i just so happen to have a 629 led and a 669 led sitting around... so i took them apart a little..
this is the driver circuit, the IC is labeled IL68G, but i can't find that number in any IC database-- i was hoping to find a 'enable' pin on it to make pwm really easy, but no..
didn't open it up yet to look at the driver, but it is just that large white connector with the pink and white wires coming out.
so either is pretty easy to overtake the led's, but no easy way to add pwm to what is already there...
i'll open up the 669 completely next and see if there is anything worthwhile in there..
edit: nope.. this one uses a different chip with a smaller external component count, but is the same form factor. it's labeled5126R, but i couldn't find anything on it either..
pics of the controller anyways:
and the connector: