HP9845 service toolkit

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Mon Dec 13 18:49:48 2004

My workbench is currently covered with a 9845 is many bits :-). And I am
slowly figuring out just what's inside that darn machine...

Anyway, I believe there was an HP service toolkit for it (based on the
markings on the PSU cover). Does anyone have it?

If so, I have some questions

1) What did said kit contain (other than normal hand tools, which I have
anyway). I am almost sure 2 of the items in the kit were a 'Discharge
Tool' for the power supply and a 'Turn on fixture' to run the machine
without a monitor

2) What does the 'Discharge Tool' consist of? I'll guess it was just a
reisstor connected to a couple of isulated probes, or a plug, or
something. There are some insulated holes on the SPU cover, under them
are bare pads on the PCB connected to the terminals of the mains
smoothing capes. The instructions are to insert the tool into 2 of the
holes, then into the other pair, then to check the voltage between the
holes you put the tool in (basically, check the caps are discharged)
before removing the PSU. From the size of those capacitors (1800uF, 200V,
small coke-can size), I would agree!

3) More importantly, what does the 'Turn On Fixture' consist of? Again
I'll make a gues. It's a little PCB that goes into one of the edge
connectors in the monitor pillars. But which connector, and what's on the
PCB? Does it just short a couple of pins together to complete some kind
of interlock circuit, does it contain load resistors, or worse, does it
contain ICs?

HAs aonone else been foolish enough to dismantle the printhead? Suffice
it to say it consists of a normal PCB that connects to the printer cable,
a seramic substrate containing the (thermal) printhead heater elements, 7
seramic hybrid circuits that contain the driver cirucits, and something
like 35 of those metal-rings-round-elastomer connectors (like those
between an HP41 logic board and keyboard) to link everything up...

Received on Mon Dec 13 2004 - 18:49:48 GMT

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