I need help identifying these parts, which I believe are SOT89-3 packaged, and I'm guessing are regulators. I have a board which is not working and my troubleshooting leads me to want to replace this part. They are marked only as "A6 55" and "A6 66".
They are each from different generations of the board. It may be that both chips are the same, and that 66 is just an upgrade/replacement of 55 - I don't know.
Note: these are two separate images. Ignore the apparent size difference between the two parts.
- Edit: Using a working board, it appears that pin 3 (right pin) is attached to a 12V supply, pin 2 (and 4) is connected to ground, and pin 1 (left pin) measures approx. 6.1V.