The Mighty "Fisher CZ5 Quicksilver" and it's secrets

[Nandor]

I have recently acquired a control box of a Fisher CZ5 Quicksilver metal detector. Could not get stem and coil sadly. So I would like to make a small DD coil for it to experiment with and uncover it's secrets .

For me this detector is a pinnacle analog design, nice multi frequency detector and it has everything I like in a metal detector. After a good clean I have disassembled the control box by unscrewing the two screws on the rear side near the connector. Than the front panel and the 2 pcb's just slided out.
It is very clean inside. It has a little date on the pcb and it tells 1993 and maybe week 22? No corrosion or any other bad component, each pcb looks almost new.

There are some informations on the forum about it, like schematic and coil data but no oscilloscope screenshots or testpoint measurements so I would like to upload some in the future and gather, collect as much information as possible about this great design.

I will start with some basic measurements. It works with two 9 volt batteries connected in series with a diode to prevent inverted voltage. The power supply regulates the voltage to 10.40 volts and I think that all the IC's (there is a lot) are single supply types. About power consumption I have found information on another site it says 19mA idle and 21 mA at detection, not yet measured on my unit.

The oscillator is driven by a crystal, it runs at 60kHz divided by 12 so it oscillates the coil at 5kHz square wave with 10.80 volts peak to peak approx. It has strong harmonics at 15kHz and 25kHz.

Some other info I have found on Monte's forum about the CZ series, hope he does not mind if I share it.

So far only Fisher, Minelab, and White's have dabbled in multifrequency in any real way. Fisher and Minelab both introduced their new multifrequency designs in 1991 and so both can argue the fine details of who was "first".

1991 Fisher CZ-6 5 & 15 kHz
1991 Minelab Sovereign BBS
1999 Minelab Explorer S/XS FBS
2001 White's DFX 3 kHz or 15 kHz or both at once
2009 White's Spectra Vision 2.5 Khz or 7.5 kHz or 22.5 kHz or all three at once
2012 Minelab CTX 3030 FBS2


The CZ series was developed by Fisher Research with lead engineer Dave Johnson playing a major part. Running at 5 kHz and 15 kHz, the CZ is still one of the better coin detectors ever made and is particularly effective in saltwater environments. The CZ-20/CZ-21 is still considered to be one of the best saltwater models made. The basic CZ design is the same with the exception of the still in production CZ-3D, which tweaked and moved various target responses in an attempt to deliver more and better old coin finds. The CZ series is an old analog design requiring a great deal of hand tuning. This tuning suffered greatly as the "old" Fisher at Los Banos went out of business and took time for the "new" El Paso Fisher to get right. Details here by Dave J.


I had several CZ detectors and my personal favorite was the CZ-5. The CZ series will chase coins with the best detectors made today. The only real complaint you will hear is a tendency to identify some deep nails as non-ferrous coin targets.


The Cz series is quite unique because Fisher rearranged the classic target id scale. Nickels in particular were placed at the high end along with the rest of the coins. The scale is very basic - iron (low tone) aluminum (med tone) and coins (high tone). This simple systems is very effective in practice for coin detecting; just go dig high tones. It was so effective the CZ was nicknamed the "Coin Zapper". A fourth tone was added later to break the zinc penny/indian head penny range out as a separate "old coin" range.


Fisher CZ Approximate Release Dates


CZ-6 Quicksilver 1992
CZ-6a Quicksilver 1992
CZ-5 Quicksilver 1993
CZ-20 ( Underwater ) 1995
CZ-7 Quicksilver 1997
CZ-7a 1998
CZ-7a Pro Quicksilver 1999
CZ-70 Pro Quicksilver 2003
CZ-3D 2004
CZ-21 ( Underwater ) 2009

Here is the coil data I have found
Fisher CZ Quicksilver Five pin connector from Switchcraft model SL405FX and SL175MX.
Rx 1,2 6.6-6.8mH 39 ohms 1-5 Ground!
Tx 3,4 0.96-1mH 3 ohms

My DD coil does not really works well, could not find much info about the coil null just a screenshot on a russian forum. I could not achive the voltage stated there, the phase shift or my coils are not good maybe. The detector gives low tone for Silver and high tone for low conductors and Iron.

