New and need help

[I Dig Ya Dig]

I traded a gun for an Excalibur 1000 that looks to be in mint condition, but the threshold knob turns past the off positron. When in the off position it seems to turn off, but pushed past off the metal detector makes a loud chirp. It's almost like i have two threshold settings a + and - , Is this normal?

Also, what settings are most commonly used for beach hunting verse water hunting? Should I just leave the sensitivity set in auto? I sent an e-mail to Minelab about a week ago and still no response, is this normal? If I decided to change the headphones to gray ghost, where do I get the female connector? Is there a service that does this modification? Kellyco has a

 

[erikk]

First do a search and U will find many questions U ask answered. Your knob might just be spinning-if not someone has turned it past the stop & U will need it repaired. What color head phones? erikk
Punta Gorda

 

[Critterhunter]

What is probably happening is you are going past the stop and then over the connection junction on the pot and past that. Don't force it. When you feel what feels like resistance where the stop normally would be stop there. Or, even though you say you are hearing something when it moves past that point are you sure the dial isn't slipping on the shaft? Pop the top cap off the dial and tighten it down if it is. That's a comon problem.

 

[I Dig Ya Dig]

I have the yellow headphones. The knob must have been turned to far then. Do you think it will hurt if i use it for a few months, before sending it to minelab?

 

[I Dig Ya Dig]

I upgraded the knobs and have the same problem.

 

[Critterhunter]

If it's working fine it will hurt nothing so long as you don't go past the normal stopping point anymore. Like I said, feel for that and don't push it. I guess if it goes past the stop and ends up with the POT feelers over the POT contacts there are two bad possibilities- One is that it can short over the contacts (no POT material in this spot) via the feelers and damage the machine. The other would be the feelers might get bent and so even if you spin them back into the normal "range" of the POT they may no longer make good contact with the POT surface material (it looks like a magnet).

 

[Critterhunter]

Here's some info on pots and how they work along with some cleaning tips. I don't think any of these links shows the internals of the POT but pretty much they come apart by bending back the little tabs on the case. Some have a C-clip of some sort on the back of the pot that you need to take off in order for the POT to pull apart. Once pulled apart you'll see a black magnet like material surface that is like the letter "C" in shape. The gap in the "C" is where there will be wire contacts for the POT's connection to the rest of the circuit board. The shaft will have metal "feelers" on it that glide over the black surface. Normally some form of stop will keep the feelers from sliding over the gap in the "C" where the connection points are. If that happens the unit can either be damaged or the POT it's self may stop working because the feelers get bent.

http://sound.westhost.com/pots.htm

http://www.streettech.com/archives_DIY/potCleaning.html

http://www.talkbass.com/forum/archive/index.php/t-577328.html

http://en.wikipedia.org/wiki/Potentiometer

 

[I Dig Ya Dig]

Awesome info!!!
Thank You


Think I'm going to keep my fingers crossed and hope nothing happens. It still has that new toy feel. After looking at the post and not receiving anything back from minelab, not sure I want to do without for months.I've only been out twice but this is what I found.

 

[hershey1]

erikk correct me if I am wrong. Most Excal's threshold knobs are about half way before you get a steady threshold sound. Some peoples hearing is a lot better than mine but around 11 oclock is where I get a steady tone. Sometimes it will be lower or higher but I have never seen one come on just barely turning the knob. The manual shows it around 12 oclock. Put the sensitivity on 11 discriminate on 1 get your scoop and go find stuff. HH

 

[erikk]

erikk correct me if I am wrong. Most Excal's threshold knobs are about half way before you get a steady threshold sound. Some peoples hearing is a lot better than mine but around 11 oclock is where I get a steady tone. Sometimes it will be lower or higher but I have never seen one come on just barely turning the knob. The manual shows it around 12 oclock. Put the sensitivity on 11 discriminate on 1 get your scoop and go find stuff. HH [/quote

U R correct on that. I thought he meant that the knob was turning completely around


When in the off position it seems to turn off, but pushed past off the metal detector makes a loud chirp. It's almost like i have two threshold settings a + and - , Is this normal?

