Commodore 64 Troubleshooting Guide: Difference between revisions
No edit summary |
|||
| Line 16: | Line 16: | ||
''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 == | ||
=== Visual Inspection === | === Visual Inspection === | ||
| Line 63: | Line 63: | ||
* 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 == | ||
Always verify PSU '''before''' blaming main-board silicon. | Always verify PSU '''before''' blaming main-board silicon. | ||
| Line 88: | Line 88: | ||
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 == | ||
# Check PSU rails, RESET, and system clock first. | # Check PSU rails, RESET, and system clock first. | ||
# Swap/feel VIC-II (dead clock = blank display). | # Swap/feel VIC-II (dead clock = blank display). | ||
| Line 98: | Line 98: | ||
# Remove SID/CIAs/4066 again if stuck. | # Remove SID/CIAs/4066 again if stuck. | ||
== | == RAM Failures == | ||
* '''Eight 4164 DRAMs''' (earlier boards) → each = one data bit. | * '''Eight 4164 DRAMs''' (earlier boards) → each = one data bit. | ||
* '''Two 41464 DRAMs''' (250466/250469) → 4-bit wide. | * '''Two 41464 DRAMs''' (250466/250469) → 4-bit wide. | ||
| Line 113: | Line 113: | ||
* 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 == | ||
{| class="wikitable" | {| class="wikitable" | ||
! Model!!Pal IC!!NTSC IC!!Supply(s) | ! Model!!Pal IC!!NTSC IC!!Supply(s) | ||
| Line 131: | Line 131: | ||
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 == | ||
* '''6581''' (+12 V)—heat-prone; '''8580''' (+9 V)—cool HMOS. Not interchangeable w/o mods. | * '''6581''' (+12 V)—heat-prone; '''8580''' (+9 V)—cool HMOS. Not interchangeable w/o mods. | ||
| Line 143: | Line 143: | ||
No internal fix – replace with same IC or modern clone (''ARM-SID'', ''Swinsid'', ''FPGASID'', etc.). | No internal fix – replace with same IC or modern clone (''ARM-SID'', ''Swinsid'', ''FPGASID'', etc.). | ||
== | == PLA (U17) Logic Chip == | ||
* Ceramic 906114-01 in bread-bins = hottest, most failure-prone IC in C64. | * Ceramic 906114-01 in bread-bins = hottest, most failure-prone IC in C64. | ||
* SuperPLA (CSG 251715/252535) on 250469 seldom fails. | * SuperPLA (CSG 251715/252535) on 250469 seldom fails. | ||
| Line 154: | Line 154: | ||
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 == | ||
Rare, but possible (over-voltage, ESD). After PLA/VIC ruled out: | Rare, but possible (over-voltage, ESD). After PLA/VIC ruled out: | ||
| Line 161: | Line 161: | ||
* Replace with 6510 or 8500 (HMOS) matching clock. | * Replace with 6510 or 8500 (HMOS) matching clock. | ||
== | == Keyboard / CIA Issues == | ||
* CIA-1 (U1) scans keyboard & joysticks, controls tape motor. | * CIA-1 (U1) scans keyboard & joysticks, controls tape motor. | ||
* CIA-2 (U2) handles IEC/user-port & RESTORE NMI. | * CIA-2 (U2) handles IEC/user-port & RESTORE NMI. | ||
| Line 173: | Line 173: | ||
Swap CIAs (identical), socket & replace as required. | Swap CIAs (identical), socket & replace as required. | ||
== | == Joystick Port Faults == | ||
* Trace breaks at DB-9, burnt SIP resistor networks or CIA-1 bit failure. | * Trace breaks at DB-9, burnt SIP resistor networks or CIA-1 bit failure. | ||
* Ground pin 8 often fractures causing *both* ports to mis-read. | * Ground pin 8 often fractures causing *both* ports to mis-read. | ||
| Line 180: | Line 180: | ||
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 == | ||
{| class="wikitable" | {| class="wikitable" | ||
! ROM!!IC/Location!!Boot symptom when bad | ! ROM!!IC/Location!!Boot symptom when bad | ||
| Line 207: | Line 207: | ||
[[Category:Commodore Systems]] | [[Category:Commodore Systems]] | ||
[[Category: | [[Category:Troubleshooting Guides]] | ||