103174&ta​b=features

The scant info provided doesn't include the DC volt (or any) range capabilities but almost certainly it will handle 350V DC; ask to be certain, however.

Even less expensive is an analog multimeter for $10:
http://www.radioshack.​com …ctId=2999093&ta​b=features

This meter definitely has the range you need, but my preference, by far, is a digital meter.

Before making a measurement on the cap test the meter's functionality (& verify you have it set to read DC volts) by making a measurement on a 9V battery, AA cell, or some other low level & known DC voltage.

For discharging the cap probably the best choice of what's available at RS is a 470k (470000) ohm 1/2 watt resistor:

http://www.radioshack.​com …dex.jsp?product​Id=2062336

The power dissipated at 350V will be appx 0.26W, so well within what this resistor can handle. It will take almost an hour, however, to drop the voltage to less than 1% of its initial value. That's too long for a service bench application, but for occasional use waiting an hour should be no problem.

If you happen to find the voltage is above 330V you might consider 2 of the 220k 1/2W resistors ( http://www.radioshack.​com …dex.jsp?product​Id=2062335 ) in series just for added safety (350V being the max working voltage of these resistors) rather than a single 470k 1/2 W. If you're really impatient & want to do a bit more work you can make use of parallel sets of these resistors, but that's 'left as an exercise for the reader...'

You'll need a means of clipping the leads to the resistor so pick up some insulated clip leads. These need be nothing fancy, just something to hold the resistor securely while protecting your fingers as you put things in place. The greatest difficulty will likely be mainting contact at the cap + terminal since there's no way to clip to that. A paper clip (handled with insulated pliers or clip lead!) can be pushed into the hole but you'll need a means of securing it in place during the course of discharge. It'll just take a bit of ingenuity...& care!

You can monitor the course of the discharge w/ the meter or just check the voltage after the time the cap should be safely discharged, which should be around 50 minutes or a bit more.

Hope this helps.

I'm by no means an electrical engineer here, but why so high on the resistance? My local RS has 1 ohm 10W wirewound resistors on the shelf. Flashes are designed for fast discharge, are they not? I'm not trying to make any recommendations here, but I am curious as to why this would be a bad idea.

lazer-jock wrote in post #7801061
I'm by no means an electrical engineer here, but why so high on the resistance? My local RS has 1 ohm 10W wirewound resistors on the shelf. Flashes are designed for fast discharge, are they not? I'm not trying to make any recommendations here, but I am curious as to why this would be a bad idea.

The power dissipated is given by E^2 / R, so for an E of 300V & an R of 1 ohm you're talking kW of power, albeit a very brief, instantaneous surge. If you've worked around electronics much I suspect you've seen someone discharge a cap using a screwdriver blade or pair of pliers, with the usual sparks & sometimes even molten metal flying. A 1 ohm resistor will give you a similar effect.

In operation the flash is dissipating power as heat & light in the Xe tube; it can handle it. When discharging (bleeding) the cap using a resistor the energy is dissipated as heat in the resistor; properly chosen, it can handle it. I recently had occasion to see someone use a 1k 1/2 watt resistor (which he chose in error) discharge a large cap at appx 200V; beautifully colored flame!

Chris&jess wrote in post #7796907
The Lumedyne cycler came with a warning that this could happen. I was totally into the shoot and I just didn't think of it.
We were on a family shoot at the park with three small uncooperative children. I had two identical setups of 580, Cycler, lightstand, PW, and Fong tupperware. I guess I should consider myself lucky that both units didn't go south.
How many rapid fire shots? about 20 in a row at three second intervals. We did about five sets like this. They both worked up to the very end.
Chris

Part of your problem was created by using the 'tupperware' diffuser. Outdoors, there is absolutely nothing to reflect the more than 75% of the light from the flash unit that is spread out in directions other than toward the subject. Thus, you are wasting a lot of the light created by the flash unit. Direct flash (or flash that is ALL reflected toward the subject with a different modifier) would probably have required a LOT less energy from the flash. That would have made the batteries last longer (the normal benefit) and would have created a lot less heat (which is what probably killed your flash unit).

My suggestion - trash the Fongware (or anything like it). Instead, use something like a LumiQuest Promax System instead. The Promax System can be as effective outdoors as it is indoors, unlike all of the plastic "diffusers". The Promax System also packs into a camera case very easily, as it is all stored in a flat "wallet" type pouch.

By the way - I agree with the instructions to use a resistor for a slower discharge of the capacitor(s) when working on flash units. I've been in the electronics business for several decades.

SkipD wrote in post #7801956
Part of your problem was created by using the 'tupperware' diffuser. Outdoors, there is absolutely nothing to reflect the more than 75% of the light from the flash unit that is spread out in directions other than toward the subject. Thus, you are wasting a lot of the light created by the flash unit. Direct flash (or flash that is ALL reflected toward the subject with a different modifier) would probably have required a LOT less energy from the flash. That would have made the batteries last longer (the normal benefit) and would have created a lot less heat (which is what probably killed your flash unit).

Good point and a good reminder.