Beginner would like to build Sandbanks PI Metal Detector

Xavier, I performed test #1 and yes i do have audio when I connect pin8 IC6 +9V to pin1 Neg.

Second ,on test #2 where do I check with DVM set to AC , on the unplugged coil connection?
What kind of reading should I get ?
 We're almost there guys, bare with me.

Aliman
Update;

 I did test #2  and at the unplugged coil connection with DVM set to AC I measured 20.7VAC.



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http://www.thunting.com/smf/index.php/topic,10321.msg70315.html#msg70315

Right now they are sitting at -4.3V and +11.2V

Aliman


Now, when the coil is unplugged no audio(normal), then coil plugged in and I have audio, and I can adjust the audio to a slow clicking sound with VR2 , but after about 1min. the audio starts to ramp upwards until it is no longer clicking but high pitch and VR2 looses adjustability, and TIP31C starts to get really warm. TIP31C tested OK, is it possible that it's still partially damaged.

Another observation, when I plug the coil in, there still is a voltage drop of about 2V, is that normal??


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http://www.thunting.com/smf/index.php/topic,10321.msg70449.html#msg70449

Xavier, I think you are on to something, the wire I'm using might be to thin, that would explain the 2V voltage drop.

Thanks, I'm going to build another coil with thicker wire  and see what happens.
 
Aliman


P.S  about the batteries, can I use 12V batteries with the Detector the way it is now, or do I have to do something to it ?

sorry about the stupid questions. lol

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http://www.thunting.com/smf/index.php/topic,10321.msg70454.html#msg70454

Corneius , now I'm getting audio when I plug the coil in and am able to adjust the audio via VR2 , but after about 1min. the audio starts to Ramp upwards to a point where I can no longer adust it with VR2. TIP31 still seems to get really HOT. Xavier said that the wire I was using for the coil may be to thin, but I double checked the dia. and it is 0.64mm(22awg).
 What would cause the audio to ramp upwards like that, from a very slow click to a high pitch sound with no adjustability.

 I am going to order IC1,IC2,IC8,IC7,IC5,IC6 and TR2, but I can't get IC4(LM709). I'm not sure if I should get a roll of 26 awg enameled wire. Would the 22 awg I have be OK, or no ?

Thanks
 Aliman 

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http://www.thunting.com/smf/index.php/topic,10321.msg70725.html#msg70725

Homefire , I hope you are not trying to sell this kit to Ali . Xavier and Ali are trying to get the detector to work . If it comes down to have a working detector I will send Ali another one .  Cornelius

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http://www.thunting.com/smf/index.php/topic,10321.msg70775.html#msg70775