On 2014.10.05, 22:43 , Don Tuttle wrote:

Purchased Tamron AFF004S700 SP 90MM F/2.8 DI Macro Lens for Sony Alpha
Camera. First put it on Sony A77. Auto focus fine for about 20 shots,
then AF stopped working. Turned camera off & on, re-seated lens, AF
still didn't work. Put lens on A65. AF would not work. Turned AF off
and on, messed with miscellaneous things (don't remember what), AF
started working again. Took 22 pics, then AF stopped working. Tried all
previous actions but AF will now not work on either camera.

Does auto focus failure sound like faulty unit or could operator error
or inability be the cause?

Most likely (unfortunately) a defect.

That said:

1. Some macro lenses have a limit switch to prevent focus hunting so
that you can limit the AF to the "macro end" or the longer distance
end of the focus range.

Is the limit switch engaged? Are you turning it on and off
and on again somehow?

2. are the contacts clean (bayonet area)?
gently swab them with alcohol on both the camera and
lens side.
Optionally: Use an eraser.

CAUTION: don't let the alcohol get into the camera or onto the lens
glass.
CAUTION: don't let the eraser bits get into the camera or lens.


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