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I have repaired last year these computers for a dear friend.

Commodore 64 #1

Defect:

• Black Screen.

Replaced parts:

• Replaced 4 x 4264 RAM (U9,U10,U11,U12)

Commodore 64 #2

Defect:

• Out of Memory.
• Expansion Port (Cartridge) don’t works.

Replaced parts:

• Replaced 3 x 4264 RAM (U12,U24,U22)
• PCB track interrupted of the expansion port (A5 Address Line). Fixed with a bridge.

Commodore 64 #3

Defect:

• Garbled screen and then Out of Memory.

Replaced parts:

• Replaced 4 x 4264 RAM (U24,U12)
• Replaced 1 x 74LS257 Data Selectors/Multiplexers (U13)

Commodore 64 #4

Defect:

• Black Screen and then Out of Memory.
• No Sound.

Replaced parts:

• Replaced 2 x 4264 RAM (U9,U10)
• Replaced 1 x 74LS257 Data Selectors/Multiplexers (U25)
• Replaced 1 x 6581 SID (U18)

Commodore 64 #5

Defect:

• Black screen / Sometimes normal startup without text.

Replaced parts:

• Replaced 1 x 906114 PLA (U17)

Commodore 64 #6

Defect:

• Black screen then garbage screen.

Replaced parts:

• Replaced 1 x 74LS257 Data Selectors/Multiplexers (U25)
• Replaced 1 x 74LS258 Multiplexers (U14)
• Replaced 2 x 4264 RAM (U21,U12)

Other:

• Cold solder on the power switch.
• False contacts on the socket pins of the IC 6569 (U19)

Commodore 64 #7

Defect:

• Black screen and then checkerboard screen.

Replaced parts:

• Replaced 1 x 6569 VIC (U19)
• Replaced 1 x 4264 RAM (U11)

Commodore 64 #8

Defect:

• Black screen … then garbage screen … then normal startup screen with border but without text.

Replaced parts:

• Replaced 1 x 6510 CPU (U7)
• Replaced 3 x 4264 RAM (U12,U22,U24)
• Replaced 1 x 906114 PLA (U17)
• Replaced 1 x 901226-01 BASIC ROM (U3)

Commodore 64C #9

Defect:

• Normal startup screen with garbage.

Replaced parts:

• Replaced 1 x 6526 CIA (U2)

Commodore 64 #10

Defect:

• Black screen and then Out of Memory.

Replaced parts:

• Replaced 1 x 74LS257 Data Selectors/Multiplexers (U13)
• Replaced 1 x 4264 RAM (U22)

Commodore 64 #11

Defect:

• Black screen and then Garbage screen.

Replaced parts:

• Replaced 1 x 74LS257 Data Selectors/Multiplexers (U25)
• Replaced 1 x 906114 PLA (U17)

Commodore 64 #12

Defect:

• Startup screen with 689 bytes free and after 10 minutes of operating i have seen a degradation of the image until to see a startup screen with border but without text.

Replaced parts:

• Replaced 2 x 4264 RAM (U24,U10)

Note:

• Some ram on the pcb are missing, so i don’t know if the fault was more extended.

Commodore 64 #13

Defect:

• Occasionally freezes… occasionally not… occasionally freezes… occasionally not… and so on…

Replaced parts:

• Replaced 1 x Socket PLA 906114

Commodore 64 #14

Defect:

• Black Screen. The MOS 6569 was Very hot.

Replaced parts:

• Replaced 1 x MOS 6569
• Replaced 1 x MOS 8701

Commodore 64 Repair #15

Defect:

• Black Screen.

Replaced parts:

• Replaced 1 x NE 556 (U20)
• Replaced 1 x 7406 (U8)