I just put together a power supply for the above mentioned preamp and it is working. However there are 4 little blue potentiometers mounted on the board and I’m wondering if anyone knows what they are for. I checked over the board with an infrared thermometer and the negative regulator is running a little warmer than the positive. Maybe that’s normal or maybe it needs adjustment. I haven’t run any signal through it yet just powered it up. If anyone could help it would be appreciated greatly. Thank you Mike