goldscan 5 and coiltec 17 inch dd pro

[fredm]

I finally got to hit Coronado Beach with my new Goldscan-5 Sunday...My primary interest was to be sure everything was shipshape and to test the 17 inch DD-Pro that I bought for my Alaska trip. After testing the Goldscan with the regular coil and using both modes I tied-on the big coiltec Pro to see how it worked...It didn't work. So I adjusted the pulse delay from 10 to 25 very slowly, while swinging the coil over a target, still no action, I switched to GB and tried itwith the same result. So, I hooked up the little GoldQuestV.2 with the Pro Coil...it seemed to work then it started emmiting numerous false signals....My question is what might I be doing wrong???Any suggestions???There may have been to much interference that close to the Air Base, but both detectors worked fine with the standard coil...I am not in any way complaining about the Goldscan-5 as I am fairly sure this is related to the operator or the interference I mentioned.
Beyond that problem, I was very impressed with the GS-5; different sounds for different coins, switching to Ground Balance eliminated some types of iron, and the Probe that I expected to never use was very handy for pinpointing- I just have to remember to take it off the holder before I turn it on- I am excited about having both GS-5 and GQV.2 to take to Alaska and play...
thanks for the help
Fred

 

[desertdon]

Does your GS5 have the switch to allow full current to go to the coil and bypass the current limiter? Don

 

[fredm]

I don't know, Don...Eric will have to tell us...remember, I ain't very smart about these things...
Fred

 

[Eric Foster]

Hi Fred and Don,

The switch was just an idea to be looked at, and has not been fitted to any Goldscan 5's. It resulted from the fact that Minelab/Coiltek coils are much lower resistance than I have in my coils, and one could pump at bit more transmitter current through the windings. From the tests I have recently been doing, I shall not be making any changes as the current/regulator overhead/ battery voltage range is already about as optimum as you can get.

I have tested the Coiltek 14in DD, Minelab 11in DD and 11in Mono coils on the Goldscan, and these all worked fine. Beyond that, it is an assumption that all Minelab/Coiltek coils are about the same resistance and inductance. They can't deviate much. otherwise they won't work on a Minelab PI, which is quite critical of coil parameters. The Coiltek 14in DD even works OK at 10uS on the GS5, while the Minelab 11in mono works at 13uS. Two graduations up on th P.DELAY control.

For other manufacturers DD coils to work of the GS5, relies on there being an internal RX damping resistor. The ML 11in DD, that I have, and the Coiltek 14in, have this internal resistor. If, for any reason, it is not in current DD coils, then the GS5 will not work with them, unless a supplementary resistor is fitted. This is because the receiver coil will ring like mad, and prevent proper sampling.

Perhaps, if someone from Coiltek reads this, they could comment as to whether internal RX damping resistors are still fitted.

Eric.

 

[Coiltek]

Hi Eric and all.
The damping resistors are still applied to our DD coils. They are of a lower value than the 14's and 11" coils so maybe that is why it is not working. As we increase the size of our DD coils we must lower the resistor value otherwise it throws the balance out.
Like Eric said if there was no resistor then the coils would ring and bounce around and be mighty unstable!
I hope this helps somewhat.
Trev @ Coiltek.

 

[fredm]

Thanks Eric and Trev;
One reason I bought the 10x17 dd-Pro is that the area of the coil falls between the 11 inch and the 14 inch so I assumed it would fall within tested limits per the coils Eric has tryed, would that assumption be reasonable?

Eric, is the pulse adjustment critical as in minute or very tiny adjustments?

Can I assume that interference from airports and other sources is not the problem?

Trev the Coiltec Pro series draws more power; might there be some other secret ingredient that makes the Pro function differently from the non-pro series...I ask because I am betting Eric has the older versions of your fine coils...BTW during my last Trip to Australia my two favorite coils were the 14 inch DD and the mini-ufo....

 

[Eric Foster]

Hi Fredm,

You are correct in your assumption re the coil size. I am hoping to obtain a 17 x 10 DD pro to try, then I will be able to see first hand what the problem is.

Are you referring to the pulse frequency control (FREQ), or the pulse delay control (P. Delay)? Neither control is critical in its setting, although sometimes only a small adjustment of the FREQ control is sufficient to quieten interference, however, I doubt if external interference is the problem, otherwise my coil would be noisy too.

Eric.

 

[Reg]

Hi Fred,

I have never tried this coil so I don't know what could be wrong.

Now, just for giggles, you didn't try the probe just before changing coils and forget and leave the switch in the probe position? I did this a couple of times with my older Goldscan so I know it can be done.

I would have expected the coil to work at one of the later delay settings even if there was some type of mismatch. Actually, I would think it should work at or very near the 10 usec range. Eric's machines are generally very forgiving.

You might try the coil again in a different location and see what happens. I would think it would work in your house possibly. Maybe it would be extremely noisy but should work.

Reg

 

[desertdon]

What about the fuse? I once had a problem and Reg said check furse, it was blown, did it happen after you changed coils? did you turn detector off when you changed coils? Don

 

[Eric Foster]

Hi Don,

There is no replaceable fuse in the GS5. It uses a semiconductor fuse which cuts the supply if overloaded, but automatically resets when the fault is cleared. The same applies to the Deepstar and the Aquastar (no longer made as cases not available).

A different coil cannot cause an overload as the constant current circuit reduces the TX voltage. Even a short circuit on the transmitter, will only draw the same current.

Eric.

 

[Eric Foster]

Hi Fredm,

Coiltek are shipping a 17 x 10 DD and a selection of other coils, for me to test. That way I will have the latest production models and quickly see what the problem is.

Many thanks Coiltek.

Eric.

 

[fredm]

Wow, that is great Pr from Coiltec.thanks Eric

Reg, I was surprised that it didn't seem to work at Coranodo beach, but it didn't work very well at my house either. It made some noises and sometimes was completely quiet...I had not used the probe when I was testing the DD-pro on the GS-5 and the GQv.2.

I will be taking the coil to Alaska to try it, miles from any source of interference. There are a number of possibilities for this problem, the first is operator error, possible defective coil-not likely, interference from various sources...and others I don't know anything about. I appreciate all the people attempting to solve this problem and I will likely learn it is some stupid thing I didn't do correctly.
Fred

 

[desertdon]

We all have to learn and it is great to have people like Eric and Reg to help, a big plus to Coiltek also for their interest and help! Don

 

[Largesarge]

Being a rookie in the metal detecting world but a retired 20 yr. radar tech, it sounds to me like that 17"er has a problem. If the OEM coil works fine and Eric says that all the other Coiltec coils he's tested worked fine, then i'd say there's a good possibility that you got a rare lemon. I know it's an unpleasant thought but poop do happen.

 

[fredm]

Largesarge; yes, poop does happen but I have never had a bad coil from any Manufacturer. I don't know anyone that has had a defective coil from Coiltec...I am sure I will be able to test the coil on some Minelab detectors once I get to Moore Creek. Also, I will give it another go in my back yard before I leave Sunday.
Fred

 

[Mr.Bill]

I have had a few Minelab coils right out of the box that were dead, it can happen to anyone.

It very well may work fine on the detector it was designed for. It also could be on the upper end of the functionality parameters for the Minelab circuit but the Minelab can handle it, but because of the wider tolerances, and it being on the high end, it could be out of the range of the Goldscan circuit.

Believe me, this is just a guess on my part.

Although when in Arizona testing the Goldscan 5, I did not get a chance to test it with any Coiltec coils. I only had some Minelab coils, and quite a few Nugget Finder coils. Most of them were mono type. I even got the big 18