Fixing a Commodore 1541 Disk Drive
Adrian's Digital Basement・27 minutes read
The video demonstrates the repair process of a 1541 disk drive from Lincoln City, Oregon, which initially showed faults and smoke due to a blown tantalum capacitor. Replacing the faulty capacitor, troubleshooting various components, adjusting jumper settings, and replacing the CPU ultimately restored the drive's functionality after thorough cleaning and lubrication.
Insights
- Smoke from the 1541 disk drive was traced to a blown tantalum capacitor, specifically C21, necessitating a replacement with a 4.7 microfarad 25-volt tantalum capacitor to restore functionality.
- Troubleshooting the drive involved correcting a faulty jumper setting for the Alps mechanism, addressing abnormal behavior in the 6502 CPU's address and data lines, ultimately requiring the replacement of the faulty 1982 CPU with a newer 1985 version to resolve the issue and ensure proper disk operation.
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Recent questions
How was the 1541 disk drive acquired?
From Lincoln City, Oregon.
What modifications were visible on the drive?
Square and rectangular holes.
What was the cause of smoke emerging from the drive?
A blown tantalum capacitor marked C21.
How was the faulty jumper setting corrected?
J6 for the Alps mechanism.
What resolved the lack of address line activity in the CPU?
Replacing the faulty 6502 CPU with a newer version.
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Summary
00:00
Repairing 1541 Disk Drive from Lincoln City
- Video focuses on repairing a 1541 disk drive acquired from Lincoln City, Oregon.
- Drive is observed to be dirty with visible modifications like square and rectangular holes.
- Initial testing reveals drive powers on with a red LED and continuous spinning, indicating a fault.
- Upon opening the drive, it is noted that the board appears standard with some chips from different years.
- Smoke emerges from the drive during testing, pinpointed to a blown tantalum capacitor marked C21.
- Replacement of the blown capacitor is necessary, identified as a 4.7 microfarad 25-volt tantalum.
- Various tantalum capacitors are available for replacement, with the damaged one desoldered and a new one installed.
- Further troubleshooting involves checking voltage levels, logic chips, and signals to the 6502 CPU.
- A faulty jumper setting, identified as J6, is corrected for the Alps mechanism, affecting drive operation.
- Detailed oscilloscope testing reveals abnormal behavior in address and data lines of the 6502 CPU, indicating potential issues with ROM access and code execution.
15:01
Troubleshooting and Repairing Vintage Computer Components
- The lack of activity on the data lines indicates the CPU is not executing any instructions.
- Two ROM chips are present, with chip select lines controlled by decoding logic.
- Pin 20 on the ROM chips serves as the chip select line, with only one chip selected at a time.
- The upper ROM chip, containing code at ffff, is currently selected.
- Despite correct ROM selection, the CPU shows no address line activity, suggesting a faulty CPU.
- All address and data bus lines appear normal, indicating no conflicts with other chips.
- Replacing the faulty 6502 CPU from 1982 with a newer 1985 version resolves the issue.
- Cleaning the disk drive involves using isopropyl alcohol on cotton swabs for the heads and silicon grease for the moving parts.
- Ensuring the disk clamp area is clean and not greasy is crucial for proper disk operation.
- After cleaning and lubricating the drive, testing confirms its functionality, including formatting and reading/writing disks.
