I actually haven’t opened it up to look yet, but I think I burned up the driver in a Convoy C8 I bought recently from this thread. I did a stupid newbie thing: I put 2*CR123A into the flashlight to see if it would be brighter. Well, it lit up, so I thought it was ok. I only tested it, then I put the 18650 back in it. Later, it started intermittently failing to light up. Now, it’s completely dead. :_(
Since I’ve learned about linear drivers, I’m fairly certain the driver is damaged from giving it too much voltage. It is a 105C driver with 8*7135 linear regulators. So, now what? What is it that burns up when you give it too much power? And how do I fix it? I have to say, I’m not really impressed with the UI anyway. It has next mode memory AND blinkies, which really is annoying to me! Should I just buy a replacement driver altogether? Where can I find the best deal on a reasonable driver replacement?
Update: It works now. I took it apart. Nothing seemed harmed. I put it back together. It lives! I guess there was a loose screw (as in: either the pill or the switch retainer ring was not tight).
I have not yet seen a 8x7135-based driver that didn't function correctly from 2x 3-volt CR123s.
Most Convoys use the Nanjg 105C, with the '2-group, 3/5 mode' firmware. Switch to low mode, wait 3-5 seconds and it will blink off then on, a half-press will switch it to the other mode group. Groups are H-M-L or H-M-L-strobe-SOS.
Replacement with the same UI: http://www.fasttech.com/products/1612/10001683/1186301
Same hardware but different firmware, uses the stars on the battery side to select the mode group: http://www.fasttech.com/products/1612/10001683/1122302
Also... it does not have next mode memory, it has on-time memory. You have to leave it on for 1-2 seconds before it will remember that mode at the next switch-on. If you turn it off less than 1-2 seconds after changing modes, it will not remember the last mode used.
If, as comfychair said, the driver is okay with 2*CR123A cells, then maybe there is a manufacturing flaw or something. Any ideas as to what it might be? The light was originally offered with fewer 7135’s. I had to pay $0.35 to get the 8*7135 configuration. So, could it have been messed up by someone adding chips? I dunno. Help me!
Funny. I thought crystal balls and magic wands worked because of the internet! No, seriously, I figured with all the experience the guys on this forum have with flashlights, especially C8’s and even moreso with drivers like this, there’d be someone who’d say “well 87.534% of failures in this driver are due to _.”
I intend to take it apart and see if there is anything obvious, but I’m at work right now, and it is at home. And when I get home, I have other things to do this evening and will have limited spare time, so I hoped to get a jump on it by asking around first. Thanks for the help so far. It’s good to know I probably didn’t do it myself by putting the CR123A’s in there.
Okay, I was hoping it could only be one or two things… I will check it thoroughly later. I haven’t had a chance to check it at all. It was failing intermittently before it quit altogether. In fact, it may still fire up again if I tried it. It also sometimes would flicker while in operation, like a loose incan filament. Then after a little while it would cut off on its own.
There's a path the current has to be able to follow reliably. Loose retaining ring in the tailcap, pill loose in the head, poor connection between the driver & pill, any of those minor issues will cause erratic output or totally inop. There are less issues with the positive side of the circuit since the cell + goes to the spring goes to the driver goes to the LED+, no switches or anything else in the path. If you remove the pill from the light, and hold a cell against the + spring, there will be continuity at all times all the way through to the LED+ wire solder pad on the star. The ground path has lots more parts, and therefore potential trouble spots, in it.
Yeah, I checked it out. Seems what you’re saying here is exactly what must’ve happened. I took it all apart and looked at everything. Nothing seemed to be damaged, shorted, burned, or suspicious looking in any way. But, there were some parts that did seem to come apart a little too easily. After looking at it and taking lots of pictures, I put it back together and decided to shove a 18650 in it and try again. To my embarassment, it works! Well, I did say I’m a newbie, didn’t I? :bigsmile:
Thanks for the help so far. It’s good to know I probably didn’t do it myself by putting the CR123A’s in there.