Whites Classic, II, III, ID, and IDX Modifications

[chevesne]

It seems OK for R7 & R32.
But for R24, in the first message of the tread, Mr Bill wrote:

Replace resistor R24 with a 2.2 Meg. You could have either a 470k or a 1.5 Meg there depending on when the unit was manufactured.

?

[keith777]

do you mean it's ok to change R7 & R32 ?

does R24 need replaced with either of them. 2.2 Meg - 1.5 Meg your choice.?

[chevesne]

I do not have this metal detector, and can not help you more than you ask in your first message.

i am useless when it comes to what resistor value is what etc. i have dyslexia.

to follow what Mr Bill says, actually, you have to replace:
R7 = 51 ohm
R24 = 2.2M ohm
R32 = 370 or 375K ohm

[keith777]

thanks chevesne....

i don't mind the soldering/de-soldering i am ok with that. i just would hate to end up using the wrong parts. i oltered a minelab explorer last year and love a challenge. i just wish i wastn't so dyslexia as it messes with your head. quit often something very simple to loads of people is very confusing to me. i have always been very clever when it comes to thinking of ways to repair thing that most people would just say. well that's no good now just put it in the bin. that kind of think. the brotherinlaw used to call me Q as in the guy of James bond.

here is some pics of that minelab explorer. the only thing missing on the detector is the Anderson stand which fits on in front of the small wireless control box.

[keith777]

i have another couple of questions about the mod if someone would be as so kind to answer for me.

VR1 Trimmer Replacement. which is the correct wiring setup for the potentiometer. i have seen two different wiring to the board. just 2 wires and 3 wires. which is correct? pics bellow.
i also read some were else to replace R25 for a 1K resistor? that isn't in Mr Bill's instructions.

thanks in advance guys.....

[keith777]

Hi Again Guys.

i have done the ground and threshold mod to the machine and they seem to be working ok. i have yet to add the SAT to it though as i am still waiting for the resistor coming for that. i would like to try and do the variable SAT. some info on how you would do/put together a variable potentiometer would be much appreciated.
the R24 resistor replacement. i only replaced that resistor with a 1Meg resistor. i read some were that replacing with a higher one than that can make the machine a bit chatty? is that correct. should i stay with the value that i have added. or put a higher one in?

also am i right that after the mod is done you can use other whites blue max series coils on the machine?

thanks in advance guys.

[keith777]

Hi Again Guys.

i have done the ground and threshold mod to the machine and they seem to be working ok. i have yet to add the SAT to it though as i am still waiting for the resistor coming for that. i would like to try and do the variable SAT. some info on how you would do/put together a variable potentiometer would be much appreciated.
the R24 resistor replacement. i only replaced that resistor with a 1Meg resistor. i read some were that replacing with a higher one than that can make the machine a bit chatty? is that correct. should i stay with the value that i have added. or put a higher one in?

also am i right that after the mod is done you can use other whites blue max series coils on the machine?

thanks in advance guys.

Hi again guys.
is there anyone that can help.

[Davor]

It would help if you put a piece of schematic you refer to, or at least a name and revision.
In any case, the SAT circuitry is looking at very high impedance, and for that reason only short leads and FET/CMOS switching is recommended. So potentiometer is off menu.
High impedances and long leads do not mix well because of capacitive coupling to just about anything. Having a few values to switch between electronically may work fine. Also having a switchable reset resistor of small value is a very good choice.

[SVEN1]

It would help if you put a piece of schematic you refer to, or at least a name and revision.
In any case, the SAT circuitry is looking at very high impedance, and for that reason only short leads and FET/CMOS switching is recommended. So potentiometer is off menu.
High impedances and long leads do not mix well because of capacitive coupling to just about anything. Having a few values to switch between electronically may work fine. Also having a switchable reset resistor of small value is a very good choice.

I used a pot for SAT and had no issues, worked just fine.

[DavidB]

Classic I with a lot of changes



Moded this one to death. All metal in one ear and Disc in the other. Added an additional SMD board which contains a LT1615 boost regulator followed by a LT1962 linear LDO regulator and a TI 2426 rail splitter. The board also contains an additional audio output channel. I upgraded main board components U1 to NE5534, U3-TLC2262, U5 LMC662, U6 OP291. I removed U9-LM2930. I modified the filter components for better response and lower noise. I converted the batter test half of U7 to an additional tone oscillator so I could have a low tone in the all metal ear and a high tone in the disc ear. The half of U6 that was used for the old rail splitter is now the additional Threshold amp for the all metal side. I reconfigured U5 to an auto tune all metal circuit with half used for the SAT feedback and added an auto tune switch so it can be switched off for balancing. It now has 5 controls. Disc, Sens all metal, Sens Disc, Thres all metal and Ground Balance. The internal power is now +5V and -5V so it now has 10V on the transmit oscillator. The new battery supply is 2-3.7V lithium Ion batteries in series. The batteries are rated at 5 amp hours and the total current draw is less than 45 MA, so that's better than 100 hour battery life on a charge depending on how accurate the rating is. The detector is working on the bench but I need to add a buffer between the Ground balance control at the board so the capacitance of the long wires does not affect the phase. Quite a bit of work but it's been fun.

[Nandor]

Looks very nice, great job.

[SVEN1]

Look at the board, look at the trimmer traces. Are two trimmer solder pads connected, then you only need two wires, just duplicate the connection at the pot leads. You can always use three wires as well and connect all three wires to the pot and duplicate the same connections at the pot.

[DavidB]

I had it that way already but put the trimmer back in to iron out some other changes. I am adding a opamp and a mosfet to isolate it better from the other channel reference, expand the linear range and eliminate the affects of having long wires on the control. I do this stuff all the time.

[thekevin]

Are there any reputable people in the US doing this mod for people who don't want to tear into their own.

[keith777]

Hi again guys.

all the mods are now done to my classic machine now. what exact other coils will it now accept. just someone has some spare whites coils laying about and has offered to give me one if it will work with the machine.

thanks in advance guys.........