At 08:00 AM 9/2/2025, vcf-midatlantic-request(a)lists.vcfed.org wrote:
>Message: 1
>Date: Tue, 2 Sep 2025 01:01:04 -0400
>From: Anthony Iannone <aiannone(a)nis.gs>
>To: vcf-midatlantic(a)lists.vcfed.org
>Subject: [vcf-midatlantic] Help with older HP LaserJet printers
>
>[...]
>
>I have two HP LaserJet 4P printers, both in decent condition, and both
>exhibiting the same exact problem - the printer passes all self tests
>and everything works perfectly EXCEPT printer output pages are
>completely blank or have only the slightest sheen of gray toner
>background. Forcing an engine test with the formatter board disconnected
>yields the same results.
>
>I have swapped parts between printers, tried a brand new-old-stock toner
>cartridge in both units, and even tried replacing the laser scanner with
>a supposedly known good laser scanner assembly. None of these steps have
>worked. The service manual suggests final step would be replacing the
>high voltage board, but short of finding another donor printer, I
>haven't been able to locate one.
Having troubleshooted hundreds of HP LaserJet printers back in the
day (including the HP LJ 4P) I suspect this issue is a failed
high-voltage power supply. There are several vendors of
new/used/refurbished HP LJ parts that you can find online, and I'd be
surprised if you couldn't find that part from any of them. You could
also try reseating that assy, and try yet another NOS toner
cartridge. Two printers with that same HVPS issue seems unlikely.
-bernieS
