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Goldscan 2

eiken

New member
Hello all, looking for a little help... I have an Eric Foster Goldscan 2 with no audible threshold tone/hum. I had to do a repair to this machine a few months back when i had to replace a tantalum cap. with some expert advice from Reg, but thinking back i never had a tone then either...so question being does the goldscan 2 run silently or is there some other issue and if there is, can the audible tone be adjusted internally by trimming a pot?......tried an air test and 10/11 inches on a 25mm 2 euro coin. I know air test on pi is not the best but could i be loosing depth with having no audible hum when searching....hope you are able to make sense of what i am trying to explain..should it need a repair/service is there anybody that would work on these machines now.
regards.
ken
 

LE.JAG

Member
Hi,

this is already the G2 instructions

I never use this model, can not tell more...
 

Reg

New member
Hi eiken,

Do you know anyone who has a Goldscan 2 schematic? If so, can you ask them to send me a copy so I can see how close it is to the GS4. My guess is it is almost identical, which would mean there is no direct internal pot that adjusts the threshold, but I suspect a pot in one of the previous stages would do the same.

Eric used TL064 IC's that have quite a bit of offset, so he added internal pots to correct for that. If one of these is not set correctly, the offset could set the threshold in the null region. I suspect you should be able to adjust the threshold for a putt putt sound .

Look at the meter and see if it moves slightly when the threshold is adjusted. Le me know if it does move slightly.

Reg
 

eiken

New member
hello again Reg,
Thanks for taking an interest in this thread, unfortunately i dont know anybody with the GS2 schematic i am probably the only GS2 machine here in Ireland, i have done what you suggested and the meter does move slightly ,i had to move out into the garden to be sure, but pretty certain it moves.....tried a coin airtest and the meter will deflect off the meter to the right with no tone until you get to within 6" of the coil then you will hear the phut/phut increasing as you get closer to the coil....(22mm cupro nickel coin)
Thanks in advance Reg for any help you can offer.
regards.
Ken
 

Reg

New member
Hi Ken,

I am guessing the GS 4 schematic is close enough that it can be used for troubleshooting. Hopefully, you can read a schematic and have a simple digital voltmeter. I have uploaded a GS4 schematic that is relatively accurate. Since the GS 4 has the same controls as your unit, I am guessing the schematic will work fine.

If you look at the attached schematic, you will see an IC3 that has 4 internal IC's. I suspect your iC will have a different IC number. The last two internal IC's will be the ones we will focus on. Also, notice the reset switch. That will be used also. You will need a small wire with alligator clips on both ends to short the reset switch. You might be able to do this with a single alligator clip across the switch.

Now, note the threshold pot both on your detector and on the schematic. One leg of that pot connects to U3 on the attached schematic. Since the three leads go to different places, this shouldn't be that difficult. Once you have figured out which lead is which, then short the reset and measure that lead going to the opamp. It should read 0.00V oh the lowest voltage scale on the digital meter. This voltage should read 0.00V on the 200mv scale.

Let me know what this voltage is? I am guessing there is a negative voltage. Also let me know the IC number if it is on the pc board. Measure pin 14. It should have the same voltage as that on the lead going to to the threshold pot. Now, with the gain pot an minimum, the voltage should be .00 and should be the same on PIN8, which is the previous opamp output. If not, try to find the trim pot that connects to pin 9. It might be RV7. This trim pot center leg connects to a resistor (470K) and then to pin 9. Measure the voltage at the center leg of this pot and write it down. Let me know what it is also.

When measuring voltages, I am guessing the chassis is a ground connection so you can connect the negative lead of the digital meter to the chassis.

When checking voltages, make sure to note where the voltage was taken and the measure voltage. This makes it possible to put things back if necessary. When in doubt, take pictures also. Send me clear close up pics of the pc board if possible.

That is enough for now.

Reg
 

kt315

Member
i have not good pics of GS-2 but i can compare the design with another Eric's ones. can you send me
clear pics of the board in hi res at day light on my address mdforall@gmail.com?
monitored also Geotech and found nothing on GS-2.

trully yours
 

eiken

New member
Sorry all about the long times scale in an update to to the problem with the GS2. After a lot of help from Reg here on the forum it was decided that due to my limited electronics ability a long distance repair was not going to happen, Reg had made contact with a gentleman in the uk who could and would work on the GS2. My machine was sent to the uk and returned good as new with a mod or two completed during the repair work. To the Two Gentleman who helped me get my machine up and running and out of retirement.... I Salute you both... may your swing never stop nor your purse ever empty.
all the best,
regards.
Ken
 

Alamsyam12

New member
[attachment 366277 PCBTOP1.jpg]Who are help me to finishing the goldscan4?
I dnot understand to connect switch and potensio to circuit dip
And circuit smd, i dont know what the code 000 in the pcb board, this is resistor or what?
 
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