Confusion here.... I only used AS on top of the chip and diode to bond the heatsink. The whole board, including the heatsink, etc... was potted in AA. My reply to Doug was that there was definately no overspill of AS from the bonding of the heatsink to the chip. AS provides better heat conductivity, that is why I used it. Correct me if I am wrong. There *may* be too much AS on top of the diode and that *may* have shorted the diode. Note AS *may* not be electrically conductive, per AS.com but they do recommend not to touch non-electrically neutral connections. I am merely trying to find fault with my work to reason out why I am getting therman shutdown after such a short runtime.
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BB750 shutting down after 10-12secs?
- Thread starter hotbeam
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Doug,
I do enough distructive *tests* without initial intent! Do stand by though.... /ubbthreads/images/graemlins/tongue.gif /ubbthreads/images/graemlins/grin.gif While you stand to be corrected, I am working on how to stand. In the name of science, I'll make sure I have a good working BB and then next batch of AS, I'll goop up the IC and surrounding area. If it continues to work, we won't have proof positive but I'll have a well sinked BB for use. If it fails, I'll tell Wayne some **** and bull story about my grandmother hardly ever using the thing and........
I do enough distructive *tests* without initial intent! Do stand by though.... /ubbthreads/images/graemlins/tongue.gif /ubbthreads/images/graemlins/grin.gif While you stand to be corrected, I am working on how to stand. In the name of science, I'll make sure I have a good working BB and then next batch of AS, I'll goop up the IC and surrounding area. If it continues to work, we won't have proof positive but I'll have a well sinked BB for use. If it fails, I'll tell Wayne some **** and bull story about my grandmother hardly ever using the thing and........
Let me add that AS when heated by a soldering tip will blob the AS into silver blobs and at this point the blobs can touch and conduct to anything. I've seen this happen manually with the solder iron tip, with IR reflow under the IC and with hand soldering around the Luxeon.
I used AS under the IC for a while. Had to chuck many boards in the circular file. Used AS for a while under the Luxeon and got blobing when soldering the connector pins.
So, in general the silver is in a fluid suspension and is mostly non-conductive. Squish it, burn it with enough heat and you can separate out the silver into blobs and this for sure is a problem.
As for the hall effect. I recall some additional work that was being done after AS was applied. I think a wire or connection fell off and the soldering iron tip was brought in to do some corrective surgery and after that it was a total loss.
Hmm, that was a fun project. Need to revisit that one of these days. /ubbthreads/images/graemlins/smile.gif
Wayne
I used AS under the IC for a while. Had to chuck many boards in the circular file. Used AS for a while under the Luxeon and got blobing when soldering the connector pins.
So, in general the silver is in a fluid suspension and is mostly non-conductive. Squish it, burn it with enough heat and you can separate out the silver into blobs and this for sure is a problem.
As for the hall effect. I recall some additional work that was being done after AS was applied. I think a wire or connection fell off and the soldering iron tip was brought in to do some corrective surgery and after that it was a total loss.
Hmm, that was a fun project. Need to revisit that one of these days. /ubbthreads/images/graemlins/smile.gif
Wayne
Doug S
Flashlight Enthusiast
[ QUOTE ]
hotbeam said:
Confusion here.... I am merely trying to find fault with my work to reason out why I am getting therman shutdown after such a short runtime.
[/ QUOTE ]
While I remain amazed that a potted BB750 can be made to survive at all, I cannot argue with the fact that many are reporting having success. Wayne's posts merit special credibility since he *does* have a bit of experience with these circuits. Wayne has stated that he believes [as do I] that the thermal pathway out of the top of the IC is poor. He further states that he believes the primary pathway of heat out of the IC is via the pins [which I also believe and further believe that the primary pathway is via the ground pin [#5 which is the one closest to the big capacitor]]. The heat removal from the diode is also via its two leads. If the heat is primarily exiting as described, to get it away from the board it has to next be removed from the copper traces connected to the IC and diode pins. As I understand Wayne's description of his mounting technique in a module, the heat leaving the traces has to traverse about 3mm of potting compound to reach the aluminum module. This 3mm is the height of the inductor, the tallest component on the board. Your added copper attachments to the IC and diode are forcing this path length to be greater than 3mm thus increasing the thermal resistance of this path [resistance being proportional to length]. This added resistance is not sufficiently offset by any added heat removal that you gained by your added heatsinks, a theory supported by Wayne's experiments with a heatsinked alumimum rod bonded directly to the top of the IC.
hotbeam said:
Confusion here.... I am merely trying to find fault with my work to reason out why I am getting therman shutdown after such a short runtime.
