Need help identifying a transistor in a (fried) Saferide Gen2 driver

When trying to measure the current through LEDs, I fried the driver. Looking at the board, only one (hopefully) element looks burned: the T3 transistor (on the "hidden" side, i.e. facing the batteries). To get to it, you'll need to straighten riveted plastic battery holder legs, and de-solder 2 power contacts.


(shown with red arrow; higher-res version)

Because of the burn, I cannot read the full marking code. What's written there?

May be someone can probe it with a multimeter to determine what type it is?

Probing would be better because it seems the switching driver IC they used - the "PH323" - is proprietary, and no datasheet is available. May be same for other elements.

(Looking at its connection, I'd say it should be something like pnp.. With pnp the LEDs light up, but very dim. A big p-channel power mosfet lights LEDs up bright, but only for a moment, then they become also dim)

I planned to use the headlight at least up to the fall.. - when/if I finish modifications of it.. Would be sweet to fix it and use it until then. Please.

New driver like was done here?
http://forums.mtbr.com/lights-diy-d...lips-saferide-parts-1-through-5-a-800662.html

I don't understand your suggestion. The driver I'm talking about is the stock Philips', the one the headlight originally worked with. On the other PCB side it says 20121205.

Did someone mention anything related in that thread? (BTW, the thread is very interesting; I've seen it before)

without access to a good board, this is a tough problem to solve.

One alternative is to try to reverse engineer the surrounding circuitry and figure out what transistor would be appropriate. You would have to use a meter to figure out how the various components are connected, as well as figure out what the surrounding components are! Not easy to do.

A second alternative, which it sounds like you've explored a bit, is to start putting in transistors of different types and see what happens. The downside is that you might cause further damage with this method. As such, this might be saved after all other methods have failed.
Any idea what this section of circuitry is used for??

Any idea what this section of circuitry is used for??

Click to expand...

Its middle pin ("collector") goes (among other things) to inductor. There are no big power things (mosfets/schottkies) on the board, I think they are all integrated into the (proprietary) driver booster chip. So the burned transistor had some auxiliary, switching-related purpose.

I definitely will not reverse-engineer, I was/am a physicist, not an EE. And since there's no datasheet for the driver chip, I'm not even interested.

A similar another circuit on the board (probably USB charging booster) is still different - it doesn't have this transistor.

BTW, the charging is not balanced - bad engineering. I had problems (serious) because of it right from the beginning (and I found others on the net too). I had to separately charge/discharge 1 "bad" cell few times.

If the inductor is a large one, it's probably used for the buck converter. For a buck converter, I would expect .... well, part of me expects to see a pnp transistor (or P mosfet), but there is a chance that it might still be a npn or N-mosfet.

Honestly, it might be fun to just try different transistors and see what happens, but the most practical solution would be to try a new light. Or maybe hack the design and install a new driver? Did we have this conversation a few months ago?? I do think that the optical part of the light has some value to someone who wants to experiment with electronics. It's hard to buy good parts from Digikey or Mouser and get a beam pattern as good as the Saferide.