Threshold Pot doesn't work

[waltr]

I and many others use head phones. Makes it easy to hear signals while blocking much local noise and not bothering others in the area.

[h9361]

I and many others use head phones. Makes it easy to hear signals while blocking much local noise and not bothering others in the area.

Thanks dear Walter for your comment.
Yes, i use headphone too.

[h9361]

Hello
Dear Carl
I hope you are in perfect health.
Today, i decided to make a new HH1,Rev.D for my brother. After building, i tried to set TP4 to zero,
For this, i always remove IC5, IC11,IC12 and IC8, then connect pin1-IC8 to ground using a jumper. After that, i uses R18 to reaching zero.
But today i faced to a strange, Voltage TP4 is -3V and my R18 has no any affect to the voltage. I checked more and more value of parts and i'm sure that all of them is correct. I checked the R18 multiturn using DMM and it's working. Do you have any suggestion for checking?
Thanks.

[Carl-NC]

Is IC6 defective? Is R13 installed? Does the voltage at the wiper of R18 vary? Measure the voltages at TP2 and TP3.

[h9361]

Thanks for your replying.
R13 is installed.
By removing IC6, TP4 voltage is zero. With it, it's 3V.
R18 itself is correct and its resistor is varying, but it can't vary tp4 voltage.
Voltage of both TP2 and TP3 is 0.021.
I also checked Pin6 of IC6, voltage of the pin and TP4 is identical.

[Carl-NC]

21mV sounds high but if you see it both at TP2 & TP3 then maybe it's a DMM offset. Maybe your opamp is defective.

[h9361]

21mV sounds high but if you see it both at TP2 & TP3 then maybe it's a DMM offset. Maybe your opamp is defective.

Hello
Dear Carl
Is it possible to introduce me some models much faster and lower noise than NE5534?
Do you think we can reach to 8us if i use faster opamp for 5534?
LF357, AD797 etc.
Thanks

[Carl-NC]

You should be able to reach 8us with the 5534, I've seen it done in an Aquastar. The secret is very careful coil construction. However, a better opamp can help. I often use the MAX410 which is a little better, I've also used the AD797. The best I recall is the LME49990 which is obsolete.

[h9361]

You should be able to reach 8us with the 5534, I've seen it done in an Aquastar. The secret is very careful coil construction. However, a better opamp can help. I often use the MAX410 which is a little better, I've also used the AD797. The best I recall is the LME49990 which is obsolete.

Thanks.
I could build coil that works over GPX series, but i realized an important thing.
My coil easily works over GPX but it doesn't work in my HHD at 8-10us!
Again, i built another HHD, that coil works in it at 8-10us but its sensitivity is low.
My result is that some part plays a key roles in reaching 8-10us.
I think it's better to be changed NE5534 with faster model.

[Qiaozhi]

Thanks.
I could build coil that works over GPX series, but i realized an important thing.
My coil easily works over GPX but it doesn't work in my HHD at 8-10us!
Again, i built another HHD, that coil works in it at 8-10us but its sensitivity is low.
My result is that some part plays a key roles in reaching 8-10us.
I think it's better to be changed NE5534 with faster model.

Or modify it to use a 2-stage preamp like the Minipulse Plus.

[h9361]

Or modify it to use a 2-stage preamp like the Minipulse Plus.

Thanks.

[h9361]

Hello
Dear Carl.
Time that i'm researching about GPX5000 Gain and its multi frequency method.
Please see the video.
I think maximum gain of GPX is 40-70us (according to the video).
I think also there is a direct relationship between GPX timing and its frequency.
Other words, its frequency will be changed if you change its timing.
For exp, its frequency will be changed if you changed its delay from soft to normal!
It seems that each timing works the best over a specific range frequency!
The video shows that normal timing can detect higher depth if frequency is decreased.
For this reason, GPX supports up to 5KHz!
Of course, i hope i understood correctly

[h9361]

read attached, it's part of GPX manual about using different frequency.
ِDo you think we can increase HHD frequency range up to 5-10KHz?

[Carl-NC]

As I recall, the GPX has 1 long pulse followed by 3 short pulses. Woody only shows the 3 short pulses. You can increase the frequency of HHD but you will also need to decrease the pulse width in order to have time for the EFE sample. At 10kHz you have a total of 100us so maybe 20us for TX and 80us for RX.

[h9361]

Thanks.
I think your means is the attached.
Many people believe that GPX has a vey high sensitive than nugget. Other words, they claims that the machine can detect very high depth only with coil, instead of using frame. The only logical thing that reach to my mind is that its Gain (pulse width) and its frequency.
I talked with Woody, he told me "28us to 40us on small pulse in normal mode."