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AA & UM-3 Battery Length - Differences from brand to brand?

batteries aa um-3 Pro 7A

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2 replies to this topic


Hi All,

I have an older hardwired Audio Technica Pro 7A LAV that I was hoping to use for occasional public speaking gigs ; in emergencies when wireless is a problem.

It runs with a hard-wired single AA battery pack. My issue is that AA batteries are no longer fitting into the battery compartment - the battery (brand new Duracell) is too long and therefore too tight to get into the receptacle. I'm afraid to force it in and cause damage. I could swear that when I first got the mic a AA would fit without any issues. Have they started making these current AA's a bit longer?

Inside the compartment it indicates a "UM-3" battery, a Japanese AA equivalent? Maybe there's a slight difference in the dimension/length????

Thanks for any tips - much appreciated.

Have a great day!



Eric Toline

Eric Toline
  • LocationCoral Springs Florida
A UM-3 is 13.9mm in diameter and 50mm long as are all AA batterys. Could be that the flex contacts are a bit stiff and not flexing as they did. Push the battery in and the contacts will give a bit. Also make sure there's no gunk under the contact plate that's stopping the contact from flexing.

"I push the Record button and hope for the best"

Rick Reineke

Rick Reineke
  • LocationNYC
Don't know about the AT compartment, but on most, the negative (flat end) goes in first, then compress the spring or contacts to side in the + end.