Excal Guru Technical Help Question

[slider66]

I have a question for you experts because this problem has me and my friend perplexed. Between the two of us we have 5 Excals. We have been using them for years and hunt with them at least 3 to 4 times a week. We beach and water hunt with them. We recently sent 4 Excal's to be serviced and I had one modified before we took a trip overseas. All four were serviced and I want to point out that Minelab always has done excellent work. I love their machines and have 5 myself. Here is what is going on and if you have seen this please let me know.

We have two excals that were serviced in the past and recently checked and serviced before our overseas trip. The two I am referring to have the exact same problem. As soon as we turn on either machine we get lots of chatter. We can setup all 5 machines that we have with the same settings and 3 will work perfect and two will have tons of chatter. When minelab checks them at their lab and field test them they work fine except that they are not near the ocean. Here are the settings we use.

Disc 1
Sens 7
Vol 1 to 3 oclock
Thres lowest hum possible
Disc mode

I am aware that the sensitivity can change depending on conditions. No matter what beach we go to and test both machines false constantly like there is EMI around. I took mine overseas hoping to use both of my coils and as soon as I turned it on I had the same problem in the dry sand and water. I had to stop using it and switch to my Equinox. I was happy I took 3 machines with me.

I know that there is a threshold pod on the mother board or at least I have been told there is one. My Excal sits in the closet with my new mod and two coils because of this chatter and falsing. My question is have you seen this? Do you have any suggestions on how to fix the problem? Both my friend and my detector have the exact same symptoms. Thanks in advance if you have any ideas.

 

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[OBN]

Magic word in your post is 2 coils, mods. So the machines that are doing this, both have the same mod? Inline coil connectors? Maybe a picture of?

Also were they sent to Minelabs PA service center? Neve knew minelab field tested there machines, only pressure tested as far as I know. Also who did the work on them as far as Mods? I hope not me..lol

And yes there is a threshold potentiometer. You can send me a PM if you want...

 

[slider66]

OBN only one has been modified. I’m going detecting today and will PM you tonight. Thanks for responding, Both Detectirs had the same problem before mine was modified.

 

[WaterWalker]

My 1000 with an Excal II coil, in-line connector and the old red Sword headset, started with the same symptom about two months ago. It is a bit hard on the ears, but does not seem to affect its operation at all.
But when I turn the volume up to full on, the chatter stops.
If you find a real "FIX" please post to save my hearing.
Happy New Year...

 

[dewcon4414]

Ive found the Xcals vary...... they seemed to be tuned different you notice it more using AM and switching back..... or being near others using an Xcal. Do they run poorly in PP mode? Once the coil enters the water EMI shouldnt be an issue from the coil. You might call Keith at Pa......they may have the answer or can retune um.

 

[cudamark]

I run mine at Disc 1, Sens auto or 10, Vol max on one machine because I have a volume control on the headphones and lower on the others to keep my ears from going deaf, Threshold toward the loud side. I find a louder threshold makes it steadier and less prone to false signals or "talking". I almost always run it in PP (all metal) I get an extra 2+ inches in depth that way, and it's much more stable than in Disc. I have a stock 8", 10", NEL 15", and a 15" WOT coil for the three Excals I have (two blue tubers and one 2). The bigger coils are a bit more prone to EMI and black sand chatter, especially in Disc. None of mine chatter when they're turned on, but, I don't turn them on in Disc either, only PP. Which model Excals do you have? Which coil(s)? Pin Point mods? Aftermarket headphones?

 

[slider66]

I run mine at Disc 1, Sens auto or 10, Vol max on one machine because I have a volume control on the headphones and lower on the others to keep my ears from going deaf, Threshold toward the loud side. I find a louder threshold makes it steadier and less prone to false signals or "talking". I almost always run it in PP (all metal) I get an extra 2+ inches in depth that way, and it's much more stable than in Disc. I have a stock 8", 10", NEL 15", and a 15" WOT coil for the three Excals I have (two blue tubers and one 2). The bigger coils are a bit more prone to EMI and black sand chatter, especially in Disc. None of mine chatter when they're turned on, but, I don't turn them on in Disc either, only PP. Which model Excals do you have? Which coil(s)? Pin Point mods? Aftermarket headphones?

