XL Pro depth adjustment

[vhinze]

Using a stock 9.5 coil, I got readings on a dime of 3 inches when the coil was right on top of it. Being intrepid and having an electronics backround, I took the knobs off and unscrewed the cover. Behold, a blue pot on the "tuner" side of the board labeled "depth".
I laid the detector on it's side with the green speaker wires disconnected to give me some working room. Away from any metal or electrical equipment, I Air and Ground balanced the detector, then switched to GEB Disc. The wife kindly moved a dime slowly towards the coil while I watched the meter, still off. I tweaked the depth pot clockwise to bring it to the edge of the scale as one would expect for a surface target. Put the thing back together, took it outside and checked it on the ground with the same dime.

All appears to be as it should be. If you try this be careful of the wires inside, also take care to align the pot and switch shafts with the holes when reassembling the unit. Sure beats shipping an out of warranty detector back to Sweet Home in my book. I bought this detector on eBay a couple weeks ago and have had depth reading trouble since. Everything else was fine, I wonder if this peculiarity had anything to do with the guy selling it.

 

[Monte]

The XL Pro, like the former 6000/5900 Di Pro SL's will demonstrate similar reaction between the Signal Balance setting and the Coin Depth reading function. That is, there will be a point on the Signal Balance adjustment where the unit's Coin Depth read-out will be most accurate. Any setting higher or lower than that will result in a lower or higher Coin Depth reading.

Let me review your post, if you don't mind, to explian my concerns:

"Using a stock 9.5 coil, I got readings on a dime of 3 inches when the coil was right on top of it."... First observation was that you used a dime, which is the smallest common coin we have used. Coin Depth readings are suppose to give an approximate "average" coin depth. I would have suggested using 1

 

[Butch in Colorado]

n/t

 

[vhinze]

Wow Monte,

Thank you for writing the voluminous post I'd have been hesitant to post.

All of your points are valid and well taken. I did not mention the setting of the signal balance knob, it was at the preset. It would seem to me that the coin depth should be most accurate at or near the preset. GEB norm to air and ground balance, then GEB Disc.
Removing the knobs is necessary to separate the halves of the detector and access the potentiometer in question. The bottom half carries the boards,battery,switches, pots and receptacle for the coil cable. The top half carries the speaker and wires to the meter and meter switch.
Doing a bunch of readings at various depths for the previous two weeks and digging the targets allowed me to estimate the trend as to depth accuracy on coin size targets in the ground, it was consistent with the air test.
"Still off" without further comment means almost exactly the same result as seen while in use. True, I didn't mention pulling the trigger to go into depth mode and a host of other things such as taking a breath now and then. If a reader needs to be told every single thing, I'd advise against them digging around inside their metal detector.
Thank you for fleshing out my post, I will revisit this post after using the detector for a while and let all know how my fiddling worked out.
I must agree with and emphasize your mention of the approximate nature of the depth reading and it's dependence on signal balance and where the local ground conditions require that variable to be set. I monkey'ed with mine because I was not satisfied with the performance in my area, the conditions and experience of others may differ.
"Having an electronics background", I am also aware of the interdependence of many internal adjustments on electronic equipment. However, in this case the adjustment for depth appears straightforward, controlled by one labeled pot. If one works carefully, it is possible to reverse any change without undue effort. That is, take note of any change made to the affected pot from it's original position!

My intent was and is to communicate the existence of this pot and my experience with it to those who might find the information useful. I believe it could be beneficial to someone using a 12 inch mono coil for example, I do not believe one should casually adjust such pots, for one thing, they wear out if "over tweaked. White's, to their credit, does use better quality long life potentiometers.

 

[Monte]

question your knowledge and abilities. I am sure you've seen/experienced some cases with other types of electronics where a well-intended owner thought they good goose things up a bit ... only to result in failure or ???

You're also correct that White's uses quality components.

I just felt that for those who were going to attempt to adjust their own unit, and who feel as qualified or as comfortable doing so as you or I might, then they ought to make sure they check it out initially to be certain what they are trying to set or adjust for.

Yes, the 'logic' should be a 'proper' Coin Depth Reading at the factory preset, but I have found most of them over the last 12+ years register a closer to correct depth reading with the Signal Balance set at about 10-o-clock to maybe 11-o-clock. Your post will help others, I am sure.

The XL Pro is, as we well know, a worthy detector and offers some great performance. Too bad it's no longer produced. Happy Hunting!

Monte