My detector saga just took a very interesting turn.

An experienced operator told me about three 4500's he has seen now that when they had their coil connector socket tightened up, they performed better, quieter, less 'falsing', and ground balanced better.

Intrigued, I took a look. My socket did indeed 'nip' up about 1/4 turn. This now means the locating tooth on the socket has now moved, but it's of no consequence.

Now to the findings... We just got back from a weekend out testing it. Friday afternoon was pretty good, and the machine was running very well. A few EMI spikes but nothing out of the ordinary. I'd backed off Signal a bit from JP's recommended 19 to around 14 or so, and brought Target Volume down a bit too, and it was fairly stable. This was with NORMAL audio! Before, I was forced to run Quiet audio.

Saturday, I did a bit of a side by side test with a skilled operator from this forum on a small lead ball. My machine seems noisier than his in Normal timings and Sens Extra, BUT - I was running an 18.5 GSM and he was running a 17" NF so it wasn't really a fair test. In Enhance though, both were on a par and as quiet as each other.

I went out after that with my 14" NF, initially in Sens Extra, but plagued a bit by ground noises, I went to Enhance. But, running in Enhance, I had a gain of 10, and Normal audio again and the machine was quiet as a mouse. In fact I thought someone had pulled a fast one at one point and flipped my Coil switch to Cancel, I had to check, as it really was that quiet. I found myself even putting my pick over the coil now and again to check it was ok. I have never had to do this before. Apart from the heat which was absolutely stifling, the machine was actually a pleasure to use. It really pinged nicely on the lead balls I found (no Gold sadly), and with the quieter threshold, they 'stood out' a lot better than they normally do.

Never before have I been able to run a gain of 10, in Normal audio, and have a threshold that quiet. There wasn't too much Stabiliser either... I was in V Slow motion throughout, as I normally am, and have no qualms with that.

I'm convinced tightening the socket has worked wonders. Although it was tight enough to hold the coil plug in, I'm surprised it 'nipped up' further as much as it did. I've also been wondering how something like that could be so befeficial... read on...

My thoughts are it's not so much to do with sealing a gap between the socket and fascia panel, but it's putting a gentle twist into the wires behind the socket. For those that aren't already aware, twisting signal wires is an age old technique to set up a cancellation field between adjacent wires to reduce interference. Telephone line twisted pair is a classic example. Some may know of my previous work and the missile systems I worked on in the UK, where all separate dressed wiring inside the missile for DC, signal, and pyro igniter lines was TWISTED (and shielded). We didn't just twist it for fun! It was for immunity to stray RF, EMI, cross-coupling, and coping with high density electronic warfare environments like enemy jammers etc. Twisting uses more wire, and hence more weight for a given length, but it works. Telephone companies wouldn't use more cable at greater expense if it didn't work...

The experienced operator who originally brought this socket to my knowledge has since opened his GPX4500 detector for a look, and seen the twist now introduced to the wiring, and concurs with my theory about the twist cancelling some noise. It's now like a different machine. And it ground balances very fast down to no residual 'waveriness' too - and it never did that before.

However, a word of caution - if you try twisting this socket tighter, don't go too far. I'm not sure how slack the wires inside are in relation to being able to take a twist.

You read it here first...

Regards,
Rob

great news Rob! hopefully the gold will start flowing now and the confidence in the machine too.

He's helped me a fair amount too out there

Good News Rob,

It just shows that there is always a different twist to every story- he he.

Rob, I'm so glad you are getting satisfaction from your 4500 at last, It's a wonder Minelab isn't aware of this problem, maybe you should send them an email. All the besy, Bob

Hey Rob, would you say that it was a twist of fate, or a giant leap for mankind Seriously though I am glad your machine is finally working OK and I hope it stays that way for you.

cheers dave

Now we CAN go to TIB in april Rob.....

Word has it, that at a coiltek training day (saterday) a noisey new 4500 was fixed the same way infront of the instuctor/group, much to thier suprise.
Regards

Not sure about the theory behind this latest TWIST, but who cares? If it has fixed the problem then it's all good in my book. Maybe mine and a lot of other peoples were twisted from factory? Anyway it is all good news and now we can get on with finding some gold rather than becoming all bitter and twisted about our detectors.

