Goldscan IV, 4 position switch question?

[pustareka]

legendary pi detector goldskan 4

Pictures GS4 original
https://www.geotech1.com/forums/show...020#post127020

Nesko lopuzo to li je cuveni primerak GS4 taj sto je kolega Mile Nislija narucio preko tebe iz englesku direktno od Fostera a dosao u tvoje ruke preko rumniju za cenu 2500e a ti si mu ga zabrao za sebe a podsunuo mu svoju kopiju GS4 koja nikad nije bila nastelovana kako treba. I ne bude nastelovana. Zato se starac Mile muci sa stari snifer 7-cu. Da znas da ceo Nis prica o tvojej prevari - u tragackim krugovima.

PS dobar glas daleko se cuje a zli jos dalje.

google say:
Nesko thief, is it a famous original of the GS4 that one, that colleague Mile Nislija ordered via you from england directly from Foster and came in your hands via romania for price 2500e and you had took it away from him and gave him your own GS4 copy that was never set up as it should be. And it didn't happend tuned. That's why old man Mile struggle with the old sniffer 7.You should know that the whole town of Nis is talking about your fraud - in TH circles.

PS, a good voice can be heard far away, and a bad voice even further away.

[Xtrem]

70-80 Khz

[g.s]

Good evening to all..
Can you tell me how many HZ is the frequency at this point that shows you in FIGURE the red arrow...


Thanks in advance

[TANCE]

Gold scan lv

[g.s]

for your Friends...
thinking to build and I goldsan iv ....
Can you tell me if working properly goldsan iv ???..
I want to know if there is a distinction between the CHANNEL 1 end CANNEL 2 And what are the results of these,stands out gold ???..
should I know before I make the costs..
THANK YOU very much in the advance for your help...

[didarpm]

Good evening I would like to know about the transistors Q1 and Q2 which one and which 2n and 3904 and 3906.
Thank you!

[pigeon]

HI ALL

Somebody built the GOLDSCAN? PLEASE CAN YOU HELP ME TO MAKE ONE


THANK YOU

PIGEON

[Reg]

You don't need to remove the resistors. Just change the values to a higher one such as maybe a 4.7meg. If that isn't slow enough, then try a 10 to 20 meg value. this should slow things down sufficiently and still keep things from drifting.

One thing that can be done is to add the 4.7 meg in series with the 470K and have a DPDT switch to be able to switch these higher value resistors in or out. Having the higher value resistor in series with the existing one will keep the unit from drifting but will slow down the autotune speed making any signal loss minimal while keeping things more stable. You will still need to use the reset button to adjust things periodically, especially if you don't have the ground balance adjusted right on or you leave the coil over a target for a long period of time.

Make sure the two channels have resistors that are the same value. On one of the schematics I have seen, R49 is not the same is R50. Both should be 470K. Also, when you do use the reset button, only use it when you are free of any target. This button is supposed to be used only when the coil is over the ground and the ground balance is adjusted for minimal ground signal change.

You can leave the hold on which will inhibit the fast reset signal on the coupling capacitors. Just use the reset to reset the threshold back to where you want it.

Also, use a quality capacitor for C28 and C29. The best would be a polypropylene type to minimize any capacitor memory effect. Also, you will have to reset things if you leave the coil over a target for a long time if you have higher value resistors in place.

As for the question of whether I would want to redraw the GS 4, the answer is no. I simply do not have time. However, I mentioned the circuit could be simplified and to do this, one can use quad amplifiers for U12 and U13 that have very small offset voltages. Try to use a quality opamp with an offset of less than 200 uv max and you can or should be able to eliminate some of the trimmer pots such as RV1, RV3, RV5, RV6 and RV7 that are there to set the output voltage to 0V of the opamp they are connected to. BTW, the adjustments of these pots should be done while holding down the reset button if you don't change amps. Also, Adjust from RV1 up since the setting of the initial one has an effect on the others down stream.

If you use a quad opamp with a very low offset, then there shouldn't be any error signal significant enough to deal with. So, there wouldn't be a need for some of those pots. Opamps such as opa4277 or maybe a LT1114 could be used. Other opamps can be used that meet the low offset requirements. Watch and you can catch them on sale on ebay.
Hope this makes sense.

RV4 should be adjusted for less than the 15mv. Try something lower that still works.

Reg

[zzy]

There is nothing wrong with the design of this detector, and it will be stable if you add the two resistors mentioned, R49 and R50, both 470k.

There are ways to make this design simpler to build and adjust. In fact, if you use the right two IC's for U12 and U13, many of the pots can be removed. Further simplify the design and do away with the SEL1 and SEL2 feature but add a simple switch so one can have the ALL mode or either of the two polarities and the design is really quite modern.

So, this detector should work well if built and adjusted correctly.

Hi Reg,
I remove the two resistors ,because i don't like the detector in motion type.
The motion makes me very tired and the detector lost some sensitive.
So the detector will drift and must be adjusted frequently when in non-motion type.
The auto hold button seems not work well, Maybe the schematic is incorrect.
Best regards,
ZZY.

[maikl]

Hi Reg. Do you want to set up a scheme for a simplified design Goldscan IV?

[Reg]

There is nothing wrong with the design of this detector, and it will be stable if you add the two resistors mentioned, R49 and R50, both 470k.

There are ways to make this design simpler to build and adjust. In fact, if you use the right two IC's for U12 and U13, many of the pots can be removed. Further simplify the design and do away with the SEL1 and SEL2 feature but add a simple switch so one can have the ALL mode or either of the two polarities and the design is really quite modern.

So, this detector should work well if built and adjusted correctly.

Reg

[zzy]

OK and original goldskan 4 is very unstable machine ,I thought differently but I am much disappointed with goldskan machine .

HI, Orbit:

I agreewith you opinion,I bulid the GS4 myself.Just like you have said:
The GS4 is very unstable.You must adjust it frequently after GS4 work a few minutes.
When you thun it on,nothing to do,just listen.The sound becomes gradually larger.very boring！

[Orbit]

OK and original goldskan 4 is very unstable machine ,I thought differently but I am much disappointed with goldskan machine .

[mollax]

Original 100% Goldscan Gs4 made from Eric Foster......you can see how is populated and cables distribution......good design for the circuit especially for the front end!!!

I started to draw the pcb
could you help in unseen places

[Alexismex]

Original 100% Goldscan Gs4 made from Eric Foster......you can see how is populated and cables distribution......good design for the circuit especially for the front end!!!