Tesoro Electronics Stingray
By Andy Sabisch
From Page 44
April, 1993 issue of Lost Treasure

Tesoro Electronics was founded in 1981 by Jack Gifford with the goal of providing dependable, high-qual­ity equipment to treasure hunters at affordable prices. Since its inception, Jack and his staff have kept that goal in mind and their impressive growth as a company over the last 12 years is a testimonial to their suc­cess.

A few years ago in response to the increasing popularity of shallow water treasure hunting Tesoro began to develop a metal detector that would satisfy the needs of both water and land hunters alike. After nearly three years of extensive development and testing worldwide, the Stingray was finally released to the public.


The Stingray is a silent search VLF-motion discriminator which also features non-motion TR dis­criminate and all-metal search modes. It is currently the only water detector with an adjustable ground-balance circuit which allows it to be used under a wide range of ground conditions. The control housing which is mounted on a modified 5-shape rod is easily removable and can be hip mounted with the use of an optional nylon carrying pouch. It is extremely well balanced and at 4 pounds 4 ounces with the standard loop, headphones, and batteries, is light enough to be used even for extended periods of time.

The detector is completely sub­mersible and has been designed to remain water-tight at depths up to 200 feet making it ideal for search­ing sites ranging from deep-water wrecks to shallow water beaches and even a local school yard. The head­phones are quite comfortable and block out most of the background noise which could mask the weaker signals. An improved cable is being used on the headphones to prevent breakage of the internal wires and eliminate a possible leak path into the control housing.

The Stingray features a weighted 8-inch concentric search coil which is hard-wired into the control hous­ing to prevent leakage. The coil has an open center to aid in pinpointing targets when searching on land. In addition, the coil, being only 1/4 of an inch thick, produces almost no drag when sweeping it through the water.

There are two knobs and two toggle switches mounted on the front of the control housing and three knobs located inside the housing which control the Stingrays operation. On the upper right of the face plate is a knob labeled SENSITIVITY that actually serves two functions. It turns the detector on and adjusts the strength of the signal being transmit­ted from the coil.

The Stingray utilizes Tesoros patented High Gain Sensitivity (HGS) circuitry found on some of their other models which makes it more sensitive to low conductivity targets such as small gold rings and chains. This circuit also allows users to set the sensitivity more accurately, thereby providing maximum depth with less falsing or chattering under most ground conditions. It is impor­tant to remember that hunting at a lower sensitivity setting may actu­ally result in greater detection depth due to the reduction in false signals caused by mineralization or outside electrical interference. Even at 25% sensitivity the Stingray will still pro­vide users with above average depth and sensitivity to smaller targets.

In the upper left corner of the face plate is the DISCRIMINATE con­trol. Tesoros Expanded Discrimi­nation circuitry has also been incor­porated into the Stingrays design. When the DISCRIMINATE control is turned fully counter-clockwise, the detector is almost in an all-metal motion search mode allowing very small and/or low conductive targets to be detected which are often re­jected by detectors using conven­tional discrimination circuits. As the control is turned in a clockwise di­rection, additional unwanted targets will be rejected.

Below the discriminate control is the MODE switch, a three-position toggle switch used to select either the motion or non-motion search mode. With the toggle switch pressed to the right, the VLF motion dis­criminate mode will be activated. The center position will allow either of the two non-motion modes to be selected via the other toggle switch located below the SENSITIVITY

control. By pressing the MODE switch to the left, the re-tune cir­cuitry is engaged which restores the threshold when searching in either of the two non-motion modes or de­tunes the detector when using the non-motion pinpoint mode. This position is spring-loaded so the switch will return to the center posi­tion when released.

The second toggle switch is used to select which non-motion mode is activated when the MODE switch is placed in the center position. With the toggle switch pressed to the right, the TR Discriminate mode will be selected. With the switch in the left position, the all-metal mode will be engaged. Since the all-metal mode can be used for either searching or pinpointing, this toggle switch will normally be left in the left-hand po­sition.

