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Advice sought on Excal II knobs/pot

bobamis

New member
After being repeatedly frustrated with my Excalibur II knobs either being to hard to turn or the knobs failing to turn the post on which they sit, I like many others purchased larger knobs with a set screw. Even then, I needed to file the post down on the sensitivity knob to make it work, as even with the set screw it would loosen and not turn the post. Well, as many others have predicted, the sensitivity knob and the threshold knob now does not have a stopping point, they spin around 360 degrees. My questions are these:
1. The detector seems to work fine, that is, I can still set the sensitivity to auto or manually tune it. Is there any problems or potential damage in continuing to use it as is?
2. The detector is still under warranty (I've used it only a few times when on vacation in Florida). Should I send it in to get fixed? Will the warranty cover the work, since I used replacement knobs? I assure you I was careful not to turn the knob past the stop points, but obviously somehow it still happened. The pots stopping point must be very weak, or there must be a lack of a mechanical stop of any strength.
Any advice would be greatly appreciated. I'm new to Minelab detectors, have a history of using White's (currently have a V3i) and have not had any issues like this.
Thank you in advance!
 
must send the detector with the original knobs and it will be under warranty........ any after-market part(s) will void the warranty........minlabs puts the cheap knobs on so they will not strip out the pods

others will know how much the cost to fix will be



Good luck
 
Since you hacked up the pots to put the flat on I think your up the creek with out a paddle! Even when you put the original knobs back on they will see that you had set screw after market knobs on it. The Minelab knobs are ment to slip it takes some time get them the pots to loosen up! Which is a good and a bad thing! This has been discussed here over and over and there are those that will just take matters into there own hands. Just suck it up and send it in with a note to why you did what you did. Maybe they will see it your way.
I chopped my Excalibur up when brand new but with the price of gold these days it paid for it self in the first two weeks.
This unit owes me nothing! Had I not done the mods I did, I might not have found several deep targets that paid for the unit!
Minelab customer service has improved so Make a phone call:

Customer Care Technician, Minelab USA
North American Operations
2777 Finley Road, Unit #10, Downers Grove, IL 60515
e: Darin.Brown@MinelabUSA.com | Phone: (630) 401-8162
 
There's a very easy fix for your problem. Replace the crappy brass set screws in your upgraded knobs with stainless set screws which use an allen key. Tighten them snugly (do not overtighten as you can strip the threads on the brass insert).

FYI... Be sure to carefully apply a very light application of Dow Corning 111 (corrosion inhibitor) on the threads and "inside" the brass insert of the knob. The brass insert touching the stainless knob shaft creates electrolysis (dissimilar metals touching create an electric current which initiates oxidation)...do not apply the 111 to the lower knob shaft not touched by the brass knob insert...it's sticky and attracts sand...sand is not a friend of the rubber shaft seal.

All those using the upgraded knobs in salt water should periodically check them. The brass knob insert becomes an anode and will start to oxidize (brass touching stainless shaft, brass becomes sacrificial anode). Any boat owner understands this as they replace the "zincs" on their boats/engines to preserve the aluminum.
 
I forgot to ask a couple of obvious questions.... did you by any chance break the internal stops on the switches (switch is operating...you can hear clicking of switch detent as you rotate switch through 360)?... or is the 360 rotation simply due to loose knobs (knob rotates loosely on shaft...does not operate switch detent)?

These switches (which are Minelab proprietary) have a design flaw. The internal stop is a small piece of punched aluminum which easily breaks off if you apply too much torque when rotating the switch to either extreme position.
 
Hi Dave,
I believe I broke the internal stops, which amazes me because I am pretty gentle with it (and everything I own). My wife, learning to use it last night, turned it off and now the threshold goes past the "off" and then comes back on (going counterclockwise). I am wondering, though no body has addressed it yet, if it is OK to continue to use it as is. Both the sensitivity and the threshold seem to work fine, only problem is that the sensitivity goes past the auto point in one direction and past the "1" in the other direction. With the threshold, I just have to make sure to stop when it turns off.
 
Bob,

It's okay to continue using the machine. The switch still operates (internally) and will not harm the machine. Just take care to not continue to rotate past the "off" position. The switch has a small nylon cam which activates a small spring loaded detent which is what you feel and hear when you turn the machine off, and an internal, stamped aluminum detent which is what prevents the switch from rotating further (this is the one thats failed). I've had several discussions with Minelab technicians both here in the U.S. and Ireland regarding this problem and have made a design change recommendation (we'll see if that is incorporated... :~)

Anyway, first determine how much time you have remaining on your warranty...hopefully you'll have enough time remaining to make it through the detecting season. When you determine the best time to be without your machine for a couple of months, contact Darren at Minelab and describe your problem (Darren's contact info was provided on another post below). Darren and I have talked several times about this particular problem, so he's familiar with the component failure. He'll recommend you send the machine in to have replacement switches installed. Ask Darren at that time to replace the knob shafts with new ones. If your machine is still under warranty, the switches are covered...the shafts won't be covered so you'll have to pay for them (won't be expensive). The fact that you etched your knob shaft has nothing to do with the internal switches and should not affect the warranty validity for your detector. Updating a knob will not void your warranty, just as mounting your detector on a straight shaft will not void the warranty. You would have to open the housing or to void the warranty for the main board components.

