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TDI SL mods for high conducters?:shrug:
Posted by: mschmahl
Date: March 22, 2018 05:27AM
There are some mods for the TDI SL. I think a lot of them are for finding small gold / low conducters and make the SL more stable in low conducter mode or raising the gain in this mode. Maybe I´m wrong.
Are there special mods for the high conducter mode?

Re: TDI SL mods for high conducters?:shrug:
Posted by: Reg
Date: March 22, 2018 06:48PM
"Are there special mods for the high conducter mode? "

The answer is not yet, but I have a few ideas I need to try.

Reg

Re: TDI SL mods for high conducters?:shrug:
Posted by: mschmahl
Date: March 23, 2018 03:46AM
Great news Reg. Let me know your ideas, if you want. Maybe I can help you to test some ideas. My solder-skills are ok for SMD-parts (I have build some SMD detectors, e.g. Bandido SMD, Quasar SMD). You can write me an e-mail.
My TDI SL is made 2013 and original without mods.

Michael

Re: TDI SL mods for high conducters?:shrug:
Posted by: Reg
Date: March 23, 2018 05:52AM
Michael,

What type of hunting do you do?

Reg

Re: TDI SL mods for high conducters?:shrug:
Posted by: mschmahl
Date: March 23, 2018 06:29AM
Reg, I search for bigger cooper and silver coins (over 4 cm diameter), bigger bronze objects e.g. ax heads or swords on old abandoned settlements. Iron objects e.g. middleage weapons, parts of armor, rider spurs... are also to find.. The ground is not so a big problem, most a mixture between sand and loam littered with some hot rock´s and pottery. There are also small low conducters, e.g. coins, fibulas, jewellery most made of silver, copper, bronze. I have never found some gold here. This is really rare, because it was a poor area. I support the archaeologists here and coud find a lot of objects around 2000 years old. I have also some detectors (VLF) that are good on low conducters but suffer in depth for high conducters.

Michael

Re: TDI SL mods for high conducters?:shrug:
Posted by: Mega
Date: March 23, 2018 06:57AM
Quote
mschmahl
Reg, I search for bigger cooper and silver coins (over 4 cm diameter), bigger bronze objects e.g. ax heads or swords on old abandoned settlements. Iron objects e.g. middleage weapons, parts of armor, rider spurs... are also to find.. The ground is not so a big problem, most a mixture between sand and loam littered with some hot rock´s and pottery. There are also small low conducters, e.g. coins, fibulas, jewellery most made of silver, copper, bronze. I have never found some gold here. This is really rare, because it was a poor area. I support the archaeologists here and coud find a lot of objects around 2000 years old. I have also some detectors (VLF) that are good on low conducters but suffer in depth for high conducters.

Michael

Michael,those are exactly the same type of targets that i hunt for usually on open pasture site,or deep ploughed permission,for the most part if i am on a high mineral content site then and i have access to a very productive roman villa site then i will mainly use 'low conductivity',if i suspect a deep artifact or hoard then i will use the TDI in straight PI mode for the extra depth.The VLF machine that i think that you have are the Nexus machine/s,which do offer full discrimination at great depth as well.

Main coil i use on the TDI Pro is the Coiltek 14x9 Mono,does everything that i want from the machine.



Every hole is like a scratch card. Usually it’s nothing. Sometimes you win a prize.

Quaerite et invenietis !!

Re: TDI SL mods for high conducters?:shrug:
Posted by: mschmahl
Date: March 24, 2018 11:38AM
Quote
Mega

Michael,those are exactly the same type of targets that i hunt for usually on open pasture site,or deep ploughed permission,for the most part if i am on a high mineral content site then and i have access to a very productive roman villa site then i will mainly use 'low conductivity',if i suspect a deep artifact or hoard then i will use the TDI in straight PI mode for the extra depth.The VLF machine that i think that you have are the Nexus machine/s,which do offer full discrimination at great depth as well.

Main coil i use on the TDI Pro is the Coiltek 14x9 Mono,does everything that i want from the machine.

Hi Mega,
yes I have an old Nexus (Standard SE) but rarely use it. Maybe I should use it more. Most I go with the AKA Signum. But in excavations the VLF´s are useless because of problems of changing ground (see picture going from dark ground to surrounding sandy ground)

Most it is not possible to hunt with a VLF, you have to reduce sensitivity and gain much.
There is only a chance of detection with a PI in GB-mode. With straight PI mode you get signals from pottery and this dark stains.
For low conducters the TDI is great how it is. I have found a part of a fibula last time. But my problem is to find bigger high conducters in depth, e.g. smashed weapons in urns, bigger parts under the pottery grave goods (around 30cm) to inform the archaeologists there is something. If they know there is something, than it is possible to recovery the tomb/structure in a block. In my area there are no roman structures only single coins here and there.

