IGSL

[Davor]

Something like this, LF351 not needed, Disc.Sens. joined together.
It is possible to join GEB controls too.
Make sure you understand and apply pin swap mod!

[Firebox]

Hi,
i have build the igsl Musketeer based on ivconic schematic. The NFE Part is working very well (50 Cent in 32 cm), but the FE part haven't depth enough. It gives a scratchy and tremblig noise in a poor depth.

So look at my Video on youtube: https://www.youtube.com/watch?v=SKSWcZYU4Hg

When i put a VDI on the IGSL it shows the iron signal in a high depth. So i belive that the Sound / tone amplifier is the problem, but what components are responsible for this?

Note: Best Tip für IGSL is to replace the conventional Elkos against Bipolar one!! It gives you a higher depth in the NFE Part

regards

Firebox

[ivconic]

Hi,
i have build the igsl Musketeer based on ivconic schematic. The NFE Part is working very well (50 Cent in 32 cm), but the FE part haven't depth enough. It gives a scratchy and tremblig noise in a poor depth.

So look at my Video on youtube: https://www.youtube.com/watch?v=SKSWcZYU4Hg

When i put a VDI on the IGSL it shows the iron signal in a high depth. So i belive that the Sound / tone amplifier is the problem, but what components are responsible for this?

Note: Best Tip für IGSL is to replace the conventional Elkos against Bipolar one!! It gives you a higher depth in the NFE Part

regards

Firebox

Nice work!
Maybe you can smooth up that "prrr prrr" sound with Iron treshold trimmer?
That's why i put two separate treshold trimmers; so to user being able to separatelly adjust Fe and NFe tresholds.
About Fe depth; must be something in Fe amplification chain?
You are using two separate Sens potentiometers, right?
Maybe some component with more tolerance?
Cheers!

P.S.
Using stereo pots for Sens and Tresh is generally bad idea (ruins whole IGSL concept) and that's where i don't agree with Davor.
Having comfort to separatelly adjust both Senses and Tresholds is sweet thing.
If you are searching for precious metals (aren't we all) than it makes difference when you separatelly adjust Fe Sens and Fe Treshold bit lower than Nfe Sense and Nfe treshold.
And vice versa; in case you are interested mostly in Iron targets...

[Firebox]

Hi Ivconic,

in the attachment you can see my potis. I have all Potis ouside on the Frontpanel. Turn on Iron Threshold haven´t any results in depth.

What can be wrong in the Fe amplification channel ? I think the IGSL can detect iron in a high range, but the "sound channel" is bad. When i wire my lugatek VDI on IGSL then it shows me a tweezer in about 10 inches with a -40 VDI value, but the "sound" from IGSL is scratchy. So the problem must be the Sound amplifier circuit.

Look at my Video on youtube: https://www.youtube.com/watch?v=kzg_...ature=youtu.be

So what is wrong? All voltage (positive and negativ) values are like in your circuit schematic. NFE works good, Iron only in bad depth and with scratchy sound...

Regards

Firebox

[Davor]

As I already gave you a hint on a German forum, some resistor must be wrong among R59, R60, R61 and maybe even P4. You measured 50mV minimum at pins 8 and 11 of U7, while the expected minimum is about 3mV. You may also extract all of these components from your board and instead make a connection between pins 4, 6, 8, 11. In that case a potentiometer P3 sets the sensitivity for both channels.

[ivconic]

"....You measured 50mV minimum at pins 8 and 11 of U7...." !?

Is that so?!
Than must be some faulty component!
No other reason why blocks would behave different; both are dependant on same Rx signal.
Characterisitic "prrrr prrrr" sound indicates insufficient signal at comparator inputs which than are tendable to run into selfoscillations.
Insufficient signal means (in this particular case, knowing behavior of other block) that somewhere in amplification&filtering chain signal is attenuated and choked, most probably by some faulty component.
So Davor's advice is alright; you should walk through Fe block and check each component again.
Cheers!

[ivconic]

BTW i really DO LIKE your front panel and enclosure!

[Firebox]

BTW i really DO LIKE your front panel and enclosure!

Hi Ivconic,

Thank you! that´s a big compliment for me and my work!

DAVOR:

the voltages on Pin 8 and Pin 11 from U7 are in Poti Position CCW: +0,08 Volt and in Position CW +0,05 Volt . Thats exatly the same voltages like on NFE Parts.
So this can not be the problem of the pprrrrr pprrrr Tone.
other idea ?

[Davor]

Ah! So the difference between CW and CCW is 30mV as it is supposed to be, only your voltmeter shows some offset that is not really there. OK.
I thought you nailed it
Does Fe channel react to Discrimination potentiometer? Can you accept/reject Alu foil in Fe channel? (let's eliminate switchers as culprit here)

[Firebox]

Ah! So the difference between CW and CCW is 30mV as it is supposed to be, only your voltmeter shows some offset that is not really there. OK.
I thought you nailed it
Does Fe channel react to Discrimination potentiometer? Can you accept/reject Alu foil in Fe channel? (let's eliminate switchers as culprit here)

yes, FE Disc is working, I can accept and reject ALu Foil and FE Sens is working too. Only the scratchy pprrrrrr, prrrr sound is the problem.
I have measure some voltages on the Q5, Q6, Q7 and Q8. See my picture in attachment. The voltages are sometime with a NFE / FE Object over the coil.

Regards

[Davor]

The discrimination channels are best checked at the outputs of the gain blocks, as indicated with the red dots on a snippet of your photo. GEB channels are supposed to work THE SAME on both channels, while disc channels (NFE not shown in snippet) are supposed to work ... well, that would depend on whether you made a pin swap or not. In case you left it in original layout Disc channels would also work in the same manner, only a bit different amplitude.

[Firebox]

Here are the voltages of the GEB Channel. On Pin 5 from U7 i have up to -1,9 Volt on NFE AND FE, is this right?

[Davor]

Yes, this is OK. You obviously did not mod your gain blocks, and your voltmeter shows the average DC voltage (with 50mV offset). These -1.9V are a consequence of gain block diodes that compress asymmetrically. That's one of the reasons I did all those mods in my rig. Having -1.5V at pin 10 and -1.9V at pin 9 means that your Fe gain block works fine, and that you'll have to find your problem somewhere else.

I must admit that I only now looked to your video with my headphones on, and I obviously missed some important details before. Also about your iron target, you picked a bad one - it is either stainless or chrome plated. Pick some plain naked iron instead for testing purposes. A big nail should be fine.

Could you make some close-up photos of your PCB on both sides?

[Firebox]

Here the pictures from the top and buttom side. By the way, a rusty nail is poorer in depht than a tweezers on IGSL

[Davor]

I'd say you didn't apply a pin swap mod. It would greatly improve Fe channel behaviour.