When Volume Controls Suddenly Fail

How Uncommunicated Supplier Changes in Car Radios Can Lead to Costly Complaints

Failure analysisFaulty Volume Controls: A Production Risk for Car Radio Manufacturers

"She only likes music when it's loud..."

Music fans love to crank up the volume in their car radios, especially for their favorite songs. However, if the volume control is faulty during production, it can not only dampen the listening experience but also lead to significant production issues. For manufacturers, this can potentially result in costly delivery halts and recalls, disrupting the entire supply chain.

PRoblem statementLouder, Yes,
Quieter, No

A well-known manufacturer of car radios and consumer electronics is facing a growing number of complaints. The reason: a specific radio model's volume control is failing. While the volume can be increased without any issues, turning it down is no longer possible.

This defect occurs suddenly, despite the fact that the volume control has been produced and installed without problems for years. Notably, the complaints are primarily coming from regions with warm climates and polluted air, suggesting harmful gas corrosion as a possible cause.

The picture shows a consultation, both the customer and the engineer looking at a circuit board and discussing cleaning processes for electronic assemblies. | © @The Sour Cherry Fotografie - Michaela Curtis
A green circuit board is viewed through a Keyence microscope by a laboratory employee at Zestron's analysis centre. | © @The Sour Cherry Fotografie - Michaela Curtis

TroubleshootingHarmful Gas Corrosion as the Cause?

Initially, suspicion fell on harmful gas corrosion as the trigger for the volume control malfunction. This type of corrosion occurs when electronic components are attacked by harmful gases present in the air. However, a detailed analysis involving various harmful gas tests did not confirm this assumption.

To identify the actual cause, the investigation continued. A ZESTRON Technology Analyst then examined the rotary switches used in the radios to gain deeper insights into the potential triggers of the defect.

AnalysisMechanical Rotary Switch Under Scrutiny

In the next phase of the investigation, both an "old" functioning rotary switch and a sample from the new series were examined. It was revealed that the lubricant in the new model had been changed. However, this new lubricant was not suitable for the demanding environmental conditions in warm regions. Instead, it aged quickly and clumped under high temperatures, ultimately causing the malfunction of the volume control.

Solution approachAdjusted Lubricant Ensures Smooth Volume Control

This analysis result was crucial, but another issue came to light: The change in the lubricant composition had not been communicated to the customer by the supplier, which prevented an early functionality check of the new components.

To avoid major production outages and costs, the lubricant had to be quickly switched to a more aging-resistant variant. This proactive adjustment ensured that the volume controls functioned reliably again, maintaining the listening experience even at lower volumes.
 



 

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Surface cleanliness Zestron Meier | © @The Sour Cherry Fotografie - Michaela Curtis
Autor: Dr. Helmut Schweigart

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