I have two Excal II models. On the one that is giving me problems I have it modified done by Minelab in PA with a 10x12 SEF and 13 inch Detech coil. The Detech is brand new the SEF is a few years old but I never could use it because of the problems with the Excal. I believe the mother board is bad. It was worked on by another Minelab repair center in the past and returned to me with the same problem. The new MInelab repair center has been outstanding. Having said that, the Excal of my friend and mine still don't work after being serviced. I want to give credit to them because they really went out of their way to check them. They seem to work fine in Pennsylvania but when they get to the beach they go crazy. I hunt in pinpoint an disc depending on whether it is dry sand or wet or water. I like to hunt pinpoint i the wet sand and water for the same reasons better depth and stability. Having said that, my Excal with the 10 inch coin not modified works great. The other Excals my friend has work great except for the two that we have which were worked on my another Minelab repair facility. I would recommend the new repair facility in PA to anyone. They do great work and have a great turn around time. I just want to figure out what is wrong with the two Excals giving us falsing and chatter. I have a lot of money invested in a machine I can't use.

 

[bklein]

If they were mine I’d modify all with connectors to interchange coils. That would help identify a coil problem.
I’d also try swapping batteries around. If the issue is localized to a control board, look for pc trace corrosion or perhaps a weak capacitor. Like that big electrolytic cap. Try placing another across it to check. There are things that could be done to lessen sensitivity to EMI but this is something that changed so I’d keep looking for the source of the problem. Maybe try moving a noise source like an AM radio or whatever close to the coil, battery, or control pod and see if it helps differentiate one detector from another.
Umm do they perhaps have the pp mod?

 

[cudamark]

Sounds like it was something done by whoever did the mods......maybe the coil(s) themselves. How is your friend's machine set up? Same type of mods and coils?

 

[OBN]

Sounds like it was something done by whoever did the mods......maybe the coil(s) themselves. How is your friend's machine set up? Same type of mods and coils?

I think the (2) were falsing bad before they had the mods done from what I understand. At this point I think your best op would be do what you had said, send the video's to Minelab and share the complete story with them. I'm hoping you saved your receipts from both trips to the minelab repair centers.

I would volunteer to help but I had one a few years ago that did the same thing. Out of pitty for the guy I had him send it to me, I looked at it and with out doing major repair to the board I could see nothing broken or showing any signs of a issue. Was unable to fix....it worked (picked up targets) just that the falsing was so bad it would drive you nuts.

I've replace several coils on machine doing the same thing. But they do it no matter the location. Water damage to the coil. Also many years ago I put Bulgin inline connectors on a excalibur, worked great until you hit the salt water then it would go nuts. There are so many possibles....

And, VB MAX had the same issue on his friends and they said it was the coil. See if I can find the video, I believe yours is just like. If I remember correct the coil was bad in this video...



And the one I showed you..just like. And I did replace the coil on this one with no luck...

 

[slider66]

I watched both videos and that is exactly what both excals are doing. My friends Excalibur II has no mods and mine has the inline connector to use my brand new detech 13 inch coil and a SEF 10x12 coil. Mine has Chatter and falsing with either coil. My friends does the same thing as both video's posted by OBN. Constant chatter. No one could use these machines all day without going crazy. My SEF coil is wired correctly.

 

[slider66]

One other thing. No matter what beach we take the two excals to we have the same chatter problems.

