Reg Modded TDI Pulse Scan

[Jeff McClendon]

After reading CaliGold’s posts about his bad luck doing a battery mod on his TDI SL, I am so thankful that I put a TDI Pulse Scan/TDI Pro at the top of my list of wants if one happened to become available.

I have only owned TDI SLs and the SPP both of which I battery modded to get more voltage and sensitivity/depth. Those TDI’’s even with the battery voltage increase always left me wanting for more.

So, when snakejim’s TDI Pulse Scan modded by Reg Sniff went up for sale on this site I decided that I would try it and see if it was an improvement.

All I can say is……Wow. The TDI Pulse Scan that snakejim sold me is amazing. I got a NF Sadie for it as soon as I realized its potential and sold the two Jimmy Sierra/Miner John coils that came with it since I have also always felt that those coils just didn’t measure up.  It looked like this TDI with a Sadie might actually make a decent small sub gram gold nugget detector which is something I would have never tried with my previous TDI SL variants. The Sadie and Reg’s modifications did the trick and this TDI can easily equal and out perform my Deus 2 using its FMF Goldfield mode on .25 down to .05 gram nuggets. Very impressive. It’s not a GPX 6000 by any means but this Reg modded TDI Pulse Scan is no slouch with a Sadie.

Also, I am so glad I don’t need to worry about doing battery mods and worry about my TDI being underpowered. I always assumed that the difference between a battery modded TDI SL and a normal TDI PulseScan/Pro was minimal. That is simply not the case with this Reg modded TDI Pulse Scan.

Thanks Snakejim. I am going to hold onto this TDI and when it’s time to let it go due to my age, I will make sure it goes to a good home.

[Jim in Idaho]

Been telling you guys, these modded TDI Sl's  aren't bad...LOL

Jim

[Jeff McClendon]

55 minutes ago, Jim in Idaho said:

Been telling you guys, these modded TDI Sl's  aren't bad...LOL

Jim

The TDI Pulse Scan I got from Snakejim is the big box 14.4V TDI not a smaller box TDI SL.

[RickUK]

A great write up,i have what was possibly the very last TDI Pro here in the UK was also very lucky to get a brand new spare battery for it as well....had been tempted to do some mods but never built up the courage to do them.....for the most part i only use GPX coils on mine and the main Coil that i use is the Coiltek 14x9 Goldstalker Mono,just makes a very nice reliable and stable outfit.....its also still looks like it came off the Whites production line yesterday its that clean.

[Jeff McClendon]

Here are a couple of posts from the topic TDI with Noise Reduction Mod by Rick Kempf.

Rick is referring to the TDI Pulse Scan. He wrote:

"A couple of recent posts referred to the whites TDI – so I thought I'd pass along the following.

Last week I purchased a secondhand TDI from a guy who had sent it in to have Reg Sniff's noise reduction mod done - along with replacement of the op-amp.

I had a TDI previously and the difference between that one and this one is like night and day. My old one had a warbly threshold that drove me nuts and made it very difficult to use the sensitivity higher than about 2/3 of full. My house is EMI hell, the neighborhood has underground utility service and the transformers sit on the ground. Even mildmannered VLF's like Whites Classics go nuts here at full sensitivity.

This TDI has a silky smooth threshold with just an occasional blip at full sensitivity (12). It also air tests 17" on a nickle with the standard 12" DP coil! That's 4" more than I ever got with my old TDI here at the house with the same coil."

 

And Reg responded with:

"I don't do the mods myself.  My hands don't work that well any more so I have a friend do them.  He does the work and keeps all the money since the mod is somewhat labor intensive and does require a pcb trace mod. 

A full TDI mod costs about $125 (return shipping included with $500 insurance) and that includes replacing the preamp with a much better IC, the addition of a small pc board to reduce the noise, a filter change so the regular TDI is upgraded to the filtering of the Pro for a faster response.  The mod also includes calibration of certain stages to 1 millivolt to assure the mod works as designed.  This TDI pro filter mod makes the regular TDI like the Pro but without the extra GB pot and volume control.  The volume control was added to help reduce the noise problem, but with the noise reduction mod, is not needed for that purpose any more.

One additional mod is to short out a capacitor which eliminates a third filter that is not needed and can cause weak signal problems.  This mod does increase the gain which in turn increases the noise level.  Fortunately, reducing the gain using the gain control about 20% or so makes it back to normal.  You do gain a little depth but more noise with this mod.  One advantage of this mod is weak signals become more reliable. "

Reg

 

I don't have the same coils as Rick had in his post. However, the stock 12" Dual Field is hitting US quarters in air tests out to 15" and easily hits a freshly buried 12" quarter in mineralized dirt with 6 of 12 sensitivity. The Sadie is hitting a quarter at 12" in air tests and that is in my EMI filled house with sensitivity on 4 of 12. It is not having any problem hitting .08 to .06 gram gold bits and lead bird shot either with the coil 1 to 2 inches above them on hot ground with sensitivity on 6 of 12. 

 

[Jim in Idaho]

Before I did the last mod, Reg had me do a test, and gave me specific ways to do it. I got 16" in an air test with a nickel. Reg said he thought I'd o even better with the 2nd mod in place. I get a response at 3" to a 1 grain bar...that's grain, not gram. I still have one mod to do, that should improve slightly on that. I do think a well-modded TDI pro is slightly better than mine....that's according to karelian's tests, but the difference is very slight. I do like the light weight and handling of the SL.

