Re: HP42S problem Message #2 Posted by Tony Duell on 26 July 2001, 6:51 p.m., in response to message #1 by Mark Sims
75mA supply current is only about 1/3 W at the battery voltage of the 42S. I am not suprised you don't feel anything getting that hot with that sort of power
disipation.
I've seen a 42S that took excessive supply current, but in this case, the resistance between the battery contacts looked low when tested with an (analogue) ohmmeter. It turned out that the fault was the
100uF capacitor across the battery lines. You might try removing this -- the machine will work without it, but you get MEMORY LOST as soon as you remove the batteries, and I'd not trust printing either (due to the high current spikes taken by the IR transmitter). Of course if it is the capacitor, it's trivial to get a replacement.
I don't see how it can be the LCD. So I'd not remove the PCB at this stage. You mihgt try lifitng pin 28 (Vcc) of the RAM to see if that reduces the current consumption. If so, then change the RAM chip (it's a normal 6264-type thing).
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