A Colour Classic needs some help!

[techniktobi]

I've been working on this project on-and-off for over a year now. At some point I got the CC to boot up to the point of the boot-media-question-mark (the original HDD was removed, tested, and declared dead). However, the machine didn't seem to make any attempts at reading a floppy when inserted. The question mark kept flashing, the cursor did move but no noise whatsoever from the floppy drive (already did a service on that, tested it and works). The entire logic board has been recapped at this point, as well as some of the analog board capacitors that are known to be notorious for failing on these machines (the larger ones that didn't show any signs of leakage have been left untouched). This is where I left off a few months ago.

Now as I wanted to continue on this project I started by testing if anything changed/is different from what I remember. On a first boot, everything seemed to be exactly the same as I left it. However, once I opened up the machine and tried to boot again, the behavior changed (see first video), playing part of the crash-chime, then the normal boot chime but no further sign of life after that. A few minutes later upon a second try, nothing happened apart from some high pitched sound at power up/down (see second video).

I'm not sure how to continue at this point. I've already invested quite some effort into this project and I'm sure I'm missing something rather obvious but don't really know where to continue. I'm somewhat sure that the issue has something to do with the analog board, so my next guess would be to reflow the solder joints there but I'm happy for any other potential ideas to explore here. I don't have any sophisticated equipment apart from an old oscilloscope, a multimeter, soldering iron and so on, nor a second similar machine to swap and test components with.

(Sorry if there are some errors; english is not my primary language)

 

[cheesestraws]

This may sound trivial, but have you cleaned the edge connectors that both the AB and LB plug into? The crash bong would counterindicate this, but on the other hand, they seem to get crufted up disconcertingly easily and this can cause weird issues where only some of the I/O works, or power is intermittent, or when you leave it for a while behaviour changes for thermal reasons. I had to thoroughly clean every one of mine.

 

[techniktobi]

This may sound trivial, but have you cleaned the edge connectors that both the AB and LB plug into? The crash bong would counterindicate this, but on the other hand, they seem to get crufted up disconcertingly easily and this can cause weird issues where only some of the I/O works, or power is intermittent, or when you leave it for a while behaviour changes for thermal reasons. I had to thoroughly clean every one of mine.

I did clean them at some point, but I can't guarantee that I didn't miss a spot, so I'll try that again! Any thoughts on the idea of reflowing the connections on the AB?

 

[chrisrueckert]

This may be a another trivial one: Did you try to turn it on with a different keyboard and ADB cable?

 

[techniktobi]

This may be a another trivial one: Did you try to turn it on with a different keyboard and ADB cable?

Haven't tried this since the same cable & keyboard work fine on other systems.