GC-1023

[bernte_one]

ok heres the link to my photo page

https://fotoalbum.web.de/gast/bernd.marten2/GC_1023





this pics can be the base for question for component value

full zip uploaded here (pics are better as then above)

http://www.file-upload.net/download-...c1023.zip.html

[bernte_one]

PS: How do you post a picture, tried to upload from my PC, but could not get pass MY Pictures icon to select a picture.

Cheer's Sido

upload a phot to picasa web or so
or search for picture upload
then upload it mind the adress in your browser or the picture adress that is shown
at the hoster copy it with mouse marking right click copy
then mak a post at forum and at the writing window you click the icon for insert image
then make right clikc there with mouse and paste it

[amtech2005]

Bernte One , Excellent Work !!!

I downloaded the 65 megabytes of photos you posted . I am studying the photos now .

Yours is GC 1023T from 9-10-2010 . The photo above on forum is through hole from 7-27-2005 . But the circuit looks the same . No fisher phase transformer on either one .
The spec. sheet of GC 1023 said 5.0 to 6.6 khz , that is a big range without having a frequency control on front panel ? Maybe not a Fisher !! It sure looks like good quality too !! I wish you can take dc resistance measurements at unplugged search coil connector , transmit and receive coils .

Thank-You again , now you have a fantastic topic started here !! It might be a real good stable design that just needs a perfect search coil !!! I read a rumor that one of the GC series detectors is a old Minelab VLF ?? Wouldn't that be something to find out which one it is .

Best Regards............Eugene

[amtech2005]

A lot is similar with this schematic !!!!!

Tell me I am dreaming , so now I will buy a GC-1023 as soon as I find one around here very cheap .

Look at the IC chips used , many similarities on this schematic too . The GC'S TL 431 [U7] "2.5 v voltage reference" caught my attention . A solid design , but when using a cheap Chinese search coil it does not draw any attention !!! Understand what I mean now ?


Best Regards............Eugene

[6666]

Thanks amtech2005 for the cct, been wanting to see this
for a long time, I am curious, but cannot see the pinpoint function, or mode switch ?
cheers


just for info the "specs"

The Gold Century Model GC1023 Metal Detector is considered to be one of the best values for a mid class metal detector. Easy to use and reliable functions. Press the red button under your thumb to activate the pin pointing feature and it will narrow down the search area saving you lot of wasted time digging. Once you use this feature you will never want to do with out it. The sensitivity and discrimination function are easy to adjust to the search conditions and the ground balance is automatic. The coil is water proof so it can be used in the surf at the beach where most rings are found. This unit can be used with it's built in speaker or optional headphones. It can be used in several modes:

• All metal mode - Just that, any metal object will be detected. The ground Balance is fully automatic in this mode
• Motion Discrimination - While the detector is in motion it will emitted different tones based on the metal type detected. The signal strength will also be displayed. The sensitivity and Discrimination levels are fully adjustable. The ground Balance is fully automatic in this mode.
• Tone Discrimination - In this mode the detector will emitted a high or low tone based on the target type. The sensitivity level is fully adjustable. The ground Balance is fully automatic in this mode.
  
  Key Specifications/Special Features:
  
  Power supply: Two 9V batteries required, static current < 15 mA
• Operation Frequency: 5KHz ~ 6.5KHz
• Operation modes: ALL METAL, DISC, TONE
• Target Indications: Audio -1.2 speaker or earphone jack View meter
• Knobs for adjustment: SENS , DISC/TONE
• Sensitivity: max depth > 8 inches (20cm) for a US quarter in ALL METAL mode
• Pinpoint: max depth > 16cm, help to find the accurate place of target
• Advanced discrimination ability: can discriminate between aluminum and silver
• Two tones for different metal targets in TONE mode
• Motion discrimination
• Auto ground balance
• 8 inch waterproof search coil
• Comfortable arm support, and adjustable aluminum stem
• 1/8 inch earphone jack (earphone not included)
• Low battery indication
• 
  Click here for Link to product manualhttp://www.lg-outdoors.com/manuals/gc1023.pdf

[sido]

Hi, very interesting Bernte, smd version, did not know existed. Compared both smd and feedthrough overlays, very similar if not same.

Amtech, very similar but has a lot of differences. The LM393 chip seams to be more than one used in that circuit you present. Md/Gc1023 uses only one. The circuit you have also does not have Pre-amp transistor Q3.

