Mag85 help -- blowing bulbs?

[maxhawk]

I've built a Mag85 using Fivemega's 9AA->D adapter with the stock switch and potted WA1185. I didn't get instaflash, but probably after operating about 3-4 minutes the bulb blew. I replaced it with a second bulb and it worked fine for the next few weeks with usage of minimal run-time.

So the other day I recharged the batteries. They sat off the charger for atleast a day, and after operating the light for only a minute or two, I notice that it had developed an orange hot-spot. I turned it off and found the bulb to be a frosted white color instead of clear. I'm sure it's going to blow if I run it much longer.

What am I doing wrong? Isn't 9 AA's the standard configuration for the WA1185? I checked the voltage hot off the charger and it was 12.3 volts or so, which I found quite normal for NiMH. I'm using Maha 2500mAh cells charged with a Triton charger at a rate of 1.0A.

Do I need to switch to CBP1650's? Let the batteries sit longer before using the light?

Thanks for your suggestions.

 

[bwaites]

Maxhawk,

I'm not sure about the first bulb, but what you are experiencing with the second bulb is a symptom of a glass envelope that has been cracked and, when it heats up, is allowing a small amount of oxygen to breach that crack and mix with the gases in the glass envelope.

That bulb will fail very shortly as well.

Most of the time, this type of bulb damage is found in the potted bulbs, but a very few people have also seen it in regular bi-pins.

We believe that something in the potting process causes stress on the glass and it fractures microscopically. That stresses the bulb causing the symptoms you are seeing.

The CBP's will actually hold voltage even better than the Mahas and increase the chance of an "instaflash" so that won't solve your problem.

9 cells is the proper configuration, but that IS running the 1185 right on the edge with higher output cells, so some problems do raise their ugly head from time to time.

Having sold a dozen or so Mag85's and gone through something like 50-60 bulbs in those sales and my own use, I've seen a few do this, one literally explode, and a few instaflash.

Some of it is the cost of running these high output bulbs on the edge, some is the potting process, some is unknown.

All I can suggest is trying the bipin mod and seeing if that solves your problem!

Good luck, hope that helps.

Bill

 

[Trashman]

Maybe it's just the bulb. I have the same exact setup as you, except for I'm using 2200mah batteries (Digital Concepts, the wal-mart cheapies), which hot off the charger read 12.5v! I didn't even let the batteries sit before trying it out. I've only gone through one battery cycle, but the bulb hasn't failed yet.

 

[VidPro]

did they tell you about not touching the bulbs with your fingers?

 

[Trashman]

and wiping it off when you do? I use, either, latex gloves or I just hold the bulb in a tissue when putting it in.

 

[Ginseng]

What Bill said.

And this can happen to all sorts of bulbs. Here's a 100W Osram bulb that suffered this fate. In this case, filament failure occurred at the same time as air infiltration.

Wilkey

 

[bwaites]

Cool pic Wilkey, how do you get such great closeups?

Macro lens?

Bill

 

[Ginseng]

Nah,

No macro. Just the close focus on my digital videocam.

WIlkey

 

[maxhawk]

[ QUOTE ]
VidPro said:
did they tell you about not touching the bulbs with your fingers?

[/ QUOTE ]

I already knew from car halogen bulbs that bare bulbs should not be handled with bare hands. I used a clean tissue to hold the bulb and follow up with a wipe of 91% isopropyl.

I've got a couple of the bi-pin switch mods, so perhaps I'll try that route. When I first built the M@g85 I didn't have them yet.

Thanks for all the comments everyone. I'll report back when I do the next test.

 

[nirad]

maxhawk, how do you like the Great Planes Triton? If I understand correctly, this is a DC input charger only? What type of AC to DC power supply are you using with this charger or do you charge right off another battery??

 

[maxhawk]

[ QUOTE ]
nirad said:
maxhawk, how do you like the Great Planes Triton? If I understand correctly, this is a DC input charger only? What type of AC to DC power supply are you using with this charger or do you charge right off another battery??

[/ QUOTE ]

I've only used the charger a few times so far and I've been quite satisfied with its performance. It's got advanced features that let you discharge the battery, a cycle to test battery capacity, and some others that I don't remember off the top of my head since I haven't used them.

The best features, to me atleast, are its ability to charge multiple cells (up to 24 AA), compatibility with multiple battery types (NiCd, NiMH, Li-Ion, lead acid), and automatic voltage for NiCD/NiMH.

Yes it is DC input only. I've got a 40A linear 13.8VDC power supply that I used to use to power car amplifiers that I repaired while in college. Now I use it to power my battery charger. Yes it's overkill, but it was available. The documentation that comes with it suggests a power supply with 13A capability, and that won't be cheap since a big transformer will be needed. A car battery would work nicely though. Just keep a trickle charger on it to keep it topped off.

 

[bwaites]

Pyaramid Power supplies are relatively cheap, (less than 50 bucks and you can find them cheaper, if you shop it a little.) They are linear power supplies and have big time heat sinks. (I bought a bunch for the USL project.)

Switching power supplies can also be had for reasonable cost.

The Triton, so far, is the best charger on the market for flashlight use, though the ICE is comparable, but won't do as many cells, if I remember correctly.

Bill