Jim in Idaho

On 7/23/2019 at 6:03 AM, Mark Gillespie said:

Not yet, wanting to get a correctly functioning battery pack.  That might bring a question to mind.  Do you think the sweep speed mods would help depth in any way?

Nope. What you want to accomplish with the SS mod is a less critical SS on tiny items, without losing any sensitivity to the those items. I'm not sure it would make any difference on most beach targets.

20 hours ago, Mark Gillespie said:

That is amazing.  If you're digging 12-15" nickels in the wet salt sand, you're neck and neck with my White's TDI SL.  I'll need to remember to slow down on my next beach trip.  Hope tomorrow brings more good targets.

Did you do the sweep speed mod on your SL, Mark?

Jim

On 7/18/2019 at 8:54 PM, rexhavoc said:

This is my prospecting dog Dasha, yesterday. After detecting a good spot she often helps by dropping big yellow nuggets in my pan. Now if I could only adjust her discrimination for sticks and tennis balls....

Hey Jon, How goes the battle? hope you're finding some gold up there on the NSR!

Jim

Hi HTH, and welcome! Looking forward to your finds reports.

Jim

yes...they break our hearts in the end, but all we can do is give them the best life possible, and then say "goodbye". then go get another. I'm on my 14th now. God, I pray they'll be waiting for me when I pass.

Jim

Yeah...I have to be careful where I take Heidi, too. Last fall i wanted to prospect a particular canyon and ran into signs warning of potentially lethal traps in the area. They were trapping wolves, and the rancher told me the traps were non-lethal, but even a leghold for a  wolf would probably break Heidi's leg, so I went elsewhere. I also try to never take her into snake country when the snakes are active. She's had the rattlesnake shots every year, but I'd rather not risk it. Limits where i can go, but not a big deal. I can't imagine a piece of gold big enough I'd risk Heidi to have it.

Jim

Yup...Heidi, the rabbit dog. Wouldn't know what to do without her.

Permit? I don't need no steenking permit....LOL

Jim......in Blackfoot.

Mark G. reminded me I hadn't posted the video link, to the comparison video, on here. So, here it is:

sweep speed comparison

Many thanks, Mark. You did a nice job on it, and will be rewarded with many years of use, not to mention the increased depth1

Jim

Well, it's hard to gauge people's skill, Jim. You need  a decent soldering iron with a small wedge tip, for starters. You also need some solder wick to absorb as much of the old solder as you can. It's also nice to have a really tiny drill bit, which I didn't have....the smallest I had was the one in my "number drill" kit, and it seemed it was too big, but might have been OK. (#60  .040") I ended up using a hardened steel wire, from a welding brush, heated with the soldering iron, to remove the last bit of old solder from the holes. Installing the new caps is easy, once the holes are cleaned out. The rest is just disassembly, and reassembly. A magnifying glass is a help, to check your resolder job on the new caps. The new caps need to be matched to 1%, too. The overall capacitance isn't critical, but whatever it is, they should be close to the same.

 I didn't see any difference in depth, but now wonder how much gold I've missed from sweeping too fast.

Jim

Bit the bullet and did the sweep speed mod this morning. Made a huge difference in the acceptable SS. I ran the 1 grain gold bar past the 8 x 6 Sadie coil before doing the mod, and there was a relatively slow, specific sweep speed that gave the best signal. Too fast, and the signal completely disappeared. After the mod, the SS made almost no difference. Fast, slow, the signal was steady. No change in indicated depth in the air test. Threshold was still smooth. I'll post a video of the before/after tests later on. I changed the filter caps (C20, 21) from .47ufd, to ,22ufd. A friend in Florida, who is a civilian tech working for the Navy, was kind enough to send me a few matched pairs of the caps. Without his encouragement, and help, I probably never would have tackled this. Now I'm really glad I did. One tool I'm glad I had was my fly-tying  magnifying light. My eyes don't focus like they did when I was young, and that magnification allowed me to see the soldered spots, to be sure I had done a thorough job.

