White's PI3000 re-build

[GeoMax]

The "R16" is at my PI1000 a 1/2W 5R6 Ohms resistor as stated in the PI2000&3000 schematic diagram. I measured the resistance and it is confirmed 5R6 Ohms. The resistor is also slightly bigger in size than all nearby 1/4W resistors.

[Lucar]

The yellow 950 coil is original from White's and is most definitely shielded. Thanks, Tony.

Hi,
there's a misunderstanding, The Yellow 950 coil is a Whites original coil yes, but as far as I know , it was standard on the Surf PI Pro.
My PI3000 came with a different "PI3000 original" coil:



Luca

[Octopulse]

Hi,
there's a misunderstanding, The Yellow 950 coil is a Whites original coil yes, but as far as I know , it was standard on the Surf PI Pro.
My PI3000 came with a different "PI3000 original" coil:



Luca

I think I read somewhere that PI3000 models built from 1995 onwards had the 950 coil.

[Octopulse]

Well I shall replace the 5R6 resistor and very carefully resolder the coil to the PCB......double checking no shorts on the board. The solder holes (shield and conductor) are some distance apart which makes less room for mistakes.

Why is R16 unhappy.....and where is the excess current coming from to fry R16. If a 1 watt 5R6 can fit on the board is that okay ?

[Lucar]

I think I read somewhere that PI3000 models built from 1995 onwards had the 950 coil.

I was unaware of that! Anyway here is a picture of the schematic diagram I made at that time to try to have programmable pulse timings on the PI 3000. The rotary switch was there to allow for on the field selection of a timing from a programmed set.


Luca

[Octopulse]

R16 has nothing to do with the charge pump. 3 possibilities:

1. The TX pulse is too wide or the TX timing is not working
2. There is a dead short in the search coil
3. R16 power is rated too low

From the photo R16 does not look like a 1W resistor, more like a 1/2W or maybe even 1/4W. I would need to know the TX pulse timing to figure out what it needs to be. If you replace it, try running the circuit without the search coil attached to see if the TX pulse is working correctly.

Carl,

Hypothetical question

If one was careless enough to short the IC charge pump when powered up (like being stupid and not replacing the plastic insulating piece that separates the back of the PCB to then shorting to something metallic like a battery pack)......could R16 burn because I took a look at the old charge pump and it looks bubbled. It has since been replaced with a new one. I also found some pictures of R16 before I did any updates and it is looking burnt. Obviously the problem continued after my updates and was there the whole time?? I guess I will know tomorrow when I replace R16 and then reconnect the coil wires. Stay tuned.

[dbanner]

I would like to clear up a certain contradiction, which I think is important. As I noted before, in the first post of this thread, it was stated that:

"Recently I got water inside the coil so I'm waiting for a replacement one from Whites UK.
I had then the chance to open my old coil and count the windings : 36 windings. It looks a lot for a 11" coil."

Now assuming the person who counted those windings isn't a moron, then that would put the inductance at somewhere around at least 1mH.

So what is the inductance of the 950 coil?

I found this:
Coil inductance (pulse diver 950) measure 0.224mh (hi reading) and 292uh(low)- which one is the real value? (i don't have multimeter with me to check the resistance).

So around 300uH would be ok for the pulse diver 950 coil. So there is a big discrepancy between 36 turns and 18 turns as noted on the schematic drawn by bill lhar. I am suspecting bifilar windings or some hocus pocus business.

Because a higher PRF(pulse repetition frequency) translates into more current in the coil(all things being equal). You have to use the correct coil for the given circuit otherwise things can heat up, maybe even leading to catastrophic failures.

[dbanner]

Well I shall replace the 5R6 resistor and very carefully resolder the coil to the PCB......double checking no shorts on the board. The solder holes (shield and conductor) are some distance apart which makes less room for mistakes.

Why is R16 unhappy.....and where is the excess current coming from to fry R16. If a 1 watt 5R6 can fit on the board is that okay ?

how do you know that your R16 was in fact 5.6 ohms?

It still bothers me that someone counted 36 windings in the original coil(not the pulse diver 950).

Please, if you can, check your board to see if you have 150pF cap, 100k and 82k around CD4069 clock.

[Lucar]

I would like to clear up a certain contradiction, which I think is important. As I noted before, in the first post of this thread, it was stated that:

"Recently I got water inside the coil so I'm waiting for a replacement one from Whites UK.
I had then the chance to open my old coil and count the windings : 36 windings. It looks a lot for a 11" coil."

Now assuming the person who counted those windings isn't a moron, then that would put the inductance at somewhere around at least 1mH.

So what is the inductance of the 950 coil?

I found this:
Coil inductance (pulse diver 950) measure 0.224mh (hi reading) and 292uh(low)- which one is the real value? (i don't have multimeter with me to check the resistance).

So around 300uH would be ok for the pulse diver 950 coil. So there is a big discrepancy between 36 turns and 18 turns as noted on the schematic drawn by bill lhar. I am suspecting bifilar windings or some hocus pocus business.

Because a higher PRF(pulse repetition frequency) translates into more current in the coil(all things being equal). You have to use the correct coil for the given circuit otherwise things can heat up, maybe even leading to catastrophic failures.

I'm the moron ))

[dbanner]

I believe you counted them correctly. The assumption was that you were not an idiot.

Strangely enough, the AF108 circuit bore a close resemblance to the PI1000/2000/3000 circuit. That detector AF108 had a centre tapped coil.

Another clue is R17 on the PI1000/2000 circuit. It is 1K.

So it would be nice for somebody to measure their pi1000 coil(the older coils)

[GeoMax]

Hi DBanner

I asked the same question some time ago.... Here the answers I saved.


Coil specification for a Whites PI-1000 or PI-2000 or PI-3000 detector needed
02-27-2023, 11:22 PM
Hello,

does someone knows the inductions or specification of the mono coil for a White Treasuremaster PI-1000, PI-2000 or PI-3000 underwater metal detector?
In one of the schematic diagrams I found the information that the coil diameter is about 11 inch and has 18 turns. Is this correct?

thanks...



Info posts by ALTRA, Geotech Forum (date 28.02.2023):

My old notes show 200uH, 1.25 ohms. The original 11-inch coil had 18 or 19 turns. The inductance of 200uH is an actual measured value. Several different PI-1000 coils were measured that time.
Wire size, I think something like stranded tin #24 or #26 gauge with PVC insulation will work just fine. Avoid using magnet wire; litz wire would be a waste on this detector.
The cable to the detector was equivalent to RG58A/U stranded coax.

Source:
https://www.geotech1.com/forums/foru...etector-needed


Other Info to the coils

Whites PI3000 coil info.
Early ones before 1995 had open coil, they later became available with flat Pulse Diver 950 weighted loop.
Source: https://forum.kimbucktwo.com/whites-pi-3000-t27474.html

[Altra]

Lucar may have counted 36 turns and be correct. It could be 18t + 18t in parallel? The original ML Sovereign used this technique to lower the capacitance and resistance while maintaining the same inductance. Trust Bill Lhar's information.

[dbanner]

The AF108 had the same coil, at least the housing looked the same. I am now suspecting 18+18 turns with a centre tap for the AF108.

[kt315]

I believe you counted them correctly. The assumption was that you were not an idiot.

Strangely enough, the AF108 circuit bore a close resemblance to the PI1000/2000/3000 circuit. That detector AF108 had a centre tapped coil.

Another clue is R17 on the PI1000/2000 circuit. It is 1K.

So it would be nice for somebody to measure their pi1000 coil(the older coils)

all are in files.

[kt315]