Surf Pi Longboard woes

[Pete B1]

Hi All, So after reading all the threads, i finally got round to ordering a Surf longboard kit from silverdog. It's my first attempt at pcb building and didn't find too difficult, having the silkscreen and all. However, when i connected the battery pack i get a constant squeal from the buzzer and no detection on metal.
I can turn the volume and threshold down but the buzzer is always live. Now i've got correct voltages around the board apart from the buzzer which is seeing +12v on both legs.
Studying the schematic i suspected diode d6 but it's ok. Now i'm thinking Q6 mpsa13, but i don't want to start pulling parts out if it's not necessary, so has anyone any ideas before i get stuck? Thanks, Pete

[Molzar]

What's your coil? Did you set the offset to 0 volts at TP2? If you did everything correctly it could just be your delay is too low for the coil, adjust the delay pot and see if it makes any difference. Mine behaves this way if the delay is too low. If that is not the issue recheck all components for orientation and correct soldering.

[Tarsier79]

Additionally, it is normal for there to be 12v on the buzzer: one leg is pulled down to make the beep. I had what I think was the same problem till I played with my coil and the delay pot.

Good luck!

[Pete B1]

Ok, thanks for the advice guys. Offset is set to 0v. My crappy inductance meter only measures down to 20h so i made a coil of .5mm copper, 115mm radius, 23 turns, resistance is 1.7ohms.
According to the coil calculator on here it should be thereabouts.
I'll take everything outside and have a play with the delay pot.
Thanks again, Pete

[Pete B1]

Hi, still trying to get this going. The latest problem is the negative voltage going up to -1.8v. (pin 5 7660) I replaced 7660 (u2)no difference, but noticed 555(u1) getting hot so pulled it and now again i have -5v in all the correct places.
Can i simply replace 555 or are there some other components i should check before i order? (I don't have an electronics shop nearby)
Thanks, Pete