Commodore 64 Troubleshooting Guide: Difference between revisions
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''Note: Disk drives (1541, 1571, etc.) and the Datasette are '''not''' covered here.'' | ''Note: Disk drives (1541, 1571, etc.) and the Datasette are '''not''' covered here.'' | ||
== 🧪 Diagnostic Tools & Techniques == | == 🧪 Diagnostic Tools & Techniques == | ||
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* Coloured-border flash count = faulty RAM bit/chip. | * Coloured-border flash count = faulty RAM bit/chip. | ||
* If nothing at all after stripping to bare minimum ⇒ PLA, CPU, VIC-II or clock logic. | * If nothing at all after stripping to bare minimum ⇒ PLA, CPU, VIC-II or clock logic. | ||
== 🔌 Power-Supply & Voltage Checks == | == 🔌 Power-Supply & Voltage Checks == | ||
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Never run a C64 on an unstable brick; modern replacements or crowbar protectors are highly recommended (≥1.5 A @ 5 V, ≥1 A @ 9 VAC). | Never run a C64 on an unstable brick; modern replacements or crowbar protectors are highly recommended (≥1.5 A @ 5 V, ≥1 A @ 9 VAC). | ||
== ⚠️ “Black Screen” (No Boot) Flowchart == | == ⚠️ “Black Screen” (No Boot) Flowchart == | ||
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# Inspect secondary glue (74LS629 VCO, 4044 latch, 74LS373 bank-latch, 7406 IEC buffer). | # Inspect secondary glue (74LS629 VCO, 4044 latch, 74LS373 bank-latch, 7406 IEC buffer). | ||
# Remove SID/CIAs/4066 again if stuck. | # Remove SID/CIAs/4066 again if stuck. | ||
== 💾 RAM Failures == | == 💾 RAM Failures == | ||
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* If Dead-Test still flags after RAM swap, replace '''both 74LS257 multiplexers'''. | * If Dead-Test still flags after RAM swap, replace '''both 74LS257 multiplexers'''. | ||
* Colour-RAM (2114) only affects on-screen colours, never causes black screen. | * Colour-RAM (2114) only affects on-screen colours, never causes black screen. | ||
== 📺 VIC-II (Video) Faults == | == 📺 VIC-II (Video) Faults == | ||
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Swap with same-type VIC to confirm. Never mix 12 V and 5 V variants without conversion. | Swap with same-type VIC to confirm. Never mix 12 V and 5 V variants without conversion. | ||
== 🎵 SID (Audio) Faults == | == 🎵 SID (Audio) Faults == | ||
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=== Repair === | === Repair === | ||
No internal fix – replace with same IC or modern clone ( | No internal fix – replace with same IC or modern clone (''ARM-SID'', ''Swinsid'', ''FPGASID'', etc.). | ||
== 🧩 PLA (U17) Logic Chip == | == 🧩 PLA (U17) Logic Chip == | ||
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Replace with modern cool-running GAL/FPGA-based drop-ins (PLAnkton, SuperPLA v3, RealPLA, etc.). | Replace with modern cool-running GAL/FPGA-based drop-ins (PLAnkton, SuperPLA v3, RealPLA, etc.). | ||
== ⚙️ 6510 CPU Faults == | == ⚙️ 6510 CPU Faults == | ||
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* Dead-Test cart shows nothing even with good PLA/VIC ⇒ suspect CPU. | * Dead-Test cart shows nothing even with good PLA/VIC ⇒ suspect CPU. | ||
* Replace with 6510 or 8500 (HMOS) matching clock. | * Replace with 6510 or 8500 (HMOS) matching clock. | ||
== ⌨️ Keyboard / CIA Issues == | == ⌨️ Keyboard / CIA Issues == | ||
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Swap CIAs (identical), socket & replace as required. | Swap CIAs (identical), socket & replace as required. | ||
== 🕹️ Joystick Port Faults == | == 🕹️ Joystick Port Faults == | ||
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Continuity-test each DB-9 pin back to CIA; repair connector or replace CIA-1. | Continuity-test each DB-9 pin back to CIA; repair connector or replace CIA-1. | ||
== 🔠 Character ROM & Other ROMs == | == 🔠 Character ROM & Other ROMs == | ||
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Swap with known-good mask ROMs or EPROM-adaptors (27C64/27C128, etc.). | Swap with known-good mask ROMs or EPROM-adaptors (27C64/27C128, etc.). | ||
Cartridges that use their own code/font will boot fine even with bad on-board ROMs. | Cartridges that use their own code/font will boot fine even with bad on-board ROMs. | ||
== Final Notes == | == Final Notes == | ||