[/ QUOTE ]
While I remain amazed that a potted BB750 can be made to survive at all, I cannot argue with the fact that many are reporting having success. Wayne's posts merit special credibility since he *does* have a bit of experience with these circuits. Wayne has stated that he believes [as do I] that the thermal pathway out of the top of the IC is poor. He further states that he believes the primary pathway of heat out of the IC is via the pins [which I also believe and further believe that the primary pathway is via the ground pin [#5 which is the one closest to the big capacitor]]. The heat removal from the diode is also via its two leads. If the heat is primarily exiting as described, to get it away from the board it has to next be removed from the copper traces connected to the IC and diode pins. As I understand Wayne's description of his mounting technique in a module, the heat leaving the traces has to traverse about 3mm of potting compound to reach the aluminum module. This 3mm is the height of the inductor, the tallest component on the board. Your added copper attachments to the IC and diode are forcing this path length to be greater than 3mm thus increasing the thermal resistance of this path [resistance being proportional to length]. This added resistance is not sufficiently offset by any added heat removal that you gained by your added heatsinks, a theory supported by Wayne's experiments with a heatsinked alumimum rod bonded directly to the top of the IC.
Doug S
Flashlight Enthusiast
Wayne, that is a very interesting observation about heat fostering the high conductivity of the AS. Has this be observed with both the AS and AS epoxy?
BTW, be suspicious of Don trying to return any defective BBs. /ubbthreads/images/graemlins/wink.gif
BTW, be suspicious of Don trying to return any defective BBs. /ubbthreads/images/graemlins/wink.gif
To be honest I take everything back if it is sent to me. What I actually do with it... Usually the circular file...
I inspect stuff as I get it. Most of the time I cannot see visually anyting wrong. Both types of converter boards have extremely low failures due to component or design. Most failures are MFG defects like cold solder joints, crappy burrs around the perimeter, edge hole copper shorting to something and lastly pilot errors. All these are to be expected and can be reduced buy not eliminated.
BTW: I need to send you a PM regarding something. Be on the lookout for a PM.
I inspect stuff as I get it. Most of the time I cannot see visually anyting wrong. Both types of converter boards have extremely low failures due to component or design. Most failures are MFG defects like cold solder joints, crappy burrs around the perimeter, edge hole copper shorting to something and lastly pilot errors. All these are to be expected and can be reduced buy not eliminated.
BTW: I need to send you a PM regarding something. Be on the lookout for a PM.
This is great! I had a perfectly good BB. Leads soldered on. I mounted some LED's in PR heads with AS and used the balance to put a good coat all over the IC and leads from it. The BB pulled 800 mA prior to AS when my 5W test LED was clipped on. I clipped on the test LED to the BB after post cure of AS and then brought the bench supply leads into play. Clipped the - lead and when I went to touch the + lead, the motion jarred the LED hanging and one lead fell off. Yup immediate death of BB. /ubbthreads/images/graemlins/tongue.gif SEE! That AS is just bad news!!!!!!!!
Doug S
Flashlight Enthusiast
Don, I feel your pain. At least you have probably provided some comfort to some of the novice modders who see that even the Great McGizmo can F*ckup sometimes /ubbthreads/images/graemlins/icon15.gif
Doug,
The only person I ever heard call me great was my mom. I think she said it trying to put my twin brother in his place; certainly not because she believed it for a second!
Wayne,
I have this BB that was in my grandmother's flashlight and it just stopped working during a candlelight bingo game. I was wondering if I could............
Hotbeam, /ubbthreads/images/graemlins/tongue.gif
The only person I ever heard call me great was my mom. I think she said it trying to put my twin brother in his place; certainly not because she believed it for a second!
Wayne,
I have this BB that was in my grandmother's flashlight and it just stopped working during a candlelight bingo game. I was wondering if I could............
Hotbeam, /ubbthreads/images/graemlins/tongue.gif
My existing McModule was just attacked by a tungsten Dremel cutting tool. Its entire guts, made up of copper heatsink, AA and Wayne's BB750, was entirely gouged out /ubbthreads/images/graemlins/grin.gif Boy, the curcuit board stinks when attacked with a drill bit!! And there was plenty of smoke too!!
Next up... the temperamental BB750 /ubbthreads/images/graemlins/grin.gif Stay tuned...
Next up... the temperamental BB750 /ubbthreads/images/graemlins/grin.gif Stay tuned...
hotbeam,
I was able to remove a BB from an epoxied can using acetone. I blew an LT1618 and was determined to fix it myself and successfully removed the AA'd assembly and replace the chip. I owe it all to acetone /ubbthreads/images/graemlins/grin.gif
CM
I was able to remove a BB from an epoxied can using acetone. I blew an LT1618 and was determined to fix it myself and successfully removed the AA'd assembly and replace the chip. I owe it all to acetone /ubbthreads/images/graemlins/grin.gif
CM
AilSnail
Flashlight Enthusiast
removed - thread hijack
Well well well.... maybe for the next mod, I should just sit a 5w emitter on an AA bed and use that as the heatsink. /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif
I went against suggestion and reinstalled the heatsinks on the chip and diode and then powered up the BB outside of the McModule. After ~2 minutes of run time, remember the BB only has the heatsink on it, the heatsink was boiling. It would have been easily 80C. I could just hold the touch for about 0.5 secs before having to release my finger. The bottom line.... the 5w was still lit. No blinking. No shutdown mode. I noted however that the AA (not AS) that was holding the heatsink was very very soft. In fact, after touching the copper heatsink a few times, it came off /ubbthreads/images/graemlins/ooo.gif !!!
