HP 3468A Battery Replacement

The battery in this unit is a SAFT LX1634 3.0V lithium cell.

The replacement battery is a Panasonic BR-2/3A. It is exactly the same physical size as the original.

The diode is securely soldered to the battery lead and covered with heat shrink.

The LCD ribbon cable is in the way and needs to be disconnected.

U509 is the static RAM device which needs to stay powered.

3V battery pack connected between ground and the diode junction point (which is the SRAM Vcc node.)

Old battery removed, holes cleared. All work done from the top side.

Install the new battery and solder both leads securely.

Apply enough solder to secure the battery and fill the hole.

With the power still on, carefully unsolder the external 3V battery pack leads.

Top diode (CR550) feeds SRAM Vcc from the 5V supply.

With the power still on, SRAM Vcc is 4.40V.

New battery voltage is 3.39V.

The new battery voltage should also appear on the anode of the bottom diode (CR551). If it does, it should be safe to turn the power off.

Turn power off. The new battery now supplies the SRAM Vcc node at 3.19V.

Power turned back on. Self-test passes, no errors.

Calibration still looks good.