what's wrong with my GSN?

[moko]

I bought a GSN on ebay a couple of weeks ago and just got my 3rd test roll back today. The first 2 rolls turned out to be overexposed, so this time I used a 100 fuji film but set ASA at 200, and took pictures only when the yellow arrow just went off (I assume that's the smallest aperture). However, some of the pictures from the 3rd roll are still overexposed and the rest are underexposed and are a bit yellow.

I'm so frustrated. Does any one have any idea?
I attached 2 pictures.

Thanks a lot!!!

 

[Gradskater]

Not sure about your other pictures, but those look pretty good. The "shot up at the tree against the sky" picture is a tricky one to meter, and it looks like the camera did ok.

The light goes off at different apertures depending on the light. the yellow light comes on at 1/30th of a second if Im not mistaken.

The battery could be to blame too.

 

[moko]

Thanks for the comments!
They are scanned from negs. But why the pictures are a bit yellow?

 

[btgc]

I don't see anyhing yellow here too, though have seen notes on Net that old glass when not used may turn yellowish - one can see it visually. In that case they just put glass under sunlight and after some days of bathes yellow cast goes...or at least, gets much slighter.