After that happened, I thought I would bite the bullet and just pot the BB in the McModule with AA and not worry about any extra heatsinking contraptions. Wouldn't you know it, the X3T'ed BB750 McModule works a treat! Amazing! No switching to shutdown mode after 2-3 minutes. Will run it more tomorrow night, etc..., to see if it gets too hot to handle.
I still don't know why my original version of the BB750 with heatsinking does not work.
I love this light. The X3T makes a tremendously white beam. Not white/blue or white/green. No blue rings or greenish rings. No hint of blue nor green. Just snow white! Hotbeam is a happy man /ubbthreads/images/graemlins/grin.gif
Oh, here is a pic of it.
I went against suggestion and reinstalled the heatsinks on the chip and diode and then powered up the BB outside of the McModule. After ~2 minutes of run time, remember the BB only has the heatsink on it, the heatsink was boiling. It would have been easily 80C. I could just hold the touch for about 0.5 secs before having to release my finger. The bottom line.... the 5w was still lit. No blinking. No shutdown mode. I noted however that the AA (not AS) that was holding the heatsink was very very soft. In fact, after touching the copper heatsink a few times, it came off /ubbthreads/images/graemlins/ooo.gif !!!
After that happened, I thought I would bite the bullet and just pot the BB in the McModule with AA and not worry about any extra heatsinking contraptions. Wouldn't you know it, the X3T'ed BB750 McModule works a treat! Amazing! No switching to shutdown mode after 2-3 minutes. Will run it more tomorrow night, etc..., to see if it gets too hot to handle.
I still don't know why my original version of the BB750 with heatsinking does not work.
I love this light. The X3T makes a tremendously white beam. Not white/blue or white/green. No blue rings or greenish rings. No hint of blue nor green. Just snow white! Hotbeam is a happy man /ubbthreads/images/graemlins/grin.gif
Oh, here is a pic of it.
hotbeam,
Might it be possible that the copper heatsink had the opposite effect that you intended - instead of providing a thermal path away from the BB, it instead provided a path in for the heat from the LS.
Possibly having only AA encapsulate the BB forces the heat from the LS to pass through the McModule through to the PM6 body - the path of least (thermal) resistance. The AA "draws" heat mostly from the BB and not so much from the LS.
Then again, maybe not... /ubbthreads/images/graemlins/icon3.gif
Might it be possible that the copper heatsink had the opposite effect that you intended - instead of providing a thermal path away from the BB, it instead provided a path in for the heat from the LS.
Possibly having only AA encapsulate the BB forces the heat from the LS to pass through the McModule through to the PM6 body - the path of least (thermal) resistance. The AA "draws" heat mostly from the BB and not so much from the LS.
Then again, maybe not... /ubbthreads/images/graemlins/icon3.gif
jtice
Flashaholic
AHHH glad to hear you got her working hottie! /ubbthreads/images/graemlins/thumbsup.gif
Thats an interesting looking Pelican you have there. I have never seen one like that. Was it modded? Or is that an old version or something?
Thats an interesting looking Pelican you have there. I have never seen one like that. Was it modded? Or is that an old version or something?
Lucien: The heatsink extends away from the LS, towards the batteries. The intention was to promote more heat to leave the chip towards the battery end. I suppose that could also have allowed the overall heat to enter the chip. /ubbthreads/images/graemlins/icon3.gif Thanks for your thoughts though. /ubbthreads/images/graemlins/smile.gif
Ticey: Yeah. /ubbthreads/images/graemlins/thumbsup.gif /ubbthreads/images/graemlins/thumbsup.gif /ubbthreads/images/graemlins/thumbsup.gif Hotbeam is a happy chappy. /ubbthreads/images/graemlins/smile.gif Oh, the light is a Miltech Xenon. It is threading and internal spaces are identical to the PM6.... right down to the inscription on the tailcap about the 'twist, lockout, etc..". I like the feel of the light in my hands. Its knurling is a lot more positive than the PM6. Oh, it also has 2 luminescent o-rings /ubbthreads/images/graemlins/smile.gif. At twice the price, it ought have the lot! /ubbthreads/images/graemlins/icon23.gif
Ticey: Yeah. /ubbthreads/images/graemlins/thumbsup.gif /ubbthreads/images/graemlins/thumbsup.gif /ubbthreads/images/graemlins/thumbsup.gif Hotbeam is a happy chappy. /ubbthreads/images/graemlins/smile.gif Oh, the light is a Miltech Xenon. It is threading and internal spaces are identical to the PM6.... right down to the inscription on the tailcap about the 'twist, lockout, etc..". I like the feel of the light in my hands. Its knurling is a lot more positive than the PM6. Oh, it also has 2 luminescent o-rings /ubbthreads/images/graemlins/smile.gif. At twice the price, it ought have the lot! /ubbthreads/images/graemlins/icon23.gif