Jim

I did a quick test, with a quarter, on the 12"DF and it was about 11 1/2", Mark. The battery pack was purchased 3 years ago from a guy that goes by "Reidman" on Ebay. Last time I checked, he was no longer offering them, however. Now that I have one, I could build another pretty easily. I use a charger that the output voltage can be set to any desired voltage, so I can limit the final charge voltage to 16v. Standard chargers can't be adjusted, and don't stop until reaching 16.8v. The SL handles that OK, but you get more charge-discharge cycles from a pack by limiting the charge to 80%, or in the case of a 4-cell pack, 16.0v. Doing that will almost double the life of the pack.

 I think my SL is especially "hot". Just got lucky. It detects that 1 grain gold bar farther than my GM24K, or GMT.

 I think the reason the 12"DF is more sensitive than even the Sadie coil is the increased voltage. I'd bet, if I dropped the voltage to 12v, the 12"DF would not match the Sadie 8 x 6. I doubt the Sadie would decrease....the small coils don't benefit much from the added voltage. The SL is a good machine with the added voltage. Whites should upgrade the standard battery, IMHO. Or maybe re-design some components, and go all the way up to 21v.

 I was not impressed with the SP 350. I'd like to find a good 7 x12 mono for mine. LOL....that didn't cost an arm and leg.

Jim

I finally had time to do some testing on the SL, regarding the Ground balance. Here's the result:

TDI SL GB TEST

350 Super Pulse coil. battery voltage at start of test = 16.0v

Freq. max., Switch in "ALL", Gain MAX, Pulse delay MIN.

1979 US nickel Sweeping side-to-side. The test setup was having the detector vertical, with the coil on top of a 5 gallon bucket to minimize the ground effects. I taped a yardstick to the shaft. I did NOT use headphones, but did repeatedly sweep the nickel to try and get honest results.

GB off

13"

GB on:

2     14 1/2"

3     15 1/2"

4     15 1/2"

5     15 1/2"

6      14 1/2"

7  to 11    15 1/2"

Freq. set to minimum

GB off same

GB on:

2     14 3/4"

3     14 1/2

4     14 1/2"

5     14 1/2"

6 thru 11      15"   

Switch to 12"DF coil

GB off    17"

GB on:

2-5       17"

6-11     16"

12DF with 1 grain gold bar

GB off     3 1/4"

GB on:

2-11  3 3/4"

Both coils with 6 gram men's gold ring:

 Both coils detected this very close to the same as they did with the nickel. But, turning the GB on and off had very little effect on the depth. It's apparent to me that on some items, my detector is definitely better with the GB on, but set to 2, or minimum. But on larger gold, the GB has little effect. But what effect there is favors having the GB on, but set to minimum. There was only one instance where having the GB off was an improvement.

 I also tested my NF Sadie 8 x 6, and was surprised to see it was LESS sensitive to the 1 grain gold bar, than the 12"DF. The Sadie struggled to make 3". For me the best coil is the 12"DF, where it can be used.  Where it's too cumbersome, I'll go to the Sadie.

The Sadie was better than the 7 1/2"DF, and the MJ 5 x 9. I sorta wish I hadn't sold the 7 1/2"DF...I'd like to test it more.      

I also tested a 1" thick x 4" diameter hunk of aluminum, with a 1 1/4" hole through the center. Neither coil could detect it near as well as they did the nickel.

Jim

Yup...that explains a lot, Mark...many thanks! If I can find the time, I'm going to have to rerun some tests to specifically target the GB settings, and see what's going on.

JIm

On 5/11/2019 at 9:26 AM, bklein said:

Has someone verified that sample timing stays constant with battery voltage change? On lesser pi’s it moves.

That's an interesting question, but I have no idea if that's the case with the Whites TDI SL.

Jim

It would be a help if the testers posted the year their SL's were built, along with the battery voltage at the time of the test.

Jim

On 5/16/2019 at 8:12 AM, Mark Gillespie said:

Very interesting Jim. 

What device are you using to measure the voltage? 

