C64C [PAL]
Ser. No. 440354
Assy 250469
Artwork 252311 (REV 3)
Starting point
This C64C is in for some refurbish. As I understand it should be working, at least to some extent. There might be something which is marginal, but we´ll see during the refurbish.
From the outside the machine looks to be in quite good condition. It is somewhat yellowed, especially some of the keys are partly yellowed, but not complete gouda cheese. There are some signs of use on the bottom right hand side which seems to be some small cuts or dents (?). And it is quite dirty. The pictures does not do it justice, there are more dust and grease than is visible from the pictures.
Refurbishment plan
The refurbishment plan for this C64C (order can vary and some of the tasks will be done in parallell):
- Clean and remove stains from the chassis
- Clean and restore the keyboard
- Refurbish main board (cleaning, checking, repairing, replacing capacitors etc.)
- Verify operation by testing
The plan can be updated during the refurbishment process. Sometimes I discover areas that needs special attention.
Disassembly
First step of the disassembly is to - surprise! surprise! - to remove the three 3 x 8 mm Phillips screws at the bottom.
There are some corrosion on the RF-shield, but that is not to worry about. And some dust. But otherwise first impression is good. Next step is to remove the LED connector, the two machine screws holding the keyboard and the wide keyboard connector (see position of these in the picture above). With these out of the way the complete RF-shield is revealed. First thing I notice is that someone has been here before... The screw that should be in the right hand side corner is missing. Only the traces of it are remaining... Could it be that this machine has been repaired previously?
The remaining six screws are removed from the RF-shield (Phillips 3 x 8 mm), and the RF-shield is simply lifted away. And, holy moly, there is a lot of dirt and grease inside here. There are fluff everywhere. Also, the heatsink paste is completely dried out. It is hard to see the condition of the board before some serious cleaning is done.
Now the mainboard is lifted from the bottom cover. Except from the dirt and grease it appears that the bottom cover, including the stand-offs, are in good condition. There are some corrosion on the bottom RF-shield, but this should not be a problem.
Exterior casing
First things first; it is time for a long bath. Before the top- and bottom cover is placed in mild soap water for about 48 hours the LED is removed. With a flat small screwdriver the LED is loosened from the top cover.
Keyboard
The keyboard is in quite good condition. There is quite some dust and grease, but this is to be expected. All keys appear to be undamaged, and also all springs feels ok. Some of the keys are partly yellowed so some retrobright is required. A detailed description on how to refurbish the Commodore 64 keyboard can be in the "HOWTO - Refurbish the C64 keyboard" article.
All the keycaps are removed with a special purpose puller. No keycap, plunger og spring were damaged during the operation.
Mainboard
This PCBA mainboard is assy 250469 artwork 252311 (Rev 3) - aka a "shortboard". It appears to be complete, but oh my, it is so dirty.
Cleaning
Before starting the visual inspection the mainboard it must be cleaned. As can be seen from the pictures below the dust and grease on the mainboard is substantial.
The socketed ICs are removed before cleaning. And the ICs are cleaned with some isopropanol using an old tooth-brush and some Q-tip.
The mainboard is washed thoroughly with mild soap water. It is not a problem to wash the PCBA, but make sure that it is completely dry before power-on. Below is a picture of the cleaned, but not checked and refurbished, mainboard.
Visual inspection
The mainboard appears to be in good overall condition. I can´t see any damage or significant corrosion of any kind. The only thing I notice:
This mainboard has been repaired previously. Both RAM ICs have been replaced (and socketed). And this rework is not from factory. As can be seen from the picture below (taken before cleaning) there are plenty of flux residue left after the rework.
In the table below all the custom ICs are listed. And as can be seen from this table is that all original ICs were produced between week 12 to 19 of 1987 so I think we can assume that this Commodore 64 was produced in the late spring, or summer, of 1987. Also, I think it is a fair assumption that the C64C were repaired about two years later. The RAM ICs are from week 10 of 1989.
Initial testing
Before the machine is powered on for the first time a check for short circuit on the +5V DC and 9 V AC power rail is performed. This is easy to check at the user port – see the article of Checking the C64 voltages for the position of these. Luckily, there are no short circuit so it should be safe to power on.
Powering on the Commodore 64 results in a: NORMAL BLUE BOOTUP SCREEN.
Next step in the initial testing is a test run with the Dead Test Cartridge. This will not reveal more complex issues, but it gives a good initial test of the major custom ICs. No errors were detected using the Dead Test Cartridge.
Running the diagnostics cartrigde
Knowing that the basic functions of the Commodore 64 works it is good practice to run the full diagnostics. This is achieved by running the software from the Diagnostics cartridge and connecting the harness. All tests pass. See pictures below.
Checking the voltages
For the Commodore 64 to work flawlessly all the different voltages need to present and within acceptable tolerances. A detailed article on the subject can be found in the HOWTO - Checking the C64 voltages. In the table below all the measures voltages are listed (this list will also be updated after refurbishment). All the required voltages are present and within tolerances.
