CS6PI

[porkluvr]

If you've installed a 'faster' crystal you probably need to build a faster coil.
Re-read #28 above and that should give you an idea.

Leave those darn pots alone, but I suppose that my pots advice is already too late.

[geroms]

Hi porkluvr
Thank you for the information.

Good news I did not change any settings jars)
In the Air performance is good, but it is very sensitive to the ground effects when I use it on the ground, I have much lower power, then I lose all the gain.
I almost finished copying all electronic schematic but my electronics knowledge does not allow me to understand everything and to isolate the various functions. If you could help me to understand, especially the part that handles ground effects.
On the board they missing one diode on the IMPUT of LP2950/TO92 regulator but it may be normal?
I have one oscilloscope, could you tell me how to check the signal, it is on the coil?
For example, if I replace the quartz 4Mz a 8Mz is that the delay also decreases by 2, what are the approximate values for a new coil?

[porkluvr]

Hi porkluvr
Thank you for the information.

Good news I did not change any settings jars)
In the Air performance is good, but it is very sensitive to the ground effects when I use it on the ground, I have much lower power, then I lose all the gain.
I almost finished copying all electronic schematic but my electronics knowledge does not allow me to understand everything and to isolate the various functions. If you could help me to understand, especially the part that handles ground effects.
On the board they missing one diode on the IMPUT of LP2950/TO92 regulator but it may be normal?
I have one oscilloscope, could you tell me how to check the signal, it is on the coil?
For example, if I replace the quartz 4Mz a 8Mz is that the delay also decreases by 2, what are the approximate values for a new coil?

I do not know your CS4 circuit, only what I saw from the photos you posted... I can tell it is micro (uC) controlled, but I know next to nothing in the way of specifics...

I don't even know what your front panel controls are. I am leery of your "upgrading" the crystal to 2X the original and expecting everything to work OK. It may, or it may not work. I think you should not be so ambitious. Try 1.5x first and see if that can work.

BUT

Fast coils are not extremely easy to build and unless you have a fast enough coil, simply increasing operating frequency is a bad thing to do.

As far as the "ground effect" you mention, I suspect that all you can do at this point is build a faster coil, re-install the original current limiting resistor, and hope those things take care of the "ground effect" problem. Be aware that the resistor in series with the coil serves two purposes: keeping your output transistor from overheating, and allowing faster flyback settling.

You need at least a dual trace scope to do any serious PI hacking. A single trace scope is not adequate. If you do not have a suitable scope, there is little I can do to help you. I suggest you not be thinking about hacking your machine unless your scope has at least two channels.

Regardless, this is a CS6 thread. If you have more to say and want to continue to ask for help, I think it would be good etiquette to take the discussion and either start a new thread or else add to what you started last week. Give this thread back to the CS6.

[geroms]

The others post on the CS4PI are transferred here
http://www.geotech1.com/forums/showt...288#post165288

[charleskerr]

Hi All
I've had a C6PI for quite a number of years. Quite sensitive. A few years ago I posted it back to the UK for CScope to service and align. Unfortunately it's started misbehaving and I was wondering if anyone has the alignment procedure. I have all the equipment needed, just the procedure. (I think I'll also try some mods on it!)
Thanks
Charles

[geroms]

I'm looking for CS6PI LTspice shematic , thanks

[charleskerr]

Hi I've have a CS6PI for about 10 years now, great machine.

I've done some mods to it but ended up blowing some of the components due to connecting it up in reverse ,DUH! I've replaced the components and would like to know if anyone have the calibration procedure. I have all the equipment at my disposal but just need to know how to set it up.

Thanks

Charles

[kt315]

Charles, can you give components' part list, pics of desoldered pcb anything that do you post to have some sense?

[Reg]

Hi Charles,

If I remember correctly there are only 2 pots to adjust, RV1 and RV2. RV1 sets the 0v out of the preamp. So, using a scope look at the output of the preamp and adjust the voltage for 0V once the voltage levels off. It is best to set this 0V with the lowest or most sensitive setting of the scope.

Now, RV2 sets the level that shuts off the negative half of the signal out of the high pass filter stage. You can start by adjusting RV 2 for 0V out of the amp it is connected to which I believe is U4b. You can connect to TP 4 for this adjustment. Also, to reduce noise you can remove the jumper on the Test Setup.

Once the 0V is adjusted, then replace the jumper on the TEST and then carefully adjust RV 2 until the detector seems to go quiet much like when the test connector was removed. Now, replace the TEST jumper and measure TP 4 again. It should be less than 5mv. If the voltage is 4mv then adjust RV 2 for 1 mv less or 3 mv.

RV 2 sets the trigger level at which the negative half of the signal is shut off by the FET across the autotune resistor. If you leave the output of the opamp at 0V. it will work fine but you may hear a slight chirp or signal once the coil passes the target.

