Adventures in Microcontroller Circuit Debugging
2 days ago
- The author troubleshoots a batch of Floppy Emu devices with failures such as not booting, erratic behavior, and slow operation.
- Initial investigations ruled out power, programming, and chip issues; a blinking LED test showed no activity.
- Switching the clock source to the internal oscillator allowed some boards to boot, indicating a problem with the external crystal oscillator.
- The external crystal circuit uses 18 pF capacitors, but calculations suggested 8 pF would be optimal, hinting at a mismatch.
- Replacing the capacitors with 10 pF did not fix the issue; swapping the crystal to the original model resolved most problems.
- Some boards had a gray burn mark on the crystal, suggesting heat damage during assembly by a new subcontractor.