Quote Originally Posted by Hans01 View Post
@Kevin

If you want to solve the problem by yourself, there is a known problem with the BS170, this is what the manual says about it:
2A. It turns out there are two different polarities for the BS170 (Q1) and the Fairchild product I used for the first 100 or so FreHDs is backwards which is why it is mounted reversed to the screen printing on the PCB. If you are building a FreHD from scratch and it gives flashing RED LED and otherwise won't work, try changing the polarity and see if that helps.
There's another problem with Q1. As wired Q1 doesn't do anything useful. It's supposed to convert the 3.3V data from the SD Card to 5V. The gate of Q1 should be connected to 3V3 without a pullup resistor. Consult NXP Semiconductor's App Note AN10441 for details. You can also remove Q1 & R15 and jumper Q1's Source to Drain. See the attached photo. I did this on my FreHD and it works fine with my 4p. Q1-R15_mod.jpg Hope this helps.

Tom