Gerrit Wednesday, October 8, 2014, 2:18:50 AM, you wrote: > On 10/06/2014 11:58 PM, Julian Perry wrote: >> >> It's very definitely a KU board - pictures of the worklog can be found >> at https://secure.flickr.com/photos/12745816@N04/sets/72157648230302766/ > Ok, C107 and C108 on your board are not the dangerous kind. Feel free to > replace them, but you don't have to. I probably will - they will be cooked, at best. I plan to measure a couple of the remainder, and if they're significantly out, replace them too. > Also, check the 7812, on my KU, one of the pins was almost broken, > probably from the thermal stress of heating up and cooling down over the > years. If the middle pin of an 78xx-regulator loses connection to GND, > the output voltage will go up. Thanks for the tip. Will do. >> As an aside - KU boards seem to have a bad reputation for edgy >> timing glitches, but this one seems OK. It runs an Easyflash3 quite >> happily, even in kernel replacement mode, and handles VSP without >> memory corruptons - I guess I just got lucky. > VSP problems have been linked to the VIC. So maybe your old 6569R1 is > not affected by it? Not sure. I DO know that I fixed VSP problems in my main 250407 machine by replacing the RAM. > And yes, the KU has a lot of ground issues. If you have an oscilloscope, > check what happens if you hook up GND of a probe to GND and one side of > the board and the probe itself to GND on the other side. >> I'm still puzzled that a schematic for this rather quirky board seems >> to be MIA. > I think you can use the schematics for the 250407 instead... There are a few differences I've noted, but that's what I resorted to doing. Schematics aren't always the gospel truth against the physical board, either: particularly in the Commodore world :) On another topic - Silver: I can confirm that the $C000-$FFFF ROM of that Oceanic drive is mirrored from $8000, so it looks like the upper 32K region is not completely decoded. I noticed this when poking around inside it, when dumping out the ROM. Julian Message was sent through the cbm-hackers mailing listReceived on 2014-10-07 22:00:07
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