There are three knobs mounted on the circuit board which allow the user to adjust the ground balance, audio threshold, and signal volume. To make any of these adjustments, the two snaps on either side of the control housing are released and the face plate/circuit board assembly is slid outward ex­posing the potentiometers. One feature that is immediately ap­parent after removing the cir­cuit board is that surface-mount technology has recently been incorporated into the Stingrays design resulting in more effi­cient use of the space inside of the housing as well as improved overall performance.

In addi­tion, the surface-mount circuit board has been coated with a thin plastic film to reduce the possible affects of humidity on the components. The volume and threshold controls are lo­cated on the top of the circuit board. Carefully turning the circuit board assembly over re­veals the ground balance ad­justment knob. All of the con­trols are the single-turn type and function the same as those found on most other detectors.

Care should be taken when open­ing and closing the control housing to prevent damaging the 0-ring seal which may result in inadvertently flooding the detector. Tesoro rec­ommends inspecting the 0-ring and seating surface for dirt or damage whenever the housing is opened. The 0-ring should be lubricated with the silicone gel supplied with the detec­tor periodically to ensure leak-free operation.

When the detector is initially turned on, battery strength will be checked automatically. New batter­ies produce a tone heard through the headphones lasting approximately 5 seconds. When the tone is no longer heard or lasts less than 1 second, the batteries should be replaced. The Stingray is powered by six AA pen­light batteries which are mounted on both sides of the circuit board as­sembly located inside of the control housing. They are accessed in the same manner as when adjusting the internal controls knobs. High qual­ity alkaline batteries will provide between 20 and 30 hours of use. The factory does not recommend using nicads due to their lower voltage and rapid drop-off characteristics.

If the Stingray is used in the water or on the beach routinely, the wash­ers between the shaft and the search coil should be checked for damage caused by sand and dried salt. If they show signs of wear they should be replaced to avoid having the search coil become loose and flop around when searching in the water. It is advisable to order a few extra wash­ers from the factory to keep on hand as replacements.


Shortly after receiving the Stin­gray I found out that I would be heading out of town on a two-week business trip. Since I didnt think I would have a chance to do any metal detecting while I was gone, I con­tacted Kevin Reilley, an experienced treasure hunter in southern Florida, to see if he could help in testing out the detector. In addition to running a full-service treasure hunting shop, Kevin is an avid beach and yard hunter who is extremely proficient with a metal detector as a result of spending years out in the field.

After unpacking and assembling the Stingray, Kevin performed an air test and said he was favorably im­pressed with both the sensitivity and discrimination capabilities of the unit. The first site that he took the Stingray to was a nearby beach where strong waves were causing erosion of the sand bringing coins and other objects within detectable range. Se­lecting an area adjacent to the park­ing lot, he set the DISCRIMINATE level at 4, SENSITIVITY at 2 oclock, and began searching in the VLF MOTION DISCRIMINATE mode.

Almost immediately, Kevin be­gan to recover coins from the dry sand at depths of up to 9 inches. With the discriminate control set at 4, the Stingray didnt even chatter when the loop was passed over bobby pins and pieces of tinfoil laying on the beach. Even though pull tabs and screw caps were fairly plentiful, Kevin did not want to increase the level of discrimination any higher to prevent possibly rejecting any chains or gold rings. As he approached the surf line, the Stingray began to false slightly due to the affects of the salt­water so he decided to switch over to the TR discriminate mode of opera­tion.

By varying the discrimination level on the face of the control hous­ing, the adverse affects of the salt can be virtually eliminated. Similar to the internal ground adjust knob, the Discriminate control should be ad­justed so that there is almost no change in the threshold audio level as the coil is raised or lowered to the damp sand. This setting will allow the Stingray to ignore the saltwater along with smaller pieces of iron while still responding to other tar­gets the search coil might pass over.

