I have a HP48 calculator that I haven't used in about two years. It was working fine when I took the batteries out. I need to use it again. I took a pencil eraser to the contacts, although they looked clean, and put in new batteries. It is still flat lined.
Post this over at comp.sys.hp48 . Someone will be able to help you. The only thing I can think of is to push the reset button(hidden under one of the rubber feet). Also, try pressing ON + . The calculator may be coming on but with the screen dimmed all the way.
three options - new battery screen set, system halt 1) and 2), and memory reset
new batteries --
press and release "on"
if screen then comes on blank, press and hold "on" and press and release "+" several times until you can see the characters
system halt --
1) press and hold "on" , press the "c" MENU key, release both keys
or if the keyboard isn't responding
2) looking at the back of the calculator - remove the top right rubber foot to expose the reset hole; insert a paper clip into the hole and hold for one second and remove; press "on"; then press "on"-"c menu" and release as in 1)
memory reset -- after you tried the above and it doesn't do it (reset removes any equations, etc. you ever entered ) -
press and hold these three keys simultaneously : "on", "menu a", and "menu f"; then release TWO menu keys and hold the "on"
to finsh the memory reset, release "on", to cancel reset, push "menu b" then release "on"
once you've initiated memory reset, a screen will come up and ask if you want to try to recover memory - press no to reset all memory and go to as-shipped factory state, press yes to try to recover anything you stored.
1) The screen contrast setting being too far off can also give what appears to be a blank screen e Press and hold "on" and press "+" several times to increase contrast until characters appear.
2) Try a keyboard test which verifes by sound - that should tell you if the problem is display or power/software
- press and hold "on", press and release the "d" key, release "on",
press and release the "e" key. Then start at the upper left corner and press and release each of the 49 keys one at a time - each key should emit a beep.
No beep - send it into have it fixed (bad wire, battery connection, etc.)
the repair number in my manual is 503-715-2004
I just checked the website listed in the manual and it is apparently is no longer valid - but a check on the web at
came up with the following HP link
I see where the webpage also suggests that if you can't get a display using the contrast adjustment or the resets, you can leave the batteries out for
48 hours and try it again.
I assume the same way they load it at the factory when it has none to begin with?
Based on what the manual says, it sounded like the HP 48 has loaded software, and the service center reloads it.