HP G4050 - lines on scans

[sharding]

Hi all.

I'm curious if anyone has seen (and solved) this problem, or a similar one. I have an HP G4050 I got on eBay a while back to scan 4x5 film, and I'm getting seemingly random lines across the scans. Sometimes it's just one line, sometimes it's more than one. They aren't always in the same place, so it seems more like some kind of electronic issue than just dead pixels or dirt.

Here's a straight out of the scanner (except resizing) example of a test negative scan I just did (obviously not a great photo; it was a test shot with a new-to-me camera): Attachment 145248

And here's a 100% crop of part of the same thing: Attachment 145249

I'm basically ready to write this scanner off as broken, but first I thought I'd see if anyone has ideas. FWIW I'm scanning with VueScan on a MacBook Pro, and I've seen this problem across a couple of different computers and several versions of VueScan (the scanner has had this problem since I first bought it, over a year ago -- I just boxed it away and forgot about it until recently).

I've found a few threads about similar problems on HP's help forums, but no good solutions.

[SergeiR]

Cant see it, but i would suggest
- check USB port
- check power supply, if possible - hook it up through at least APC filter.

I have two of those scanners and i haven't had a single glitch in scanning with them.

[mdarnton]

Make absolutely sure that the calibration is perfectly clean. One speck of dust gives one solid white line.

[John Jarosz]

Though I'm new at using this scanner (and Vuescan), I've not seen or had any of the issues you describe.

[mdarnton]

I meant calibration AREA---the bare strip at the beginning of the scan. I clean this before every scan--wipe it and then blow it off with air.

[sharding]

Last night I decided I had nothing to lose since it wasn't really usable right now anyway, and I disassembled the whole thing. I checked all of the electrical connections, looked over the circuit boards (no obviously bulging or exploded capacitors, etc.), and did everything I could to eliminate dust. And... It seems to be working for now. I didn't see any dust in there before opening it up, but mdarnton may very well have been right and there was something I just didn't notice.

Fingers crossed that it keeps chugging along...

[Jody_S]

I used a slightly older model for about 5 years, I did frequently get this problem. I eventually figured out it was a combination of dust/dirt in the calibration area, and sometimes a bad connection at the power jack. I cleaned both whenever it happened (power off, rubbing alcohol or electronic contacts cleaner on the plug, microfiber cloth on the glass). I did eventually develop a permanent dead pixel on the sensor leaving a line in the same spot on every scan, unfortunately near enough to the middle that I couldn't scan to one side or the other. The effect of a dead pixel is quite different from the weird banding it does otherwise.

[richardspies]

I had a vertical line problem on my G4050. When scanning light objects (e.g. that back of a photo that had notes I wanted to capture) there would be a white line right down the center. After opening up the scanner to clean the glass, I found a brown spec between the glass and what I assume is the white calibration area. The glass is generally permanently attached so I couldn't clear the area. However, I was able to use a shot of compressed air to blow the spec away. This fixed the problem.

[stan7926]

Another question on the G4050. I have dust in the lid's transparent material adapter. Does anyone know how to open the tma for cleaning?

[pdh]

Its possible to open both top and bottom of this scanner for cleaning the glasses.
The screws holding the lid together are hidden beneath grey adhesive paper circles round the underneath edge. Lever them off gently (or forcefully should you so desire) and have at the selftappers beneath with a Phillips or similar