Barracuda Legend Kit Problems

[ivconic]

[Old cart]

R21 is depending mostly on coil.
It's value certainly can make a difference, because if it was not chosen properly; coil will ring.
It is easy to see on scope while adjusting the damping value.
Major trouble there is to obtain precise value which would ideally fit actual coil.
Pretty often common values are not perfect match.
I noticed that not so many people do pay special attention on this.
And offset too.
But precisely at Barracuda i noticed interesting thing; static mode will not work properly if offset is not perfectly adjusted.
That's why we seen several cases where is advised to omit that fet and few components around it, simply because many people didn't managed to make it work properly.
So i adopted pretty funny method to solve this; i wire it up in static mode, put Tune and Delay in middle positions and than fine readjust offset at front end (by listening audio response).
And it works! Sweet and easy!
Now is up to more "technical" people here to explain why it works that way!

Agreed about the damping resistor. Easy to adjust if you have a good scope that does not load the circuit and monitor the input AND output of the preamp at the same time. Final tuning usually has to be done either by looking just at the output.
The comment on the static mode of Baracuda is easy to understand now that you have explained it. You should probably set the DC offset in the static mode because DC current passes then. When you release the button it is AC coupled and the DC offset has only a minor effect. That is essentially what you are doing. Thanks for the hint.

In either case offset can have a minor effect on preamp output waveshape because it affects the operating point of the preamp.

[ivconic]

Ray the 390 vS 330 ohms can make quite a difference. Not for troubleshooting but for optimizing. On my detector critically damping the finished coil, adjusting the offset and carefully adjusting the delay gives 30% more depth. This is more than all other changes I have made combined!
We will optimize that later once the coil is finalized, that is, if you wish.

R21 is depending mostly on coil.
It's value certainly can make a difference, because if it was not chosen properly; coil will ring.
It is easy to see on scope while adjusting the damping value.
Major trouble there is to obtain precise value which would ideally fit actual coil.
Pretty often common values are not perfect match.
I noticed that not so many people do pay special attention on this.
And offset too.
But precisely at Barracuda i noticed interesting thing; static mode will not work properly if offset is not perfectly adjusted.
That's why we seen several cases where is advised to omit that fet and few components around it, simply because many people didn't managed to make it work properly.
So i adopted pretty funny method to solve this; i wire it up in static mode, put Tune and Delay in middle positions and than fine readjust offset at front end (by listening audio response).
And it works! Sweet and easy!
Now is up to more "technical" people here to explain why it works that way!

[Qiaozhi]

Hi Qiaozhi,

The only differences that I can spot are minor: a buzzer rather than a headset socket; a 20K pot replacing both R27 and R29. (My R21 was 390 rather than 330ohms, but another post suggested this was not usual).

It would be wonderful if this was added to the Sticky, tagged as the Silverdog kit version. I gave up trying to read the hand drawn schema in the zip file. It is just not a very clear digital copy.

I failed to pick out this schema to work with, instead picking the latest posted. The differences were very confusing, but ultimately I've learnt more.☺

Ray

Well ... we will find out soon!
Impulse is sending me his Baracuda PCB (with coil and cable) for testing, so we'll get to the bottom of this in the near future.
Once testing is complete I will post a sticky with the official schematic, and ask Silverdog to put it on his website as well.

[ivconic]

Thanks to all who are helping here. It is good see international cooperation working so well. Too bad the larger world is not so cooperative.

I appreciate the difficulties non English speakers have, it must hard to have to translate everything.

I find the the different communication styles fascinating but it is good that we can have healthy debates without getting into real fights!

Cheers

Indeed too bad! World would be a better place if it was based on enthusiasm like we are having it here.

"... the difficulties non English speakers ..."

Actually, the language itself is not a problem. It is easy to learn and understand. No need for translators. At least i don't use them at all in last dozen years.
What can be problem from time to time is not the language but the context and a way of thinking.
Different people, different minds, different way of thinking and expressing here.
And over the top there is also a "modern" way of talking; using too much abbreviations!
Internet introduced too many funny and crazy abbreviations lately. Sometimes it is problem to connect all those together in a thought which is making any sense!
And additional obstacle may be difference in education and different levels of knowledge here.
Highly educated and conversant people can easily understand each other with use of strictly "technical" language and common professional phrases and terms.
Lightly educated enthusiasts and hobbyists (my category) however will need a bit of more "human" explanations and help to understand some of the articles.
So it's not always about language, pretty often is about many other "side" factors.

