Newbie to F75 SE - Posible coil problems.

[Ringmoney]

Hi I recently purchasd a F75 Se off ebay and all looked ok till I went to use it. I brought it to a site that has some nasty EMI to see how it reacted. I put the 11" on it and off I went. To start off I done the uasual frequency check and set the unit at disc 5 and all Emi dissapeared in air with the sencitivity set at 70 in boost mode, all ok so far till I went to ground ballance the machine. I could not get the fast grab to work at all and the unit was very eratic while swinging. I could not get the unit to stabilise at all no matter what I tried to do. I tried all sorts of disk and sensitivity settings with no luck. I know the ground is not to mineralised as it measures at around 85 on my XP deus.

I returned home and convinced there was somthing wrong with the Fisher, I tried out the machine in my back gardin with both 11" and 5" coils. Started off with the 5" and it ground balanced at 52 and it seamed to work well in all modes. When I tried to use the 11" it ground balanced at now but at a value of 98 but it still was eratic. My question is, do you think the 11" is faulty, is it normal to have such a big difference in ground balance values between the two coils?

 

[sprchng]

90% of the ground I detect GBs above 85 and changes rapidly , like 15 points in 20'. My experience is that the 75 does not like sensitivities above 40 in ground that balances that high unless you like to listen to constant chatter and high tone falsing. DP tones are unusable. Try 2f if you insist on that high of a sensitivity reading and resign yourself to a lot of checking for repeatability. The 75 also does not track the ground , so fast grab often to maintain some level of ground nuetralization. It's possible you have a bad coil as a I think FT's quality control is poor and they have had trouble before but your 98 GB number sounds like you had something under the coil while balancing. I find I can run substantially higher sens levels when the ground GBs under about 83.

If you have a Deus I must assume you only bought the 75 for a backup and the price must have been too good to refuse

 

[D&P-OR]

The 11" coil sounds "suspect" to me.-----If, as you say, (and assuming) you have tried all the other checks---the next thing I would do is try another 11" coil--(in the same spot-same everything)--if it takes care of the problem---that's your answer, a bad coil.----If not, you probably have a problem with the detector itself.

 

[Ringmoney]

Now I am a bit confused, I always thought that the higher the ground balance value the less mineralisation there is in the soil. Am I wrong? If I am not wrong, the higher the the ground balance value the easier a detector can cope with the ground, from what you are saying it is the other way around, and the F75 does better on medium mineralisation than on light mineralisation.

Ps i lost all faith in the deus for deeper pasture work, they are great in iron invested sites, but on cleaner pasture they just do not have the depth.

 

[MarkCZ]

High amounts of knowing EMI,
Running in boast mode,
Using the 11" DD coil,
equals =
The detector became to sensitive to the ground and actually starts to react to everything that in the ground. EMI isn't EMI different types of it produces different effects. I can setup my Tejon and run it in my front yard and all is well! until around 6:00pm and its just like somebody switched on an EMI switch, it will be fine in the air, but put the coil to the ground and the ground seems to be sprinkled will HOT targets, its so bad that the first few time it happened I thought the detector was broke. My other detector reacts to the EMI with the coil in the air.

The F75 and that large and boost mode is just a wrong combination for areas of bad EMI.
Turn off the boast mode,
use a smaller coil and you'll find you'll do better.

The main purpose of the boost mode is for areas of taller grass where you can't get the coil close to the ground, yell, its deeper, but if you can get the coil close enough to the ground then it most cases it will go pretty deep.

The F75 can have a huge learning curve, and getting it setup for different areas will be a big part of that learning curve.

I'm going to say that you were running to hot of settings and to large of a coil.

Also, the ground balance numbers of the 11" DD and any smaller coil will be vastly different.

Mark

 

[Ringmoney]

Now before anything else is said, I started off at Disc 5 Sens 65 and in boost mode, but I tried all settings and modes. Je and boost was unusable in all settings even with sens as low as 30. It was most stable in de at disc 11/12 and at lower sensitivities but it still was unstable.

 

[jacco]

Have you tried the factory reset, to make sure some unseen setting is bothering you?

Pull trigger and push red button while switching on the detector.

