Threshold Pot doesn't work

[Carl-NC]

I don't see anything obvious. You'll need to take an o-scope and troubleshoot what the problem is.

[h9361]

I don't see anything obvious. You'll need to take an o-scope and troubleshoot what the problem is.

Dear Carl,
I had an original speaker for White spectra V3 and tested it to my HHD.
Its audio level is very nice and we don't need any other audio driver, just we must find the speaker (16R-0.3W).

[h9361]

In the thread "my take on the HH2" I have scope pictures of trying to balance a DD coil.
Take a look.

Hello
Dear Walter.
I remember that you have built both DD and concentric coils for your HH2.
I also remember that you tested your concentric coil (400uH for both RX and TX, RX tuned 10KHz resonance by 470n) over Voodoo project.
You stated that your concentric coil works without any problem.
My question is that have you ever tested your DD coil over Voodoo?
Actually, i have built DISC part of voodoo and tested it by DD coil of GPX-5000 (minelab).
As you know, the RX of GPX coil has 940uh and i added a 270n capacitor as parallel (10KHz resonance).
I adjusted my delay and sampling over outer lobes via Scope, but my result is strange.
For both Ferrous and non-ferrous target, the outer lobes on DISC signal goes positive!
Have you had the same experience as me? Do you think my GPX coil has problem or i must test over concentric coil?

[waltr]

Thought you were asking about DD coil for HammerHead detector. That is what I covered in my HH2 thread.

I have built the VooDoo but did not spend much time on it and have never finished it to use in the field.
Just got on to other projects.

You will need to experiment with the DD on the VooDoo. It should work.
If the DISC output signal is inverted try reversing the leads from the RX coil.
I've never try a GPX coil on any detector so would be guessing on what to do.

[h9361]

Thought you were asking about DD coil for HammerHead detector. That is what I covered in my HH2 thread.

I have built the VooDoo but did not spend much time on it and have never finished it to use in the field.
Just got on to other projects.

You will need to experiment with the DD on the VooDoo. It should work.
If the DISC output signal is inverted try reversing the leads from the RX coil.
I've never try a GPX coil on any detector so would be guessing on what to do.

Thanks dear Walter.
Have you done any test with your concentric coil (400uH for RX and TX) in Voodoo project?
Did the coil work correctly for voodoo?
I think inductance of RX must be high (for exp, 6.5mH, not uh range).

[waltr]

Only testing I did with PI Concentric and VooDoo circuit is see that it did discriminate against iron.
This is the same concentric coil I used on my HH2 PI detector in my thread. So probably the coils are in the 400uH range.

VooDoo is still connected to coil:
Looking at this I see only one coil wire pair connected to VooDoo. This is on the two terminals closest to the TO-220 part and has a 400nF film cap across the coil connection.
The other Terminal has a 100 Ohm resistor on it. It seems I did not run a concentric coil configuration on the VooDoo but maybe did and I have the other coil disconnected for some other reason.
The VooDoo project is half buried under other projects and don't remember where my notes are. So this will not be checked any time soon.
.

[h9361]

Only testing I did with PI Concentric and VooDoo circuit is see that it did discriminate against iron.
This is the same concentric coil I used on my HH2 PI detector in my thread. So probably the coils are in the 400uH range.

VooDoo is still connected to coil:
Looking at this I see only one coil wire pair connected to VooDoo. This is on the two terminals closest to the TO-220 part and has a 400nF film cap across the coil connection.
The other Terminal has a 100 Ohm resistor on it. It seems I did not run a concentric coil configuration on the VooDoo but maybe did and I have the other coil disconnected for some other reason.
The VooDoo project is half buried under other projects and don't remember where my notes are. So this will not be checked any time soon.
.

Thank you dear Walter.
It seems that Voodoo works in concentric and DD (RX must be mH range) coils.

[Qiaozhi]

See page 75 of The Voodoo Project (Table 6-2) for coil parameters and detector settings.

TX coil inductance range tested = 300uH to 1.12mH
RX coil inductance range tested = 467uH to 15.36mH

[h9361]

See page 75 of The Voodoo Project (Table 6-2) for coil parameters and detector settings.

TX coil inductance range tested = 300uH to 1.12mH
RX coil inductance range tested = 467uH to 15.36mH

Thanks.
I checked TP4 and TP11 on scope.
Coil is GPX, TX=300uH, RX=940uH, 270n parallel to RX
No target


Iron


Copper


For both Ferrous and non-ferrous target, the outer lobes on DISC signal goes positive!
I also changed terminal of RX, no result.
Maybe i must use concentric coil, instead of DD coil.

[h9361]

Before everything, i have to thank you from dear Qiaozhi for his Voodoo project.
After trying, i could find my problem.
Yesterday, i built a concentric coil and tested its disc.
The project discriminated very nice between F and N-F metal.
In addition, the Voodoo also works over GPX coil.

[h9361]

Only testing I did with PI Concentric and VooDoo circuit is see that it did discriminate against iron.
This is the same concentric coil I used on my HH2 PI detector in my thread. So probably the coils are in the 400uH range.

VooDoo is still connected to coil:
Looking at this I see only one coil wire pair connected to VooDoo. This is on the two terminals closest to the TO-220 part and has a 400nF film cap across the coil connection.
The other Terminal has a 100 Ohm resistor on it. It seems I did not run a concentric coil configuration on the VooDoo but maybe did and I have the other coil disconnected for some other reason.
The VooDoo project is half buried under other projects and don't remember where my notes are. So this will not be checked any time soon.
.

Hello
Dear Walter.
I have a question about your experience.
I built concentric coil and checked its sensitivity. It's very good but i see a strange form at scope.
Please see attached, there is two forms for preamp. First is original and the second is its reverse.
When my concentric coil works very nice, my preamp form is the second (revers). Do you have suggestion for this?
Thanks.

[waltr]

Is this on the Hammerhead (Forum topic) or the VooDoo (Not this forum topic)??

[h9361]

It's on hammerhead.

[waltr]

Look at photo 'coils nulled' in post #6 of my HH2 thread.
This looks close to yours.

DD or Concentric coils when Nulled give a very different wave form in a PI compared to a mono coil.
For more go read Tinker's threads.

It takes a bit of tweaking and testing to find best null.

[h9361]

Look at photo 'coils nulled' in post #6 of my HH2 thread.
This looks close to yours.

DD or Concentric coils when Nulled give a very different wave form in a PI compared to a mono coil.
For more go read Tinker's threads.

It takes a bit of tweaking and testing to find best null.

Thanks dear Walter.
After trying, i learned how to find null point for concentric coil (45cm).
I tested it over my HHD, HHD+GB and Voodoo. It works very very nice.