My beloved but ancient HP5, which I inherited several years ago, is now the best part of 20 years old (firmware is dated 1996 !). It has an old duplex unit and works perfectly.
It was built like a tank - it was clearly meant for heavy duty work, and is generally easy to strip for manintenance. Currently it shows a page count of 300,940 but my guess is that it was probably reset at some stage.
Yes, it really needs a new fuser, but it's a real workhorse and generally problem free.
I recently had an issue with a false Paper Jam error message. I stripped it down and made sure there was nothing inside it, but as soon as it started up it showed the Paper Jam error message. I have a full service manual for the machine that I found somewhere and this said that there is a possibility that the paper sensors were faulty.
One of the weak points of the machine is that it is not easy to access to test voltages etc when it is powered up - even the HP service manual states as much - so it is diffcult to test the sensors themselves.
There are two main sensors to check. The first is (1) "PS1 Input/Registration Sensor" situated in the front paper loading mechanism. Open the top cover, remove the toner and to the left by the lifting plate you can see the small arm. This connects to a IR sensor but is difficult to get it out - according to HP you can remove it without dismantling the assembly, but I couldn't. I had to remove the front loading assembly and removed the end with the Paper Control PCB.
I took it completely apart and cleaned the dust, but no joy. From the manual to test :
PS1 (Input/Registration Sensor) Check
1 Power ON the printer with the top cover open. Wait for the
12 PRINTER OPEN (or CLOSE PRINTER COVER) message.
2 Engage PS1 by taping it down.
a For the LaserJet 5, install the toner cartridge.
3 Close the top cover. The 02 WARMING UP message should
display.
4 After the fuser warms up, the main motor should turn on.
5 The 13 PAPER JAM message appears if the sensor is working
correctly.
6 If the 13 PAPER JAM message does not appear, check that PS1
was fully engaged, then replace PS1.
7 Remove the tape from PS1, install the Toner Cartridge and
close the top cover.
8 The display should change from 02 WARMING UP to 00 READY.
If the 13 PAPER JAM message persists, replace PS1.
Next I looked for the second sensor (2) which is at the back left of the machine (when looked at from the front) which is linked to an arm in the Fuser unit plus in my case a tab on the rear door which acts as a door warning interlock.
This is much easier to access and remove, and in my case was the source of the problem. Again I removed it, stripped it right down, cleaned all the dust and reassembled and Voila ! It all worked.
From the HP Service Manual :
PS3 (Exit Sensor) Check
1 Open the rear door (cover) of the printer.
2 The display should read 13 PAPER JAM (or REMOVE PAPER JAM)
immediately after the door is opened.
3 Close the rear cover. The display should change from
02 WARMING UP to 00 READY.
a If the 00 READY message does not appear, check that the
rear door is not damaged, and the the door closes and
latches properly.
b If the PAPER JAM message does not appear, replace PS3.
HP may have gone down hill in recent years, but IMHO this machine was their finest hour :-)
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