Downboy Rev.3 Stability Problem?

[darkzero]

What other issues could cause the downboy stability problem (not lighting up on 3x123)? I figured the problem would be non-existent on the lastest version boards but I'm having problems with one. As I always do with my McLux builds, I setup the board in the ecan and solder the leads to a test luxeon. I checked it on fresh 3x123 and it lit up fine. So I then potted the ecan/board and went ahead with the build. Now it won't light up correctly on 2xR123s nor on 3x123 as it did before I potted it. On 2x123 it works perfectly. I used 2ton devcon epoxy mixed with alumina oxide powder as I always have with all my builds. Any ideas? Thx

 

[dat2zip]

I know of a few builds that after the epoxy fill it didn't work. Since I've never gotten to the root cause, I can only speculate.

My best speculation is that the epoxy expansion/contraction is shearing one of the components like the inductor. If the inductor broke away it would open Vin and it would not draw any current at all. That's my best speculation, but, this appears to be common to all converter boards and not specific to any one in particular.

I don't know if the curing fast and letting the exothermic reaction generating a lot of heat or letting it cure more slowely and not let the exothermic heat build up.

My gut guess if this is related that letting the epoxy cure as slow as possible minimizes the exothermic expansion.

Again, this is just a guess. This probably has nothing to do with the Downboy stability as the new layout doesn't have this issue.

Wayne

 

[greenLED]

Just wanted to give this a :bump: since I've had this happen with one sammie. Worked fine while "bare", and then ...nothing after I potted it. I was using faster-cure epoxy. I've used 24 hour epoxy in my last 3 sammies and no problems so far.

Any alternatives to epoxy? :thinking:

 

[dat2zip]

I have seen problems like failure after potting in Ecans more than sammies and I'm not sure what that is. My guess is that the epoxy curing shrinks a bit and possibly shears the inductor off the board which may be a poor solder job on the inductor. This could result in the board not functioning after epoxing.

As for DB stability issues. I'm not aware of any with this version.

If you think this is the case and you emailed me I'd be happy to send a replacement converter board. I would have to review the details on a case by case situation, but, I'm not picky about the situations in general. If you have a legit description of the failure that's usually good enough for me.

Wayne

 

[greenLED]

Ooops, sorry, Wayne! I just realized I highjacked your DB stability thread.
:stupid:

I'm learning about DB's, though... :) I have a LuxV-module in mind for my Pila and the DB (@500 or 750 mA) looks like the way to go (if I can solve the heatsinking...) :thinking:

Sorry again about the highjack!

 

[darkzero]

Ok here we go again. For a long time I learned to live with not being able to use 3x123s or 2xRechargeable123s.

This is on my EDC McLux 2x123 DB917 TWAK that I first built in late 03'. Sometime last year I swapped in another DB917 and again would not light up on 3x123 or 2xR123s. Then the rev3 board came out and I tried one of those which worked fine on 3x123s before I potted it and installed it in the head which is when I posted this thread.

Today I decided to mess with it again since I really would like to use the 2xR123s. I tested the very first DB917 I built on 3x123 and shockingly it lights up. So I test the second DB917 I built it it lights up fine on 3x123 too! What's going on here?

So I go and test the DB917rev3 that's currently in my EDC McLux and it lights up fine on 2xR123s (not fully charged @ 7.7v)! However it does not light up on 3x123s still.

Could it be the TWAK itself somehow? Slug isolation from ground important here? Any suggestions? This is driving me nuts! :hairpull:

 

[Bob_G]

I'm sure you know that the relationship of the LE to the battery tube is critical in Alephs - a quarter turn off in the wrong direction and you got no light. since there seems to be no consistency in your problem, there's always a good chance it's something silly that you're not noticing - like when you go to the 3x123 setup, you must be changing tubes, so it's a new tube, so it's different than the old tube, so maybe something as dumb as backing off the LE a bit to see what happens.

I have one combination where I have to use a little piece of copper wire down there (on the shoulder of the LE) to assure contact with the tube, but that head on other bodies works fine. It's just that one tube that gives me problems with that one head.