Jim

 

[CaliGold]

@Jeff McClendon Yes I had quite the scare with the over 20volt battery I frankensteined together... Luckily I was able to replace a couple resistors and a mosfet and my tdi sl is back to good performance. I have been doing tests on small/medium gold coin and bullion I have from .9999 fine 2 gram bars to 20 swiss francs (about 6.45 grams 90%gold 10%copper) and some regular modern junk metal nickels and quarters etc. Fun fact the 2 gram Argor Heraeus kinebar registers as a high conductivity target with ground balance on and goes back to low conductivity tone when you turn ground balance back below 3 or 4. So weird to me... I'm a rookie FYI.  Even with the 4 panasonic 18650 cell 16.5 volt battery I made it doesn't push that stock Miner John 8x12 folded mono coil to perform on small targets. I don't have any small placer gold melted into targets yet but a half gram of fine gold in a glass vile doesn't register to the coil AT ALL. Thats all the gold I have here now from recent trip. I have fishing lead weights I've been manipulating into .5, .25, .65, etc size nuggets and testing. The .5 lead nugget does sound off at a  couple inches but the coil is simply underwhelming. It will NOT pick up a .15 gram lead nugget.  I'll have a sadie coil from Nugget Finder 8x6 on the detector in the next day or so. Looking forward to something worth taking on bedrock in the California river systems. Fingers Crossed! Seems like MJ 8x12 folded mono ( what  does folded do anyway???) is meant for bigger targets or maybe a different detector. Why spec a coil like that on a "Super Light" PI machine thats North American targeted?  My back yard needs Ground Balance at 7 to run smooth, basically erasing any chance of a sub-gram gold target being acquired in the ground out in the wild. Make it make sense.... I like the lightweight TDI SL package, just wish it had came with a coil that would have allowed people to find the most likely size of gold they were probably going to waltz over in the desert alluvial fans or river benches here. Glad to finally start dialing this thing in and make it a real asset to supplement my crevicing and sluicing.  Have fun out chasing gold in Colorado. Got family in Lafayette. I hit clear creek in Denver last time out with a impulse bought plastic Geo Sluice. Good gold in that creek all the way out to Denver metro area. Impressive... Definitely wanna go see the values upstream...

Heavy Pans!

-Pat

[Jeff McClendon]

8 hours ago, CaliGold said:

It will NOT pick up a .15 gram lead nugget.  I'll have a sadie coil from Nugget Finder 8x6 on the detector in the next day or so. Looking forward to something worth taking on bedrock in the California river systems. Fingers Crossed! Seems like MJ 8x12 folded mono ( what  does folded do anyway???) is meant for bigger targets or maybe a different detector. Why spec a coil like that on a "Super Light" PI machine thats North American targeted?  My back yard needs Ground Balance at 7 to run smooth, basically erasing any chance of a sub-gram gold target being acquired in the ground out in the wild. Make it make sense.... I like the lightweight TDI SL package, just wish it had came with a coil that would have allowed people to find the most likely size of gold they were probably going to waltz over in the desert alluvial fans or river benches here.

 

I basically have a TDI Pro that was modified for even more sensitivity to smaller targets by Reg Sniff. Your results with a Sadie coil and a voltage upgraded TDI SL may not be the same as mine but I hope it will at least hit a 0.15 gram lead sample. Whether it will hit sub 0.1 gram gold..........?

Even some very sensitive VLF gold prospecting detectors will not hit vials of flour gold.

I have spent a lot of time in Clear Creek from the last tunnel all the way to north Denver. Finding a tenth of a gram of flour gold per hour with a good sluice and good water flow is not unusual if ice out created plenty of early summer flow. 

good luck

[Steve Herschbach]

On 8/22/2023 at 8:45 PM, CaliGold said:

I like the lightweight TDI SL package, just wish it had came with a coil that would have allowed people to find the most likely size of gold they were probably going to waltz over in the desert alluvial fans or river benches here.

The coil has nothing to do with it. It's a limitation of the machine imposed by the pulse delay.

• How Metal Detectors Work by Mark Rowan & William Lahr - Originally published by White's Electronics as a booklet P/N 621-0395. Basic technical information on how induction balance and pulse induction metal detectors work.
• Understanding the PI Metal Detector by Reg Sniff. An excellent, understandable primer on pulse induction metal detectors.

[CaliGold]

17 hours ago, Steve Herschbach said:

The coil has nothing to do with it. It's a limitation of the machine imposed by the pulse delay.

• How Metal Detectors Work by Mark Rowan & William Lahr - Originally published by White's Electronics as a booklet P/N 621-0395. Basic technical information on how induction balance and pulse induction metal detectors work.
• Understanding the PI Metal Detector by Reg Sniff. An excellent, understandable primer on pulse induction metal detectors.

Thanks for the reply, Steve. I've gotten a pretty good idea of how metals detectors work, not near to the extent you gentlemen on this forum have, but well enough to go out and find objects of interest (and trash) with them proficiently. The TDI Pro also has pulse delay 10us lowest setting. So what is it about the TDI SL that makes it so underwhelming to everyone? (even with increased voltage)   I'm installing a sadie 8x6 coil this afternoon to get better small target response or any signal reading at all for that matter on sub .6 gram targets in the ground. When I run GB at 7 as I have to in the soil here in all of the Sierras, Angeles forrest, and deserts from Mojave to Death Valley the sub gram response is poor or non existent with MJ 8x12 coil. It misses 1/4 and 1/2 gram gold on bedrock crevices 1-2" deep even. Are all the folks saying the NF coils blow the MJ coils away placebo or is that just on Minelab units?  If it doesn't have anything to do with the coil why all the coil talk on here? I'll check out the links because the info is very valuable so thank you for that. Anyone got a old minelab for sale so I can learn the difference? Should I bee looking at an old Minelab 3500 to get my feet "wet"? The weather is starting to cool a bit here in California so hopefull the next month I'll have some scenery and gold to share with the forum. 

 

Thank You!

-Patrick