 

[shooter]

Had the same problem with my F75 LTD, totally erratic op. with the 11" coil, could not get it to do anything but EMI noise. changed my coil to the 5" ( which is like the old style coil design) and the 75 worked perfectly, I had used it in the after heavy rain and it had gotten water in it, talked to felix and they said the coil was bad , lok at the coil where the wire goes in if it's not sealed up then that mostly could be the problem, my new one was sealed and I use it in the water and never had that problem again,Fisher changed the way they seal the newer coils. You might want to call Felix about it maybe they can help you out on a manuf. error. I know it was a common problem.

 

[Ringmoney]

It was the very first thing I done.

 

[Ringmoney]

When you say sealed up what do you mean. Mine has a rubber fitting as it goes into the coil but I cant see and other evidence of any other sealet used.

 

[Ringmoney]

I just went out to an area that I know has no EMI problems to try out the two coils.

With the 5" it again ground alanced at 51/52. It seamed to work well, in boost mode I was able to raise the sensitivity to the high 80's and disc as low as 1 with very little falsing.

With the 11" I could only use the de mode with disc around 12 and sens at 30 before falsing was bearable.

So my thinking is that the 11" coil must be at fault, the unit is just under 3 years old and if you look at the coil it look as if it was never used, not a scratch on coil or cover. Prehaps it never worked from new. I have a detech coil on the way so hopefully by using it will solve the problem.

 

[sprchng]

I just went out to an area that I know has no EMI problems to try out the two coils.

With the 5" it again ground alanced at 51/52. It seamed to work well, in boost mode I was able to raise the sensitivity to the high 80's and disc as low as 1 with very little falsing.

With the 11" I could only use the de mode with disc around 12 and sens at 30 before falsing was bearable.

So my thinking is that the 11" coil must be at fault, the unit is just under 3 years old and if you look at the coil it look as if it was never used, not a scratch on coil or cover. Prehaps it never worked from new. I have a detech coil on the way so hopefully by using it will solve the problem.

What did that ground balance at with the 11" coil?
What you are descibing with the 11" is typical of what I find in ground that balances say 88 to 92 -- and this machine was tested and attested to be "right" by Fisher techs in El Paso earlier this year

 

[Ringmoney]

Sory I omitted that, it balanced ain the 97/98 area. I am in contact with fisher at the moment and so far they think that 97/98 is very high.

 

[Ringmoney]

Out in the gardin again with both coils. DE mode Disc. 5 and sens 50

5" Fast grabed at 52 and when lowering the coil in pinpoint I ge neither a negitive or positive response and it ran smooth.
11" Fast grabed at 98 and got a positive response when lowering the coil, it ran totaly crazy. Manual GB'ed at 80 with no response when coil was lowered, It ran a lttle better but still had a lot of falsing.

 

[shooter]

Here's some pic's of my 11" coil, my org. coil didn't have that sealant around that cover piece and water had gotten in and they replaced it. All the new have the are sealed this way. Yours could have been that way from the previous owner.

 

[Ringmoney]

Cheers for that, I see what you mean now, mine does not look like that at all.

 

[Steve O]

I had 2 ----11" coils go bad. The second one went crazy after swinging it in heavy dew. Sent it back and they sealed it better. The first one they replaced. Now I'm leery of getting near moisture with this coil.
It's an awesome coil though.

 

[markg]

I've had the same thing happen at two different locations. Try a few more locations. Suggestions: Switch to all metal mode and find the cleanest place you can, then do a ground grab. make sure the machine is in DE mode and sensitivity is at about 60 when you do this.

 

[Ringmoney]

Cheers for all the replies lads, I am convinced the coil is faulty, went out today to a new location free from any emi. Fast grab kept getting values in the high 90's and I know my soil is nothing like that over this part of the world it should be in around 50. I manual ground balanced the machine in many spots with values in the 50's, ran it in de mode with disc at 15 and sens at 30 and it ran totaly eratic. Ever blade of grass the coil hit produced false signals, I even put a

 

[sprchng]

This is going to sound really dumb , but,,,,,,,you haven't said anything about a coil cover. Sounds like the coil is bad as those GB numbers are off the track but if you have a cover on that coil and something under it---just saying. Fisher doesn't sell their detectors with covers and the one I had too buy for my 11" is an absolute bitch to get off for cleaning. Is it possible you have a cover on there that has never been removed an has a ton of black sand under it?