I was using a calibrated Fluke True RMS and was measuring directly from the TX output on the board.

All this said I noticed a very large difference in voltage from a complete counter clockwise frequency offset to a complete clockwise setting.  Even though there was a large difference in output voltage I didn't see any extra air test advantage.  The manual states this feature function is "This control makes small adjustments to the transmitter pulse rate".  I was guessing a small shift in the frequencies and wasn't expecting the voltage span.

Now you have me to wondering if the inductance of my coils might be different than yours because if the inductance is quite a bit larger (value) that would limit the current flow considerably.

 

I picked up one good thing about this discussion, besides the overall stuff. That is, there's a benefit to running the frequency maxed out, as far as energy to the coil goes. I'll be doing that from now on, assuming it doesn't cause an excess noise problem. On mine, that's over an 8% gain in coil voltage. Nothing to sneer at.

Jim

1 hour ago, auminesweeper said:

Jim, Mine was built in 2013 as well, but none the less mine did not show any depth advantage with the GB switched Off,  all I noticed was that smoothing effect that the TDI pro does with the GB off my SL did it when the GB was On which means it was trying to balance out the target. 

Well we have 3 for 3 that all show zero dept the '13's are different somehow.h increase with the GB off, which is making me start to doubt the many posts I have read claiming that there is a depth increase with the GB Off, Yes there is with the TDI Pro but Not the SL.

Sorry, John. I thought you'd said '14. So, it's possible the '13's are different somehow.

Sure looks that way, Mark. John (auminesweeper), and I both have machines built fairly early, and we get very similar results. His was built in '14, and mine in '13. So it looks like yours is different, for sure. What did you have a for a batterry voltage in that test?

Jim

I'm measuring mine with a digital multimeter set on A/C volts. On the frequency, I'm seeing, with the 14.5v pack, 6.05v on the low, and 6.54 on the high. MIddle was 6.29.

 I'd be surprised if your coils have much difference in inductance, but it's possible.

EDIT:   I just did the inductance test on the 12"DF and got the exact same reading of 1.4 microhenrys. I assume that is the design inductance for the coils for TDI's. and probably the other brands of PI's. But, I don't know this to be fact.

Jim

I just tested the voltage output on mine, and it tracks perfectly with the battery pack voltage. With the 4 cell pack at 14.53v, I got 6.29v of output to the coil, and with the 3cell pack at 12.03v, I got 5.3v of output. So the higher battery voltage does push more current through the coil on mine. Thus a stronger magnetic pulse going into the ground. I figured out the correct terminals by using my inductance meter to see which terminals showed a coil across them. Looking at the connector, with the gap at the bottom, the correct terminals are the second from the left, and the second from the right.

 Inductance on both the NF Sadie 8 x 6, and the Super Pulse 350 14 x 9 showed 1.4 micro-henrys.

Jim

3 hours ago, auminesweeper said:

Yep so was mine a 2013 Jim,  I don't know how digger bob got is to see his tiny test pieces in that video but mine wouldn't see them, It ran as smooth as silk even with a thunder storm going on right about the house Nothing phased my TDI SL, all it took was a minute tweak of the Tune knob and it was good as gold,  My 3500 didn't like storms 100 to 200 miles away but the SL has the best threshold ever put in a detector. 

With the 12"DF,  and 16.8 v battery, mine will easily see a 1 grain gold bar at 3" in an air test, John.  Might do even better with my NF 8x6 Sadie, but I haven't tested that coil.

Jim

1 hour ago, Mark Gillespie said:

I used a calibrated, Fluke TRUE RMS volt meter for my measurements.

I think, to use a voltmeter, you'd have to put a capacitor across the connections to get a true reading. I'm not sure about the capacitance needed...maybe 5mfd?

Jim

I've never checked mine, but find that interesting. Mine was built in '13. Do you have a diagram for the coil connector? I'd like to check mine. Something's fishy, for sure, as the voltage clearly makes a big difference. It's possible, because the voltage pulses at 100kh, that you can't read the voltage difference, except with a synchroscope, or other similar device.

Jim