Re: HP 19C printer repair Message #5 Posted by Tony Duell on 17 June 2001, 2:08 p.m., in response to message #1 by Kenneth Garges
First make sure it is the printhead!. I've never worked on a 19C, but if it's like all the other
HP thermal printers you will find that the printhead is connected to one of the circuit boards using a flexible PCB ribbon cable.
Open the machine up and unplug -- CAREFULLY -- that ribbon from the circuit board. You will find 1 connection per dot row and 1 common connection. It's normally at one end of the connector
and normally a wider track on the ribbon. Measure the resistance between each of the other contacts and the common one with an ohmmeter.
A good heater element is < 10 Ohms or so, dead ones are much higher.
If the printhead is good, first make sure the ribbon is connected properly to the connector on the circuit board and then
trace back to the driver circuitry. Often HP used standard transistor arrays to drive the printhead elements so it is possible to repair this circuitry.
If one of yor printhead elements is open, then you've got problems. I've never managed to repair an HP thermal printhead, and I've tried
a couple of times. One problem is that the metalisation layer on the printhead is aluminium, so you can't solder to it. You can't
even repair broken contacts between the ribbon and the printhead and expect it to 'hold'.
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