Barracuda Legend Kit Problems

[raygdunn]

I use to replace ICs on home computer everyday with a solder sucker. The holes on Silverdogs are quite small and tough to de solder using this method.


liquid flux + solder wick works well for me.

If you are drilling out holes make sure you dont drill out any vias, solder wick and a solder sucker usually does a sufficient job
but if you are only reducing the value of a resistor no need to remove it, just solder another resistor in parallel, or solder in a pot.

Thanks for the advice guys. I have a solder sucker, but I suspect the nozzle is too large.. And not very heat resistant. Time for an upgrade I think☺

I've not been very successful with the solder wick in the distant past. Time I tried it again.

Good point about the drilling. I was enlarging the holes very slightly.

Ray

[Old cart]

Thanks for the advice guys. I have a solder sucker, but I suspect the nozzle is too large.. And not very heat resistant. Time for an upgrade I think☺

I've not been very successful with the solder wick in the distant past. Time I tried it again.

Good point about the drilling. I was enlarging the holes very slightly.

Ray

I use solder wick and a toothpick to clear the holes. Put the wick down and press firmly with the hot soldering iron. It will suck up most of the solder. Then heat the component one lead at a a time and gentlly pull on the lead with needle nose pliers. Takes some practice but works fine once you get the hang of it. Might practice on an old scrap board if you have one. For IC's many just cut the leads then extract the pins. FLUX is a godsend! But don't use the acid type, use the rosin type.

Your timing looks fine except the 2nd pulse is too wide. The pulse controls how much earth field cancellation you have which keeps the detector from sounding when you move the coil in the earths magnetic field. You could parallel that resistor then adjust your 100K pot for 44uS. Disconnect and measure the pot then solder that value of fixed resistor parallel to the one on the board. No need to remove the resistor on the board.

An even better method might be to adjust for 44us then wave a small magnet ceramic magnet near the coil, adjust the pot for minimum response to the moving magnet. I think it is better not to use an iron magnet.

Then do the remove, measure, parallel thing.

If you get this right there will little or no response to to the moving magnet.

The 5534 0 adjust is not for this. It looks fine now. Once we get the earth field cancelled then we can optimize the damping resistor and the 0 adjust to give the fastest recovery. This is in direct correlation with the narrowest negative going pulse. Fast recovery is the key to detection of small gold.

[Polymer]

Hello raygdunn,

Don't doubt your part replacement skills. The holes on the Baracuda PCB are too small and unsoldering parts off it is a real f*#?$~ pain.

I have more joy experimenting with components on the Suf Pi longboard as the holes are normal there.

[dfbowers]

Hey guys.
I have been following this thread for the last few days. This thing about the coil motion problem seems all so familiar! I have built three Silverdog kits so far. The first one worked like a champ for a couple of season. Then it died and for the life of me I could not resolve it. I built a second. It works well but suffers badly from coil motion problems. I used it at the beach last summer well away from electrical noise sources. The coil is shielded and potted. Same coil as Baracuda #1. I tried matching resistors and FETs without success. So.. I built a third paying careful attention to detail. Same problem : / I cannot offer a solution at this point. But can only suggest that it's not just one or two builds with the same issue. I have pretty much ruled out electrical noise and unpotted or unshielded coils as the sole source.
Don..

[6666]

I have more joy experimenting with components on the Suf Pi longboard as the holes are normal there.

Use pcb pins and just solder component on to pins. or use machined IC pins as socket.

[Michaelo]

Just a note re the 40106 operated from Ground (0 volts) and -5 volts...

The IC itself will operate from 3 to 18 volts (although some manufacturers max voltage may be as low as 15 volts)... more importantly, most datasheets that actually bother to provide the maximum differential (between input voltage and supply voltage) quote 0.5 volts...

In effect this means that pins 1, 3 and 5, exceed the maximum voltage differential for the device... basically they could potentially fail...
Of course modifying R17, R18 and R19 so that they are connected to Ground would also modify the timing so values might require tweaking but it's probably better to operate the 40106 at +/- 5 volts instead (tweaking may still be required)...

Having said that, I have used 40106's for level shifting but only from 3.3 to 5 and vice versa and so far I haven't had one fail...

