Bandido 2 Modified

[Merc]

I have posted a video of my FireballCNC milling my new PCB for my Bandido. I'll try to post a picture of the finished product. The best part of using CNC is that it drills all those holes for you and it does not miss any pads.

Merc

http://www.youtube.com/watch?v=kqA4ohzdEus

[Merc]

Here is the finished board after drilling. Not perfect but getting better. I learn a little each time.

Merc

[Qiaozhi]

I have posted a video of my FireballCNC milling my new PCB for my Bandido. I'll try to post a picture of the finished product. The best part of using CNC is that it drills all those holes for you and it does not miss any pads.

Merc

http://www.youtube.com/watch?v=kqA4ohzdEus

That's cool.

[ApBerg]

Hello Merc,

Thanks for the circuit and video's on YouTube !

Nice that audio disc...

Best regards.

Ap

[Merc]

I've been working on stuffing components on the PCB all weekend. I was really hoping to finish it, but it looks like I have run out of parts. I'll have to order a few items here and there. I thought about just stealing them off of my previous Bandido PCB, however, I may want to compare signals between the two. So for now the old board is still complete.

I have the power supplies working, the TX oscillator works and the receive amplifier is working. I'm hoping this board is a somewhat better layout than the previous. I placed the TX and RX coil connections together this time so theres no long leads there. The threshold and sensitivity control wires should be much shorter as well. Headphone jack wires are much shorter too. I haven't yet tested the new battery test circuit because that's the IC (TLC2262) I have run out of.

[Merc]

Well, I couldn't wait. It's too hot to do anything outside so I cannibalized my original Bandido clone for parts to finish this one. With a few minor issues such as pots wired backwards it works. It seems to be a bit quieter than the first one. Just need to mount a speaker. I have never bothered because I use headphones anyway. I want the speaker to make it "complete". Here are some pics including the front panel label I had made. It cost $20 for the sticker with lamination.

Merc

[Merc]

Here is the layout of my board. I will try to post a black and white image of the traces.

Merc

[Merc]

The mounting holes are a bit deceiving in the picture above. Placing a pad there is just an easy way to get a hole at that point. When I milled the PCB, I only used the hole and not the pad so there was much more copper present than is shown in the image above. I'll try to correct before I post the black and white image of the traces.

Merc

[cr15]

Further ruminations.

Very nice job there Merc. I just built a second pair of boards as specified to see what problems there might be. I agree with what you said about the negative supply generator. I kept the rail at +v (5v) and used two different transistors (2n2907 for the 2n3906 and 2n2222 for the 2n3904) and biased them by just changing R5 and R6 to 2K2. I swapped D4 for a 1N5817 schottky, removed R67, R68, C42 and Q5, then linked the E and C positions. Now I have 3.2V which is the same as in my Rapier.
I noticed one more thing too. The Rapier is essentially the same circuit but auto balancing. I modified it to give me manual balancing if I wished. It is fitted with a preset pot that I removed and replaced it with an adjustable one fitted in the front panel. I found that manual balancing was very difficult except on some soil types so I started to investigate why. All the resistors in my Rapier are the same value as the Bandido II. I couldn't measure the capacitors as they are chip type. I checked the preset I had taken out to see what it was set to only to find it is a 100K pot! Not a 50K as specified by Carl. Now it is quite possible that C12 is a different value in my Rapier to the Bandido's 180pF, but I doubt it given that everything else is the same. So I've swapped the pot to a 100K which should enable easier ground balancing.

[porkluvr]

....The Rapier is essentially the same circuit but auto balancing. I modified it to give me manual balancing if I wished. It is fitted with a preset pot that I removed and replaced it with an adjustable one fitted in the front panel. I found that manual balancing was very difficult except on some soil types so I started to investigate why. All the resistors in my Rapier are the same value as the Bandido II. I couldn't measure the capacitors as they are chip type. I checked the preset I had taken out to see what it was set to only to find it is a 100K pot! Not a 50K as specified by Carl. Now it is quite possible that C12 is a different value in my Rapier to the Bandido's 180pF, but I doubt it given that everything else is the same. So I've swapped the pot to a 100K which should enable easier ground balancing.

You are possibly overlooking that when a detector has manual ground balancing, Tesoro may intentionally use component values that will limit the amount of adjustment the user has. A wider range of adjustment is not necessarily a good thing.

The ground control may be 'very difficult' to adjust properly because each turn of the knob covers a wider angle.

[bernte_one]

hello merc

very nice project

where did you get the female connector plug for the original coil ?

im short before using microphone 5pin plug but it has no screw wheel and i would remove the original thinkthats not good

[Merc]

Here is the information about the connector. Take a look at this earlier post in this same thread.

http://www.geotech1.com/forums/showpost.php?p=102709&postcount=15

Merc

[Merc]

You are possibly overlooking that when a detector has manual ground balancing, Tesoro may intentionally use component values that will limit the amount of adjustment the user has. A wider range of adjustment is not necessarily a good thing.

The ground control may be 'very difficult' to adjust properly because each turn of the knob covers a wider angle.

My Bandido uses a 50K 5-turn, but I find that I only use a very small part of its travel. Maybe a range of 1/2 turn. Of course, this may be because where I live there is little or no mineralization. No gold in these hills.

Merc

[cr15]

GND balance pot

OK, did the bit in the garden last night. Ground balanced fine (100K single turn pot). When
I measured the setting it was 38.4K so I should have been able to achieve balance with a 50K pot. No worries, 100K single turn preset was in the Rapier so that's good enough for me. Saves getting different values.
The box is running off two PP3 batteries, and I've omitted R66 and connected the sensitivity pot to the negative rail. This gives way more sensitivity adjustment than I need but the results are very good. Turned all the way up I get a "bip bip bip" so I just back off until it stops. It looks like I'm getting about three more inches of depth, but I need to quantify that better and check it out "in the field".

[woody]

Here is the information about the connector. Take a look at this earlier post in this same thread.

http://www.geotech1.com/forums/showpost.php?p=102709&postcount=15

Merc

maybe if there is anoth interest sivlerdog could get some