Continuing to search parallel to the ocean in the damp sand Kevin recovered several additional coins at depths averaging 6 to 7 inches. In all cases, the signals were clear and easily discernible from the broken signals caused by iron trash. After nearly three hours of hunting, dark­ness forced Kevin to head back to his truck. His finds included 43 coins, many of which had evidently been buried for many years.

A few days later Kevin took the Stingray to an area containing sev­eral old homes and vacant lots near West Palm Beach. He enjoys hunt­ing these sites due to the potential for finding older coins; however, most of them are extremely trashy from years of neglect. In order to avoid digging a large amount of the trash, he set the discriminate control to MAXIMUM which would reject everything except for copper pen­nies and clad or silver coins. With the SENSITIVITY set at 1 oclock, Kevin began by searching along the sidewalk leading up to an older home. The first few signals turned out to be memorial pennies; however, he knew there should be at least one or two older coins in the yard.

Finally, near the front porch steps he received a solid signal and switched to the all-metal mode to pinpoint the target. Cutting a 3-sided plug and removing the loose dirt from the bottom of the hole, Kevin found a 1942 wheat penny at just over 7 inches.

He spent 2-1/2 hours hunting the remainder of this yard along with two other sites nearby and recovered 27 coins including 8 wheat cents from the 1940s and 1950s and two silver Roosevelt dimes. Kevin said that he was highly impressed with the fact that he had dug almost no trash yet had been able to find coins at depths of up to 8 inches with very little falsing or chattering. Overall, he felt that the Stingray was an ex­tremely versatile detector that would fit the needs of virtually any treasure hunter.

A few days after Kevin returned the detector, I was talking to Dennis Koutouzis, a coworker, about metal detecting. During the course of the conversation, he mentioned that he lived near one of the local Civil War skirmish sites and was wondering if there might be anything to find in his subdivision since there was still a fair amount of construction going on. I brought in several maps of the area and we discovered that both Union and Confederate forces had moved through the area during the Atlanta Campaign of 1864. Hoping to turn up a few relics, we made plans to get together early the fol­lowing weekend.

Arriving at Dennis house, I gave him a brief demonstration of how to operate the Stingray and the type of response he could expect from various targets. We walked into a small wooded area that had not yet been cleared and selected a promising spot to begin searching.

Placing the SENSITIVITY con­trol at the 3 oclock position and the DISCRIMINATE level at 2 to avoid rejecting any larger iron ob­jects such as shell fragments or gun parts, Dennis started sweeping the search coil through the dried leaves and pine needles. After several min­utes without a signal from the detec­tor we both wondered if the area had already been hunted-out by others before us.

Continuing into the underbrush, Dennis received a solid signal near the base of a large oak tree. Using a small mattock, I removed several inches of dirt from the area of the signal. Passing the search coil near the tree indicated that the target was still buried in the bottom of the hole. I continued digging in the hole and at slightly over 10 inches, pulled an old ox shoe from where it had lain for nearly 130 years. Dennis was ex­cited at finding a piece of history and began hunting again in earnest.

A few minutes later as he ap­proached a briar patch, the Stingray produced a clear, repeatable signal. Switching to the ALL METAL mode, Dennis was able to quickly pinpoint the target. Digging into the red clay, he found a .58 caliber minnie ball that appeared to have been dropped by a soldier many years earlier. A short distance away, another signal produced a second minnie ball; how­ever, this one was quite deformed indicating it had struck a solid object of some-sort.

After spending nearly three hours searching the small wooded area I literally had to force Dennis to turn the detector off and head back to the truck. Emptying our pockets, we looked over the mornings finds which included the ox shoe, three minnie balls, a round musket ball, a broken clamp from a gun carriage, and half of a horse shoe.

Once we got back to his house all Dennis could talk about was the history behind the artifacts he had re­covered. Based on his enthusiasm, Dennis wife, Pat, said she could see that he was about to pick up a new hobby.

