SMT Bandito Info/Build

[Silver Dollar]

Well the mini H Bridge isn't working. I found a mixed transistor and fix that but still no joy!
Maybe the 3904's and 3906's Need a different resistance value?

I made up a mixed through hole/SMT Minelab oscillator today and it's working great!
I defiantly need some stable caps for the TX oscillator's. I got .47 and .22's from Mouser
not realizing I need .33 for the Minelab coil.

The TGSL is working with it's original oscillator for now. I'll do some testing before I change
it out (if I do). There are still some mods to the filters. I'm not sure if I will remove those for testing....

[Silver Dollar]

Those schematics are all about the same we are looking for one with LM358's and LM308's instead of 2262's.
Thanks for your help though!

SL3 is the Disc pot I think.

[mschmahl]

Here are some schematic´s. Don´t know if they are older.

[6666]

is this schematics close to your original Bandido

[ATTACH]29992[/ATTACH]

What function is SL3 ?

[6666]

hit wrong reply

[Silver Dollar]

Hmm not really... I'd love to find an older schematic though. I'm sure there was one back in the day.

I put the original TX on the TGSL today. The TX is 17V tall at 15khz. For the negative supply I got -7.6V!
I see a lot of noise on the sine wave though. I think my scope is getting funky on me. Both channels look
noisy even with no signal going in. I may bring it to work and check it on the scope there...

[Koala]

is this schematics close to your original Bandido

[Silver Dollar]

The 4 pin is the right inductance's but this oscillator requires the TX to not be tied to ground.

The Minelab oscillator would work with the 4 pin and a standard Tesoro coil and get you some
additional current into the TX. The big question is will it make any difference? It appears the Deux
has different power levels available and most people say there's no difference other than the battery
not lasting as long.

It might be a big field charges the target too much and it doesn't decay fast enough to see it...

I have the original Bandtio and the SMD one with no mods so far that I just got the connectors on
so can now compare. My TGSL was reworked several times for various mods and now I have put it
back to stock but it doesn't work! I probably missed a cut etch somewhere. I'll try to get it going and
do a back to back comparison (maybe this weekend).

[mschmahl]

And if you use original 4-Pin tesoro coils with RX: 15,04 mH,66,9 Ohm and TX: 0,929 mH, 4,3 Ohm? These are for 14-18 khz.

[Koala]

I am waiting for parts

Only have the board and the toggle switches so far. Everything is ordered quite a large parts list.

What are your thoughts on the Bandido both the original and Silverdog one before any mods and how do they compare with your TGSL

[Silver Dollar]

So I whipped up this tiny transmitter (oops I noticed a jumper missing). It's an Hbridge
designed by Davor. Unfortunately you cannot use it with a stock Tesoro coil.

It puts a lot of current into the coil for not much battery use and fixes some other
problems with harmonics and such. I'll have to tickle the value a bit to get it to 10khz
and I'm not sure if it will work with the 6mh coil or a 1mh Minelab style is needed.

[Silver Dollar]

I was thinking about the 27L2's on the bandito and had a look at some other schematics when I found this one;



I'm pretty sure that's how the original Bandito I have is configured. I remember reading 2.xx megs and 3xxk around
the 27L2 and there are .47's there too.

Should look something like this;



Anyone know how to calculate the filter frequencies for this type of filter? I usually do that but cannot find this configuration
on any calc sites....

I also found some unsoldered pins on my Bandito II so I hope that fixes my glitching. I used the microscope at work. That makes quick
work to spot mistakes!

[Silver Dollar]

Ya I'm thinking the small TX might help with seeing good targets in trashy areas.
The original TX was 7.8v p/p and the new board is 8.5v p/p.

The RX caps are .015 and .015 off the substrate but on the mounting board.

I didn't do a baseline of the original board with the current setup and target. I cut the
coil connector off as the stock wire was 8' long and I'm switching out the connectors
so all my units can use each others coils. So I can't test the original board right now.
I hope to finish the bracket for the original unit tomorrow then I can close up the cable
and use it on both units.

It seems like the new board is a tad less air test distance. I'm thinking the schematic is
not quite right or they changed it on later boards. For one thing the 4.7uf caps on the
first filter stage are not present on the original board. That would make it a no motion
unit but it should have lots of falsing. I'm not sure I will ever have the complete schematic
as it is difficult to measure things on that substrate...

[Koala]

Sounds Like good progress

Was surprised that the original had less than 8V pp but works as expected.

How does the new SMT board compare to the original in air tests

Reading through one of your old posts are you saying that the RX and TX capacitors are half on the PCB and half in the coil ? not hear anyone mention this before.

[Silver Dollar]

Well the negative voltage problem turned out to be the 100uf electrolytics that I
scavenged from some old equipment. It turns out sometimes the marked end is
positive! After getting that straightened out I had 2.9V for the negative supply.
I also was getting around 9" in air for a gold ring. I took the capacitive multiplier
out and now have 4.0V! The air test is now 10" but there is some instability. I
jumped the sensitivity to the negative supply so maybe I'll put it back to ground
and see what happens...