I "rediscovered" something interesting tonight...

[Streak!]

I thought I'd post it in case someone had a similar problem..
I had my F70 out in the backyard tonight........and it seemed to have a severe case of the heebiejeebies. Rang true on the targets in my test garden.....but was VERY noisey......with the ID's jumping all over the place.............. you could just hold it steady three feet of the ground.......and it chattered constantly.
I ran through all the usual possible culprits...........
Changed the freqs.....one at a time........NO difference. Backed the sens WAY down....and went negative with the threshold........ NO difference. Switched from De to SL speed. NO difference. Tried another concentric........AND the BIG DD.....NO difference. Even reset it to factory settings......and again......no discernable difference. Well.....I'm not one to give up......and tend to go through things methodically....till something shows itself. I even went as far as to disconnect the coil....and it was STILL there............telling me it WASNT RF interference......but internal circut noise of some sort.
Well I had NO other options.............and though the batteries were virtually new...... I thought ...."what the Heck".....and put in a new set, (different Brand).......Took it outside....and fired it up.

It made maybe two little chattery sounds.......then went dead slient. I thought I'd broken it!!! I didnt though....and a few swings of the coil over the garden confirmed it was indeed working properly......BUT without the noise.
I tested the batts in question...........but didnt find anything obvious wrong with them. They looked good....and voltage was the same on all 4 of them.
Now I wont disclose the brand of the batteries I took out...or the brand I put in (Actually...neither is the brand I USUALLY use), as it may have been some sort of fluke...but the batteries were positively the source of the problem. (No it wasnt just a case of a bad connection, as I had the batts out probably three times looking at them to be sure they were making good contact... AND it started acting up again when I put the old ones back in)) it reminded me of my XLT years ago when I used it on the salt beach a lot. It positively liked certain batteries on the beach better than others....and always ran quieter and smoother when I used a particular brand of Alkalines. Ran VERY noisey with the nicad pack that came with it. I discovered that by accident one day....and always made sure I had the right batteries after that when I beach hunted.
I guess the lession here is to not necessarily blame the machine right away................because the problem can in fact be due to something else!! Streak!

 

[RonNH]

Thanks, Streak. That info might save someone from sending their machine in to the shop. I use a Bullseye probe and 2 weeks agoit seemed sluggish, so I changed the battery and still nothing. I took 'er apart looking for a loose connection (I'm stubborn and a thrifty Yankee), nothing seemed amiss. So with the battery cover off, I pushed in on the battery.... bingo...it worked. I found a piece of foam and padded the cover and it's been fine. In this case, it wasn't the battery, it was the connection.

It pays to do some fiddling and probing and once in a while, the problem is something real simple. Ron

 

[Bill Ladd]

really stressed batteries. Things like being sure to use alkalines, not to mix brands, etc......these are things I always did in the past with other detectors. I think this was addressed before but are NiMh recharageables OK of the newer Fisher's?
HH,
Bill

 

[Rick(ND)]

If you use a multi meter the voltage will show good as there is no load on the battery so it will show good. Now some of the better battery tester will put a load on it and that is where you will see it is bad. I just got a Minelab X-Terra 50 with complaint of shutting down and some of the pixels were not working correctly and was told the batteries were checked and they were good, so before I sent it in I put in new batteries for my customer and it worked perfectly and when I checked the old batteries I found one that when I shorted it out with a paper clip and tested it right away is was low and then started to climb. after closer look at that battery I seen where it was also getting a little white looking from leaking. I always try new batteries or recharge them before I send them in just to be sure it is not the problem.

 

[jim tn]

I've had that same situation on two occasions over the past few months. I usually use the coppertop's with never a problem, but when I had my wife pick me up some batteries some time back she picked up another brand and those have been the problem ones. That is a good reminder for everyone, Streak. HH jim tn

 

[ziphius]

I have been using rechargable NiMH batteries with the F-75 for some months now. They work fine. - Jim

 

[Doug[Manila]]

n/t

 

[SRLance]

I had taped the ends of the batteries for the flight home. Put batteries back in and detector just was not working right. Found out the tape glue had adhered to the terminals and partly blocked the connections.

 

[wingnut]

A similar situation can occur if the coil cable connection is loose or dirty or corroded. Like mine was. It was really noisy then it got really quiet.