As an interesting side note, a number of local relic hunters had searched this site previously and many of them had complained about the falsing and chattering caused by the damp red clay prevalent throughout the area. The Stingray had only pro­duced an occasional false signal even with the sensitivity set at 75%, and its detection depth had enabled Dennis to find a handful of artifacts at a site that had been heavily hunted in the past.

Since the Stingray is designed for use as a water-detector, I decided to take it to a beach located on the North Carolina/Georgia border. Set­ting the DISCRIMINATE level at FOIL to avoid possibly missing any small pieces of gold jewelry and the SENSITIVITY control to 4 oclock, I waded out into the roped off area swimming area. Almost immediately I noticed a large num­ber of unfilled holes from a previous treasure hunter. Its this type of de­struction that has resulted in many beaches being closed to metal detectorists.

After nearly 20 minutes I had still not received a single good signal, so I decided to try heading out into deeper water to see if the person that had been there before me had ne­glected searching there. As the water reached my shoulders, I recovered a few coins and a rusted set of car keys. I spent almost 2 hours hunting the deeper portions of the beach when I headed back into shore to check my float. I was pleased to see a heavy mans 14KT gold wedding band lay­ing amongst a handful of coins and other items.

At the far end of the beach there was a diving platform which ap­peared to have been there for a num­ber of years. I walked over to it and saw that the stenciling on the deck indicated the depth was 15 feet. Hop­ing that no other divers had already searched beneath it, I put on my scuba gear and waded towards the platform. Shortening the Stingray all the way, I put the regulator in my mouth and dropped to the bottom. As I approached the spot where people would be entering the water I began to receive signals which turned out to be coins at depths ranging from just under the surface to almost 7 inches.

Unfortunately I wound up spending over an hour in this area and when I was finally ready to try under the diving boards themselves, I discovered that I was low on air forcing me to surface. In addition to almost $7 in coins, including a few silver dimes, I also had four more sets of keys, a sterling silver chain and medallion, a few junk rings, and a 1OKT gold and onyx ring with a small diamond chip in it.

The only complaint I had with the Stingrays operation underwater was that the length of the shaft was too long to be used comfortably by a diver. Optional upper and lower rods, which have been shortened for use by divers, are available from the fac­tory and if one is planning on using the Stingray while diving, either or both are highly recommended.

I used the Stingray at several other sites, both on land and in the water, and found it to provide excellent depth as evidenced by the number of keepers I was able to recover. Even when searching sites that were quite trashy, the detector was easily able to locate valuable targets including five silver coins and a number of wheat cents from amongst the trash.


While the Stingray was designed with the shallow-water hunter and diver in mind, it provides top-notch depth and discrimination capabili­ties for land hunters as well. Its three modes of operation combined with the adjustable ground balance circuitry allow the Stingray to be used under virtually any possible ground condition. With its water­proof design, coin hunters, relic hunt­ers, and beach hunters will be able to search their favorite sites regardless of adverse weather conditions.

There is one aspect of the Stingrays design that users need to be aware of. In order to adjust the ground-balance, threshold, or vol­ume controls, the control housing has to be opened. While these con­trols should not require frequent ad­justments, care must be taken when opening the housing on a beach or in the desert to prevent the wind blow­ing sand and salt inside of the detec­tor. Despite this minor area of con­cern, the overall performance gained through these controls far outweigh any potential problems which may be caused by opening the housing.

The Stingray sells for $599 and comes with the Tesoro Limited Life­time Warranty. Optional accessories include a coil cover, a nylon bag for hip-mounting the control housing, as well as both shortened upper and lower poles for divers.

If you are looking for a water detector that is equally at home on land, take a look at the new Tesoro Stingray before making your pur­chase.

For more information on the Stin­gray and the complete line of metal detectors and accessories produced by Tesoro as well as the name of your nearest dealer, write them at 715 White Spar Road, Prescott, AZ 86303 or call (602) 771-2646 and be sure to mention you read about the Stingray in Lost Treasure.

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