"Gary's Pulse Induction Metal Detector, TESTS"

Updated: June 16, 2009
Possible Problems and Suggestions.

Since I can't see your board its Impossible for me to determine what is wrong?

However:

1) Make sure the -10 (Actually about -9.75), -5 and +5 Voltage Reading are OK.
 
2) VR2 Should adjust the pizo Frequency with No Metal present.
It should be set to a Low Beat, (possibly between 50 to 300Hz) with No Metal near the coil.
(Whatever Frequency is best for you to hear the Difference as metal approaches the coil.)
Setting it to NO Tone will result in Poorer sensitivity.

3) Did you WASH the Board and REMOVE All the Solder Flux from it?
If Not, DO THIS!
(If you used "Resin Flux", You will need to use Flux Remover or Acetone to clean the board,
possibly followed by water to clean it thoughly.)
 
4) Did you set VR1 to have about +0.5 volts on Pin 6 of IC9?

5) If you use a conventional Speaker, instead of the Pizo Transducer, it May result in BAD Oscillations.
 
Now, Some Possible Tests:
 
A) First TEST. Connect a Voltmeter to Pin 6 of IC9 and Note the Voltage Reading.
Now Bring a large piece of metal Near the coil, and this voltage should go Higher.
(Possibly up to 2 Volts.)
 
B) If "Test A", Does Increase in Voltage, Now Repeat the test with the Voltmeter Connected to pin 6 of IC10.
(It should measure aproximately -0.3 to -0.8 volts with No Metal.)
Now when you bring that piece of metal near the coil, The voltage should go MORE Negative.
With Metal near the coil, It should measure about -3.0 Volts or more.

Now, Let me know your Results.