The Pictorial C64 Fault Guide
pictorial64.com
pictorial64.com
Is there a way to load software into it? The "Load Snapshot" menu option is blank ...
I've put up some stuff here (mostly recent demo scene demos, it's mixed with other systems though): https://floooh.github.io/tiny8bit/
The Snapshot menu is just for storing and restoring emulator snapshots (e.g. the current state of the emulator, mostly useful for debugging)
Take a dead 64 showing nothing but a black screen, try the dead test cartridge, follow its lead or start desoldering, socketing and replacing chips.
And suddenly you have a working forty year old Commodore 64.
I fixed our two C64s that had been stored broken for 30+ years. Black screen to full working condition.
Last time I had seen them working I was about 5 years old. Very satisfying and nostalgic.
Some RAM chips were getting hot, so I socketed and replaced these. No progress otherwise, so I got myself a dead test cartridge.
One of the C64s had video capture card blink the screen on power on, the other not even that.
From this I correctly guessed dead VIC-II. Moving the working one to the other machine made that machine show the memory error blinks from the test cartridge. Swapping the other PLA finally allowed the memory test to end, and the display to show up.
I also had to replace a 74-series logic chip in one of the RAM rows, not sure which computer, do not remember how I figured that out. A color SRAM was also bad.
The remaining machine, I found that 6510 clock output was missing, from which I deduced dead 6510, which a swap confirmed.
Oh, and one of the two sids caused errors, so I had to replace that too.
When this happens, depending on how long it's on it can fry every chip on that line.
That's why everyone advises not to use the original power supplies even for a quick test. Even if it tests 5 volts before you plug it into the computer it can fail at any moment.
Back at the time, we (little me and my family) already knew it was bad. But we weren't aware of its failure modes. All we observed when measured was low voltage, and that it "sometimes worked".
That's why so many C64s were damaged, and still are, when people connect their old supply without the knowledge (or against warnings) of such a nasty design flaw.
My Christmas 1982 model died with a faulty PLA well within the warranty period.
The real takeaway: Do not ever use CBM's C64 PSU. Get a modern one; they're all safe.
A thousand times this! The C64's PSU is a pretty awful voltage regulator that badly creates two voltages (5V DC and 9V AC, so even two different types), and only gets worse with age, to the point that it overshoots the 5V DC by so much that it fries the chips.