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Manual for HP48 Classroom Display
07-09-2017, 07:35 PM
Post: #1
Manual for HP48 Classroom Display
Does someone has a manual for this overhead display?
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07-10-2017, 07:02 AM
Post: #2
RE: Manual for HP48 Classroom Display
(07-09-2017 07:35 PM)HP-Collection Wrote:  Does someone has a manual for this overhead display?

I own a later model of overhead display from the same company, though mine looks substantially different from yours. While I don't have a manual, here's what I've figured out. Mine has 1 button and 2 knobs.
  • The button is for vertically moving the display downwards (vaguely like the "vertical hold" controls on old CRT TVs).
  • One of the knobs is for controlling the display's contrast.
  • I haven't figured out the last knob since nothing visibly changes on the display. All I know is that I can feel detents as I turn the knob.
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07-10-2017, 10:17 AM
Post: #3
RE: Manual for HP48 Classroom Display
(07-10-2017 07:02 AM)Chris Dreher Wrote:  
(07-09-2017 07:35 PM)HP-Collection Wrote:  Does someone has a manual for this overhead display?

I own a later model of overhead display from the same company, though mine looks substantially different from yours. While I don't have a manual, here's what I've figured out. Mine has 1 button and 2 knobs.
  • The button is for vertically moving the display downwards (vaguely like the "vertical hold" controls on old CRT TVs).
  • One of the knobs is for controlling the display's contrast.
  • I haven't figured out the last knob since nothing visibly changes on the display. All I know is that I can feel detents as I turn the knob.

So it handles exactly the same way as my item. Can you drop us some pics of your unit?
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07-10-2017, 06:10 PM (This post was last modified: 07-10-2017 06:17 PM by Chris Dreher.)
Post: #4
RE: Manual for HP48 Classroom Display
(07-10-2017 10:17 AM)HP-Collection Wrote:  
(07-10-2017 07:02 AM)Chris Dreher Wrote:  I own a later model of overhead display from the same company, though mine looks substantially different from yours. While I don't have a manual, here's what I've figured out. Mine has 1 button and 2 knobs.
  • The button is for vertically moving the display downwards (vaguely like the "vertical hold" controls on old CRT TVs).
  • One of the knobs is for controlling the display's contrast.
  • I haven't figured out the last knob since nothing visibly changes on the display. All I know is that I can feel detents as I turn the knob.

So it handles exactly the same way as my item. Can you drop us some pics of your unit?

Sure. Here's a URL to an eBay item that is very, very similar to mine. http://www.ebay.com/itm/Invision-48-HP-4...2451231150

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.

Update: Scratch the florescent lights theory. I just tested it under a cliche florescent tube light and the knob had no effect.
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07-10-2017, 06:16 PM (This post was last modified: 07-10-2017 06:18 PM by Joe Horn.)
Post: #5
RE: Manual for HP48 Classroom Display
(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.

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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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07-11-2017, 08:58 AM
Post: #7
RE: Manual for HP48 Classroom Display
(07-10-2017 06:27 PM)Chris Dreher Wrote:  
(07-10-2017 06:16 PM)Joe Horn Wrote:  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. :-)

Aha, this is the same unit? What a nice thing: I do have a original packed unit with manual... here it is - with the explanation of the three knobs (the older unit has one slider instead of a knob).
By-the-way: InVision uses a display which is about 9x the size of the older unit.


Attached File(s)
.pdf  InVision48_OD.pdf (Size: 511.64 KB / Downloads: 30)
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07-12-2017, 05:40 AM
Post: #8
RE: Manual for HP48 Classroom Display
(07-11-2017 08:58 AM)HP-Collection Wrote:  
(07-10-2017 06:27 PM)Chris Dreher Wrote:  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. :-)

Aha, this is the same unit? What a nice thing: I do have a original packed unit with manual... here it is - with the explanation of the three knobs (the older unit has one slider instead of a knob).
By-the-way: InVision uses a display which is about 9x the size of the older unit.

That manual is for the same one I own. Thanks for sharing.
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07-12-2017, 08:06 AM
Post: #9
RE: Manual for HP48 Classroom Display
(07-12-2017 05:40 AM)Chris Dreher Wrote:  
(07-11-2017 08:58 AM)HP-Collection Wrote:  Aha, this is the same unit? What a nice thing: I do have a original packed unit with manual... here it is - with the explanation of the three knobs (the older unit has one slider instead of a knob).
By-the-way: InVision uses a display which is about 9x the size of the older unit.

That manual is for the same one I own. Thanks for sharing.

This IS the manual of the newer item (InVision48). My older one does not have a manual.
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