C128 fixing video signal
Revamping the Commodore 128 Video Output: Removing the RF Modulator for Enhanced RGBI Output
Today I’ve decided try to fix the video signal on my C128. The video signal was not as bright as it should be.
The Commodore 128 (C128) is a vintage computer that has carved its niche in the hearts of retro computing enthusiasts. When it comes to video output, many users have wrestled with the limitations and quality of the original RF (radio frequency) modulator. This article delves into the process of removing the RF modulator and replacing it with a high-quality RGBI output using the TSH7316 IC, a specialized HDTV video amplifier. Leveraging RGBI not only enhances the video quality significantly but also makes connectivity with modern displays much easier.
History of Commodore 128 Video Technology
The Commodore 128 was introduced in 1985 as a more advanced version of the C64. It featured capabilities for 80-column text display through its Z80 co-processor, and initially, it utilized a simple RF modulator for video output. While satisfactory for its time, the modulator provides limited resolution and color fidelity, which can be quite undesirable for contemporary viewing standards.
The introduction of RGBI (Red, Green, Blue, and Intensity) output made it possible for the Commodore 128 to connect directly to monitors capable of delivering higher resolutions and superior color accuracy. However, many users are unfamiliar with the RGBI output or may not have the correct hardware connections. By utilizing the TSH7316, a high-performance video amplifier, one can enhance the video signal to be clearer and more vibrant, significantly improving the output experience.
Features of the TSH7316 IC
The TSH7316 is a highly-regarded video amplifier IC designed for high-definition applications. Here are its notable features:
- High Video Bandwidth: Capable of processing signals up to 5 MHz, which supports better resolution and minimizes blurring for moving images.
- Low Power Consumption: This efficient design ensures minimal heat generation, which is critical in compact systems like vintage computers.
- Integrated Signal Processing: The TSH7316 allows for fine-tuning of color and intensity signals, making it possible to calibrate the video output based on user preferences or display requirements.
- Flexible Input and Output Connections: It can accept RGB input signals directly, interfacing smoothly with typical display technology, including modern CRT and LCD monitors.
By transitioning to this advanced solution alongside the RGBI output, hobbyists can reinvigorate their Commodore 128’s graphics capabilities.
Detailed Description of the Process
Step 1: Disassembling the Commodore 128
Start the process by ensuring the Commodore 128 is powered off and unplugged. Careful disassembly is crucial to access the internal components without causing damage.
The image depicts the C128’s internal circuit board, showing various electronic components.
Step 2: Identify and Remove the RF Modulator
Locate the RF modulator on the motherboard—the component with multiple pins connected to the motherboard and a coaxial output. desolder the connections carefully using a soldering iron to avoid damaging the board.
The image shows a disassembled electronic device indicative of a hands-on repair task.
Step 3: Connecting the TSH7316
The TSH7316 is a HDTV video amplifier IC that can be used to replace the RF modulator in the C128. (3-Channel HDTV Video Amplifier With 5th-Order Filters and 6-dB Gain)
Once the RF modulator is removed, you will use the RGBI output pins that were connected to the modulator. Solder the TSH7316 IC onto a pre-designed or custom PCB that matches the original pinout requirements for the RGBI signals.
A custom PCB showcasing various components necessary for interfacing with the TSH7316.
Step 4: Finalizing the Circuit Connections
Next, ensure that all the signals (R, G, B, and Intensity) are correctly routed from the TSH7316 to the appropriate outputs. Follow the original signal paths as indicated in the layout diagrams to avoid confusion.
Close-up showing the intricate detailing of the connected components, including capacitors and ICs.
Step 5: Testing the Installation
Once you have completed the modifications, it’s time for a test. Reassemble the Commodore 128 securely and connect it to a monitor that supports RGB input. Power on the device and check to see the video quality.
Conclusion
By removing the antiquated RF modulator and replacing it with the TSH7316-based RGBI output, you can substantially enhance the visual fidelity of the Commodore 128. Not only do you revive an iconic piece of computing history, but you also make it capable of displaying rich graphics that are befitting of modern standards. This process is not only a rewarding technical challenge but also fosters a deeper appreciation for the engineering behind vintage computing devices. Whether you are a hobbyist or a seasoned collector, this upgrade will certainly breathe new life into your Commodore 128.