zinc pennies kind of broken audio?

[muddyrock]

I just got my AT-Max and during an air test (Quarter, nickle dime and penny) all went well except the penny? Date on the penny (1999) gave a solid 74/75 vdi but the audio was almost broken and had like a blip to it. The other coins where nice and clear. I then looked through some more pennies and got a 1975 penny which gave me nice clear audio and pretty much a solid 80 VDI.

I was using the zero mode with disc at 38 and sensitivity 2 bars from full. I guess what I am asking is, is this normal and if so why is the audio no clear like the 1975 penny?



Thanks in advance for any help on this,
MR

 

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[JoeVal]

Zinc is low quality metal with a bit of copper cladding. That’s why the nasty sound. 1982 and older pennies are copper. I actually separate my pennies and keep the copper ones and turn in the zinc to the coin machine at my bank. Someday they might be worth more as scrap per pound than their face value.

 

[DiamondDan]

My M6 does the same thing. It makes a terrible, ugly sound when there's a zinc penny under it. I call it the "zincoln squall". I can tell with 100% accuracy whether it's a zinc or not because it's such a unique sound. I still dig em most of the time, but the machine has never been tricked. Not once. It's very handy when I'm in an area with tons of modern clad and I'm fed up with digging rotten zincs. I just walk right over 'em.

 

[A2coins]

You will learn the machine I .love my Max