Problems with BB750 and 5W

[Lichtgestalt]

I have extremly short runtimes with my bb750.
"extremely" means that with a pack of fresh batteries regulation falls out after ~2 minutes.
I tried 2 different high-quality sets of batteries.
If I switch of the light, after it gets dim, and then restart it, it even lights up for only 10 seconds.
[img]/ubbthreads/images/graemlins/confused.gif[/img] [img]/ubbthreads/images/graemlins/confused.gif[/img] [img]/ubbthreads/images/graemlins/confused.gif[/img]

[lemlux]

You have the same problem I had. The BB750 is very heat intolerant. It shuts down when too hot. The 5W application appears to be right at the ragged edge of one or two components' tolerance.

You'll need to repot the board with a substance that transmits heat well but doesn't conduct electricity.

I think my W3V McModule will be my only BB750 5W light, although I might use one for a 1W or 3W.

[tvodrd]

There was a discussion here about heatsinking the 750. I was serious about sawing/filing/lapping a copper penny.

Larry

[Rothrandir]

be warned though, that it's a crime to do that [img]/ubbthreads/images/graemlins/wink.gif[/img]

instead, you should all ask larry to make us these:


[img]/ubbthreads/images/graemlins/grin.gif[/img]

[Shark]

Pennies havent been made out of copper for a long time they are actualy copper plated zink. Would just hate to see someone go through all that trouble and then find out [img]/ubbthreads/images/graemlins/icon15.gif[/img] with that being said that heat sink looks AWSOME. I gotta have one!

[Lichtgestalt]

thx
I simply potted the hole thing in arctic-alumina, and then fixed it at the aluminium on the inside of my 3d-mag.
The contact-area is pretty small, but obviously it is enough to run longer than 6 minutes (didn't have more time to test)

[Chief_Wiggum]

Here's what I did. Works great!



Potted in Arctic Alumina to the back of my 5W heatsink.

[dat2zip]

Chief,

Could you elaborate a little more. What is the copper looking thing in the picture?

[Rothrandir]

[ QUOTE ]
dat2zip said:
...What is the copper looking thing in the picture?

[/ QUOTE ]

i'm guessing copper [img]/ubbthreads/images/graemlins/thinking.gif[/img] [img]/ubbthreads/images/graemlins/grin.gif[/img]

very nice job cheif! is the copper heatsink making any contact with the ic?

[JonSidneyB]

hmmm, my BB750 5W seems to be working perfectly

[Chief_Wiggum]

It's the copper slug for mounting the 5W. The only thing making contact is the tallest component on the board. I think it's a resistor??? (Not to sharp with electronics [img]/ubbthreads/images/graemlins/grin.gif[/img] )

[AilSnail]

How come it looks disformed in the pcb end and discolored in the other? Looks nice, did you turn it on a lathe?

The tallest thing on the badboys are the inductor but a brown capacitor comes close. It's the two black boxes that get hottest, a diode and an IC.

[Chief_Wiggum]

It's disformed, because I made it by hand with a file [img]/ubbthreads/images/graemlins/smile.gif[/img]

It's discolored because it's actually two pieces of copper soldered together. The silver is the solder.

So then, the only component in contact with my heatsink is the inductor. The rest transfer heat only with the AA.

Although, I seem to remember Wayne saying that the BBs don't need much heatsinking, but they do need it.