 

[bklein]

In the videos you hear two behaviors - one with the whoop whoop whoop "issue" and another where the threshold takes the tone of the last target the coil hit.
I don't have a lot of experience with excals but I wonder what the preferred behavior really is/should be? I'd rather have a third behavior where the threshold takes a constant frequency tone that is not associated to the last target hit.
Regardless, it makes me think back to my electronic music design experiences. There may be a sample and hold capacitor that stores the voltage of the last target hit assigned by the processor. I could be mistaken - this could be done by a microcontroller and not in analog design - but if it is done in analog with this capacitor the capacitor has to be a low leakage type along with low leakage traces associated with it. There typically would be a ground ring around the signal side of the cap. If any corrosion occurs between the cap lead/pad and this ground ring the voltage leaks through it and it doesn't hold the tone frequency control voltage. If the leakage is to some higher AC current signal it could go random like you hear. The boards have a conformal coating that is meant to prevent such inter-trace leakage. But still, I'd look for a polycarbonate low leakage type cap somewhere and check the cleanliness of the board. Might be good to spray the board set with a contact/flux cleaner meant for electronics and see if it helps.
So is it true that if the last target tone isn't there in the threshold it has this random noise issue?

 

[RustyGold]

First thing I thought was a capacitor. Although it may not be related, years ago I was working on a digital guitar amp that just would not do clean in the clean (no distortion) channel setting. It always had a small amount of distortion.
I found some leaking capacitors on the circuit board and replaced them. That fixed the noise problem. Clean channel worked after that.
It may not be related though. Good luck!

 

[bklein]

One other thing, I've read where there is some similarity between Excal circuitry and Sovereign Elite. The Elite had threshold issues if the battery dropped below 12V. There is a voltage regulator that needs at least 12V to guarantee a solid 10V for board circuitry. So I'd advise temporarily replacing your battery with a lab power supply capable of 12-14V. But don't go above 14V as I've read there are components that may fry if over 14.xV. Start with the voltage like at 10V and raise it and see if the threshold gets stable at some point. Keep wires/jumpers to the detector short. Set your current limit (if you can) to something like 3-400mA so less risk of frying something if you do something wrong.
And on the caps, just a cap meter will not tell you enough. You need a fancier instrument that measures leakage, ESR, etc.
My excal battery packs are 11.1V lipoly. Wonder what you discover...

 

[cudamark]

Have you tried raising the threshold volume to see if it smooths out?

 

[slider66]

Have you tried raising the threshold volume to see if it smooths out?

Yes it goes crazy. Like I said one Excal has an inline cable mod. The other is a 10 inch coil. Both Excals have constant chatter or falsing no matter what beach we take them to.

 

[cudamark]

If it does the same thing everywhere, and with the coil up in the air, it needs to go into the shop for diagnosis.

 

[slider66]

If it does the same thing everywhere, and with the coil up in the air, it needs to go into the shop for diagnosis.

Yes both machines go crazy with the coil up in the air. I’m going to try and post a video later after I make it at the local beach

 

[slider66]

One other thing, I've read where there is some similarity between Excal circuitry and Sovereign Elite. The Elite had threshold issues if the battery dropped below 12V. There is a voltage regulator that needs at least 12V to guarantee a solid 10V for board circuitry. So I'd advise temporarily replacing your battery with a lab power supply capable of 12-14V. But don't go above 14V as I've read there are components that may fry if over 14.xV. Start with the voltage like at 10V and raise it and see if the threshold gets stable at some point. Keep wires/jumpers to the detector short. Set your current limit (if you can) to something like 3-400mA so less risk of frying something if you do something wrong.
And on the caps, just a cap meter will not tell you enough. You need a fancier instrument that measures leakage, ESR, etc.
My excal battery packs are 11.1V lipoly. Wonder what you discover...

Bklein and all of you who responded to my problem and questions. Thank you. Special thanks to OBN . I tried swapping out my Excal standard battery with my EB 3000 60 hour battery and it cleared up the problem. It's weird. My other Excal works just finevon the standard battery. I now have a kick butt modified Excalibur with a 10/12 SEF and the Detech 13 inch. The 13 is an awesome addition to my detector. Thanks again. Happy Hunting.