Barracuda Legend Kit Problems

[Koala]

Yep depth sounds right. Delay setting is a compromise. Just set for best depth on targets your interested in.

[wakko]

Thanks Koala,

I was refering to the delay between the main sample pulse and the earth field pulse to reduce the beeping at the ends of the swing. Most likely I'll have to adjust in it the real world for best earth field rejection.

[Koala]

Qiaozhi had to modify a board to stop the beep. Here is his data


Earth field sample pulse width = 120us
Earth field sample pulse delay = 440us

[wakko]

Wow, those timings are a bit different to what I've read. I'll see how I get on with the in field tests and go from there I guess.

[Koala]

http://www.geotech1.com/forums/showt...486#post215486


Info here

[Tim]

Hi. I wonder if anyone can help with my Silverdog Bara. I had it working somewhat. Coil 1.8 ohms to the board.330R damping. I had no luck with several(new) CD40106s and ended up with HEF40106. But very poor sensitivity. I also had to try 3 different 7660s before I got one that worked. (Also new). Voltage is regulated to 10v(78L10). Originally had 0 volts adjustable on 5534. Changed 5485/102 for matched 5485s-sense better. Threshold tone was intermittent, and seemed to be there only when case top, with pots and wires, was in some positions. I thought it may have been loose jumper connections, but it may be due to a capacitance issue(?). Then I fiddled with the damping, replacing 330R with sockets. While trying different ohms there with machine turned on, I had a power surge/spark, then no coil sensitivity whatsoever. Thought I may have blown the 9640 so changed that. No difference , so changed the 2222. No difference. Now I have a constant +4.46 at pin6 on the 5534, with no adjustment via pot.
It beeps on startup, but no sensitivity whatsoever.
At no stage has the sensitivity been better than an OZ 10c piece right on the coil (435uH). I have also tried 350uH, 260uH and 200uH coils with similar results (before it frazzled).
Now I am starting to think I may have blown a 4148 or other component.? Maybe the offset pot wiper?
I have just bought a Hantek 6022BE scope, but have no idea how to use it yet. Because all my info is on my one computer, I am petrified I might fry it mis-using the scope.

Any suggestions where to go next? Perhaps I should just buy/etch another board and start again........???
There is 560Hz at the coil. Correct voltages at the 78/7905s. Correct voltages at the 40106 (1,3,5,7,14).
So close, and yet so far....
I am using PN2222 oriented with silkscreen, and double-checked on datasheet, but perhaps that is still wrong?
Also I need a 100R inline with LED otherwise speaker(32R) was barely audible. Could this also be an indication of a problem somewhere??
Perhaps I should buy another brand/batch of 5534s?
All resistors were measured and diodes orientation double-checked during build.
Wima caps used.
I tried a TL062 for LF412 at one stage, and it seemed a clearer signal .

[ripsdevala]

I dont know how to work with oscilloscope and other measure tools, I use only analog multimeter to measure, the last broblem with my barracuda is not far from wrong part, reversed fet,short component and dead IC after short.
Very poor sensitivity = wrong resistor value
Unadjust 0 volt from 5534 is because of short
Burn smell = 4001 roasted

When I use HEF instead of CD40106 its have better sens but decrease in sound.

The only dead IC when i built is 7660, Q says that 40106 is kaput when using rev.2 but still working normal with beep on every swing, still waiting for rev.3
Hope other senior member can answer your problem.

[silverdog]

when you say PN2222 orientated with silkscreen - that should be turned 180 degrees relevant to silkscreen
A P2N2222 can be inserted as the silkscreen

[Tim]

Great advice thanks Andy and ripsdevala. I will replace reverse the PN2222 and replace the offset trimmer and persevere.
Geotech has been a wonderful educational resource for me. I will buy ITMD asap, and learn to use my scope.
It may be a day or 2, but I will report here for the benefit of others. Thanks.

[6666]

Great advice thanks Andy and ripsdevala. I will replace reverse the PN2222 and replace the offset trimmer and persevere.
Geotech has been a wonderful educational resource for me. I will buy ITMD asap, and learn to use my scope.
It may be a day or 2, but I will report here for the benefit of others. Thanks.

Its very easy to test any NPN or PNP transistor. When you have the correct pins the led will light.

[6666]

To Silverdog

Andy its time to change the 2222 to another npn transistor that matches the silkscreen and is manufactured with only one type number and leg configuration.
This confusion just causes to much heartache for some constructors.

[Tim]

Woo-Hoo! PN2222 reversed. Offset pot removed and checked. 0v available at offset-best signal at approx.100mV. I just can't understand how it was working with the 2222 reversed before??. Now for delay/coil/damping/ic swap experiments, as still only and inch with the Oz 10c piece.
I have read all of the build thread, and all the probs thread previously, but I'll keep browsing. Jeez, I hope I can get this thing working usefully.
Thanks for the input boys&girls, especially 6666. I was about to bin this one and move on- my next project is the Newhobby Magnum clone.
That tranny tester's a keeper 6666-showed me the PN2222 did indeed need to be reversed. Despite checking the datasheet, I still stuffed up.
The Magnum also has an auxillary circuit, for coil setting, which I will add to my arsenal.
Now, back to getting a bloody threshold signal...any ideas why I have none? Anyone?

[ripsdevala]

Maybe your cable joint to 10k pot is loose, or not join properly

[Tim]

Maybe. I should have these joiners to pots soldered, but for now I need the serviceability to be able to remove the lid.
I now can detect an Oz 10c piece at 4inches.
My coil is 10x5 elliptical, .5mm enamelled. 445uH and 2.1 ohms at board. Changing between RCA cable and lowR speaker wire cable(both 1.5m) makes no difference to sens or measurements. Moving my electric drill closer to coil increases sensitivity, to a point, then moving it closer sense decreases dramatically.
For best sens on coin I have delay trimmer at halfway and max. sens is with 10K about 1/3.
Going back now to try a few more 40106s,5534s, and return the TL062 to the 412 spot-one at a time. Also will try 220R and 470R dampers. More offset twiddling too.
I need at least a doubling of sensitivity to justify this detector.
Still no threshold tone.....

[kt315]

Its very easy to test any NPN or PNP transistor. When you have the correct pins the led will light.

CHILDREN GARDEN!!! i give you right way! you can CAN NOW! check all semiconductors and MOSFETS too!