Improving the Tracker IV

[Skippy]

SilverD, your Tracker seems below-spec in performance, it would be worth devoting your enthusiasm towards getting it working properly, first. Then look into MODEST changes - increasing depth slightly (increase RX gain 50%, maybe ?) and maybe change the front-end RX op-amp to a lower-noise part. Maybe try a DD coil on it, could be fun.
What Dave means re. sandbagging etc is this: the entire machine is designed and constructed to a price and performance. If you were, for example, to increase the sensitivity, you would then find out that the search-coil would need re-nulling (possible) , or the shielding improved (not really that practical), you might find the machine's ability to cope with a wet beach is compromised. Etc etc. It's like taking a family car, and doubling the engine power. You find out that you then need a bigger water coolant radiator, better brakes, a stronger gearbox with more ratio's, better shock-absorbers, stiffer springs, higher speed-rated tyres, blah-blah...

[Silver Dollar]

Well I am just trying to get 5" in beach sand. I think some of this model are capable of this.
I thought the sandbagging was holding back something. Like if it can use a gain of 100 but
it is set to 50 so it doesn't work as good as their more expensive detector.

I did make a few tweaks and got 7" in air with a gold ring. Not sure how that translates to
in ground performance but it is encouraging!

Without the complete schematic it is tough...

[Skippy]

Well, true, sandbagging IS holding back, you don't want a 100 dollar machine equalling a 200 dollar machine in performance. But it's more a question of why / why not to sandbag. Maybe the search-coil is actually a fair bit better than the Tr4 specs demand, because it is shared with several other BH models, some of which are better performers? So upping the gain MAY be possible, because the coil, and it's null-levels / shielding / thermal drift are up to it. But perhaps other aspects are not so tightly defined. They have to mass-produce these things reliably, they can't have one in ten needing re-work because ti has a high input-offset voltage op-amp, which wouldn't be a problem if the machine was less sensitive, for example.
So you probably could up the sensitivity on YOUR machine, but maybe another TR4 owner in Florida tries it and his machine is poor afterwards.

[Silver Dollar]

Well for anyone who wants to experiment. Look at the input opamp,
notice C2 and C27 in parallel? C27 reads ~10nf and C2 reads 140pf.
Remove C2. It's a very subtle change to the circuit but changes the
RX signal significantly. The tone becomes raspy and you get a bit more
range.

I also tried increasing the sensitivity by changing R43 to 150 ohms (a short
would be find too), the schematic I drew is incorrect in that R43 goes from the
pot to ground. This allows a lower threshold so maybe catch a smaller signal?
It does chatter a bit but you can adjust it out with the pot. Not sure it is all
that useful..

The one other thing I did was remove R5, I'm not sure what this does it sort
of crossfeeds some signal of 7hz or something. I haven't tried putting it back
yet or even tried these mods outside in the real ground so proceed with caution.

I may take it outside this afternoon and see how it does!

[Silver Dollar]

Well I put R5 back in as it didn't do much to improve things.

So it looks like removing C2 and shorting R43 will get you a little bit more depth.
I estimate 1 - 1.5 inches more. That's good enough for me!

[Silver Dollar]

Well it looks like it was a bust. The MD was falsing all over the place. Totally unusable!

[Silver Dollar]

Well the ultamite mod will be to put a SMT TGSL or Bandito into the Tracker case.
The Bandito might be better as it has low current draw and only needs one 9V Battery.

To use the stock coil (7khz) you can use the Minelab board to get you to 8khz and
maybe a cap tweak to make 7khz? I'll give it a test tonight.

The Minelab oscillator uses up to 13 ma's though, the whole rest of a Bandito uses 14 so
you double the current running it. I have a possible solution using the old AB+C biasing
that Davor suggested. That uses only 5 ma in a demo oscillator I made.

I wish it was easier to get inside the coil as changing the TX cap would allow you to run
at a higher frequency.

I've started running an exacto around it but it's slow going.

[Silver Dollar]

Well hooking up the Minelab oscillator to the Tracker TX directly with no cap gives
6.5 khz at 17.2V peak to peak not bad!

The Minelab TX gives 8.2 khz with only 16.2V peak to peak.

The Bandit Tracker could be a possibility. I'm still waiting for my board then I'll give it a go!

[sinclairuser]

there does seem to be quality control issues with the bounty hunters, ive seen juniors that will do 8" and tracker 4's that do 4", there a bit of a lottery it seems, what you said before is correct about some being better, some worse and most ok.
but to be fair this disappears higher up the bounty hunter range, the problem is once you get to fisher and teknetics prices, people tend to go that way.
the lower end teknetics models dont seem to suffer from this, before my better half bought her t2, we tested loads, the teknetics eurotek and eurotek pro are way better for the money than the bounty hunters, in fact the eurotek is an excellent starter machine in either version, and seem to be really consistent

[Silver Dollar]

I suspected that the better ones would be more consistent. I got the Tracker because of the price and figured
it was a good price for a control box, stick and coil but I really expected the coil might be the problem. It still could
be, I haven't been successful in creating a working detector yet. I'm still working at it though...

[sinclairuser]

just as an aside, my better half has an f2(t2 as main) as a backup well worn and out of warranty, and is wanting to replace it i asked if she wanted another f2 but she wants the eurotek pro instead, i think credit must be given to first texas, bh, fisher, teknetics and now titan brands, it would be easy to build the same machines with different branding, but they dont do that different detectors, with their own fans, price points and design features, my only complaint is about coils and the fact that cross compatibility exists between some of their brands but dont make it known, when its a plus IMHO.

[Silver Dollar]

So here's the Bandito SMT board almost ready to upgrade the Tracker;


And a new Front Panel!

[Koala]

So here's the Bandito SMT board almost ready to upgrade the Tracker;
[ATTACH]29898[/ATTACH]

And a new Front Panel!

that's some upgrade

[Silver Dollar]

Here's the Tracker board stripped of chips so you can see the etches. Now I can pin it out fully.
But I'm not going to re install this board so why do that?


Now lets see where is that bandito board?...

[sinclairuser]

Here's the Tracker board stripped of chips so you can see the etches. Now I can pin it out fully.
But I'm not going to re install this board so why do that?
[ATTACH]30036[/ATTACH]

Now lets see where is that bandito board?...

nice work sd, scans of the board and pinouts may be useful, if not for reverse engineering, it may help repairs,after all, all correct information is useful information.