Aquasearch Problem

[cjc]

Ive managed to keep my Aqua running for all these years--two cases later. Its now in a BHID case--rock solid. the problem is that it blares unless the SAT is almost full. Wondering if there is some internal adjustment to settle it down. I've swapped out the SAT pot--no difference. The board is well shielded.
cjc

[Carl-NC]

Is "almost full" minimum resistance or maximum resistance? I hope minimum. If so, it could be a leaky SAT cap or the following opamp has a bias current problem. If it's maximum R, then that's a head-scratcher.

[cjc]

Thanks, Carl--that's highest SAT. Not sure I should have come here kind of reminds me of when I ask Bill Lahr a question...
Regards
clive

[dbanner]

Although not familiar with this particular circuit, on the SAT pot, the wiper is tied to one side of the pot and goes to ground. So if your are turning clockwise to increase the SAT, then that would correspond to minimum R, I think. If there is a tantalum cap in the SAT circuit, then you become suspicious of it. There are a bunch of other things that could go wrong, starting with a dry solder joint or faulty pot all the way up to a bad opamp.

[kt315]

The board is well shielded.
---
you do not give pics of the shield. also, the pots (enclosures) i do not see they are shielded.
ie inside side of the box seems is not covered by conductor material.
very blur pic.

[kt315]

also, can you read a text in this thread before to do the pics?
https://www.geotech1.com/forums/show...here-share-out

[kt315]

i have some pics from a member but would like to get high resolution pics. i believe AS is same as C-scope 6pi, but
i have to see your board. also Eric's magic sign like as 'PPD4' somewhere on the board.
your activity Clive will give more light on the matter.
i learn detectors inside, outer box view and naked texts do not speak nothing to me.

[cjc]

Let me work on it the case is a BH case with all the screws a big disassembly to photograph. Not quite the same as a CS6 though have on e of those too.
cjc

[kt315]

Not quite the same as a CS6 though have on e of those too
---
same or not same thats still left under a question. Eric all his life did/does just one detector. with small variations but one.
that is hard fact.

[eclipse]

Here is your older post with board photo https://www.geotech1.com/forums/show...p-10-quot-Coil

[dbanner]

Here is your older post with board photo https://www.geotech1.com/forums/show...p-10-quot-Coil

Time sure does fly. That was since 2011. And still no hi-res photos of that board. This is Technical forum, is it not? Here is discussed matters related to design and electronic engineering of metal detectors, yes or no?
Good photos of pcb should be standard protocol, in fact, no need to request such things. Just assume everyone has such a detector and is intimately familiar with its schematic and circuitry. They could magically "see" the circuit in the minds, knowing instantly who and where is the miscreant.
Eric's designs are so special, so elaborate, like British state secret.
It has not escaped my notice that close-up, hi-res photos of this particular pcb front and back " aquasearch"(also Goldscan5), is nowhere to be found, even on Eric's own forum!
Yet one can pretty much find Hi res pics of almost any detector pcb out there, regardless of manufacturer. I don't see what the fuss is all about. That's terrible Muriel.

[dbanner]

Although not familiar with this particular circuit, on the SAT pot, the wiper is tied to one side of the pot and goes to ground. So if your are turning clockwise to increase the SAT, then that would correspond to minimum R, I think. If there is a tantalum cap in the SAT circuit, then you become suspicious of it. There are a bunch of other things that could go wrong, starting with a dry solder joint or faulty pot all the way up to a bad opamp.

Also there is an N-channel jfet that switches the SAT back into the circuit, it should be very similar to the Cscope design.

[kt315]

Also there is an N-channel jfet that switches the SAT back into the circuit, it should be very similar to the Cscope design.

all part list is sure Cscope design. i can put pics that i have. look on 4017 there. we can do it with new name 'Aquasearch Geotech Legend +'.

[kt315]

Also there is an N-channel jfet that switches the SAT back into the circuit, it should be very similar to the Cscope design.

-----------------10ohm coil----
Beachscan

Posted by: Eric Foster (---.ipt.aol.com)
Date: April 6, 2000 04:35PM

This is an example of a PI detector that breaks with traditional principles to some degree. Instead of pulsing a high current through a low resistance and low inductance coil it pulses only 0.2A peak through a 10 ohm coil that has an additional 39 ohms in series. The coil also has an inductance of over three times the usual amount but we are still able to sample at the magic 15uS for use on a wet beach. The MosFet can be a small one with a relatively low voltage rating and the mean dc current taken from the batteries is only 65mA giving good life from 8AA cells.
Eric.
-------------
Re: Beachscan

Posted by: Jeff Kinzli (---.cisco.com)
Date: April 6, 2000 05:42PM

So Eric, what does this non-traditional PI gain by going to a higher resistance coil and lower current into the coil? Is it better around RF interference or something?
------------switch faster and sample earlier
Re: Beachscan

Posted by: Eric Foster (---.proxy.aol.com)
Date: April 12, 2000 11:33AM

Hi Jeff,
Just an alternative way of doing things really. The low pulse current means that you can switch faster and sample earlier; except in this case the inductance of the coil is much higher so you end up at square one. Noise performance is no better and no worse. The higher pulse frequency results in more samples into the integrator in a given time but the greater number of turns on the coil means more noise to average. The reason for using this technique in the Beachscan is the small 4 pin DIP Mosfet and the small reservoir capacitor. This saves quite a bit of space on a high density board.
Eric.

[kt315]

DIP4