Mike

[jladre]

Just a note re the 40106 operated from Ground (0 volts) and -5 volts...

The IC itself will operate from 3 to 18 volts (although some manufacturers max voltage may be as low as 15 volts)... more importantly, most datasheets that actually bother to provide the maximum differential (between input voltage and supply voltage) quote 0.5 volts...

In effect this means that pins 1, 3 and 5, exceed the maximum voltage differential for the device... basically they could potentially fail...
Of course modifying R17, R18 and R19 so that they are connected to Ground would also modify the timing so values might require tweaking but it's probably better to operate the 40106 at +/- 5 volts instead (tweaking may still be required)...

Having said that, I have used 40106's for level shifting but only from 3.3 to 5 and vice versa and so far I haven't had one fail...

Mike

In my bara i dont have issue in motion problem. Just be sure that all contacts from board to coil is clean and tight.

[Old cart]

BAracuda needs some redesign?

Hey guys.
I have been following this thread for the last few days. This thing about the coil motion problem seems all so familiar! I have built three Silverdog kits so far. The first one worked like a champ for a couple of season. Then it died and for the life of me I could not resolve it. I built a second. It works well but suffers badly from coil motion problems. I used it at the beach last summer well away from electrical noise sources. The coil is shielded and potted. Same coil as Baracuda #1. I tried matching resistors and FETs without success. So.. I built a third paying careful attention to detail. Same problem : / I cannot offer a solution at this point. But can only suggest that it's not just one or two builds with the same issue. I have pretty much ruled out electrical noise and unpotted or unshielded coils as the sole source.
Don..

Don, that is good info. I would not argue that point. My thinking has changed somewhat. While I still believe it is necessary to have a stable coil with no windings moving relative to one another, it is looking more and more like the 40106 is being pushed beyond it's limits. When this happens the part degrades and causes extra sample pulses, both the main and earth field pulse, to be generated at incorrect times. These extra pulses cause instability and noise . For an example see here:

http://www.geotech1.com/forums/attac...4&d=1457211532
if you look at the datasheet for the 5485 switches you can see that they will be in part on mode with these voltages applied. Worse the amount that they are turned on varies with temperature and supply voltage.

http://www.utdallas.edu/~jblee/EE3110/2N5485.pdf


So those extra sample pulses in the earth field could be causing the earth field to be flawed thereby causing this sensitivity.

At this point this is an educated guess. We have not proved it though Ray wil be doing some tests to confirm. George is also investigating. We have have successfully tried pulling the device inputs to ground rather than +5 and so far that appears to work, but does require changing 3 resistors. It also may prevent the 40106s from degrading.

It appears that many have Bara's that work then fail, and some have Bara's that work very well for a long time. Several others have expressed concern over the quality of the design. I suspect that the design is flawed and needs a little work.

Perhaps that is why the company went out of business.

Don could you measure and submit photos of the 40106 pin 2 and 4 waveforms measured relative to ground from Bara 2 above? That might help us figure out what is going wrong.

[raygdunn]

Your timing looks fine except the 2nd pulse is too wide. The pulse controls how much earth field cancellation you have which keeps the detector from sounding when you move the coil in the earths magnetic field. You could parallel that resistor then adjust your 100K pot for 44uS. Disconnect and measure the pot then solder that value of fixed resistor parallel to the one on the board. No need to remove the resistor on the board.

An even better method might be to adjust for 44us then wave a small magnet ceramic magnet near the coil, adjust the pot for minimum response to the moving magnet. I think it is better not to use an iron magnet.

Hi,

Thanks for your advice.

I replaced the 13K with a 3K fixed plus 10K variable. Also went the other was and used a 10K fixed component. However I couldn't find a quiet spot. I may have been pushing things by using an old medium wave aerial, which would be relatively powerful. Detection range was approaching an inch I would say. Only detectable swinging past one edge of the 10" coil.

At times I did have trouble with a beat frequency, which drifted through the zero point. That was when the threshold was set towards maximum noise. I don't understand the audio process. It feels a bit like it's using positive feedback like the old super-regen radios. .☺

I can probably find a ferrite ring if that would be better for testing.