Here is the scope screenshot of the original coil from that forum, uploaded by Mr Foma.


Anybody some guidance, info about the proper phases?

regards

[ivconic]

Fisher CZ
Rx 1,2 6.8mH 30 ohms
Tx 3,4 1mH 2.8 ohms

Fisher Quick Silver
Rx 6,69-6,7mH / 31-32Ohm
Tx 0,945-0,960mH / 3-3,1Ohm

We have been dsicussing CZ series so many times in the past here on forum.
I am sure you can get a tons of infos if you search back through the many topics.
I had Fisher CZ5 twice so far. And one CZ3D once so far.
I like those. 100% serious machine, almost flawless.
One of the rare with which you can be absolutelly sure about unwanted horse shoe signals before digging.
There is a little trick in manipulation with switches when you want to check is it a horse shoe or something precious in the soil.
Unfortunatelly a time has passed and i totally forgot the procedure.
But it was simple, checking signal in one position of the switch and than switch it in another position and compare what you hear.
In case of precious metal; response will be the same. In case of deep horse shoe; response will be obvously different.
Maybe i explained the method in the past, somewhere on forum, can't tell.
You can also find several pretty correct schematics from different sources, also here on forum.
Fisher CZ5, CZ3D and CZ70 (had all 3 so i can say only on them) are based on pretty much the same platform.
Yet there are some differences amongs them. But in essence it is the very same platform.
Use search option on forum and you will be amazed to see how much info we already posted on this subject.
First one, the CZ5, i had back in 2000/1. if recall correctly.
Today is hard to find one in good shape.
Be carefull with it and don't experiment with replacing present battery supply with some "alternative" and "ingenious" solutions and ideas...
as it appears; CZ is not so tolerant on such brave experiments.
Also is not tolerant on punches, hits and sudden mechanical stress.
I saw several of those busted like that. Later not so easy to repair.
Weakest part is the crystal itself. It dies sudden for not so obvious reason. And than is impossible to find the one on the market.
Those would be the downsides of the design. It demands "handle with care", tender and gently and not like
wild pig on the run (80% of detectorists i know are best described as; "the wild pig with bipolar disorder on the run" !!!
Speaking here as long time servicer! I am sure i saw everything in this life!!!)
So it is unlike Tesoros and Fishers from the 12xx series. You must treat it nice and with care.
...
As for coil making, i was surprised to see that CZ3D is very tolerant upon diy coils. It was very easy to make a coil for it.
I made 39cm DD coil and balanced it so easy.. much easier than coils for numerous Tesoros that i made so far... i could not believe!
Or maybe it was just a strike of luck, once in 20 years.. can't tell for sure.
Original coils are made with very hard to obtain litz wires. Don't bother. I made it with single wire and it worked just fine, excellent.
Don't ask me about number of turns, i forgot, right now i am searching through my database on the disks and i can't find it.
But i remember that i followed to achieve only genuine inductances.

[Nandor]

Happy New Year to everyone

I always enjoyed reading your posts and Im happy that you are the first here, Ivconic
Before I made this thread I've searched the forum and read all the topics regarding to this machine, but non of these were informative enough to make serious repairs or diy coils for it.
Did not post the schematic because it has been posted many time so I did not see reason but there is a user who made a photo of the original schematic, only the powersupply is visible, hope he posts the entire original one.
Made some measurements and of course I handled it with care, waited 10 months for it to arrive from England it's my precious one. I love analog detectors!
I would like to post first some scope screnshots of the oscillator and than the receiver so people can see how an analog multifrequency detector works.

About the coil
I dont know how to set up the detector before nulling ! What search mode, how much ground balance? The oscillator coil works decent maybe the receiver coil has something problem because the received signal is pretty ugly, does not look like on the photo I've found on the russian forum. It was partially functionable, all metal and pinpointing worked pretty okay decent depth but the ID tones were messed up. No proper phase shift maybe?!

Before sharing my progress, first I have to gather myself because last night I was the "wild pig on the run"

regards!

