RK05 data problems with misaligned drive?

[Tony Duell]

> 
> Hi folks,
> 
> I'm just reviving a completely misaligned RK05 drive. I want to get it fully up and running and 
> tested before I use an alignment pack. So I started debugging and got it to the point that I can 
> play with the formatter.
> 
> Here comes the question: The formatter (RKLFMT under OS/8) threw MANY CRC errors when reading back 
> the freshly formatted disk. Changing the head cables at the drive proved that the problem is only 
> with one head i.e. the failures change "side" when you change the head plugs.
> Now I ran the test several times. With random failing disk addresses. And they decreased and 
> decreased... Now I've run two error-free formatter rounds.
> 
> Could it be possible that new data on new tracks (keep in mind that the drive is actually misaligned 
> by means of mechanical alteration!) suffers from interference from old tracks? That's the only 
> reason I can see for this kind of behavior.

I think that's unlikely. There is a tunnel erase head which essentially 
wipes out any old data that might be picked up by the read head. 

Do you know if the heads are good? I've had at least one RK05 head that 
tested OK electrically, looked clean, but which procuded no signal 

> 
> On the other hand that would mean that I'd have to degauss the pack before I ever could use it 
> reliable again.

Since there's no servo infromation or anything like that on an RK05 pack, 
there is no reason why you can't degauss it.

Do yuo have any more packs? If so, try formatting another one. If that 
passes with no CRC errors, it would appear to be a head problem which has 
got better as the drive was used. If you get CRC errors at first which go 
away if you format it a few times, it would apperar to be your suggestion 
of old data causing problems.

-tony