Ray

[dfbowers]

Don, that is good info. I would not argue that point. My thinking has changed somewhat. While I still believe it is necessary to have a stable coil with no windings moving relative to one another, it is looking more and more like the 40106 is being pushed beyond it's limits. When this happens the part degrades and causes extra sample pulses, both the main and earth field pulse, to be generated at incorrect times. These extra pulses cause instability and noise . For an example see here:

http://www.geotech1.com/forums/attac...4&d=1457211532
if you look at the datasheet for the 5485 switches you can see that they will be in part on mode with these voltages applied. Worse the amount that they are turned on varies with temperature and supply voltage.

http://www.utdallas.edu/~jblee/EE3110/2N5485.pdf


So those extra sample pulses in the earth field could be causing the earth field to be flawed thereby causing this sensitivity.

At this point this is an educated guess. We have not proved it though Ray wil be doing some tests to confirm. George is also investigating. We have have successfully tried pulling the device inputs to ground rather than +5 and so far that appears to work, but does require changing 3 resistors. It also may prevent the 40106s from degrading.

It appears that many have Bara's that work then fail, and some have Bara's that work very well for a long time. Several others have expressed concern over the quality of the design. I suspect that the design is flawed and needs a little work.

Perhaps that is why the company went out of business.

Don could you measure and submit photos of the 40106 pin 2 and 4 waveforms measured relative to ground from Bara 2 above? That might help us figure out what is going wrong.

Sure can. Give me a day or so and I can post. I could actually do it for 2 builds that have the problem. I did substitute a couple 40106s in last night.. different manufacturers with no change in symptoms. I also changed coils with another PI machine I have that is working just fine (not a Baracuda). No change..

I think this issue is worth fixing. When the Baracuda works it works very well. I dug a lot of deep stuff in the surf two summers ago.

[Old cart]

Hi,

Thanks for your advice.

I replaced the 13K with a 3K fixed plus 10K variable. Also went the other was and used a 10K fixed component. However I couldn't find a quiet spot. I may have been pushing things by using an old medium wave aerial, which would be relatively powerful. Detection range was approaching an inch I would say. Only detectable swinging past one edge of the 10" coil.

At times I did have trouble with a beat frequency, which drifted through the zero point. That was when the threshold was set towards maximum noise. I don't understand the audio process. It feels a bit like it's using positive feedback like the old super-regen radios. .☺

I can probably find a ferrite ring if that would be better for testing.

Ray

Are you saying you used a ferrite rod for the field testing? If so it has to be magnet, it must attract iron.

[ivconic]

Sure can. Give me a day or so and I can post. I could actually do it for 2 builds that have the problem. I did substitute a couple 40106s in last night.. different manufacturers with no change in symptoms. I also changed coils with another PI machine I have that is working just fine (not a Baracuda). No change..
I think this issue is worth fixing. When the Baracuda works it works very well. I dug a lot of deep stuff in the surf two summers ago.

That is true.
That is why i said it is most desirable "small and cheap" diy PI project.
You get a lot from it for such small investment.
...
Just a thought, when having "coil motion problems": what kind of coil cable is used?
Anything else but good coaxial cable will simply not do.

[Impulse]

That is true.
That is why i said it is most desirable "small and cheap" diy PI project.
You get a lot from it for such small investment.
...
Just a thought, when having "coil motion problems": what kind of coil cable is used?
Anything else but good coaxial cable will simply not do.

I started off with a 2 core foil wrapped shielded cable and was told that it probably had to much capacitance so i changed it to coax, i will post my barracuda to qiaozhi today (if i get the chance, busy week!)

[Koala]

Out of curiosity how was the original coil made. Solid wire or coated stranded wire. Suspect solid wire would be used as the original only went down to 22 uS

[Koala]

Thanks for the advice guys. I have a solder sucker, but I suspect the nozzle is too large.. And not very heat resistant. Time for an upgrade I think☺

I've not been very successful with the solder wick in the distant past. Time I tried it again.

Good point about the drilling. I was enlarging the holes very slightly.

Ray

Quality of solder wick makes a big difference.

Loctite branded just works well

Bought some cheap of DX.COM useless unless you add some liquid flux first.