[Old cart]

Hi Qiaozhi,

The only differences that I can spot are minor: a buzzer rather than a headset socket; a 20K pot replacing both R27 and R29. (My R21 was 390 rather than 330ohms, but another post suggested this was not usual).

It would be wonderful if this was added to the Sticky, tagged as the Silverdog kit version. I gave up trying to read the hand drawn schema in the zip file. It is just not a very clear digital copy.

I failed to pick out this schema to work with, instead picking the latest posted. The differences were very confusing, but ultimately I've learnt more.☺

Ray

Ray the 390 vS 330 ohms can make quite a difference. Not for troubleshooting but for optimizing. On my detector critically damping the finished coil, adjusting the offset and carefully adjusting the delay gives 30% more depth. This is more than all other changes I have made combined!
We will optimize that later once the coil is finalized, that is, if you wish.

[Old cart]

Thanks to all for the help

Thanks to all who are helping here. It is good see international cooperation working so well. Too bad the larger world is not so cooperative.

I appreciate the difficulties non English speakers have, it must hard to have to translate everything.

I find the the different communication styles fascinating but it is good that we can have healthy debates without getting into real fights!

Cheers

[raygdunn]

Thanks Ray.
These all look as you would expect, so clearly the circuit is working.
Main sample delay ~40us
Main sample pulse ~40us
EFE sample delay ~180us
EFE sample pulse (cannot see width, but assume this must be ~40us)

Can you confirm that the circuit is wired up as per the attached schematic with the CD40106 connected with VDD=0V and VSS=-5V?
[ATTACH]35564[/ATTACH]

Yes standard wiring. I reversed out the mod for the job... Also to confirm the old delay timings on the samples. ☺

Ray

[Old cart]

why?? CMOS CD4000B series have 20V max rating and 10V is OK for them (with the timing resistors connected to +5). i do not see something wrong here.
yes, that seems unusually but perfectly acceptable.

KT the max voltage rating is NOT the problem. It is the Input voltage range. In this application the maximum voltage on the power pins is 0 volts. This design pulls 3 of the inputs to about .5volts or a little higher. Basically this causes the input protection diodes to turn on hard. After some time these diodes break down and this causes the chip to generate spikes. Not al chips do this, only some brands and variations.

Some brands are not destroyed. The fact that it works most of the time is just luck. But this is bad design practice and should be avoided.

Several people have made note that their Barracuda's work fine. I do not argue that some, if not most of them do. But clearly some work only for a while then break.

Final note- I really have no idea what is actually going on inside the chip because I do not have an electron microscope but it seems plausible...

[raygdunn]

Closest would be "Attachment 35162" from #324.
I checked it partially with my pcb.
So far i haven't found mistakes.

Thanks. Got it!

Hi Qiaozhi,

The only differences that I can spot are minor: a buzzer rather than a headset socket; a 20K pot replacing both R27 and R29. (My R21 was 390 rather than 330ohms, but another post suggested this was not usual).

It would be wonderful if this was added to the Sticky, tagged as the Silverdog kit version. I gave up trying to read the hand drawn schema in the zip file. It is just not a very clear digital copy.

I failed to pick out this schema to work with, instead picking the latest posted. The differences were very confusing, but ultimately I've learnt more.☺

Ray

[kt315]

If your timing resistor ties to +5V you will be outside the chips reference of -5 to 0.

CMOS chips do not like that.

So maybe that's why the latchup would occur?

why?? CMOS CD4000B series have 20V max rating and 10V is OK for them (with the timing resistors connected to +5). i do not see something wrong here.
yes, that seems unusually but perfectly acceptable.

[Qiaozhi]

Closest would be "Attachment 35162" from #324.
I checked it partially with my pcb.
So far i haven't found mistakes.

Thanks. Got it!

[ivconic]

The Baracuda PCB, supplied by Silverdog, was designed by Apberg.
Can someone post the schematic that corresponds to that particular board?

Closest would be "Attachment 35162" from #324.
I checked it partially with my pcb.
So far i haven't found mistakes.

[Qiaozhi]

I live in kent near dover. It would be great to send it to you and find out what I'm doing wrong with it.

OK - I'll send you a PM.

[Impulse]

In which country do you live?
If it's the UK, you can send it to me.

I live in kent near dover. It would be great to send it to you and find out what I'm doing wrong with it.