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

[Blissterd1]

A quick question...would there be an issue using 1/8 TH watt resistors in this project? Is the wattage critical? Thanks!
IDXKevin

I wouldn't do it. The worst that could happen is that you might burn them up, but the resistors used in the machines are 1/4 watt. They are 6.3mm long x 2.2 wide. 1/8 watt resisters are half the length (3.2mm) and 1.9mm wide. The electron flow through them causes friction and heat is dissipated away. The 1/8 watt'ers will only require half the current to heat up the same amount. At full power, they will create twice the heat of a 1/4 watt. High heat in a resistor causes the rating in ohms to change well before it is destroyed. I would not use them for that reason alone. For the low cost, It couldn't possibly cost more than $2 to $3 for all resistors that are replaced. And you will only have to do the job once! Bigger is OK, but never replace a component with a current rating that is less than the original. Especially less by 100%.

[IDXKevin]

A quick question...would there be an issue using 1/8 TH watt resistors in this project? Is the wattage critical? Thanks!
IDXKevin

[Koala]

My question was about opamps, JFETs and coil pre-amps.

Not much to be gained from changing to better components. You would have to increase the gain also but that would make the detector unstable in the field.

Not tried putting the pre amp in the coil.

If you are using the 8" coil the biggest bang for buck would be to change to the 950.

[TH'r]

Where'd you get those cool dial decals?

Those are Ohmite Rheostat dials. Mouser #588-5007E. Additional knobs are from White's, and writing is Dymo tape writer. As you can see, I took out the frequency control and used that space for GEB.

[Blissterd1]

My question was about opamps, JFETs and coil pre-amps.

[Koala]

I would VERY MUCH like to know more about these opamp and JFET mods! I have heard about U4 and U8 (maybe others) being switched out for better components. And that coil mod sounds insanely cool! And a pre-amp in the coil? How cool is that? I am a HAM tech and that sounds just like how we bring in radio signals from around the world. Pre-amp at the antenna, not the radio! Please point me in that direction!!

If you are using the 8" coil. The biggest bump in performance would be going to the bluemax 950


Now you have the threshold POT you can use your machine on some wet sand but not all. No good in gullies or round rock pools but if the sand is fairly even just turn the threshold down a bit. There will obviously a small loss of depth to.

[Koala]

Where'd you get those cool dial decals?

you can print your own with special paper

[Blissterd1]

SAT is SAT and has not a relation to the depth. if you use JFET opamps (if no so change its on JFETs) you need to operate not 100's kOhms but MEGAOhms, in the SAT. 1...2M may be good. you second mod would be an RX opamp in a coil. for that you need to open a coil and insert a board inside on manner that greedlab does it always and why wins any testing on the gives much better depth than normal.

good luck

I would VERY MUCH like to know more about these opamp and JFET mods! I have heard about U4 and U8 (maybe others) being switched out for better components. And that coil mod sounds insanely cool! And a pre-amp in the coil? How cool is that? I am a HAM tech and that sounds just like how we bring in radio signals from around the world. Pre-amp at the antenna, not the radio! Please point me in that direction!!

[Blissterd1]

The finished control box of my IDX Pro. with "Mr. Bill's" modifications.
[ATTACH]28084[/ATTACH]

Where'd you get those cool dial decals?

[Blissterd1]

I successfully completed the GEB/Thresh mods on my Classic III and IDX Pro and am confident that it's all working well. (I would also like to know where TH'r got those cool 1-10 dial decals!) Having had my HAM Tech license for many years and also having great soldering skills, I wondered if I might be able to pull of the last Mr' Bill mod that I don't know much about and have yet to find the secret to. That being the "beef up" of board level components. Something tells me that this was more than a swap of R7 and R24 with 51k and 2.2M resistors. I am thinking that he might have actually swapped an op-amp chip and more. Any ideas? Has anyone had that last mod done in addition to the two pots and two resistors. I am certain that electrolytic caps have weakened a bit in the 15 or so years but that couldn't make that big of a change. I'd sure like to know what he changed!

[Koala]

Interesting about the swing speed. Have to re try mine at some time. In the real world of an iron infested field it really likes a slow swing. Can winkle out targets right next to iron. The only problem I in counter is iron with a hole in the centre gives a good signal. A horse shoe will give a broken sound over the centre and a good signal near the open end. Using different headphones makes a difference. Some are better at hearing the difference between a good and bad signal. Also some are louder on the very faint signal in all metal mode giving you an extra 1/2 to 1 depth


Was really please with my detector until I repaired a golden mask for someone. That was getting over 7" on a tiny Henry V cut half with a 7" coil

[Lucas26]

My home made Classic tested with a English copper or iron clad 2p is 15" with a 10" coil Diameter of coin is 25.9 mm

Thank you Koala I have done some more air test today. After reading your post I went to my world coin jar and the only large copper I have is a 1943 Australian Penny I did get a solid repeatable signal at 15 to 15.5 inches the problem was I had to move the coin much faster than I would swing the detector in natural hunting conditions. That being said I did get a good solid signal at 12 or 13 inches at about my normal swing speed. Maybe after I do the self adjusting threshold mod I can slow it down enough to get repeatable signals at that depth at a more natural swing speed. Still with just replacing R24 with a 2.2M I am very satisfied with the test results hope it carry's over to ground hunting. I must say that my sens was turned all the way up and was quite stable with being inside. I am very new to this forum and it has been a wealth of knowledge. I am using the stock 9.5" coil.

[Qiaozhi]

My home made Classic tested with a English copper or iron clad 2p is 15" with a 10" coil Diameter of coin is 25.9 mm

Wow, that's a small coil.
I guess you meant to say 25.9 cm.

That's a good result for a 2p coin.

[Koala]

I changed out R7 with a 51k and R24 with 2.2M have not added the ground balance or the threshold pot's yet still in the mail turned on machine and it was beeping and going crazy when I turn up the sens it would beep non stop. The detector would not pick up any targets at all replaced R7 with 100k from factory and it was back to normal. I lost my slight hum of the threshold by adding the 2.2 meg I can only assume so I adjusted the threshold trimmer got my slight hum back didn't touch the gb trimmer and the air test added 2.5" to 3" to depth and the tone is smoother on deep targets. That is air test my ground is frozen solid with feet of snow right now but as soon as the ground thaws I want to get out and test in real world conditions. I cant wait it is a whites classic lll sl and air test is producing digable signals at 11.5 inches on a dime if I didn't see it myself I wouldn't believe it that seems to be it tho even with a quarter the gain over a dime is only 1/4 of an inch that is kinda puzzling to me have not tried any larger coins.

My home made Classic tested with a English copper or iron clad 2p is 15" with a 10" coil Diameter of coin is 25.9 mm

[Lucas26]

I changed out R7 with a 51k and R24 with 2.2M have not added the ground balance or the threshold pot's yet still in the mail turned on machine and it was beeping and going crazy when I turn up the sens it would beep non stop. The detector would not pick up any targets at all replaced R7 with 100k from factory and it was back to normal. I lost my slight hum of the threshold by adding the 2.2 meg I can only assume so I adjusted the threshold trimmer got my slight hum back didn't touch the gb trimmer and the air test added 2.5" to 3" to depth and the tone is smoother on deep targets. That is air test my ground is frozen solid with feet of snow right now but as soon as the ground thaws I want to get out and test in real world conditions. I cant wait it is a whites classic lll sl and air test is producing digable signals at 11.5 inches on a dime if I didn't see it myself I wouldn't believe it that seems to be it tho even with a quarter the gain over a dime is only 1/4 of an inch that is kinda puzzling to me have not tried any larger coins.