Waiting for the deadtest

So since CP/M is acting all wrong, there is clearly something up with the C64. I hadn’t opened it yet, and I almost regret doing so as despite it ‘working’ it was a MESS!

After separating the case halves, and unplugging the top LED, I saw that capacitor C66 had exploded. There was some faint hint of staining from the top, but I didn’t expect it to be something like this.

The board was disgusting, like the cap had something spilt onto it? Then it ruptured? or did it rupture? it still powered on and ‘worked’ despite this gunk.

Isopropyl is in short supply still, so I did something probably dumb, I took a 50% baiju a brush and gave it a quick rinse.

Cleaned up board

with all the fuzz removed it’s a 250469 REV.B… which I understand is a pretty late model. It’s one of the short boards, which not a lot of chips, which I’d hope means fewer things to fault, although at the same time, some of these chips are going to be impossible to source.

Also, I should add that I found various C64 schematics online, and none had a 470uF cap for C66. Maybe I’m going crazy? I found an E-bay auction for replacement caps, and yep, they also have a 470uF in there. Am I crazy?

TONEREX 50v 470uF(M)

Now I was hoping that being in Hong Kong, that means I could actually find some retail shop actually selling capacitors. So I went around the audiophile places and scored this higher voltage cap for a whopping $5 USD! The store owner was insistent that this was for ‘high end audio gear’ and not my toy 80’s computer. That this thing was somehow some magical ‘audio only’ capacitor. Has anyone heard such a thing? Is this like audiophile grade SATA cables?!

Massive cap installed!

So I replaced the cap, and NOTHING. The power led turns green and that’s about it. I had to dig up a simple volt meter and yeah power is going places. I gave up and went home for the night. Turned it on this morning expecting a POP or further disappointment, and it fired up.

A bit of digging around I found HeadAlign v1.1, which I transferred to the SD2IEC, and much to my amazement the stupid tape drive started working, although it was a full screw turn out of alignment, and it looked normal (no picture). I rewinded the tape, and loaded up Hans Kloss, and it worked!

Sadly CP/M still is printing far too many things to the screen. I guess I need to replace more caps, and keep on waiting for that dead test cart to get a bit of a further hint. Although my soldering skills are terrible.

5 thoughts on “Waiting for the deadtest

  1. I know Nichicon has their “gold” line for audio use, but even those are overpriced snake oil when you compare the specs to their low leakage capacitor series. Any low leakage capacitor is fine in audio paths, especially compared to what was available in the 1980s.

    Tonerex is ELNA’s “audio grade” cap line. Not a bad part, but still expensive when any 470uF cap could have done the job.

    C64s can be fussy. Start with a simple re-seat of all the ICs (what few there are) and cleaning contacts on everything.

    • I was expecting to pay under $1 Hong Kong for them, as it’s a capacitor after all.

      The whole thing was so over the top buying it, as it was a crowd of someone buying vacuum tubes, face masks and temperature lasers…

      The whole “for audio only” and crazy prices really had me wondering, especially as the machine did nothing after I swapped it. But so strange it works fine the next day. And it’s still working today.

      So odd.

  2. Seriously, don’t even go there when it comes to dumbasses doing stupid things that ‘massively improve’ the quality of their audio.

    I was looking up how to create a RAM disk in 2016 without resorting to the dumb iSCSI target hack, and I found someone who was giving instructions on how to run Windows Server 2016 entirely from a RAM disk because he ‘swore’ that it made his music sound better. I wish I was joking. I just don’t get it.

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