Re: R-DOS (REX DOS??) on an oceanic 1541 clone drive

From: Gerrit Heitsch <>
Date: Tue, 07 Oct 2014 17:18:50 +0200
Message-ID: <>
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

Ok, C107 and C108 on your board are not the dangerous kind. Feel free to 
replace them, but you don't have to.

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.

> 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?

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...


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Received on 2014-10-07 16:00:07

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