JP

In my experience as a design engineer with the kit I've worked on, wiring has an awful lot to answer for...

Building a working board is one thing; interconnects are something else entirely.

From the evidence so far, putting a gentle twist into these wires does exactly as time-proven electrical theory says it does.

It would be very easy for the wiring from this socket to the board to be slightly different in EVERY detector, depending on how the sub-contracted assembler (in Korea? China?) soldered it up. Also, who's to say the wire used could be a different gauge or length, or whatever they had in stock at the time? As I mentioned, wiring is sadly always the neglected factor.

Will be interested if Coiltek feed back their observations on the 'right there in front of their eyes' fix to Minelab. I hope they listen.

Regards,
Rob

Hi All,

Isn't it amazing that such a simple thing like a twist in a wiring circuit or loom can be the cure for the frustration that Rob has no doubt experienced??? It makes you wonder just how many other problems that some of us have experienced in our sometimes very intricate and finiky machines have been caused by something that has such a simple sounding cure.

On the other hand when someone with Rob's obvious experience in electronics can be fooled by the simplicity of such faults, it is quite understanable how the everyday detectorist can be confused and so frustrated when nothing seems to cure a faulty new machine. I'll bet that from now on every suspect 4500 that plays up will recieve a check on that suspect connector. Lets hope that Minelab can learn from this and perhaps make this a part of their pre-delivery check on new machines or perhaps even devise a method of electronically testing this area of the machines circuitry when such a complaint is reported.

Rob, you are no doubt pleased that you have stuck to your guns knowing something was not right and now even more satisfactorily, you have fixed it yourself but you have also generously shared your find and the information of it's cure with everyone else including Minelab, well done.

I have a few spots in mind

Regards,
Rob

hi Rob, my 4500 is at minelab at the moment for exactly that reason, so rang kevin in the repairs department this morning to pass on this info, he tells me that yes everything uu said is correct and he will bring this to the notice of the ones higher up the chain, so lets see if this now becomes standard practice for minelab(and hopefully put a twist in my wires) regards, gary

As a complete aside Rob I think you have answered something I've wondered for some time. All or almost all hi end stereo speaker wire is platted [twisted] or weaved
these days, I've wondered why and I think you have resolved it for me. Now I'm tempted to take the front end plate of my 4500 to see if the wires have a twist in them
but just a bit worried about warranty issues arising from such an action. I did take the coil lead out of the plug and discovered the nut holding the connector is only finger tight
so I guess I should nip it up a bit and hope it also improves my machines performance.
Cheer Rob.

I'm glad Minelab are listening. Just remember you heard it here first, on the leading Australian detecting forum

And RobP, be careful taking the front off. Don't mash the screw heads - they would be a warranty loss give-away!

I didn't have to take the front off to do my socket incidentally, I just twisted it from the outside. I didn't twist too far as I have no idea how much slack there is inside. If anyone has taken one apart and has pics, would be interested to see.

Regards,
Rob

Let's twist again... like we did last summer... Oh hang on, that was actually last winter!!!

Well Done Rob!

Good stuff Rob, persitance pays again eh!

and me? yep I was one of the doubters

Regards, JK.

Rob, Congratulations on sticking to your guns and finally solving the problem.

Minelab plug connections. Always had problems with them and the problems often won't show up when they fire up the machines on the slab in the MInelab maintenance dept. The biggest weakness of the machines i have had has always been the back (and occassionally the front) plug connection. The back lead flaps around as you detect and effects the plug, actually twisting the socket back and forth a minute amount. This causes wire connection problems in the socket as well as in the plug on the end of the lead. Had to put a few new plugs on the end of curley leads over the years.

Brothers old extreme mucked up, was opened up and the wires had worked loose on the inside of the socket and were just connected. This was caused from just using the machine and the vibration cord flapping i guess.

Would be nice if the Minelab connections and cord reinforcing at the connections (that get a flogging from continual flapping cords and tapping) were high quality ones (designed bomb proof) rather then the $2 each variety.

Rant aside, looking forward to detecting somewhere out there with you and J.

Duck

Hi robp, don't take the front panel off as there is no length in the wiring to really view inside. front panel, board and rear panel are slid into the box as one unit from the rear.
Regards