 

[NamVetLesTreasureSeeker]

Hi Dig, I have own several EXCALS for the past 10 yrs.!! My current EXCALS are the Older Red Headphones with a SWORD on the
label, and have different BETTER QUALITY KNOBS!! That being said, when I had my first EXCAL, which had your type of KNOBS, I had a similar problem with the knobs TURNING
BEYOND THEIR STOPPING POINT!! Robert, one of the main EXCAL TECHS at MINELAB, told me to take a FINE POINTED
TOOL or PENKNIFE and POP-OFF the Yellow Cap INSERT on the knobs!! Then, either try an PULL the BLACK PLASTIC KNOB off, but if it is GLUED ON DON'T FORCE IT OFF!! Or
you can try and TIGHTEN the POD at the BASE of the CHROME NIPPLE (which is your switch) by SLIDING a 1/4" NUTDRIVER TOOL, which looks similar to a screwdriver, but has a different type of an end on it,
DOWN INSIDE the Black Plastic Knob, and GENTLY and I mean G-E-N-T-L-Y TIGHTEN the POD at the base of the INSIDE of
the knob!! Then, try the KNOB SWITCH OUT, and if that WORKS, YOU JUST FIXED the problem!! Then LINE-UP the Black
Line on the Yellow Cap Insert with the OFF POSITION, and you are done!! If that does not work, then MORE THAN LIKELY
the POD is DAMAGED, and will need repairing, and I CANNOT HELP YOU with that!! BEST OF LUCK, HOPE THIS WORKS
FOR YOU, Les Robinson

 

[Critterhunter]

Sounds like when you go past the OFF position were it should normally stop you are getting over the POT connection points where the feelers never should be. If it's getting into that area and making contact with the right contacts there is no resistance from the normal POT surface material since it is now making direct contact. Based on where the feelers are on the normal POT surface certain values change and that's how the machine knows where the dial is. What probably is happening is when the feelers make contact with the right connection points and there is no POT surface material it's like turning the threshold all the way up, hence the loud noise.

I probably should condense down the above paragraph and also make it more clear but I'm sure you get what I mean. Here's a picture to more clearly show you, since I don't think I did a good job of describing it...

The most common problem with pots going bad is the black surface area or the feelers getting dirty. When that happens it can cause strange things to happen, including dead spots or eratic control (going from say a low volume to something real high with no control in between). Often the resistance due to the contamination can cause "drift", where things work well for a while and then the control setting drifts off. Another problem is the little feelers can get bend and no longer make good contact with the lower black surface area. You can gently bend them down to insure better contact but not so much that it will cause excessive wear.

To clean the pot's black surface area and the feelers the best thing to use is non-residue contact cleaner. Second choice would be rubbing alchohol. If that doesn't fix it then try sanding the black surface area lightly with a piece of paper. The paper will act as a very mild abrasive. Once done then clean it with the cleaning solution. You can use a Q-tip to do this but then make sure there is no lent from the Q-tip left on the feelers or surface area. Sometimes you can clean a POT without taking it apart by just spraying the solution into any access area from the side. Once you do that quickly move the pot it's full rotation several times as this will help to clean the surface area.

 

[I Dig Ya Dig]

I think the POT is broke. Well almost broke. I will send it back to Minelab in Jan. when it is to cold for most of the people in FL to be in the water. Who knows by then maybe Minelab will have contacted me?

Thank everybody for the help, I am amazed at all the knowledge on the site.

I have uploaded some shots to help anyone else that may run into this problem.

When you guys talk about cleaning the POT does it involve disassembling the detector? Could I try spraying something like CRC elec. cleaner past the O-ring? Wouldn

 

[I Dig Ya Dig]

n/t

 

[John(Tx)]

I've thought about removing the knobs and the plastic sleeve and putting a light coat of silicone grease on the O rings to make it easier to turn on/off so the stop doesn't mess up but don't know if it can be done or if it will void the warranty, might just leave things alone until and when I ever have problems with it. HH

 

[Critterhunter]

EDIT: I had a brain freeze on this one thanks to how fast I threw it up. The shaft portion of the pot normally only has one contact (feeler). Usually this connection is made to the shaft via a C clip at the base of the shaft which also can be what holds the pot together. Electricity travels through a wire to this clip, up the shaft, down the feeler, and onto the black surface area of the lower half of the pot. The "feelers" in the above picture would in reality only be one, but I have seen pots with variations to the single contact point in order to insure constant/good surface contact.

