HammerHead1 TP4 question - Help needed

[emir506]

Hello,

Am new here, and need some help.
I am building now HH1, opt1.

Am following Carl's instruction and building step by step as described in his document.
On (+)C27, I get values from -1.6V to +1.6V adjusting R18.
But on TP4, I get values form -0.9V to +2.1 V.

1) Is this behaviour correct ? Why I don't have -1.6V to +1.6V on TP4, like described in document...
I tried without R12 ,C27, D3 and D4, but got the same thing.

2) Can I use osciliscope now to test signal on TP4, or is it possible when the whole circuit is assembled.

Any help is appreciated !

[emir506]

[Qiaozhi]

Hello,

Am new here, and need some help.
I am building now HH1, opt1.

Am following Carl's instruction and building step by step as described in his document.
On (+)C27, I get values from -1.6V to +1.6V adjusting R18.
But on TP4, I get values form -0.9V to +2.1 V.

1) Is this behaviour correct ? Why I don't have -1.6V to +1.6V on TP4, like described in document...
I tried without R12 ,C27, D3 and D4, but got the same thing.

2) Can I use osciliscope now to test signal on TP4, or is it possible when the whole circuit is assembled.

Any help is appreciated !

Don't worry about the slight discrepancy. The point is to be able the adjust the null offset of the opamp, and you easily have enough range to do that. Leave off the coil and adjust the trimmer to give 0V (or close to 0V) at TP4.

[emir506]

Thank you for the help. I will continue with the next step.