White's PI3000 re-build

[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]

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.

[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.

[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.

[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]

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 ?

[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.

[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

[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.

[kt315]

to define the value is easely. remove paint with a scalpel, do accurately. then you must see a point of burn on metallization strip. use zoom glass.
measure one part and second part of intact strip - from a pin to the point edge. add both values and you get whole value.

[Octopulse]

It might be the coil.

The clock is 30kHz. It looks like the PRF is 3kHz? With a pulse width of 30uS. Time to first sample is 30uS after end of Tx pulse. Time to second sample is 270uS after end of Tx pulse. All pulse widths are 30uS in duration.

In the notes on the first post, the original coil was opened and found to have 36 turns @ 11 inch diameter which works out to app. 1200uH.

The 950 coil is around 300uH????.

Put in a higher power rated resistor for R16.

What value is ideal.....wattage and resistance?
Although I am still unsure why the original spec R16 is too small....assuming no other problems with the coil connection.

[Octopulse]

Hi,

I'm Luca , the author of the posts You resumed from Findmall if I recall; I don't remember anything about that, it was a long time ago, but I still have the PI 3000 somewhere in my house and one thing for sure is that the 950 coil is not the original one. As far as I remember the original coil was not shielded and that was a damned noisy detector. Anyway adding a pic16F did allow for flexible timings programming.

Cheers
Luca

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

[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.

Thanks Carl.....I got the R16 values from the schematic.Might be wrong on the wattage though. I think maybe Point 2 you mentioned is worth revisiting. I re-wired exactly the same as the original with the shield and centre conductor going to the correct pins on the board. As mentioned earlier, nothing has changed from the original specs. I will have to check my coil connection again and re-solder.
Unfortunately I don't have an oscilloscope.

[GeoMax]

Hi folks,

the yellow Pulse Diver Coil 950 is an original coil by Whites for the PI3000. The first issues of the PI3000 came with a 3-spoke yellow coil which looked the same as the orange coil from the PI1000 & PI2000 detector. The later versions of the PI3000 came with the Pulse Diver Coil 950. Whites offered also this coil as an upgrade to the 3-spoke yellow coil. The coil specification was the same. The orange coil from the video belongs to the Whites PI1000.

[kt315]

the original coil is orange and looks different : https://www.youtube.com/watch?v=q951...RlY3RvciB0ZXN0

Eric used orange coil enclosures and orange cable.