Basic Fax Modem Hardware Troubleshooting

This document contains basic troubleshooting procedures for fax modem card difficulties. Portions of this document contain information supplied to Gateway 2000 by Traveling Software, Inc. For a complete listing of Commworks documents available from the FaxBack® service, you may order FaxBack® catalogue 5 by calling 800-846-4526 with a touch tone telephone.

Possible causes:

  • The fax modem is not installed, not connected, or not turned on.
  • The fax modem is not configured for the correct COM (serial) port and /or IRQ (interrupt) setting in your System Setup or CMOS.
  • The telephone line is connected to the wrong connection on the Fax Modem card.
  • The Fax Modem needs to be reseated in the computer.
  • Newly added hardware is conflicting with your Fax Modem.
  • The computer does not recognize the COM (serial) port and/or IRQ (interrupt) values or combination of values that is available.
  • The telephone line from the computer to the wall jack is defective.
  • Excessive static or line noise is distorting the fax modem’s transmission or reception of faxes or modem communications.

Basic Troubleshooting

Fax modem card connection

Make sure that the Fax Modem card is securely seated in its slot in the computer. Power the computer off. Remove the outer case from the computer as instructed in your User’s Guide. Once inside the computer, locate the fax modem card. Remove the screw that is holding the card in the computer. Gently but firmly pull the fax modem card straight out of the computer. Align the card in the slot that you just removed it from and push it firmly back into the slot with the heels of your palms. Slide the case back on the computer and try to access your modem again with your communications program.

Telephone line hook up to the fax modem card

The physical telephone line that connects your fax modem to the wall jack must be plugged into the Telco or Line jack on the fax modem. The jack labeled phone is strictly for a voice phone. Make sure that the line coming from the wall is plugged into the correct jack. If the telephone line is plugged into the wrong jack, you will receive "No Dial Tone" or "No Carrier" error messages in your communication software.

Telephone line defects

The telephone line from the computer to the wall should be checked to insure that a regular telephone will work when it is plugged in. If you have another phone line available, try using an alternate telephone line to eliminate any possibility that the phone line is defective.

Telephone line static or noise

Excessive static or line noise distorts the fax modem’s ability to communicate with other fax modems. Have your local telephone personnel check your telephone lines to make sure that the lines do not need any modifications to reduce static and noise.

Newly added hardware

If you have added any new hardware, such as network cards or sound cards, remove it. The hardware may be trying to access the same COM port or IRQ as your fax modem card. Once you remove the new hardware, try to access your fax modem with your communication software.

COM port and IRQ settings

The fax modem requires a COM (serial) port address and an IRQ (interrupt request) in order to function. The COM port and IRQ for the fax modem can not be used by anything else within the system. The only way to be absolutely sure what these settings are is to consult the fax modem User’s Guide and compare the settings with the physical jumpers and switches on the fax modem card. If another device is using the COM port or IRQ that your modem is attempting to use, the fax modem will not work.

COM port and IRQ setting in System Setup or CMOS

Your computer, by default, uses certain COM port and IRQ settings for serial connections on the back of the system. If these settings are not modified, the fax modem will not work. Consult your Computer System Technical Reference for information on enter Setup or CMOS and for the location of the Onboard COM port or Serial port settings. Follow the on-screen instructions to Disable the COM port setting that your fax modem is using. For example, if your fax modem is using COM1, IRQ4, highlight Onboard COMA or Serial port 3F8H and change the setting so that it says Disabled. Follow the on-screen instructions to Save and Exit Setup. Once the system has finished rebooting, try to access your fax modem with your communications software.

Valid COM port and IRQ values or combinations

It is important to remember that computers have standard sets of COM port and IRQ values or combinations. COM 1 and COM 3 share the IRQ setting of 4 while COM 2 and COM 4 share the IRQ of 3. The most common addresses (COM port) for fax modems are COM1, IRQ4 or COM2, IRQ3. Other combinations are available but make sure that you are using valid combinations or your modem will not work. For more information on COM port and IRQs, reference the computer section of your local book store.

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