The MD1023 Color codes for connection to coil connector inside detector on either board are as follows:
TX- Blue/Green
Rx- Yellow/Orange

Lunamay, have you tried looking for any dry joints, maybe a idea is to re-solder as many component pins, taking more care not to over-heat any IC pins, diodes and transistors. If all is still no good disconnect coil and try to measure resistance and inductance at coil connector from the coil lead itself. You might have a faulty coil lead connector. You should have roughly these parameters:
TX-2.0mh, Resistance-7ohms
RX-9.0mh, Resistance-32ohms.
Hope that helps.

As for mods, see below picture, will be same for smd and feed through version from what i see from Bernte's SMD version.

Please understand if you decide to mod your unit, you are doing it your own risk. I recommend doing one change at a time and see if there is a difference in sensitivity to even smaller targets like a small round ball of lead/solder. Dont re-adjust Rv1 until you see a difference in sensitivity or you get a unstable operation. Use metal film resistors if possible.

Hint: Remove Rv1 and measure Rv1's resistance at each 3 points and note them down on paper so you can re-adjust back if need to so if you want to reverse mod if it does not work out good for you.

I actually replaced Rv1 with a external ten-turn pot, made it easier to adjust, was not so critical for my detector. Remember every detector might be operating different in performance, so might have different results.


This is only for preamp and op-amp mod. If you need to: re-adjust Rv1(All metal mode only), use care, adjust very slightly either left or right with a small ferrite core 5cm in front of coil for nil response or a bit of threshold sound breaking through, but still have greater sensitivity than before the mod. This will make sure Ground balance and when lowering coil to outside ground soils is at optimum and still remains with a quite threshold in use. Remember the detector is a motion type in all metal mode, so you will need to wave the ferrite left to right in front of coil. Pinpoint mode when in use is non-motion for your info.

Regards Sido

[amtech2005]

Thanks amtech2005 for the cct, been wanting to see this
for a long time, I am curious, but cannot see the pinpoint function, or mode switch ?
cheers


just for info the "specs"

The Gold Century Model GC1023 Metal Detector is considered to be one of the best values for a mid class metal detector. Easy to use and reliable functions. Press the red button under your thumb to activate the pin pointing feature and it will narrow down the search area saving you lot of wasted time digging. Once you use this feature you will never want to do with out it. The sensitivity and discrimination function are easy to adjust to the search conditions and the ground balance is automatic. The coil is water proof so it can be used in the surf at the beach where most rings are found. This unit can be used with it's built in speaker or optional headphones. It can be used in several modes:

• All metal mode - Just that, any metal object will be detected. The ground Balance is fully automatic in this mode
• Motion Discrimination - While the detector is in motion it will emitted different tones based on the metal type detected. The signal strength will also be displayed. The sensitivity and Discrimination levels are fully adjustable. The ground Balance is fully automatic in this mode.
• Tone Discrimination - In this mode the detector will emitted a high or low tone based on the target type. The sensitivity level is fully adjustable. The ground Balance is fully automatic in this mode.
  
  Key Specifications/Special Features:
  
  Power supply: Two 9V batteries required, static current < 15 mA
• Operation Frequency: 5KHz ~ 6.5KHz
• Operation modes: ALL METAL, DISC, TONE
• Target Indications: Audio -1.2 speaker or earphone jack View meter
• Knobs for adjustment: SENS , DISC/TONE
• Sensitivity: max depth > 8 inches (20cm) for a US quarter in ALL METAL mode
• Pinpoint: max depth > 16cm, help to find the accurate place of target
• Advanced discrimination ability: can discriminate between aluminum and silver
• Two tones for different metal targets in TONE mode
• Motion discrimination
• Auto ground balance
• 8 inch waterproof search coil
• Comfortable arm support, and adjustable aluminum stem
• 1/8 inch earphone jack (earphone not included)
• Low battery indication
• 
  Click here for Link to product manualhttp://www.lg-outdoors.com/manuals/gc1023.pdf

Thank-You 6.666 k for posting your information . My schematic is not an exact match , it is for reference . The Chinese cloned many different M.D.'S so the above schematic is just a starting point , maybe someone else can positively identify [like a detective] what manufacturer and model was cloned in the GC-1023 ? !! We have to start somewhere , if we do nothing then nothing will get done . It looks like a very professional circuit board not cheaply done like some of the Chinese Seben-7's !! So far I found a GC-1023 for $40. u.s. dollars , not bad if it is still available ?

