Agilent Technologies 2712A HOW to Replace the Memory Backup Battery, Tools and Supplies, Parts

Model 890412 Service

HOW TO REPLACE THE MEMORY BACKUP BATTERY

Description

The battery that backs up non-volatile memory has a limited lifetime. It should be replaced every five years or whenever it shows signs of deterioration. Replacing the battery must be done carefully so as to not interrupt the contents of the RAM. If the RAM looses its contents, the entire A2 Digital Assembly will have to be replaced because its serial number and option information will be lost.

Replacing the backup battery consists of unplugging and freeing the A2 Digital Assembly, wiring a power supply and resistor to RAM power supply pin, removing the old battery and soldering in the new one, removing the power supply backup, and re-assembling the instrument.

The normal precautions against electrostatic discharge must be followed but

do not place the A2 Digital Control Assembly on a conductive metal

surface, which could short the battery or the RAM power supply pin.

The substitute power supply must be floating if the solder iron has a grounded tip. (All soldering is done with the HP8904A completely disconnected from the power line.)

Do not apply too much heat to printed circuit connections when soldering. The traces on the multilayer board are easily damaged.

Do not overstress the interconnecting cables.

Tools and Supplies

Desoldering Tool	Resistor, 10 kR
Needle Nose Pliers	Solder Iron
Power Supply (Floating) or 3V Battery	Torx Driver

Parts

If the instrument has serial prefix 2942A and below order a 2.8V battery (HP 1420-0281)and three insulators (HP 3050-0990). If the instrument has serial prefix 2942A and above order a 2.8V battery (HP 1420-0338).

Procedure

1.Switch LINE to OFF and disconnect the power cord.

2.Remove the instrument’s top cover. The cover may be tightly secured in the groove of the bottom cover. If the top cover does not pull off easily after backing out the screw on the rear edge, back out the screw on the rear edge of the bottom cover also.

rev.15DEC89 Troubleshooting (Memory Backup Battery) 8-48.1