Re: 82240A Printer Problems/Questions Message #11 Posted by Tony Duell (UK) on 15 Feb 2002, 8:06 p.m., in response to message #1 by Y. Samuel Arai
I've only ever openned up a 82240A once, years ago. I know rather more about the 'B'. I do remember there are electronic differences between the A and the B (particularly in the IR preamp circuit -- both use chips
designed for TV remote control sensors, but different chips). So some/all of what I say below may not be applicable to the 'A' -- it all comes from notes I made on the insides of my 'B'.
Yes, there are screws under the feet. And inside the battery compartment. With those out, the top comes off. Don't loose the switch actuators.
The printer mechanism is held in by 2 small screws. It connectes to the logic board by 2 connectors. One carries the motor/tacho/home switch signals. The other is the tapewire from the printhead. On the logic board there's the IR input circuitry, some PSU stuff, a standard microcontroller (an 8050 in the 'B') and the printhead/motor driver chip. The printhead is essentially driven by one 8 bit port on the microcontroller, one bit per heater. The intenstity slider is a pot, read out using an RC network and a couple of port pins on the microcontroller.
If you're getting no printing, first check you're using HP thermal paper and that it's in the right way round. If so, then take the cover off and unplug the tapewire from its connector. One end trace is common, the other 8 are the other end of each heater. Check the resistance from 'common' to each of the other pins (expect a few ohms). If they're open, then you've got printhead or tapewire problems.
Then check the intensity pot and the surrounding components. I have no idea what happens if it goes open-circuit, but it might well result in no printing.
Then check the printhead driver chip. Trace the PCB tracks back from the printhead connector to find it.
|