AB64 Reliability Advisory

Analog Power Modification

For enhanced reliability, the following modification is recommended, but not required, for all AB64 units containing analog input / output cards. There can be up to four analog input / output cards in an AB64 unit.

To identify an analog input / output card: The card has four DB25 connectors that appear on the right side of the back panel of the AB64 chassis.

Two 4.7 ohm resistors have been involved in analog input / output card failures in the AB64. These two resistors are not required for proper functioning of the card, and the card will function more reliably with these two resistors removed and shorted out with a wire.

The procedure, which must be carried out at a static-free workstation, is as follows:

1. Open the AB64 chassis and remove all analog I/O boards. DSP cards must be removed in order to remove the analog cards. Place DSP cards in static shielding bags during the time that they are out of the unit.
2. Locate chip resistors R16 and R17 near the upper right corner of the analog input / output card. See diagram below.
3. Remove R16 and R17. This is most easily done using two solding irons, and heating both pads of the resistor simultaneously.
4. Solder a solid wire, 20 to 30 gauge, between the pads of R16. Do the same for R17. Make sure the wire only makes contact with the intended pad and does not short to any other point on the circuit card.
5. Reinstall the analog and DSP boards, and replace the unit cover.