Not DEC related but still hoping for some help: Problems w/ LJ 4+ Printer

[Dave Mabry]

Ali via cctalk wrote on 4/2/2019 3:56 PM:
> I rescued a LaserJet 4+ printer that I have been trying to restore.
> Initially everything seemed ok and it seemed as if there may be just a bit
> of an issue with paper pickup which I attributed to old paper in the tray.
>
> However, soon I started getting the accordion paper jam which led me to
> replacing all the rollers including the transfer roller. Now the paper flows
> freely! However, I am having a new problem with printing. When I print, the
> first 5-10 pages initially come out blank. The printer does not produce any
> errors or error codes. The blank pages are warm (not hot though) as expected
> out of a LJ.
>
> After closer inspection it seems that the pages are printed SUPER light and
> gradually get darker the more I use the printer continuously. Eventually the
> printer starts printing continuous crisp black pages like new. This is a
> whole page phenomenon (i.e. not gaps, missing areas, etc.).
>
> A picture of the effect can be seen on VFC at:
> www.vcfed.org/forum/attachment.php?attachmentid=52120&d=1554074105
>
> Sorry for the poor quality picture.
>
> Things I have checked/tried:
>
> 1. Using a brand new NOS toner (according to HP toner does not go bad as
> long as it was sealed - which this was)
> 2. Swapping the new transfer roller for the old one - same problem, I have
> to print out a bunch of pages until the printer starts acting normally.
> 3. I have checked the HV and an image is being transferred to the drum on
> the toner cartridge.
> 4. A visual inspection of the fuser shows it to be ok.
>
> Obviously this is happening printing demo pages so it has nothing to do with
> computer, OS, SW, drivers, etc. Anybody run into this before? Any
> ideas/suggestions. My Google fu turned up a bunch of discussions on the
> laser door not being aligned correctly but that would seem to be a more
> permanent issue i.e. unless you fixed the door no pages should print ever.
> Mine gets better on its own after a number of pages are printed. Plus the
> door and spring are fine - I checked them just in case.
>
> I tried posting on FixYourOwnPrinter.com but for whatever reason the site
> was not accepting the question. Any other forums you guys would recommend?
> TIA!
>
> -Ali
>

Just my little bit of input on this...the high voltage power supply is 
just about the only thing that there is no error code for.  I had one 
fail and the printer didn't flag any errors.  Changing the HV supply 
fixed it.

It sounds to me like your problem is related to the high voltage supply.

Dave