Nulling a Nautilus coil for a IIB

[NostalgicMeditations]

About 2 years ago I sent my coils to the factory to have them rebalanced (common with these detectors). Well after having them in storage for about 2 years or so and only using them a couple times since I find that they are starting to drift and one is already out of balance. Last I heard the factory was closed but someone is still doing repairs but the last price I heard was $70 a coil (before the factory closed). Used to be $35 but at $70 + shipping I can't really afford to all 4 coils at that price.

Its a great detector and sometimes finds things the more expensive Minelabs have write off as junk (besides it is pretty deep- I do more than just coin shooting). I'd like to keep her going if possible. Besides it was my first real detector and I really can't afford to buy another one at this point. I'm a bit handy and do have an 2 channel oscilloscope and some basic electronic skills. I know I clip one lead on the TX (assuming right at the connector and both grounds to the ground of course. Not sure where to clip the other probe to for the RX on the board. From researching online I understand its supposed to be after the preamp but unfortunately I don't know where that is on the circuit board. If some one could point that out to me I would greatly appreciate it. Thanks

Heres some info and pictures of the IIB inside and the guts of the coil I found on the forum.

http://photo.qip.ru/users/interwert9...#mainImageLink

And I've attached some schematics someone else was kind enough to post (unfortunately I can't remember the link so I'll just post them again)

[kt315]

Aziz does low noise preamp on transistors while Nautilus had the preamp many years ago. at bottom I copy a message in russian from wert9 alias, sorry if in russian, pics which you give the link.
so I hope russian collegies will read the message and maybe help by anything.

На геотече вы просили схемку для наутилуса, там вроде как кто-то выложил, не могли бы вы архивчеком заделится, я с геотеча пароль потерял и терь не могу восстановить, а срочно нужно оживить катушку от Наутилуса, там на схеме вроде был нарисован блок встроенный в катушку. Он там сложный оказался, 2 транзистора 4 емкости и покрайней мере 3 резистора, так вот проблема терь с номиналом емкостей, никак маркеровку понять не могу((((((((
На схеме не указаны транзисторы, они 2n5088. Схема на наутилус без ручной балансировки катушки, у меня с ручной, так что номиналы резюков и кандеров отличаются.
Замерил диаметр проводов в катухе и сопротивление:
ТХ и СХ имеют по 4.2 Ом, толщина провода 0.45мм - одна пара хвостов соеденена вместе и кинута на землю, вторая пара на платку в параллель им пленочный кандер неизвестного номинала ( не выпаивал его из воска, так и остался в обойме)
РХ имеет сопротивление 26 Ом толщина 0.3 мм, в параллель РХ стоит кандер 22Н.
Корпус катушки изнутри промазан графитом (напыление), и обе половинки корпуса.

[dfbowers]

The Nautilus is no longer manufactured? I thought I just saw the DMCIIB for sale at Kellyco.

[kt315]

That looks like the schematic for the DMCII as I the DMCIIB has null adjuctments (R &C) in the box.
I think Troy Gallow told me once that the preamp is in the coil housing. Also, I do have a schematic of the search head
but not sure if it's for a IIB. 2N2222's for the preamp??
Don.

2N5088. Don look pls the pics at link NM gave above. there are the coil board pics, layout.

[dfbowers]

Sorry! Disregard my last reply. I saw the second schematic..

[NostalgicMeditations]

Thanks for the help guys. I really appreciate it. I googled 2n5088 and it appears very common use use them as preamps in guitar preamps, etc so it would seem that the Nautilus has its preamp in the coil and is sort of like the Minelab Sovereigns in that respect. Might be slightly harder to make a custom coil for it because of that but it does seem that it would be easier to make an inline adapter to null the coils (which is what I'm planning to do). I can't see a need to make a custom coil for it from my experience (I have the 6in, 8in and 2 15in) and it goes real deep when its working correctly) but if anyone does want to the first link I posted has a picture somewheres that gives the layout of the circuit board and all the component values. I haven't verified if they are correct but looks like the guy tested each one. Would be nice to make a probe similar to the Sunray for it though at some point.

By the way any idea what signals should look like on a properly nulled concentric coil? Is the RX supposed to be close to zero or is it supposed to look similar to the TX? I have found pictures of nulling D coils but no concentric. Does it look like the screen on the attachment below or the one on this link http://www.geotech1.com/pages/metdet...ti1500_150.pdf (not sure of what type of coil is on this unit though)?

The picture attachment is from http://www.aspeluut.nl/tgsl.php- great site. I know one is the TGSL and the other is a more standard layout. Not the same thing quite as mine so I'm not sure. Any help would be greatly appreciated on that. I know which wire in the coil I have to move and pretty much everything else so all set once I figure this out.

Yes- Nautilus is not making anymore detectors as of a few weeks ago. Steve Garris who owned most of Nautilus passed away recently- may he rest in peace. Never knew him personally but my dealings with the company were always pleasant. Due to that I hear the factory has been closed and most of the equipment has been moved to storage for now. It is not known if they plan to resume operation. However, Wayne who owns 25% of the company I hear now is still doing repairs and providing warranty service for those units still under warranty as well as again balancing coils. As of right now no new units are being made and it has been nearly impossible to get a new unit for some time. Call KellyCo and I hear they will say they don't have them in stock. If they don't now then they may not ever. If you are looking to get a Nautilus then now is probably the time. The used ones go fairly cheap on Ebay sometimes. It is one deep detector. Not as deep as my other unit though (which I still have to repair- long story). That one goes about 30 ft according to the Koden (got a good deal on it some time ago). Not a metal detector though it can detect metal in a manner of speaking.
Thanks again.
Bob