a simple PI detector schematic

Hello the T1 transformer has been discontinued . But you can find a substitute on the Toko america website . Ic 3 is an unbuffered oscillator running at 30 khz is then amplified by Tr-3 producing a 50 volt ac peak voltage . Transformer T1 is tuned sharply to 30 khz and then diode D1 just passes the positive D.C. side of the Ac cycle and is further filtered by the 47 micro-farad C6 . And then finally regulated by the 78L12 to become a very stable 12 volts . So if you look on the pcb photo you can see it is uses a VARIABLE 5 pin "I.F. Metal Can" only using one side , which is the primary winding that is center tapped . The original article states the can must be at resonance 30 khz with the tuning slug un-touched "flush at the top" ? Maybe for phase reasons ?  But the New Toko replacement will be a 10khz to 100 khz variable , tuning might be required .......It was a Great circuit for its Time !!...And is a Great Learning Circuit Project for this Forum !!!............Regards............Eugene52

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		Quote:			Posted by Cornelius
	Better yet Eugene is when you throw away  C4 R8  IC3  C5  R9  Tr3 T1 and D1  .  Instead connect a second power source  of   + 12 V  ( two 9V in series ) to IC8  and grnd .  The problem of the Transformer is solved this way without cutting down on the working of the detector  .  Cornelius

Cornelious , you are 100% correct !! I wonder why they did not just add an extra battery in the first place , because it was too easy !!!  And the sandbanks is not the first Metal detector to do that . Voltage conversion and power supplies can be very tricky , especially when noise or voltage ripple is created . Whites Metal Detectors did that , when they changed over from the12 volt battery supply  to the use of 4 "C" cells batteries to run from 6 volts , actually 4.8-5.2 volts off of rechargeable ni-cads !! Whites makes some of the best machines in the world , but I do not trust the Power supply circuits...........Just my opinion , other comments are very welcome ........................Regards...................Eugene52

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		Quote:			Posted by Cornelius
	Eugene with this litle bit of change the Sandbanks is very easy to buid by the new-comers . It is however a good detector . so my advise to a lot of builders on this forum is to try this schematic out . You and I can help them with it . OK ?      Cornelius

This is what everyone is here for , on this "Great New Forum"  !! To help each other and to make sure , when each of us are out Metal detecting that our VLF or P.I. Machine is running close to perfect and at the end of the day we will find something good !! ...................The Technical Side of this Thunting.com Forum is just beginning , Great things take a little time , I estimate in just a few months ,  we will have made some Great Progress here !!! I am very optimistic , but it takes patients and help fom all the Great Members here . And remember if anyone has his Metal Detector torn apart , do not be afraid to take a picture and post it here , "A Picture Says a Thousand Words"  : : :..................Regards

......................Eugene52

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  can you help me with the DBP-2010 schematics

Eugene52 is PI 2 any good it use 5 555 IC

Thanks

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Hello . It looks like R1 is a 22K ohm that goes between pin1 and pin2 of IC1a which is a ICM7556IPD integrated circuit . Remember there are a couple of transistor placement corrections before you complete and test your finished circuit ........Regards.....Eugene

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