Garrett Ace Coil problem

[nalag46]

Has anyone experienced coil "falsing" with the new Garrett open coils. Both the DD and concentric?
Over the past two years I have had two 9X6 "sounding off" with no metal presence and with both, coil static above ground and with swing motion close to it. They still respond when metal is passed under and above coils.
Same thing happening with a larger 12" DD coil on an Ace 250.
I have measured the resistance of a good 9X6" at 4.2 ohm TX and 15.9 ohm RX, against the "falsing" one at 5.1 ohm TX and 33.4 ohm RX and similarly with the other coils too.
All the coils have been working fine to start off with, so why the resistance change on well and solid built coil frames and is it possible to do anything about it?
Return to manufacturer is not an option as all of them are out of warranty.

[golfnut]

Im not sure these have changed? What were they before??

In the back of my mind, so info may be sketchy at best, here may be 2 types of coil for these and latter ones a bit diffeerent construction.

The Tx is BiFilar I think as if you snap a coil probe right around the Tx there in no Output - from my experiments

[nalag46]

The two 9x6" coils must have been the same from new, since I had an Ace 150 and a 250 and I used two swap the coils round without any difference whatsoever.
One of these two coils has now the higher resistance reading I mentioned above, and hence lots of false sounds, while the other one is still working perfectly well on the two machines.
I had the same problem last year with a 12" DD as used now on the Ace350. That coil worked very well on all the machines but I sold it as faulty because I could not tell the difference
between good and bad targets as it was sounding off all the time.

[kt315]

be cause you measure the resistances while you must see the inductivity. the R does nothing. garrett coils have a pot inside on RX that tunes the balance
and this is why your measured R may be variating in the value.

[nalag46]

I understand that but my problem is still not clear. The two coils were working fine. Nothing has been changed or altered inside the control box but one of the coils is emitting all sorts of noises that makes it impossible
to detect with so something has happened to the coil windings or other components inside the casing?
If I try now to retune the "noisy" coil by adjusting the pot and assuming that makes any difference, what will the "good" coil be like afterwards?

[kt315]

not, you can not adjusting the pot be cause the coil is epoxed. no access.
try to change a cable.
http://www.findmall.com/read.php?22,2162307
if this is not help search the coil looking microcracks in epoxy. you will need in a magnifier zoom glass x3-x6 for this job.

[nalag46]

Garrett coil problem

I have a shallow dent on the underside of the coil end with a small amount of resin worn off. It is just superficial and the coil was working well like that.
Could this be the reason for the signal falsing?

[kt315]

may be reason. but only if you touch by the coil something wet. at dry ground without grass and leaf has not be the problem.
write your hunting conditions -
- mainly beach of sea
- field with neitral ground
- lake beach
OR???

[CAS]

If the housing is damaged, moisture may have entered the coil. This can cause corrosion and noisy joints within the coil circuit. This may be the issue by looking at the photo you posted.

[kt315]

no answer as always. sea water is BEST CONDUCTOR. if soil water moisture went through the cracks electrolize process can begin.
you will get a good conductivity between the e-static graphite layer and the winding wire, the coil could be ripped.