Actually I have a Miner John 5x9 folded mono and a detech WSS 15x8 mono.
Detech 15x8 mono


Re: TDI SL mods for high conducters?:shrug:
Posted by: Mega
Date: March 24, 2018 01:29PM
Quote
mschmahl


Michael,those are exactly the same type of targets that i hunt for usually on open pasture site,or deep ploughed permission,for the most part if i am on a high mineral content site then and i have access to a very productive roman villa site then i will mainly use 'low conductivity',if i suspect a deep artifact or hoard then i will use the TDI in straight PI mode for the extra depth.The VLF machine that i think that you have are the Nexus machine/s,which do offer full discrimination at great depth as well.

Main coil i use on the TDI Pro is the Coiltek 14x9 Mono,does everything that i want from the machine.

Hi Mega,
yes I have an old Nexus (Standard SE) but rarely use it. Maybe I should use it more. Most I go with the AKA Signum. But in excavations the VLF´s are useless because of problems of changing ground (see picture going from dark ground to surrounding sandy ground)

Most it is not possible to hunt with a VLF, you have to reduce sensitivity and gain much.
There is only a chance of detection with a PI in GB-mode. With straight PI mode you get signals from pottery and this dark stains.
For low conducters the TDI is great how it is. I have found a part of a fibula last time. But my problem is to find bigger high conducters in depth, e.g. smashed weapons in urns, bigger parts under the pottery grave goods (around 30cm) to inform the archaeologists there is something. If they know there is something, than it is possible to recovery the tomb/structure in a block. In my area there are no roman structures only single coins here and there.

Actually I have a Miner John 5x9 folded mono and a detech WSS 15x8 mono.
Detech 15x8 mono

Michael,that is interesting and similar to one of my sites,have found that running the TDI in low conductivity works very well on our silver hammered coins and roman coinage as well,of course one will miss out on some high conductivity targets as well,but at least the detector works in these type of ground conditions and also help reduce the amount of iron i dig,although not 100% accurate it does help.

I also have a Nexus SE,and also the latest MP model which does work basically as well in high mineral content sites that other VLF machine cannot work in,but with the massive advantage of having full discrimination and that is the trump card that this Nexus has.

Good to see someone else using the same type of machines for the same type of hunting scenarios.



Every hole is like a scratch card. Usually it’s nothing. Sometimes you win a prize.

Quaerite et invenietis !!

Re: TDI SL mods for high conductors
Posted by: Reg
Date: March 24, 2018 02:01PM
The problem with modding the SL is like so many detectors, much of the design is inside a microprocessor and not available. So we are limited as to what can be done. So, we have to look at other parts of the design to see what we can do. Since the SL was designed for nugget hunting, we also have to work around the fact that GB is needed and has a lot to do with some limitations.

Most noise comes from the GB channel and that noise limits overall gain of this detector. Add this to the fact, the + v is limited in current capability doesn't help. So, any mods are limited at best.

Those of you who hunt for silver and copper coins here in the US know you can reduce the GB to a point where most if not all iron is ignored but do so at the expense of depth. Many of you who do this know that if you get the coil too close to iron you can get an unwanted iron response caused by an overload that sounds like a good response. Many of you have learned that simply raising the coil some distance and checking again will find the overload signal gone.

So, in the SL, the GB channel is the limiting factor. Now what if we increased the gain of the metal or gold channel and left the GB channel alone? we could leave the GB channel at normal GB and simply increase the gold channel (also called the metal channel) to the point where the ratio of the GB to metal channel is again at iron disc, we should see a net gain of depth plus have iron reject of, maybe 2" or so.

Come up with a new GB design that doesn't require so much gain and again, you have the potential for depth increase. Reduce the noise in the input circuitry would also help.

Finally, whatever is done, it needs to be simple and easy to add. Finally, it needs to be built and tested before it can be made available.

See, how easy it is?



Reg



Edited 1 time(s). Last edit at 03/24/2018 02:05PM by Reg.

Re: TDI SL mods for high conducters?:shrug:
Posted by: doc holiday232
Date: March 24, 2018 02:24PM
You can bet your money that Whites ain't gonna do any of this.

