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:
- 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.
- Locate chip resistors R16 and R17 near the upper right corner
of the analog input / output card. See diagram below.
- Remove R16 and R17. This is most easily done using two solding
irons, and heating both pads of the resistor simultaneously.
- 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.
- Reinstall the analog and DSP boards, and replace the unit
cover.
