Threshold Pot doesn't work

[h9361]

If you probe the signals at CH1 and CH2 are they noisy? Be sure to increase the o scope sensitivity to compensate for the gain of IC10.

Circuits generate their own noise and I have no idea where your noise might be coming from. You will need to probe the circuitry, including the power supplies, to figure it out. Noise is more sensitive in the preamp because it sees the most gain through the whole signal path. Also, it would help if you posted a real schematic instead of a block diagram.

Thank you dear Carl for your guidance.
I checked all voltage +5/-5 on scope, it is clear without any noise.
After a lot of trying, i could find my noise path.
First, please see my schematic (attached).
I have a noise (incorrect signal form) only in IC8b-pin7 (my main channel).
I checked its last path (IC8b-pin5), no noise and it is clear.
I also checked IC9b-pin7, no noise. If you see in scope, it is pulse form, it is because of my gain pot.I increased it in last position, maximum gain. If i decrease the gain, it will be a clear line, no pulse. In my scope, channel 1 is IC9-pin7, channel 2 is IC8b-pin7.
I think gain of IC8b is high, do you think i should decrease R53 value?
(for better understanding, i show my noise path with blue line)
I measured all result without connecting coil.
Thank you

[Carl-NC]

I checked its last path (IC8b-pin5), no noise and it is clear.

IC8 has a gain of 100 so you will need to increase the oscope sensitivity to 50mV/div to get an equivalent measurement. Did you do that? I suspect you will see the same problem and that it is just a normal integrator waveform. This means you either have too much gain in IC8 or not a high enough integration tau.

[h9361]

IC8 has a gain of 100 so you will need to increase the oscope sensitivity to 50mV/div to get an equivalent measurement. Did you do that? I suspect you will see the same problem and that it is just a normal integrator waveform. This means you either have too much gain in IC8 or not a high enough integration tau.

Thank you for your response.
Is is possible to tell me definition of tau?
I will measure the result with 50mV/div and share here.
For another test, i will decrease gain of IC8 (value of R53).
About tau, is your mean that i should play (increase gain) with R64-R47/R49-48 (attached)?
I forgot to tell you, my frequency is 2.6KHz.

[Carl-NC]

R64-C21 and R49-C20 set the tau of the integrator. Try increasing C20 and C21 to 470nF (also C22,C23), your ripple should decrease but your target response speed will be slower.

[h9361]

R64-C21 and R49-C20 set the tau of the integrator. Try increasing C20 and C21 to 470nF (also C22,C23), your ripple should decrease but your target response speed will be slower.

Thank you.
I will test and share my result.
Do you think i should also increase or decrease C22 and C23 (GB channel)?

[Carl-NC]

Yes, the ground channel needs to match the target channel.

[h9361]

Yes, the ground channel needs to match the target channel.

Hello
Dear Carl.
Thank you for your guidance.
After changing TAU capacitors, my main channel output (IC8-pin7) is good form.
In addition, gain of my main channel also was high and i changed to 1.
But see my ground channel form, do you think it is normal?
I measured results with a connected coil over ground (free metal)

I change my ground channel gain (GB pot), you can see its form in follow

[h9361]

Yes, the ground channel needs to match the target channel.

Hello
Dear Carl
First, thank you for your supporting and my amatory questions.
First see attached, it is my GB part schematic:

Now, see my Delay chart as follows,


TP4 and Del1 (main delay)= 8uS



Del1 and Del2 (GB delay)=4-5 uS


Del2 and Del3 (first EE)= 150uS


Del3 and Del4 (second EE)=10uS

But my GB pot is not working. The only model that it works, i increased Del3 and Del4 (both EE delay) so that Del4 went out of my time period (over next TP4 pulse).
See it, it is my Del4 (second EE) and next TP4 pulse.


All of my measurement was based on a 45cm coil (litz, i tested the coil over GPX5000 and works very nice). But my HHD-GB work very nice if i change my coil to 8cm with inductance 500uH.

Do you have any suggestion for testing and solving my GB problem?
Please forgive me for my questions.

[h9361]

Yes, the ground channel needs to match the target channel.

Before everything, i need to thank you for your tips and help.
After a lot of trying, now my HHD (motion mode) works very very nice with GB and over 3.7-4.2 pps.
Now, i want to develop Voodoo project. Now, i edited its code for producing 4 delays.
Do you think i continue this on the thread or i should make a new?

[Carl-NC]

New thread, please. There is a Voodoo-specific forum.

[h9361]

New thread, please. There is a Voodoo-specific forum.

Hello
Dear Carl
I hope you are in a good health.
About building Coil, i tested many cables for connecting Coil to unit. The best result was with RG59.
But as you know, the cable is not flexible. Since you have a lot of experience in this field, can you introduce me some good cables for this?
Thank you.

[h9361]

New thread, please. There is a Voodoo-specific forum.

As soon as connecting shield, the cables will destroy my TP4.
Only the RG59 keep TP4 very nicely.

[Carl-NC]

Does it have a solid center conductor or stranded?

Generally, you want a coax with a stranded center conductor and a high characteristic impedance. The cable I use is custom made for the company I work for.

[h9361]

Does it have a solid center conductor or stranded?

Generally, you want a coax with a stranded center conductor and a high characteristic impedance. The cable I use is custom made for the company I work for.

Thank you.
Do you have any suggestion (cable) for DD coil?

[pito]

SVGA Monitor Cable