We're getting some odd behavior from the Scanstation. Here are the symptoms when we try to scan a slide:

1) On positive bias the dark current start off nicely around +2V. However, the background on the scan is above 10 V (blue screen of death). Dropping the bias lowers it, but not by much.

2) We seem to get better results with a negative bias scan, at least we see an image. However, the background photocurrent during the scan is positive (+2-3V).

3) While observing the dark current before starting the scan, I noticed that if you flick the laser to continuous, the current bounces up by a LOT (up to 5 V) and then settles back down in a second or so.

I think number 3 is the cause of the odd results. It appears that turning the laser on induces a positive surge in the photocurrent. I haven't seen this in previous posts. My question is: 1) Is there anything we could be doing wrong that would cause this? or 2) Could there be something wrong in the box that would cause this?

Dan F