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phrunt

T2 Circuit Board Wire Question And Possible Emi Upgrade

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I just ran my T2 inside my house at 50 gain in all metal mode with no EMI at all.  That's something I've never been able to do before.  I can stand 2 meters from my high powered long range wifi modem in my lounge room with the gain at 50 in all metal and not one false signal, this is with the 12x13" Mars Tiger coil.

I wonder if this is what they've done to the newer more EMI resistant T2's.

I tested in discriminate mode too, I can run at 60 gain with discrimination at 10 in my lounge room with virtually no falsing, prior to this paint I was unable to run discrimination at 10 even in my front yard it would go absolutely nuts, I had to get to at least 20 to calm it down, now I'm standing here in my lounge room right next to my wifi modem in gain of 60 with disc at 10 and it's fine.

Even have my mobile phone in my pocket.

Of course I can't go higher without falsing but that's pretty impressive.  I hope the conductivity does improve overnight as it dries properly and it get even better, I've still got a lot left, I might give it a couple more coats over the coming days 🙂

I'll do my Gold Bug Pro's too.

Steelphase saves the day, I was all disappointed it didn't do a thing originally, but oddly that's how the factory did it, I just copied their method. 🙂

This is a good article by Dave Johnson (First Texas) on EMI and metal detectors for those interested

https://www.tekneticsdirect.com/blog/the-tek-files/191-electrical-interference

 

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Glad you got it sorted. Hopefully it will get better as the coating dries.

regards Pat

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After leaving it overnight to dry out more I ran the sensitivity at 60 inside my house working this morning in all metal, sensitivity at 63 with discrimination of 13 working, no falsing, this is holding the coil up in the air too as I can't go down near the floor as it goes off on the floorboard nails 🙂

Sensitivity at 70 with disc at 30 works indoors with no falsing.

I put the little 5" coil on after that and tested, sensitivity at 88 in all metal mode, sensitivity at 90 in disc with disc level set at 15 with no falsing.

I would say now I consider my T2 to be pretty immune to EMI with it's new PST, the new T2's may have DST (Digital Shielding Technololgy) but my T2 has PST, Phrunt Shielding Technology :biggrin:

I'll give it another coat each day for the next few days, just because I can.

Thanks to SteelPhase for the wire mounting method, it's the thing that made the most difference.  It's pretty amazing the difference really.

I can now say it is worthwhile doing this shielding mod.  This is a link to the paint I used

https://www.catmusic99.co.uk/product/shielding_paint

I should try the stock 11" coil next, if I remember correctly it sucked for EMI and I just didn't like it in general so I've never put it back on once I got my Mars Tiger.

People who don't own an original T2 probably don't know how bad they can be for EMI, especially inside a house. It makes you wonder why they didn't put it in an Alloy housing.

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I think I've reached peak EMI resistance now, two more coats today.  I'll take out the circuit board tomorrow and put some on the front of the housing and edges where it joins where I can but there is nothing I can do about the screen area so that's always going to be the area EMI gets in I guess.

I always thought a Faraday shield needed complete coverage to work properly but it's certainly improved a lot since applying the paint.

I guess I could always take off my tin foil hat and put it over my detector 🙂

 

 

 

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I'm now satisfied I've got my T2 as good as I can get it.

My house is bright at the moment so the screen was hard to see, I put the protective cover on the T2 as the extra layer over the screen seemed to help with the glare on the video recording as my phone was struggling to record the screen in a way it could be seen on the video.

You'll see I can get up to Sensitivity 92 out of 99 now indoors inside my house with no chatter at all with disc in 30 which is the low end of the Iron range, If I go over 92 the chatter starts, In hindsight I probably should of went over that in the video to show the chatter kicking in, I might do another video.  Keep in mind this is with the 12x13" Mar Tiger coil, if I go down to the little 5" Teknetics coil it's even less sensitive to EMI.   The Mars is a good EMI resistant coil for it's size.

At the end of the video I wave my watch hand in front of the coil just to show it's working and the volume is up high.

For my T2 this is an amazing feat, normally I couldn't even run it at 50 sensitivity inside my house.

Here is a video showing once I get to 94 sensitivity the chatter kicks in

I'm pretty amazed by this, it's a huge improvement over how it was from the factory in regards to EMI resistance. 

It's a risk free mod for a T2 too, there isn't really much you could do wrong, it's just removing the shield wire which is just hot glued on to the back of the housing.  To remove it I used a hair dryer to soften it a bit and then just used a knife under it to lever it off.  It was then easy to separate the wire from the glue.

The key to making it work however is following the suggestion by Steelphase.  Taping the wire down by it's shielding and then painting the exposed part of the wire onto the plastic casing, the more coats the better, then hot glue it back down once the paint is dry.

The biggest obvious benefit I've noticed so far is my VDI numbers are even more accurate now as there is no falsing even with very high sensitivity levels I'm able to really get good ID's on targets.

I can now get my T2 sensitivity higher inside my house than I can my Equinox and Gold Bug Pro :laugh: Keep in mind this is a first generation old Green T2 which are the worst for EMI, I believe it was purchased in 2009, I got it second hand, not the newer classic or any revised model.  Firmware 8.8

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Simon, you have done the excellent EMI shield tuning on T2,..... now I wonder what you can do on GoldBug PRO ...

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Just now, EL NINO77 said:

Simon, you have done the excellent EMI shield tuning on T2,..... now I wonder what you can do on GoldBug PRO ...

I'm going to do the GBP next, I'll have to find somewhere to attach a ground wire as it doesn't have one attached to the housing like the T2 did.  I could probably just connect it to the back side of the negative terminal on the 9v battery compartment.

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13 hours ago, phrunt said:

 I could probably just connect it to the back side of the negative terminal on the 9v battery compartment.

Rather than the battery, look on the circuit board for a ground plane of some sort. Only reason being is that some detectors dont use the negative of the battery as a ground. 

regards Pat

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3 hours ago, SteelPhase said:

Rather than the battery, look on the circuit board for a ground plane of some sort. Only reason being is that some detectors dont use the negative of the battery as a ground. 

regards Pat

Thanks Pat, I can always rely on your electronics expertise.

opening-the-fisher-gold-bug-pro-repair-i

I'm not seeing a big light area like you sometimes see on boards for the ground plane.

 

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opening-the-fisher-gold-bug-pro-repair-in-pictures-00011.jpg.be742d09dc09c7931775dd5e060380e1.jpg

Check the cases of the pots I have circled. Check and see if there is continuity between them. Often they are grounded - you may find its a multilayer board and the ground connections may be on an alternate layer.

If they are connected then the odds are they are grounded. I'd just solder a wire to one of them if thats the case.

Otherwise look for a common connection between things like the ground of the headphone socket, negative of electro caps etc.

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