HP Forum Archive 21

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HP-97 Printer Head Message #1 Posted by aj04062 on 11 Sept 2013, 7:44 p.m. I have a HP-97 that had a printer head failure. It has clearly overheated and burnt out. The plastic holder and rest pad are slightly melted, but usable, I think. I have a new head. However, I am concerned about the failure mode of the prior head. Do you know how this would have happened? I don't want to install a new had just to see it burn out as well. Could it have occurred if someone tried to print without paper? I looked at the service manual on the DVD set, but nothing jumped out at me regarding this kind of failure.

Re: HP-97 Printer Head Message #2 Posted by Randy on 11 Sept 2013, 9:18 p.m., in response to message #1 by aj04062 Quote: Do you know how this would have happened? No, but individual element failures are common. FWIW, I've never seen one that melted the surrounding plastic. Quote: I don't want to install a new had just to see it burn out as well. I would agree, not a good idea. It would be a very expensive fuse. Quote: Could it have occurred if someone tried to print without paper? I doubt it. Doing it long term might cause a few elements to fail but not melt things. I would first measure the elements and see how many are failed. One or two is normal. More than that and I'd be concerned that the PIK is gone. A shorted driver transistor (Q1-Q7) would certainly cause a head element to fail if it was powered on for a long time and possibly generate enough heat to melt plastic. You could provide seven dummy load resistors the same value as the head elements (~10-12 ohms) and power it up. See what the voltage drop is across each element - any with high drop are on all the time and should not be. Next step would be to print and verify that each transistor switches...

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