Commodore 64 Diagnostic Instruction and Troubleshooting Manual (326070-01)
The C64 Diagnostic Instruction and Troubleshooting Manual (assembly #326070-01) is Commodore Business Machines' manual for the C-64 Diagnostic Kit, the dealer test kit for the Commodore 64. The title page carries a 1992 Commodore Electronics Limited copyright. The scan has 25 pages: cover, title page, contents, Section 1 (pp. 1-1 to 1-8), Section 2 (pp. 2-1 to 2-10), Commodore's three-page "64 Troubleshooting Guide" and the back cover. It has no text layer.
Contents
[edit | edit source]Section 1, Operation and Test Instructions: unpacking, p. 1-1; basic diagnostic theory, p. 1-1; installation, p. 1-2; operation, p. 1-2; diagnostic test description, p. 1-3.
Section 2, Basic Troubleshooting Guide: basic preliminary checks, p. 2-1; system power supply, p. 2-3; system reset, p. 2-4; system clocks, p. 2-4; system video, p. 2-6; system RAM, p. 2-7; system ROM and I/O, p. 2-9; PCB replacement, p. 2-10.
The kit has a diagnostic program cartridge, a user port hardware adapter, a keyboard PCB and a cable harness. The cartridge sits at $8000-$9FFF; at power-up the C64 reads $8004-$8008 and runs the cartridge if it finds "CBM80" there. The program tests the 6510, RAM, ROM and the internal I/O and displays each test, its status (OK or BAD) and a possible failed IC (p. 1-1).
| § | Test | § | Test |
|---|---|---|---|
| 5.1 | Zero page | 5.10 | Keyboard |
| 5.2 | Stack page | 5.11 | Control port |
| 5.3 | Screen RAM | 5.12 | Serial port |
| 5.4 | RAM test 1 | 5.13 | User port |
| 5.5 | RAM test 2 | 5.14 | Timers 1A, 1B, 2A, 2B |
| 5.6 | PLA | 5.15 | Interrupt |
| 5.7 | Colour RAM | 5.16 | Sound |
| 5.8 | KERNAL, BASIC and character ROM | 5.17 | Lower screen display |
| 5.9 | Cassette port |
Section 2 is a measurement-led procedure for a machine with no video at power-up. Every reading is taken with an oscilloscope and the diagnostic cartridge fitted, within 10 %. Eleven preliminary checks cover the +5 V, +5 V CAN and +12 V supplies at U5 and U19, RESET at U7 pin 40, the 14.3 MHz, 8.18 MHz and 1.0 MHz clocks, and the three video outputs at CN5. Each later step gives the expected reading and the parts to suspect if it is wrong. Steps are marked B (basic), A (advanced) or P (signals at power-up).
What this manual settles
[edit | edit source]- Expected supply readings: 9 to 12 V AC at CN7 pins 6 and 7, +9 to +12 V DC at VR2's input, +15 to +18 V DC at VR1's input (pp. 2-3 and 2-4).
- A known false result. On some older 5-pin video boards the control port test reports BAD and names the 6581 SID (U18) every time, because C48 and C93 at SID pins 23 and 24 were fitted at a different value. Commodore gives the correct value as 1800 pF and says the capacitors need not be changed, since paddles still work (p. 1-6).
- The CIA time-of-day clocks shown during the run should agree: a wrong AM clock points to U1, a wrong PM clock to U2, both wrong to the 60 Hz TOD input (p. 1-8).
- Several failed RAM chips may indicate a bad power supply (p. 2-7).
What this manual does not contain
[edit | edit source]- No schematics, parts lists or board layouts; for those see Commodore 64 / 64C Service Manual.
- Long-board designators only. The checks do not cover the 250469 (E) board's numbering.
- The diagnostic program itself; the manual describes the cartridge but does not list its code.
Pages that cite this document
[edit | edit source]- Commodore 64 Troubleshooting Guide (preliminary checks, supply, reset, clock, video and RAM steps)
- Commodore 64 General Maintenance (supply readings, reset timing)
- Commodore 64 Capacitor Replacement Guide (regulator input voltages)
- Commodore 64, Commodore Test Cartridge Index, Maintenance Guides
Download: C64 Diagnostic Instruction and Troubleshooting Manual (326070-01).pdf (10 MB)