HP Forum Archive 18

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Changing display contrast on HP 27s Message #1 Posted by MitchT on 3 Jan 2008, 2:15 p.m. Hi everyone, I'm new to this forum. I've lost the manual for my HP 27s calculator so maybe someone can help me here. I want to change the contrast of the LCD display on my calculator, I know this is possible but I've forgotten how to do it. Can anyone help? Thanks!

Re: Changing display contrast on HP 27s Message #2 Posted by Karl Schneider on 3 Jan 2008, 3:09 p.m., in response to message #1 by MitchT Mitch -- As with all Pioneer-series models: While holding down clear ("CLR"), press "+" repeatedly to darken the pixels; press "-" repeatedly to lighten the pixels. Less well-known: Turn the calc off while holding down "1/x" and "+" simultaneously to put the calc into a battery-conserving "coma" that stops the clock. Memory contents will be unaffected; "MACHINE RESET" will be displayed upon powering on. -- KS Edited: 3 Jan 2008, 3:23 p.m.

Machine Reset: (was Changing display contrast on HP 27s) Message #3 Posted by Martin Pinckney on 3 Jan 2008, 4:33 p.m., in response to message #2 by Karl Schneider Karl, You seem to be pretty knowledgeable about the 27s. Maybe you can explain this: Just a few days ago, I was sitting in a meeting with a client, and grabbed my 27s for a quick calculation. Turned it on, did a few calcs, then it spontaneously BEEPed and displayed "Machine Reset". I discovered that the display setting (FIX) was gone, but all my equations and variable values were intact. What happened? Anyone else had a similar experience? Martin

Re: Changing display contrast on HP 27s Message #4 Posted by MitchT on 3 Jan 2008, 9:57 p.m., in response to message #2 by Karl Schneider Karl, thanks very much!! BTW what's the advantage of putting the calc into "coma" mode? And how do you get it out of this mode when you turn it on again? --Mitch

"Machine Reset" and coma mode on the HP-27S Message #5 Posted by Karl Schneider on 3 Jan 2008, 11:51 p.m., in response to message #4 by MitchT Martin and Mitch -- I'm not sure why Martin's HP-27S reset itself (low batt, perhaps?); the reset will retain memory contents, and change settings (including display contrast) to default values. The only advantage to "coma" mode is battery conservation. The clock cannot be turned off otherwise, and its constant running will discharge the expensive cells significantly faster (at $10 for a set of three quality Silver Oxide cells). Of course, if you use the time-based functions, then it's best to turn it off normally. Simply turning the calc back on will awaken it from "coma" mode, with a Machine Reset. All of the above also applies to the HP-17B, HP-17BII, and HP-42S, except that the latter has no time clock. -- KS Edited: 3 Jan 2008, 11:55 p.m.

Re: "Machine Reset" and coma mode on the HP-27S Message #6 Posted by MitchT on 4 Jan 2008, 9:00 a.m., in response to message #5 by Karl Schneider OK I just tried pressing the "+" (bottom right) and "1/x" (top right) keys simultaneously, then I power off and on and MACHINE RESET isn't displayed. What am I doing wrong? It would be nice to save on batteries... ;-) --Mitch

Re: "Machine Reset" and coma mode on the HP-27S Message #7 Posted by Ken Shaw on 4 Jan 2008, 10:30 a.m., in response to message #6 by MitchT It worked for me, but I pressed the 1/x key first, which caused a beep, then the + key, then the CLR key while holding the other two.

Re: "Machine Reset" and coma mode on the HP-27S Message #8 Posted by MitchT on 4 Jan 2008, 10:51 a.m., in response to message #7 by Ken Shaw Ah, didn't realize I had to keep holding down the 1/x and + keys when I press the CLR key...thanks! --Mitch

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