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Manual for HP48 Classroom Display
07-10-2017, 06:27 PM
Post: #6
RE: Manual for HP48 Classroom Display
(07-10-2017 06:16 PM)Joe Horn Wrote:  
(07-10-2017 06:10 PM)Chris Dreher Wrote:  Regarding the middle knob, my only guess is that maybe it is for adjusting the Hz refresh rate to reduce flickering effects with florescent lights (probably by dropping frames). However, that is just a wild guess.

If anyone knows what the mysterious knob does or has the manual, please let us know.

I vaguely remember (possibly correctly) that it controlled the position of the first scan line at power-up (not while turned on). If you have to always press the "vertical hold" button to position the screen correctly, then try twisting that knob and see if it changes the initial screen position (you'll have to power off and back on). After a few such adjustments, you should be able to have it power on correctly framed without needing to press the "vertical hold" button.

Thanks, I just tested it and that is exactly what the knob does. Cool.

Amusingly, I added my update about the florescent lights theory not working at the same time you posted what the actual purpose was. :-)
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RE: Manual for HP48 Classroom Display - Chris Dreher - 07-10-2017 06:27 PM

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