Best Regards................Eugene

[6666]

It would be a good buy for $40.00
the components would cost more than that to buy,

Yes the Chinese hide this circuit very well from us

[bernte_one]

hello
got mine for 38€ for that prices nobody should build it by himself
but i think there are some tuning options that can be done
my greatest interest is to increase the coil quality and performance
but the sens mod above is nice too
i will try it next weekends

[sido]

Hi Bernte-one, just wandering how you went with the sensitivity mod...

Did google search, some site say's the 8 inch round coil supplied is effectively a 4 inch tx coil. The inner tx coil is part of the outer bucking coil in series. The way i interpret it is the bucking coil is on the outer and tx coil inner with rx. Would explain why it has such a good sensitivity to small items and great separation between targets.

This detector was also supplied with a 12 inch coil, hard to get though and very critical to match to different detector of same brand. I would say they followed the same principle of where the tx is around 6 inch, rx 6 inch and bucking coil 12 inch, effectively a 6 inch coil.

Would like if someone has a broken coil to show us with pictures of the inside or if someone is willing to sell me a broken/not working one i will be interested in buying, otherwise will keep trying some more experiments with larger concentric coils for now based on the coil parameters.

Regard's Sido.

[sido]

Forgot to also mention, if this detector was built by known big Manufacturers, with their build quality and circuit board design capabilities would have made this circuit into a good quality low budget detector where more people would be talking about it now, oh well.

If it is genuine Chinese design, i take my hat off to them on a very good simple circuit.

Regard's Sido

[HECTOR]

As for mods, see below picture, will be same for smd and feed through version from what i see from Bernte's SMD version.

Please understand if you decide to mod your unit, you are doing it your own risk. I recommend doing one change at a time and see if there is a difference in sensitivity to even smaller targets like a small round ball of lead/solder. Dont re-adjust Rv1 until you see a difference in sensitivity or you get a unstable operation. Use metal film resistors if possible.

Hint: Remove Rv1 and measure Rv1's resistance at each 3 points and note them down on
I actually replaced Rv1 with a external ten-turn pot, made it easier to adjust, was not so critical for my detector. Remember every detector might be operating different in performance, so might have different results.

[ATTACH]15809[/ATTACH]
This is only for preamp and op-amp mod. If you need to: re-adjust Rv1(All metal mode only), use care, adjust very slightly either left or right with a small ferrite core 5cm in front of coil for nil response or a bit of threshold sound breaking through, but still have greater sensitivity than before the mod. This will make sure Ground balance and when lowering coil to outside ground soils is at optimum and still remains with a quite threshold in use. Remember the detector is a motion type in all metal mode, so you will need to wave the ferrite left to right in front of coil. Pinpoint mode when in use is non-motion for your info.

Regards Sido

I have one of these units. Got it for $30 never used. Impressive discrimination in air test but completely unstable in my soil. (high iron)
I'm assuming that it's "fixed" GB and not "automatic" as I assume RV1 is the internal GB adjustment pot?
What about RV2?
Might be an outstanding beach machine but it doesn't pass the coin garden test.
Would like to use it but compared to my modded Cibola, it's WAY too unstable for me to try and figure out.
Have had it open but haven't touched RV1 or 2.
I'd be up for doing any mods to make it a better machine.
Let's keep this post rolling!

[bernte_one]

hello

the 1023 seems to hate wet ground maybe it could be your main problem
i think it can be solved by changing the original coil with a selfmade and another way of shielding and connecting coils to shield then make a new ground balance
i never done that but i think most problems are made by this bad original coil of the older models this one which looks so massive

[bernte_one]

search coil

hello

yesterday ich checked my GC 1023 20cm coil
it seems to be different to the one above which has 2mH and 9mH

my coil specs are:

1,93mH 7R
2,65mH 15R

the coil inductance difference seems to be like the older tesoros
i think the measurement is not 100% correct -the pins were hard to get
but a difference of 0,7mH seems to work maybe also less? 0,5 or 0,6
i will try it with diy coil dd shape coil with 28cm diameter
report follows

[sido]

Hi Bernte, i did the measurement again. I am using a cheap handheld multimeter with Inductance measurement. Could be giving me wrong reading, i hope so as the values you have a very close to Bounty hunter coils.

What Inductance measurement equipment are you using?

I live in Melbourne, Australia and the only problem i have using this detector at full sensitivity is at the beach on wet sand only. I have to turn the sensitivity down to half way to use it on wet sand.

As most people know here in Melbourne/Victoria we have one of the worse mineralised goldfield soils in the world that i have been using the detector with no falsing.

Below is the pins diagram i took measurements from.