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HP 48g Series Calculators - Hardware Troubleshooting

Description
These procedures are used to help determine the best course of action for possible hardware problems with the HP 48g and HP 48gx calculators.
 note:
RS denotes a right-shift (the green arrow key next to the number 1) and LS denotes a left-shift (the purple left arrow key next to the number 4).
Calculator resets
Occasionally, the HP 48 will freeze up while executing a program or system operation and will not respond to the CANCEL key. If this happens, try to interrupt the system with a system halt or a memory reset. Verify that batteries are installed according to the diagram below:
Figure : Battery position
System halt
A system halt will interrupt and cancel all executing programs and system operations. The stack and the temporary system storage section of memory will be cleared, and the calculator will return to the HOME directory with the MTH menu keys displayed.
To halt the system using the keyboard:
  1. If necessary, turn the calculator on.
  2. Press and hold the ON key.
  3. Press the C key.
  4. Release both keys at the same time.
If the HP 48 will not accept input from the keyboard, bypass the keyboard and attempt a system halt using the reset hole in the back of the unit.
To halt the system using the reset hole:
  1. Place the calculator face down.
  2. Remove the upper right rubber foot. Underneath the foot is a reset hole with the letter "R" beside it. If the hole does not have an "R" beside it, remove the upper left rubber foot, and check the reset hole beneath it.
  3. Straighten and insert an average-gauge metal paper clip into the reset hole labeled "R" until it hits bottom, and hold it there for at least two seconds.
  4. Remove the paper clip, turn the calculator face up, and press ON. This should cause the machine to reset, and in some cases display the message "Try to recover memory?"
  5. If the "Try to recover memory?" message is displayed, press the A key to attempt to recover memory or the F key to erase the user memory. When A is pressed, occasionally the objects in memory are recovered in new sub-directories of HOME labeled D.01, D.02, et cetera. Pressing the F key will cause all information stored by the user to be erased from calculator memory. This will also affect any RAM card that is merged with main memory. If the card is not merged or it is write-protected, it will not be affected by this reset.
Memory reset
A memory reset will return the HP 48 to its factory-default state, which will erase all stored user memory. Use this feature very carefully.
  1. If necessary, turn the calculator on.
  2. Press and hold the ON+A+F keys simultaneously.
  3. Release all three keys at the same time. This should cause the calculator to display the message "Try to recover memory?"
  4. Press the A key to attempt to recover memory or the F key to erase the user memory. When A is pressed, occasionally the objects in memory are recovered in new sub-directories of HOME labeled D.01, D.02, et cetera, although there is no guarantee that all of the variables will be recovered. Pressing the F key will cause all information stored by the user to be erased from calculator memory. This will also affect any RAM card that is merged with main memory. If the card is not merged or it is write-protected, it will not be affected by this reset.
Hardware symptoms and solutions
II. All of the pixels on the screen are lit (blue)
  1. Try to adjust the contrast by holding down the ON key and repeatedly pressing the [ - ] key.
  2. If the screen is still dark, try to halt the system using the keyboard.
  3. If this does not correct the problem, try to reset the system using the reset hole with the batteries removed.
  4. If this does not work, remove the batteries and let the unit sit for 48 hours. After 48 hours, replace the batteries. If the problem persists, attempt a memory reset. Although removing the batteries for 48 hours should erase the user memory, performing a memory reset will ensure that the calculator is reset to its factory defaults.
  5. If the problem persists, the unit requires service. Please contact HP.
III. Sometimes the display flashes when the calculator is first turned on
This is normal for HP 48g and HP 48gx calculators.
IV. The screen is "frozen" with an hourglass at the top of the display
  1. Try to halt the system using the keyboard.
  2. If this does not correct the problem, try to halt the system using the reset hole.
  3. If this does not work, remove the batteries and let the unit sit for 48 hours. After 48 hours, replace the batteries. If the problem persists, attempt a memory reset.
  4. If this does not correct the problem, the unit requires service. Please contact HP.
V. The ((·)) annunciator stays on, even when the calculator is turned off
This indicates a low-battery condition in the calculator or a RAM card, or an alarm that is past due. To determine what is causing the ((·)) annunciator to stay on:
  1. If necessary, turn the calculator off and then on again by pressing RS, ON, then ON. A "Warning:" message will appear in the display for approximately three seconds:
    • "Warning: LowBat (P1)" refers to the battery in Port 1's RAM card.
    • "Warning: LowBat (P2)" refers to the battery in Port 2's RAM card.
    • "Warning: LowBat (S)" refers to the calculator batteries.
    • "Warning: Alarm" indicates that an alarm is past due.
  2. To respond to the low battery warnings, replace the appropriate batteries as soon as possible.
  3. To respond to a past-due alarm:
    • Press RS, then TIME; then use the down arrow key to highlight the appropriate alarm. Press the OK menu key to view and acknowledge the alarm. Press the PURG menu key to delete the highlighted alarm, if desired.
      OR
    • Press LS, then TIME, the ALRM menu key, then the ACKA menu key to acknowledge all past due alarms at once.
VI. The screen is blank and the unit does not turn on, even with new batteries
  1. Verify that the batteries are inserted correctly.
  2. Try to halt the system using the keyboard.
  3. If the screen is still blank, attempt to adjust the contrast by pressing and holding the ON key while repeatedly pressing the [+] key.
  4. If this does not correct the problem, try to halt the system using the reset hole.
  5. If this does not work, remove the batteries and let the unit sit for 48 hours. After 48 hours, replace the batteries. If the problem persists, attempt a memory reset.