I sent you a PM earlier with my contact info. Give me a call if you have any questions.

Regards,
Dave
 
Why doesn't Minelab incorporate a mechanical stop on the exterior of the tube so the potentiometers could not be made to over travel. A few well placed plastic bumps on the outside of the tube should be all that is needed. Knobs that strip seems like a indelicate and complicated solution to a simple problem.

I have thought of making my own and plastic welding those on. Of course has no warranty to worry about.
 
Minelab does have a mechanical stop on the PP/Disc switch. Unfortunately, it is designed to "limit the switch rotation" and "stop the switch" when traveling one direction fm "PP to Disc". They incorporate this mechanical stop since only the "on/off" component of the variable POT is wired (used). For the mechanical stop, they use a pin set through the knob shaft which contacts a small brass rod mounted on the mainboard. For the switch travel in the opposite direction, fm "Disc to PP" the switch stop is the internal stop which often breaks (discussed previously in this post). Your thought of applying a housing mounted plastic stop will be very difficult to achieve (if not impossible) since installation of the mainboard into the housing requires it to be slightly rotated to allow clearance of mainboard components around knob shafts and would certainly impact anything mounted on the wall of the housing in the location required to support a mechanical stop. (Simply put, you could successfully bond the plastic stop to the housing, but you couldn't get the detector back together)
 
According to Minelab the use of extra large knobs voids the warranty. I went through this in 2009 with
Ewout A. Kozel Operations Manager, Minelab USA North American Operations who along with the VP of Minelab we worked on this very issue for 6 months. The knobs that are currently use are made to slip prior to the interior stop braking. We could not get the stop to break using the stock knobs,as soon as any set screw type knobs were employed the end user broke the stops within weeks of use. Problem Minelab was having was proving that over the counter knobs were used! If you cut a flat spot on the shafts it will clearly indicate there use! Minelab is a great company and still may warranty your detector. We also found that shortly after the stop on the threshold on-off stop was broken that the unit failed to work properly. I hope everything works out in your favor. Good luck hunting.
 
davespen,

I know exactly what you are speaking of when installing the main board, I have had mine out a few times and discovered just how to hold your mouth to get the board back in the tube.

My thoughts were to place the plastic mechanical stops on the exterior of the tube, these could be glued on (actually plastic fusion welded) to the outside of the tube as a retrofit.

If Minelab changed the design to incorporate these as part of manufacturing process they could make it aesthetically pleasing as well .


davespen said:
Minelab does have a mechanical stop on the PP/Disc switch. Unfortunately, it is designed to "limit the switch rotation" and "stop the switch" when traveling one direction fm "PP to Disc". They incorporate this mechanical stop since only the "on/off" component of the variable POT is wired (used). For the mechanical stop, they use a pin set through the knob shaft which contacts a small brass rod mounted on the mainboard. For the switch travel in the opposite direction, fm "Disc to PP" the switch stop is the internal stop which often breaks (discussed previously in this post). Your thought of applying a housing mounted plastic stop will be very difficult to achieve (if not impossible) since installation of the mainboard into the housing requires it to be slightly rotated to allow clearance of mainboard components around knob shafts and would certainly impact anything mounted on the wall of the housing in the location required to support a mechanical stop. (Simply put, you could successfully bond the plastic stop to the housing, but you couldn't get the detector back together)
 
To get the knobs to turn easier, and to lube the pot. shafts and preserve the seals, get some silicone spray ( dive equipment quality). This makes a world of difference and prolongs the life of the parts, and is good preventive maintenance. Spraying it on the headphone and battery wires will help prevent dry rot and will extend the life of the unit. After cleaning and rinsing off the detector, let it dry and then apply the spray. This works great for me, and you will notice that it is much easier to turn the knobs. I still use the original knobs, no problem. HH
 
Just the outside. No need to remove the knobs when using the spray can, because the spray will make it to the shaft and seals. Just blast it under the knob, wipe any excess off the detector, and work the knobs back and forth slowly. Repeat if necessary. You will notice that they get a little easier to turn. Hope this helps. HH
 
dave said:
installation of the mainboard into the housing requires it to be slightly rotated to allow clearance of mainboard components around knob shafts
Definitely a tight fit.........



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