All of a sudden this printer ON light went off after a click sound and stopped
 working. I checked the power cable and there is 32V and 16VDC at the
printer end of 3-pin socket. But when this is plugged & the printer ON
button is pressed nothing happens. When the power cable is pulled out &
re-tested for above voltages, they are absent! Turning OFF & On the main
120V AC source from a power strip causes the the DC voltages to
reappear at the input end of the printer. I guess there is some
internal short (?) in the printer. I want to open the printer and examine/
replace any component that might have blown. I request any tips as to
how to go about opening the enclosure, likely failed and relatively
easily replaceable component, and how and where to procure such
component?

---

Clarification of Question by kag5-ga on 16 Dec 2004 14:38 PST

The repair of my printer seems to be an expensive and time consuming
affair. I have bought a similar model from Ebay  and in a few days I
should be all OK. I may cannibalize my old one for future replacements
if needed. Thus my problem with my printer is resolved. On opening the
printer, I measured a direct short between common & 16V point on the
PCB mounted 3- pin socket that accepts the 3-pin plug from PSU. Common
to 32V pin was OK. The thing was wierd because the 16V socket point in
the printed circuit when traced seemed to be connected to nowhere.
This suggested an internal short in the PCB mounted socket. Anyway I
got fed up and resorted to obtain a completely new printer- still in a
cheapy way!

Again I thank Guzz-GA for his insightful comments.

Could you clarify what you mean by the power cable. Are these voltages
from a cable mounted power supply or is it raw mains?

The ?click? is likely to be a fuse -- but why it blew? Old fuses do
spontaneously blow, even new ones sometimes, but more often there is a
reason. Not usually the sort of thing which can be fixed without
expert knowledge I?m afraid.

If you can clarify, we can take it from there.

Best

The power cable has a black box at one end that one plugs directly
into 120V AC socket and at the other end is a small 3- point socket
that one plugs into the printer. As per the inscriptions on the black
box, at the printer end the voltages are 16VDc and 32V Dc with center
socket as common. These are the input voltages into the printer. I was
able to open the main enclosure and peer in to see any obvious damage.
There weren't any that I could discern. The guts were too intriuging
and daunting for me to figure out if there was any fuse at all! The
printer is just over a year old (as warranty luck would have it!) and
it was sparingly used. Just prior to the incident I noticed the "ink
cartridge empty" message on my screen as I clicked for printing a
document. Could empty ink cartridge cause such a problem? Thinking it
be farfetched I haven't tried inserting a new ink cartridge. The old
cartridge is presently out and the problem still persists i.e printer
is dead.

Unusual for a dual voltage o/p PSU on a printer. Glad you managed to
get it apart. Sometimes I?ve struggled for fifteen minutes trying to
figure out where to slide a finger nail.

From what you say, it sounds like there is an overload cut-out on the
PSU. Unusual again. ?Ink out? wouldn?t kill, though having no
cartridge might look like it?s dead. But that doesn?t explain the PSU
cutting out. There is a possibility that the measured voltages,
although correct, are just residual bleed voltages and the thing can?t
supply current. If you have equipment, try the voltages with a bit of
load -- preferably a resistor but low wattage flashlight light bulbs
in series would do. Are you familiar with ohm?s law, bearing in mind
that the resistance of a cold bulb is a small fraction of the hot
resistance. You could also see if the voltage drops with conduction
through wet fingers to the common.

Is the PSU a heavy lump or is it quite light? I looked up HP but the
info wasn?t given. If it?s heavy, it?s a transformer with rectifier
and perhaps regulator etc. If it?s light, it?s switch mode, far more
complex. Does the PSU unscrew or is the case bonded?

You have tested it out on a different outlet I presume? But I?m
inclined to think it?s the printer itself and since it disables the
PSU there is likely to be a short circuit on one of the inputs. Can
you measure with a DVM?

This is difficult for you without specific expertise, but you?ve
nothing to lose so I?m game if you are.

Best

That?s unfortunately the way it goes:-(

Reason for the supply not appearing to go anywhere BTW, in case you
don?t know, is that it was probably a multilayer board. Tracks inside.
Boards are commonly now 8 layers and more.

Sorry for your loss. Out of curiosity you could buzz out the pin to
components and you never know.....

Best