  6. If this does not correct the problem, the unit requires service. Please contact HP.
VII. Certain keys do not respond, while others do respond
  1. Look in the upper right corner of the display to read whether the calculator is in User mode.
  2. If "1USR" is displayed, press CANCEL to exit the User mode.
  3. If "USER" is displayed, press LS, then ALPHA to exit the User mode.
  4. If the machine is not in User mode, try to halt the system using the keyboard.
  5. If this does not correct the problem, try to halt the system using the reset hole.
  6. If this does not work, remove the batteries and let the unit sit for 48 hours. After 48 hours, replace the batteries. If the problem persists, attempt a memory reset.
  7. If this does not correct the problem, the keyboard is not functioning properly, and the calculator requires service. Please contact HP.
VIII. The calculator does not seem to be operating properly
Run a diagnostic self-test on the calculator:
  1. If necessary, turn the calculator on.
  2. Press and hold the ON key.
  3. Press and release the E key.
  4. Release ON. Various patterns and messages will be displayed on the screen as the unit performs the internal tests. The messages "IROM OK," "IRAM OK," and "OK-48" should be displayed during the test. Allow the calculator to complete one full cycle before ending the test. If these messages do not appear, the calculator requires service. Please contact HP.
  5. To halt the self-test, press and hold ON, press the C key, then release both keys.
IX. The keys respond but some of them do not seem to be operating properly
  1. Look in the upper right corner of the display to read whether the calculator is in User mode.
    • If "1USR" is displayed, press CANCEL to exit the User mode.
    • If "USER" is displayed, press LS, then ALPHA to exit the User mode.
  2. If the machine is not in User mode, run the self-test on the calculator (see symptom VIII above). If the unit passes this test, perform a keyboard test:
    1. If necessary, turn the calculator on.
    2. Press and hold the ON key.
    3. Press and release the D key.
    4. Release ON.
    5. Press and release the E key. "KBD1" will appear in the upper left corner of the display.
    6. Starting at the upper left corner (the A key) and moving left to right, press each of the 49 keys on the keyboard. When the 49th key, [+], is pressed, the display message should change to "KBD1 OK." If this message does not appear, rerun the test, being careful to press the keys in the proper sequence.
    7. If the HP 48 fails the keyboard test repeatedly, the unit requires service. Please contact HP.
X. After responding "YES" to the question "Try to recover memory," the calculator pauses and then displays the question again
The user memory was not recovered. Continue attempting to restore memory by responding "Yes" a few more times. If the attempts repeatedly fail, however, press the F key to erase the user memory and regain use of calculator.
XI. The calculator cannot communicate with a computer via a serial cable
  1. Verify that the cable - and the adapter, if used - are plugged into the calculator with the HP logos facing up.
  2. Verify that the settings on both the calculator and the computer are correct.
  3. Perform a serial loop-back test on the calculator wire port:
    1. Disconnect the serial cable and the calculator.
    2. If necessary, turn the calculator on.
    3. Press and hold the ON key.
    4. Press and release the D key.
    5. Release ON. Three vertical lines will appear on the screen.
    6. Position a paper clip between the center two pins such that both pins are touched simultaneously. Be careful not to bend the pins.
    7. Keeping the pins bridged, press the PRG key. "U_LB" will appear in the upper left corner of the display. If "OK" appears to the right of "U_LB," the calculator passes the serial loop-back test. If repeated attempts fail, the calculator requires service. Please contact HP.
    8. Press and hold ON, press the C key, then release both keys to exit the serial loop-back test.
  4. If the calculator passes the serial loop-back test, attempt to connect using a different computer or cable, if possible, to isolate which piece of equipment is causing the failure.
XII. The calculator is not transferring data to (or from) another HP 48
  1. Verify that the arrow marks (near the Hewlett-Packard logo just above the display) on both of the HP 48s are aligned and that the units are no farther than two inches apart.
  2. Verify that both machines are attempting to transmit or accept data by displaying "Connecting" messages. If one of the calculators is not displaying a "Connecting" message or is displaying an "Awaiting Server Cmd." message, perform a system halt on that machine. Press RS, then I/O, highlight either "Send to HP 48..." or "Get from HP 48" (whichever is appropriate), and then press the OK menu key.
  3. Verify that system flag -33 is set and flag -35 is clear on both calculators:
    • Press LS, MODES, FLAG, 3, 3, +/-, then SF to set flag -33.
    • Press LS, MODES, FLAG, 3, 5, +/-, CF to clear flag -35.
  4. Perform an IR loop-back test on each calculator:
    • If necessary, turn the calculator on.
    • Press and hold ON
    • Press and release the D key.
    • Release ON. Three vertical lines will appear on the display.
    • If the machine being tested is an HP 48gx, verify that the plastic plug-in card cover is in place and that it covers the clear bulbs in the top end of the calculator.
    • Press EVAL. The message "IRLB" will appear in the upper left corner of the display. If "OK" appears to the right of "IRLB," the calculator passes the loop-back test. If "OK" does not appear, the calculator requires service. Please contact HP.
XIII. When the calculator is turned on, the message "Invalid Card Data" is displayed
  1. Verify that the plug-in card is inserted correctly. If not, remove the card and reinsert it into the card slot, making sure the card is lined up properly with a slot opening.
  2. If the message appeared after a new RAM card was installed or when a RAM card contains ports that have not been used:
    • The message may be disregarded, because ports will be initialized automatically the first time they are used.
      OR
    • Press LS, LIBRARY, NXT, and the PINIT menu key to initialize all available RAM ports. The PINIT command should not affect data currently stored in any port. 3. If the problem persists, remove the batteries and let the unit sit for 48 hours. After 48 hours, replace the batteries.
XIV. The calculator beeps and displays a message different from those listed above
Refer to Appendix B, "Error Messages," of the HP 48G Series User's Guide. If the error message is not listed in the User's Guide, refer to the documentation that accompanied any ROM cards or libraries currently installed in the calculator.

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