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Garrett AT Detector - Emi When In High Sensitivity Even Away From Emi - Fixed


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I've had an AT Gold now for about 12 months I guess, I swapped it for my QED PI machine as I never used it and the guy with the AT Gold never used it as it wasn't ideal for his soil conditions in Australia.  Since getting the AT Gold I'd only ever fired it up a couple of times to test how it performs on some nuggets/shot pellets and to see how well it does on my coin test garden, other than that it's been hanging in my cupboard waiting for a day I need it.

That day came as I wanted to buy a Detech Arrow coil and had to work out which detector to buy it for, it came down to the AT Gold or the Gold Bug Pro, seeing I have so many coils already for the Gold Bug Pro I decided I'd buy one for the AT Gold, both detectors perform equally well on small gold, and I've no idea how the AT Gold performs on coins as I've only got it's stock coil 5x8" coils which I guess performs similar to the 5x10" on the Gold Bug for coins at depth in my soil so I would assume it performs reasonably well.  

For this reason and that the Arrow coil is made for such a small range of detectors due to some manufacturers preventing aftermarket coils for their detectors the AT Gold seemed the best choice for me.

So I've paid for my Arrow coil and it's in the process of being shipped at the moment so I thought I'd best dust off the AT Gold and learn how it behaves properly and get used to using it, however when I turned it on it went absolutely ballistic, the most crazy EMI I've ever seen a detector do, I noticed the battery meter was saying they were flat so I promptly turned it off and put new batteries in.  This improved the situation somewhat, but in the top 3 sensitivities it was still very erratic, the higher the sensitivity the worse the EMI, I wasn't sure if this was normal as I'd given it so little use since getting it.   Then I remembered I took a video of it in my coin garden when I first got it and to my surprise I was using it in the highest sensitivity and no EMI at all, so something was up, either there is a new source of EMI around or I've got a problem. 

I tried more batteries, I tried doing a factory reset by turning it on with the button held down until it does it's little blip noises indicating a reset, I tried cleaning the contacts on the coil cable with 99% pure Isopropyl alcohol and nothing changed it.  I tried unplugging and plugging in the coil many times and making sure it was very secure.

The exact symptoms were in frequency shift F1, F3 and F4 it was erratic even 4 notches off maximum gain, in F2 it was more stable and would work 2 bars off maximum gain.  At 1 bar off maximum it would EMI false about every 10 to 20 seconds, and at maximum gain it would just go wild.

So I drove to an area away from my house into the middle of nowhere and fired it up and although it improved slightly and with it in F2 with 2 bars off maximum gain it would still false about every 30 seconds and would just go nuts in maximum gain.

I also noticed performance had dropped, I was sure when I got it I was able to detect a #9 lead pellet, albeit very close to the coil, now I was having trouble detecting a #4 lead pellet even touching the coil.

I went home again and cleaned the contacts on the coil cable's connector and the control box again using significantly more alcohol in the hope it would help and it didn't.

I decided to turn it on with the coil unplugged and see if the control box would behave and it did, flawless, maximum gain and no EMI so I didn't think it would be a faulty control box, I was sure it had to be my coil has gone bad or I have a problem with the connectors.  I was going to just wait for the Detech Arrow to arrive and see if it worked then when I decided I'd give it another go at cleaning it, this time I used my electronics clean and lube, I use this stuff on my GPZ coils to keep their contacts clean as they often get dirty as I usually take a couple of coils with me when I go detecting and the one not used in the backpack gets dusty dirt on it.   Anyway, a squirt of this stuff onto the coils cable pins and into the detectors plug socket and let it dry for a minute or two and then fired up the detector and EMI gone, maximum gain in F1, F2, F3 and F4 are now no longer a problem, even inside my house, even standing right next to the wifi router it is flawless.   That's how I vaguely remembered it.  I then tested some shotgun pellets on it and now it's picking up the #9 lead pellet again, and gets really good depth on the #4 pellet that was only just registering when it was playing up.

This is the exact cleaner I used, I'm sure there are alternative products on the market as you can only buy this stuff at Jaycar in Australia and New Zealand.

792084372_cleanandlube.jpg.c5a0a72cf5d035cd512ddbf1117ff519.jpg

 

So if anyone has an AT Gold, Pro or Max that is behaving in a similar way don't write it off, or automatically assume it's a faulty coil, even if it works with your other coils as it maybe just a bad contact on the coil cable's pins, the AT detectors seem very susceptible to this problem from a dirty cable by the looks of it.  This detector has never been in the water, and even the first owner rarely ever used it as it didn't work in his red Aussie soils and he had a GPX for that anyway and I'd only used it for an hour or so since getting it, so it was a pristine detector, when I got it it looked barely used, not even many scratches on the coil,  yet still something caused the connector to be contaminated, maybe my greasy KFC fingers or something when I tested it, unlikely but you never know 🙂

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With the AT Gold, set the ground balance neg if you're ground can handle it. It makes it much more powerful in mild ground. I don't know what that would do in bad ground.

With the 5x8 coil I could hit a 9" test dime.

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Those Garrett connector pins are pretty thin. Wonder if that cleaner is similar to the radio shak potentiometer cleaner I use on my machines?

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7 minutes ago, kac said:

Those Garrett connector pins are pretty thin. Wonder if that cleaner is similar to the radio shak potentiometer cleaner I use on my machines?

If it is this then it's very similar, it would do the trick. 

https://www.radioshack.com/products/radioshack-control-contact-cleaner-and-lubricant

My AT Gold is flawless now, max sensitivity inside my house is no issue, it's smoothed out the all metal threshold a fair bit too, the threshold in discriminate mode is perfectly smooth on the AT Gold, I wish the all metal one sounded like that.

There must have been something on the pins preventing good contact, it's just strange how it behaved, with frequency shifts even slightly improving it.    I've come to the conclusion the previous owner may have put some silicone grease or something on the O-ring, or perhaps it came from factory with some on the O-ring and it rubbed onto the pins causing the bad contact, I can't think of anything else that could have caused it, the pins looked nice and shiny clean.  I know the Garrett Carrot recommends putting silicone grease on it's o-ring so I guess the AT Gold manual probably says the same, I've not read it's manual but when I was googling my problem it seemed a really common one but everyone was just sending them to Garrett for repair, for me in NZ that's not an option.

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That is the stuff I used. Still have a little left. I used it on the potentiometers on my Tejon and it worked wonders.

I noticed that any over spray can collect dirt so make sure you wipe off extra around the connector. Never used it on the connectors on my AT Pro but never had any issues with it. Good chance the connection had some crap on it and just enough to mess up the connection.

If your coil is knock sensitive then check for any cracks on it. I had cracked my stock coil on a log. Just tapping with your finger would make it go nuts.

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Thanks yea the coil is all good, not even remotely knock sensitive, I could wrap it around a tree and it'd not false. 🙂

 

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