The Beocord 9000 utilizes a 3V battery to power its 16-word memory chip, an MCM144102, which is described as a peripheral memory unit in the Motorola 6804 manual but lacks readily available detailed specifications. This chip is responsible for storing calibration data and potentially the system time, although further investigation is required. A visual representation of the circuit is included below.
A positive aspect of the design is the inclusion of diode D27, which safeguards the battery against reverse polarity connection. This suggests that replacing the soldered battery with a holder-based solution is a viable approach.
The battery is situated directly beneath the TIME CAL indicator on the cabinet. In this instance, the original battery exhibited leakage of the lithium compound, evident as a green-grey substance surrounding it. During the battery removal process, a minor explosion occurred due to the leaked compound reacting with heat. Lithium’s high reactivity with oxygen in the presence of heat necessitates caution. Fortunately, protective eyewear prevented any harm. However, it is strongly advised to sever the battery leads using wire cutters before desoldering to minimize risk. Additionally, cleaning the area with ethanol to remove residual compound is recommended. The image below displays the battery location after cleaning.
A 1/3N battery holder was chosen due to the scarcity and cost of tabbed 1/3N batteries. A holder also facilitates easier future battery replacements, as it can be accessed by simply removing the glass panel without tools. The subsequent images show the new battery and the holder.
The Newark 25T0455 battery holder, magnified:
The image below shows the soldered holder. Maintaining correct polarity during installation is crucial; ensure the + and - markings on the holder align with those on the PCB to avoid future confusion.
Finally, the image below shows the holder with the battery inserted. The modification blends well, appearing almost intentional. It is unusual to encounter a soldered battery in such a high-end device, but consumer electronics are often engineered with a limited lifespan in mind.
