Pulling Chip Out Of 6000 Coil

[Aureous]

3 hours ago, Chet said:

Yes, this was a factory defect. Yes, the GPX 6000 screen wire is wired differently. It is carried on separate/isolated wire within the coil cable and terminated on the printed circuit board within the control box.

Wow, OK....this is the info I was missing. I am also a 'coil winder' and have built dozens of SD, GP and GPX coils over the years. So the screen wire is soldered to a dedicated pin on the coil cable plug?...and therefore finally terminated on the PCB? Wonder if the Aliexpress 6000 cable and plug has this wire correctly installed 😒 Im sure you'll let us know lol. Nothing wrong with using tape to secure screen wire onto the coil shield, Ive been using super strong automotive painters masking tape for over a decade. Sometimes when I deconstruct a coil to re-use parts, I see the tape still holding strong. There are graphite pastes available which bond well (prob what the Plexus coil sub-contractors use) but cost a heap more $$ to buy than quality tape.

[Aureous]

3 hours ago, phrunt said:

I hope they're not just masking taping it on.  That's designed to fail, might last the warranty period but not a long-life product.

I have deconstructed Coiltek coils from over 20 years ago and their screen is perfectly attached via masking tape.  if a quality tape is used, its a terrific and simple way to secure the screen wire....saves $$ and time and does a great job. On the other hand, Ive seen Korean made Commander coils with heat-affected tape already peeling after only a couple years 😞 

[Chet]

Over the years I have repaired several coils with dried out masking tape and a couple of dried out carbon sponges.

I will relate on of my experiences with one coil while detecting in a new undisturbed gully. Detected and dug a few square nails then the detector goes crazy making all kinds of noise.

 With more than 60 years of electronics experience I know how to fix most problems. Turn it off and back on; several cycles later go to plan B; tap it gently; after banging it into rocks and trees; give up and have lunch on a big flat rock.

Since we car pool going home early isn’t an option. From the previous scientific diagnostic testing (remember the banging of the coil test) it was determined that the problem was inside of the coil. Probably getting revenge for allowing myself and it to slide and crash into a gully the previous week. And there is no spare coil available; it’s time for another plan.

A Pulse Induction Mono coil is a simple three wire circuit inside of a sealed waterproof plastic shell. So simple even that MacGyver TV guy could handle this. Have you ever seen someone whetstone their prize Buck Knife until they can shave with it. Well it’s that time to put it to work.

 Working on my leg-top workbench I peeled off the tape that holds the skid plate to the coil housing. Then with my razor sharp Buck Knife cut and pried through the sealed plastic seam around the perimeter of the coil. Spliced the broken shield wire and secured it with a piece of the skid plate tape. Closed it up and secured it with the remaining tape. At this point I realized that I hadn’t stabbed my leg or cut a single finger!

Now for the test; turned it on and it purred like a kitten; went about 10ft and got a soft nice sounding target. Dug down about 10” and came up with a beautiful 13.8 dwt / 21.5 grams nugget! Some days it's just written in the stars.
 

[IdahoPeg]

24 minutes ago, Chet said:

Over the years I have repaired several coils with dried out masking tape and a couple of dried out carbon sponges.

I will relate on of my experiences with one coil while detecting in a new undisturbed gully. Detected and dug a few square nails then the detector goes crazy making all kinds of noise.

 With more than 60 years of electronics experience I know how to fix most problems. Turn it off and back on; several cycles later go to plan B; tap it gently; after banging it into rocks and trees; give up and have lunch on a big flat rock.

Since we car pool going home early isn’t an option. From the previous scientific diagnostic testing (remember the banging of the coil test) it was determined that the problem was inside of the coil. Probably getting revenge for allowing myself and it to slide and crash into a gully the previous week. And there is no spare coil available; it’s time for another plan.

A Pulse Induction Mono coil is a simple three wire circuit inside of a sealed waterproof plastic shell. So simple even that MacGyver TV guy could handle this. Have you ever seen someone whetstone their prize Buck Knife until they can shave with it. Well it’s that time to put it to work.

 Working on my leg-top workbench I peeled off the tape that holds the skid plate to the coil housing. Then with my razor sharp Buck Knife cut and pried through the sealed plastic seam around the perimeter of the coil. Spliced the broken shield wire and secured it with a piece of the skid plate tape. Closed it up and secured it with the remaining tape. At this point I realized that I hadn’t stabbed my leg or cut a single finger!

Now for the test; turned it on and it purred like a kitten; went about 10ft and got a soft nice sounding target. Dug down about 10” and came up with a beautiful 13.8 dwt / 21.5 grams nugget! Some days it's just written in the stars.
 

Great story Chet!

[中国 张]

Yes, this Chinese company sells most of the mass-produced cables from MineLab (except those without chips). The prices are very low and the quality is pretty good. It’s very convenient to buy from us,,,

[phrunt]

3 hours ago, 中国 张 said:

Yes, this Chinese company sells most of the mass-produced cables from MineLab (except those without chips). The prices are very low and the quality is pretty good. It’s very convenient to buy from us,,,

Do you think they are the actual cable used by Minelab? they certainly look like it and I just can't imagine it was worth the effort for a Chinese cable manufacturer to specially make these cables to sell as separate cables, the market would be so small for them, surely the reason they exist is they're made to supply Minelab to meet their demands and also sold off separately this way.

Making copy GPZ cables is even more unrealistic as they have no chip, the market for these GPZ cables would be absolutely tiny, so unless the same cable maker was supplying Minelab I just can't imagine they would bother to copy and make an aftermarket cable.  

[Aureous]

2 hours ago, phrunt said:

I just can't imagine it was worth the effort for a Chinese cable manufacturer to specially make these cables to sell as separate cables, the market would be so small for them, surely the reason they exist is they're made to supply Minelab to meet their demands and also sold off separately this way.

In major Chinese manufacturer cities (Shenzhen for instance) there are numerous small sub contractors working from tiny facilities, some even as small as a car garage, all vying for a tiny section of any industry. This sort of re-manufacture of a single assembly is right up their alley. Super easy for them and often just a side-business from their usual product. This manufacture concept is extremely common in most Asian economies, as well as India and Pakistan, Bangladesh etc.

[Norvic]

OK coil winders ??? Does the proximity/size of the shield influence the induction of the windings? and to what extent adds or takes away from value?... shield passive and active extent same or different?

[Chet]

1 hour ago, Norvic said:

OK coil winders ??? Does the proximity/size of the shield influence the induction of the windings? and to what extent adds or takes away from value?... shield passive and active extent same or different?

It does not change the inductance.

It acts as an active fixed circuit capacitance that reduces outside variable capacitances caused by changes in height and conductivity of the soil as the coil moves over it.
 
If the shield is too close to the windings it can add considerable capacitance to the circuit which lowers the frequency response and response to smaller nuggets. 

I try to space it around 0.25 inches with a graphite resistance of around 100 ohms per inch. I have seen some Minelab coils be as low as 50 ohms per inch. If you go that low I recommend a long thin unpainted gap to prevent a circular short circuit. The gap should start top center, across, down, back across the bottom to center.

On size; I shield the entire coil. Large coils could be shielded around the winding areas with satisfactory results.

Metallic conductive spray paints can be a problem and should not be used for metal detector shields. 
 

[Norvic]

OK if I go with 2x0.25" Divinycel, form the coil (spiral/flat) and fix and position on one half of the divinycel, adhere the 2 divinycel half's together then paint the shield top and bottom giving that 0.25" gap from windings. Recommended litz wire and shield paint too please Chet?