Without the negative half of the a/c signal that happens when the signal goes through the capacitor, you would hear a wee/woo signal instead of the normal wee response.

Once RV1 and RV2 are adjusted, the detector should work fine.

Reg

[charleskerr]

Hi
Many thanks for your help. My board is the one with the 3 pots. The first adjusts the off set voltage from the input op-amp, the second seems to balance the inverting / non-inverting inputs to the second op-amp and the 3rd adjusts the gain of the second half of u4. The strange thing is that when I measure the off-set from the pre-amp, It can go from 2.4v down to min of 0.6v, I can't get it to 0v, and is heavily influenced by the freq pot as well. If I scope the outputs of the 4017, I am not getting clean pulses at different frequency's. (I have a 200Mhz dual chan scope). If I remove the 3 1N4148's, (which I have already replaced with new) I get clean pulses. (at different frequency's, some outputs are just noise, no pulse) The input to the 4017 is a variable high pulse adjustable between 17us and 50us and the low pulse is 9us. I have also stripped and cleaned the 2 front panel pots. Is it also right that my coil pulse can vary between 80v and 130v depending on the frequency?
I am working from the following schematic which is confusing regarding the 12v and GND. It also does not include the second balancing pot which on my board is on pins 10 / 11 of the 4017 driving the 2 fets.

[kt315]

Charles, people go in forum for THE INFORMATION. you ignored my request. WHY? you went in forum to fix only your problem and come out while people wait info from you.
this is very mutually and two sided.

Reg, if you have info that absent on the DVD please add it by your info. I promise you everybody will get DVD with your info and info from everybody.

Regards

[kt315]

circuit diagram of CS6PI. Eric Foster's design.

[Reg]

Hi kt315,

I am not familiar with the DVD you mentioned, so I don't know if I have information that is not on it. As such, I can't answer your question.

Sorry. CAn you tell me where I can access the DVD you mentioned?

Reg

[kt315]

Reg, I do not ask to pay for shipping of DVD, it is free for but only in case anyone gives useful additional info - desoldered board pics, full part list, may be some sketches,
may be one has company schematic, that will be nice, etc.
I also do not want share files from forum again in the forum, in 10th time and in 100th time. because that is nonsense and very un-productive way. everybody who wants will get all info one time outright all-in-one. this way will get up of any begginer at the level of a prepared guru in metal detecting electronics in my hubble opinion.

files on CS6PI on the time

[Reg]

Hi Charles,

I am not familiar with the board version you mentioned, but I will try to answer your questions and respond to your concerns.

First, are you measuring the output of the preamp with your scope and not with a meter? What opamp is in your preamp stage? Eric's early designs had a 709 and later designs used a NE5534. If using the NE5534 be careful, some are better (faster) than others. Some TI versions are not as fast as some Philips types.

The third pot, if I understand you correctly, does balance the signal between the first and second sample. The reason is to minimize any false signal that is the result of the lack of equal signals. This false signal would be because of the earth field effect portion of the signal not being equal. Too much droop in the rise time of the preamp signal can also cause this false signal as well as poor sensitivity.

Now, have you replaced the 4017? These fail easily. If you replace it I recommend you install a socket to make changing it easier in the future.

I am trying to figure out what you are saying and which signal you are referring to when you discuss "signals".

The 4017 is driven by pulses from a 555 timer on which the frequency control adjusts the timer (which sets the pulse frequency). If everything is normal, this pulse should be continuous regardless of the frequency control setting.

When you refer to the three diodes I am assuming you are referring the ones connected to the 4017 which drive the pulse width. The diodes are nothing more than a primitive "or" gate, meaning the output of the diodes is high when any one of the diode input signals is high. This makes the first three pulses out of the 4017 the pulse on time.

If you look at the pulse drive signal at the gate of the mosfet ird113, you should see a relatively square wave. The critical part would be the shutoff of the mosfet and should be quite fast, maybe a microsecond or two at max.

As for your pulse spike, this can vary with the pulse frequency. What FET are you using? The IRD113 clamps at 80V I think? Yes, the shorter the pulse on time, the less of a spike you might get. Remember, the on time is short and the length of the on time determines the maximum current generated in the coil. The maximum current will determine spike height.

You should get signals out of the 4017 throughout the frequency range. If you don't, check the input signal from the 555 time to make sure it is working. If it isn't at some position of the frequency control, then the pot may be bad.

Did you build your own coil? If so, what did you use for wire and shielding? Can you post a pic of the output of the preamp? You should have a fast rise time and the signal should level off at 0V by the time you sample. If the signal is still drooping, it indicates you may have too much shielding.

This should get you started to a solution, I hope.

Reg