[shahrayar]

Originally Posted by FrancoItaly

Hi darkman,

The values seem correct, the correct value of sensitivity is a bit less than the beginning of the compass effect. Have you tried this test? If you are unable to have this effect means that there is not enough amplification. This is confirmed by the fact that you are using 6.6pF for C2, C3 and C4, typically this value is about 1pF. Also for the gain of the stage it is the rule that maximum gain is before the stage starts to self oscillate. Controls the gain of TR2, TR3 and Tr4, beta must be 500 or higher, try to lower the value of R10-R12 from 1K to 560 ohms or less. Of course there is also the possibility that the buried metal not issue the "phenomenon."

Best regards

Yes, the solution is to reduce resistance 10 and 12