[Nandor]

Found this pic, it shows the original coil "opened up"

[Nandor]

Some new oscilloscope screenshots.
First the oscillator unloaded than with coil and lastly the spectrum mode measurements .

[Carl-NC]

Weakest part is the crystal itself. It dies sudden for not so obvious reason. And than is impossible to find the one on the market.

The crystal was a custom frequency (60.12kHz) intended to minimize power line interference. It went obsolete a few years back so I designed a replacement module that uses an Atmel processor to emulate the crystal.

[ivconic]

The crystal was a custom frequency (60.12kHz) intended to minimize power line interference. It went obsolete a few years back so I designed a replacement module that uses an Atmel processor to emulate the crystal.

Our deceased colleague Jackdetect once tried to replace it with small "piggy back" style pcb, with cmos oscillator.
As i recall it worked almost alright, except that for some reason the current consumption has noticeably increased, so it drained batteries faster.
It was big problem back in a days, to successfully solve such fault. We had here many CZ detectors at the time. It was huge popular among people.
Today i guess it would be much easier. Attiny45-85 would easily solve the problem.

[ivconic]

Hey! This chat brings up the idea!
CZ3D re-packed in new MCU based style!

It would be cool to pack it in the same enclosure, but now "shallower", shorter, the same control panel, a large lcd with an imitation of the analog scale.
Lipo power supply ...
...
CZ series draws its all quality and performances from few obvious facts;
it is designed almost flawlessly,
it is "multi-f" machine, a kind of...
No need for many frequnecies, obviously.
One from the low side and one from the high side would do.
5kHz is just right for deep targets and 15kHz is enough good for smallest ones.
I would rather pick 7.7-8.3kHz (SMW&IGSL kills at those, Deus is a killer at 7.7kHz) and x3 one from the "high side", so 23.1-24.9kHz.
My imagination is a dangerous thing, you say the right word and the "trigger" works, the imagination starts to spill all over the place ...

[ivconic]

Let me explain my behavior and such attitude.
Someone may ask "why the hell bringing up from dead those old machines, while we progressed so far by now with numerous much more advanced technology in new machines?
Answer is simple.
Those old machines proved their quality and performances already.
The whole point about the metal detector is the end result, at the end of the day what you found on the field with it.
I don't care at all if the machine is high-tech, if it has this or that ... whether it spits out 1, 2 or 128 frequencies, serial or simultaneous ...
The only thing that interests me and what matters is; will this machine find something valuable at greater depths than before ...
Simple as that.

And CZ proved so far it is extra deep and extra accurate. Not only competitive but much better than hugh majority of todays top machines.
I sign this statement!

[Nandor]

Well it looks like that the crystal is a really exotic type.
Carl, could you please share some more information about your work? There is very little place to work with, I bet your design is fully SMD

Old machine does not mean its out of order . Nice pure analog signals and harmonics, no software that can go nuts.
I also think that 2 frequencies are enough, as you can see on the attachment the second harmonic is much weaker than the fundamental so the third is even weaker.
Many years ago you shared pictures of your CZ5 Ivconic, I have them on my CZ folder!

Sadly the CZ3D is no longer available on the Fisher site. So maybe it is not illegal anymore to share original schematic, if somebody has it.

Here is the LTspice model for the square wave oscillator of the CZ, I hope it's accurate enough, picture first.

CZoscillatorASC.rar

regards

[Nandor]

Almost forgot there is one more "exotic" component of the oscillator part, it is the little light bulb with a specific resistance of 17.3 ohms.
Here is a photo of the oscillator on the pcb. The little bulb on the left and the crystal on the right side.

[kt315]

we had discucced that the bulb (does a work of the) is the baretter. yours.

big thank again for the detailed manual and schematics to the guy sent me that on email for the archive. your help is fantastic.

[ivconic]

Yes, the bulb is sort of current stabilizer.

[Carl-NC]

It's a current limiter in case someone puts a dead short on the TX pins.

[ivconic]

In 1265, 1266... probably other models too; it has different role.
Is it the same type of bulb after all?
Anyway it is interesting solution.
What other type of bulbs can be used too?
Once i opened large speaker system and saw small 12v bulb put on crossover in series with the speaker.