Line 6 floorboards, particularly those employing expression pedals, utilize a phototransistor film strip system for converting pedal position into a digital signal. Specifically, the Line 6 expression pedals commonly use a custom-designed phototransistor array built on a flexible film strip, often manufactured by companies specializing in optical sensing components, with specific models varying across different Line 6 product generations. This design allows for precise and reliable measurement of the light reaching the phototransistors, directly corresponding to the pedal’s angle.
The Inner Workings of Optical Expression Control
The magic behind Line 6 expression pedals lies in their clever use of optics. Unlike traditional potentiometers which rely on mechanical resistance, these pedals employ a phototransistor-based system for transducing pedal position into an electronic signal. Here’s a breakdown:
- Light Source: An LED (Light Emitting Diode) acts as a constant light source. Its consistent output is crucial for accurate readings.
- Optical Flag: A small, opaque flag is mechanically linked to the pedal. As the pedal moves, the flag rotates, obstructing the light path between the LED and the phototransistors.
- Phototransistor Film Strip: This is the heart of the system. The film strip contains multiple phototransistors arranged linearly. These phototransistors are semiconductors that conduct more current when exposed to light.
- Control Circuitry: The signals from the phototransistors are fed into a microcontroller or other signal processing circuitry. This circuitry interprets the analog signals from the phototransistors and converts them into a digital value representing the pedal’s position.
The key advantage of this optical system is its inherent durability. There are no physical contacts that wear down over time, a common problem with traditional potentiometers. This translates to a longer lifespan and reduced maintenance for the expression pedal. The system, however, can be susceptible to dust and dirt if not properly shielded.
Dissecting the Phototransistor Film Strip
The phototransistor film strip is a custom-designed component, rarely available off-the-shelf. While exact specifications are proprietary, we can infer several characteristics:
- Material: The strip is usually made of a flexible substrate, often a polyimide film like Kapton, which provides heat resistance and flexibility.
- Phototransistor Density: The number of phototransistors per unit length (density) determines the resolution of the pedal. Higher density results in finer control and smoother response.
- Spectral Sensitivity: The phototransistors are designed to be most sensitive to the wavelength of light emitted by the LED used in the system, typically in the visible or near-infrared range.
- Response Time: The phototransistors need to have a fast response time to accurately track rapid pedal movements.
- Individual Calibration: In some designs, each phototransistor may undergo individual calibration during manufacturing to compensate for slight variations in sensitivity. This enhances accuracy and consistency across different pedals.
Understanding the Implications for Repair and Maintenance
Knowing the underlying technology behind Line 6 expression pedals is essential for effective troubleshooting and repair. While replacing the phototransistor film strip is often not a feasible option for average users due to proprietary designs and limited availability, understanding its function allows for targeted troubleshooting:
- Symptom: Erratic or jumpy pedal response.
- Possible Cause: Dust or debris blocking the light path. Solution: Carefully clean the area around the LED, flag, and phototransistor film strip with compressed air or a soft brush.
- Symptom: Pedal not responding at all.
- Possible Cause: LED failure. Solution: Check the LED with a multimeter. If it’s not emitting light, it needs to be replaced.
- Possible Cause: Phototransistor film strip damage. This is less likely, but physical damage to the strip can render the pedal unusable.
- Symptom: Calibration issues.
- Possible Cause: Misalignment of the optical flag. Solution: Carefully inspect and realign the flag to ensure it properly obstructs the light path.
Frequently Asked Questions (FAQs)
Here are 12 common questions concerning phototransistor film strips and Line 6 floorboards:
Q1: Can I buy a replacement phototransistor film strip for my Line 6 expression pedal?
Generally, no, these film strips are not sold separately as they are proprietary components. Replacement usually involves replacing the entire expression pedal assembly or contacting Line 6 directly (if they offer such services).
Q2: How can I tell if the phototransistor film strip is faulty?
Signs of a faulty film strip include: erratic pedal response, dead spots, or the pedal not registering any movement. However, other components like the LED or control circuitry could also be the culprit. Proper diagnosis requires careful testing with a multimeter or oscilloscope.
Q3: Are all Line 6 expression pedals the same in terms of their optical system?
No. While the basic principle remains the same, different Line 6 models and product generations may use slightly different configurations, including different LED types, phototransistor densities, and film strip designs.
Q4: Does temperature affect the performance of the phototransistor film strip?
Yes, temperature can affect the performance. Extreme temperatures can alter the sensitivity of the phototransistors and the output of the LED, leading to inaccurate readings.
Q5: What kind of maintenance should I perform on my Line 6 expression pedal to prevent issues?
Regularly cleaning the pedal enclosure, particularly around the moving parts and the optical components, is crucial. Use compressed air or a soft brush to remove dust and debris. Avoid using liquids, as they can damage the electronics.
Q6: Can I use a different LED in my Line 6 expression pedal if the original fails?
Yes, but it’s crucial to select an LED with the same wavelength and intensity as the original. Using an incorrect LED can lead to inaccurate pedal readings and performance issues. Review the Line 6 schematics, if available, or carefully document the failed LED before replacement.
Q7: Is it possible to upgrade the resolution of my Line 6 expression pedal by using a film strip with higher phototransistor density?
While theoretically possible, it’s highly impractical. The microcontroller and control circuitry are designed to work with a specific phototransistor configuration. Modifying the system in this way would require significant hardware and software modifications.
Q8: What tools are needed to diagnose issues with the phototransistor film strip system?
A multimeter is essential for checking the LED and the voltage output from the phototransistors. An oscilloscope can be helpful for analyzing the signal waveforms and identifying noise or distortions. A logic probe can assist with evaluating the digital signals to the floorboard’s processor.
Q9: Are there any known vulnerabilities or common failure points in the phototransistor film strip system?
Dust and debris accumulation are the most common problems. LED failure is also possible. Physical damage to the film strip is relatively rare but can occur if the pedal is subjected to significant impact.
Q10: How does the phototransistor film strip compare to traditional potentiometers in terms of accuracy and reliability?
Phototransistor systems generally offer better long-term reliability due to the absence of physical contact wear. They can also provide higher resolution and smoother response. However, they can be more susceptible to environmental factors like dust and extreme temperatures.
Q11: Can static electricity damage the phototransistor film strip?
Yes, static electricity can potentially damage the sensitive electronic components on the film strip, especially during repair or handling. Always use proper ESD (Electrostatic Discharge) precautions when working with electronic devices.
Q12: What are the advantages of using a film strip instead of discrete phototransistors?
Using a film strip simplifies manufacturing and assembly. It allows for precise alignment and spacing of the phototransistors, ensuring consistent performance across all pedals. It also provides a more compact and robust design.