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Reuilding a Metz 402 flash unit

Ken Holtane , Apr 01, 2004; 10:18 p.m.

I have an old Metz 402 unit and would like to rebuild it for use. I've had it in storage for about 10 years and when I load a dryfit battery, the power pack makes the traditional "whine" sound but never powers up the flash head. The voltage coming off the power pack cord is reading about .6 volts, and I know from previous testing that it should be about 6.5 volts. My question is, could the power pack problem be the capacitor inside? Is the powwer from the dryfit being stored in this capacitor, and if bad would replacing it only solve the problem?? I also opened the flash head and will be looking for a replacement capacitor fpor that as well. Any info, insight, help would be appreciated.


Bill Cornett , Apr 01, 2004; 10:59 p.m.

Ken-- I am assuming that the battery you are using has also been in storage for ten years, but you don't say. Working on that assumption, I've known rechargeables to go dead in a year, and over ten years with no maintenence is something that very few batteries can stand. Personally, I'd switch to sealed lead-acid batteries. You can pick them up at any good electronics store. The ones that put out 6 volts as opposed to 6.5 won't denude the flash unit's performance much, as the original battery pack probably went down to that level after a few flashes anyway. You will most likely be able to fit a single sealed LA battery in the place of the cell pack.

I can see a good, fully-charged battery going down to about four volts under a massive drain, but not 0.6 volts, as your post states and assuming that wasn't a typo. Typically I see my batteries going down to 4.5 volts for a fraction of a second after a flash goes off, if I'm running say, two Vivitar 285's off of one 1.5 amp-hour battery. If I'm using a 12 amp-hour cell, then the needle barely drops even with two 285's on it. 0.6 volts isn't going to charge anything.

A couple of questions-- One, if the battery is new, is it getting hot when it is trying to recharge the caps? If not, then there is something wrong with the battery. It would take a very low impedence short circuit to pull the voltage down that low, and in that case, something should be smoking, either the power cables or the caps or the circuitry inside the flash. The fact that it still whines probably means that the charging circuitry, including the voltage doubler, is still OK, and that means that the current draw shouldn't be too massive. I'd put my money on a bad battery.

Now, there is a chance that it could be both the battery and the capacitor, but you can spend $15 for a new battery and see how much good that does before shelling out for the cap.

Best of luck, and be careful. -Bill C.

Yance Marti , Apr 02, 2004; 09:54 a.m.

The cord could be bad too. Its an easy check to test it with a meter.

Ken Holtane , Apr 03, 2004; 01:41 p.m.

Bill, thanks for the info. However, I probably didnt state the case exactly in my post. The battery I used was a newer, totally charged Dryfit battery which I use in my Metz 60CT. When I put it in to the 402 power pack, it whines as if charging the cap, and will beep every 3 seconds when it's ready. When I get beeps I hook up the cord to the flash head, but it never charges the head enough to be able to flash it. There's a capacitor in the head that I assume is the "triggering" cap, and this could be faulty, and I've determined that the capacitor in the power pack is the one that holds the voltage until tripped. I'm going to try replacing both if I can find the right ones and see what happens. The triggering cap could be fine , but without the power pack putting out the right voltage, ( .6 volts VS. 6.5 volts) I'm figuring that the power paqck cap is the culprit. What do you think?

Ken Holtane , Apr 03, 2004; 01:43 p.m.

FYI , it's not the cord because I tried the 3 cords that I have and got similar readings with all. I also measured the voltage out of the power pack and it's about .6 volts as well.

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