Re: TDI SL mods for high conducters?:shrug:
Posted by: stephenscool
Date: March 24, 2018 05:15PM
Toss the new design in a waterproof box and it's the SL2

Re: TDI SL mods for high conducters?:shrug:
Posted by: stephenscool
Date: March 24, 2018 07:41PM
Any way to adapt the battery tray/door to accept 10 1.5v battery? Delivery services are real tight with restrictions on batteries now.

Re: TDI SL mods for high conductors
Posted by: mschmahl
Date: March 26, 2018 04:36AM
Quote
Reg
Those of you who hunt for silver and copper coins here in the US know you can reduce the GB to a point where most if not all iron is ignored but do so at the expense of depth. Many of you who do this know that if you get the coil too close to iron you can get an unwanted iron response caused by an overload that sounds like a good response. Many of you have learned that simply raising the coil some distance and checking again will find the overload signal gone.

So, in the SL, the GB channel is the limiting factor. Now what if we increased the gain of the metal or gold channel and left the GB channel alone? we could leave the GB channel at normal GB and simply increase the gold channel (also called the metal channel) to the point where the ratio of the GB to metal channel is again at iron disc, we should see a net gain of depth plus have iron reject of, maybe 2" or so.

Come up with a new GB design that doesn't require so much gain and again, you have the potential for depth increase. Reduce the noise in the input circuitry would also help.

Reg

Good idea to split the gain-setting for both channel. If I´m right, than in an unmodded SL you raise the gain for both, the GB-channel and the metal channel with turning the gain high. The gain-pot is on a point, where the GB- and metal-channel is added together. So we only raise the added(or substracted) signal. So we have to raise the gain of an IC before the signal is added together. Is this the OP2177, between pin 6 and 7?

Here is a picture of the RX-input stage. To reduce the input noise should we reduce the big resistor R9 to 500 Ohm?

or change some surrounding parts?



Re: TDI SL mods for high conductors
Posted by: Reg
Date: March 26, 2018 11:55PM
I let this set on purpose so people might think about any possible answers and whether there would be negative issues if any ideas were to be tried.

With that said, people should realize for every action, there will be some negative reaction. The question then becomes is the problem created worth it and why did it happen.

Also, I need to mention that it is becoming extremely difficult to type any more.because of medical issues. For example, here is a paragaraph typed where Idon't correct the errors. It is toughto read ad eveh more difficult for me to correctl. Hitting th wrong key, missing keys and fojbining words are common issues. It isn't fun going back to cldan up the problems.

Anyway, years ago, I had a guy plead with me to modify his SL to see just how far I could increase the depth. I started out with a detector that would get about 12" on a nickel in an air test,. With a few changes, I obtained about 16.5" or so. Had I tried a 4 cell battery at 16V I suspect it would have made the 18". Unfortunately, I didn't do that, nor did he, so he sold the unit and looked for a Pro based upon the bs on you tube.

Ironically, one thing I did was parallel R9, the input resistor with another special low noise resistor (making the R9 appear as as 500 ohm resistor). (no, I will not tell you just what type of resistor I used). This doubled the system gain, which is a huge increase. Because I used a special ultra low noise resistor, the noise didn't increase much at all. What I suspected but didn't measure was the decay curve to see how close to max the coil diameter was. You see, when you increase the preamp gain, you increase the amplified decay curve which can cause problems including reducing the size of coil that will work at minimum delay. Also, part of the reason for not building up a 4 cell li ion battery was I wasn't sure it would work with a 12" coil with the 500 ohm input resistor at minimum delay.

So, if you decide to try this, make sure you make it easy to go back.

As for your question about the OP2177 the answer is yes. I would leave the circuit alone and just use an add on pot,.

Reg

Re: TDI SL mods for high conducters?:shrug:
Posted by: mschmahl
Date: March 27, 2018 04:47AM
Reg, thanks a lot for your hints and ideas.
First I will make a schematic from the parts of the original SL that I want to change/test. Thank´s to your help with the GS4 I think I can use some idea´s on the SL. As reference I have a modded GS 4 (newer parts how you suggested, fewer trimmers ,...)
Than I will try some ideas and recheck if they are improvements and what is the negativ attribute of them. It is a good tip to make all in a way to go back if necessary.
One question I still have:
What is the job of the microprocessor? If I get it right it does all of the different pulses/timing, but the analyse of the signal is done through the IC´s and not the micro.

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