Laser printer went blank

If there is no dusting or latent image on the drum/transfer sheet, when halting the machine mid-cycle and opening up, then failed corona generator perhaps

That would be my guess - AFAICR: the laser discharges the static charge on the photoconductive film at the points where no toner should be attracted to.

I think a failed laser would result in a completely black page, maybe the transistor that drives the laser going leaky - but that's in a critical constant current loop, a leaky transistor would probably destroy the laser.

If it faded like that, I would guess(tm) that you're out of toner. Try a different or new toner cart anyway.

Also, I've seen the shutter mechanism jam or break on the toner cart or at the entrance slot to the laser scanner. Play with the toner cart mechanism and see if the protective shutters are operating normally.

Just for grins, try a test page from the printer, not the computah. If the test page works, look for computer problems.

On 24 Oct 2015, Ian Field wrote (in article):

Any idea the approx voltage of the corona wire? I could check, but it would be nice to know if it?s 300, 600, 1000?

Thanks.

More like 2,000 to 5,000V. The generator is often a selfcontained unit off 28V or so, with just an on/off control line. Flop a 100M resistor to the corona wire and insulated lead out to a neon bulb to frame , in the first instance.

Pretty sure I've seen one at 6kV, most were somewhere around the 5kV mark.

Some older types are pretty sturdy and can give a nasty nip. Unlikely to be as dangerous as microwave oven innards, but I still wouldn't bother sticking my fingers in there!