another question........and odd occurance Tom.....

I just posted this on the Fisher forum at findmall. A little account of my experience in my backyard tonight. Have you experienced this before????

My Post:

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!

Had the exact problem a couple of months ago. New batteries had a problem. Swapped to ANOTHER set of (also) new batteries. Problem resolved. Several times... I reinstalled the 1st set of (bad) batteries,,,, and problem encountered again.

--- Brought the 'suspect' batteries home. Measured each AA battery with a DVM. Batteries all good with voltages being 1.676VDC, 1.677VDC, 1.676VDC and 1.606VDC. The new set that corrected the problem were old stock and voltages were nearly identical at 1.602VDC each. No problems with these batteries.

Sooooooooo,,,,,, I NEEDED an answer. I had a single-cell penlight flashlight. I tried several different batteries of varying voltages..... measuring 1.485VDC to 1.694VDC. Each time.... the flashlight was bright. Installed 'suspect' failed battery (the 1.606VDC battery) and the flashlight would NOT light.

Conclusion: The ONE defective battery had a nominal 'surface charge'..... BUT,,,, with a small load applied; it went 'flat' (dead)........ to a voltage of 0.303VDC and would not light the single-cell flashlight. Suspect battery could not handle a load.

Tom

Now see I would have said EMI or that I had bad "juju".

Bad batteries are the 'exception' ...... and QUITE a rare occurence.

I have bought batteries that were bad from the get go and remember just one has to be bad to affect the performance of the unit. I think Charles Garrett hit the nail on the head when he said many units are sent in for repair and the only problem is bad batteries so always carry an extra set lest a hunting trip be ruined even if they are new..

Very good post streak.. and good observation info...I have run across this with DC equipment..man lift units and always load test the Batts..I would suspect the micro circuitry in Detectors is more touchy to voltage drains..Tom thanks for the precise test and explanation.james