Overvoltage protection F70

[Lowbatts]

Put four new Rayovacs in my F70, walked over to the field and turned it on. Display flashed, got some fast intermittent buzzing in the headphones for about 5 seconds, then all dead.

Had a DMM with me and since I couldn't do anything else on the spot but needed to hunt that site at that time, decided to check the batts. They were each a bit higher than normal, reading >1.8V each for a total of >7V.

Reseated them and tried again, same results. Replaced two with run down batts, one on each side and the unit worked fine.

Went back to copper tops and it's all good again. Any answers on where the OV protection is set on this machine? Probably best to check your batt values if you change makes first.

 

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[Sandman]

Most detectors are made to spec. but mistakes can be made in detectors and batteries too. Checking them before inserting them is a wise move. I've also had new batteries from a package that were low too.

 

[Streak!]

that seems a bit odd. Metal detectors have voltage regulators in them like most electronic equipment. Doent seem like it wouldnt be able to handle an extra volt or two. also.......................those must have been some GREAT batteries! I've never had an AA read higher than 1.5. (rechargeables are usually a tad lower at 1.2 Incidentally.......those rayovacs are nothing more than Energizers relabeled. Exact same battery. I have had a number of instances where batteries have caused problems..but never with over voltage. did they ALL read 1.8??

Put four new Rayovacs in my F70, walked over to the field and turned it on. Display flashed, got some fast intermittent buzzing in the headphones for about 5 seconds, then all dead.

Had a DMM with me and since I couldn't do anything else on the spot but needed to hunt that site at that time, decided to check the batts. They were each a bit higher than normal, reading >1.8V each for a total of >7V.

Reseated them and tried again, same results. Replaced two with run down batts, one on each side and the unit worked fine.

Went back to copper tops and it's all good again. Any answers on where the OV protection is set on this machine? Probably best to check your batt values if you change makes first.

 

[Lowbatts]

Thanks guys.

Streak, these were part of a 12 pack and I had used the other 8 up already, no problem so I never bothered to check them prior to use. I'm on a set of copper tops right now and they've never failed me.

Yes, part of my past life was doing a lot of parametric evaluation on those glorified garage door openers called cell phones. I remember doing a first-run evaluation on a new product from the Flensburg, Germany plant that took double A's.

First thing to check is turn-on, right? The German's, in their infinite wisdom and precision-minded perfection had used 6V regulators for a unit that was to use 4 double A's. The things never power-cycled or finished the POST. They just shut down at mid-start-up. So we ordered a HOARD of AA's from all kinds of MFR's. A lot of them read very near 2V.

Since my F70 seemed to be doing the same thing, that drove me to check the batteries. Changing banks with lower-powered batts worked with these high V batts, but I figured they'd serve me better in a flashlight for now. Not too many flashlights have V+ regulator in them, that I know of.