When I threw it together I was thinking of the last POT I cleaned on a servo for a micro RC airplane. The tiny servos it uses are what's known as a worm gear style. Instead of rotating like a normal servo and pot this type slides up and down in a straight line on some parallel traces on the circuit board. Each feeler has it's own line trace they slide on. That's how sliding volume controls have their pots configured. Conventional POTs normally only have one feeler contact point and the other two (in the gap portion of the "C") are connected to the pot surface area at each end.

This is getting even more off topic but it's kind of cool how servos work. Most plane servos aren't linear in fashion like the worm gear style above, but they all have the same components- A motor to move the servo gearing and servo arm back and fourth, and a POT that also is moved by the motor via the gearing as well. You move the stick on your transmitter to the right, it's position is read via a POT inside the transmitter. The TX sends this signal to the receiver on the plane and it moves it's servo pot to match that of your transmitter. That's all pots do for the most part- indicate where their current physical position is, meaning where the feeler is on the pot's black surface area.

I realize this is all way off topic and none of this matters when it comes to cleaning the pot or bending the feeler(s) back into good contact, but this brief overview helps to understand how things like volume and threshold controls work and how to fix them. They aren't mysterious or hard to understand at all in how they work and usually can be easily fixed on a detector if it's no longer under warranty.

 

[Critterhunter]

Forgot to mention- On a place servo when the POT gets dirty the servo will jitter, drift, or not center properly. That's the first sign of a dirty pot on one of those. On your detector you'd expect dead spots, going quickly from a low volume to a loud one with no "in between" setting, scratchy audio, or any other odd behavior that seems to either happen all the time or at least when the dial is set to a specific point.

On a normal non-waterproof POT sometimes you can get cleaner down inside it by just spraying down the side of the shaft. That avoids having to take the device apart. If you do take the detector apart then you should be able to squirt some contact cleaner into the internals of the POT via any access areas it may have on it's sides. Some pots are sealed to keep out dirt and moisture, and even if they aren't the best way to clean it properly is to take it apart. First try cleaning it by spraying into the POT some way and move the dial around. That might fix it but sometimes the only way to fix it is to take it apart and clean the feeler and surface area separately, along with bending the feeler down a bit to insure good contact with the lower pot surface area.

I'd have to figure that there is going to be no way to get cleaner into the POT via the shaft on the outside of the Excalibur since it's built to be waterproof. You'll at least have to take the machine apart enough so you can spray some cleaner into the pot's side somewhere where it will allow you to get some spray inside it. Move it around right away in full rotation to clean the entire surface area that the feeler makes contact with. If that doesn't work then you'll have to take the POT apart.

I have used WD40 to clean things like the linear volume control on the boom box I keep in my garage. For years I suffered with the aggrevation of getting the volume slider into just the right place. Often it would drift higher or lower or cause some other strange things to happen. SInce I didn't care about the boom box I just forced the spray into the slider without taking it apart and it worked, but WD40 leaves a residue and I wouldn't trust using it unless you don't really care if it might make things worse. That was about 5 years ago and so far the volume control on it works great, but over time the residue the WD40 leaves behind will attract more dirt to the POT.

Be careful using any oils or grease on the shaft O-ring. If that stuff migrates down into the internals of the pot it won't work until it gets a good cleaning.

A long ramble and mainly off topic over the last few messages but hopefuly you'll find some use for this info. I'd have no problem cleaning the POTs on my GT should I think one was bad. Beats paying big bucks to have some guy spray them for me or replace it when it didn't need to be.

Here, I re-drew the picture to make things more sense and also to correct the feeler/contact setup it should have.

 

[Crispy Critter]

Could it be that the knob is not mounted in the correct position on the pot shaft? Or does it go on in one position only?