Originally posted by JohnX Sorry to possibly contradict you photolady95, but I'm not sure it's aperture block failure, as the OP says his camera works ok on AA batteries but not the stock battery, and I've never read anything about AB failure that suggests AA batteries change it? Would be interested in sources please?
If you would kindly read the thread about the aperture failure and repair in the K-30/50 forum (see the link above), then you would realize that it's common knowledge that the failure shows more often/earlier with the D-Li109, using Eneloops in the adapter mitigates the problem somewhat, although this may be temporary.
@OP: this is most certainly the common aperture failure, which unfortunately happens to many cameras of these series.