RK05 data problems with misaligned drive?

Tony Duell ard at p850ug1.demon.co.uk
Tue Jun 15 12:45:05 CDT 2010


> 
> Salut Tony,
> 
> > 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.
> You mean that the erased trace is guaranteed to be broader than the area that can be sensed by the 
> read head?

Yes, I beleive so. 

> I'll grab some heads and throw them at the drive. Then I'll try again. 
> Currently I have to find a 
> new blower for the unit 0 RK05 of my test system. It shorted and 
> burned yesterday while playing with 
> the rotten drive.

They don;t normally short, what happens is the insulation on the windings 
breaks down, and you get an unwanted earth. And then te magic smoke (and 
flames) come out.

I will have to check the scheamtics, but since this is a 115V motor run 
off the primary of the PSU transformer, is it wired so that it has to 
stand 230V between one end of the windings and chassis ground? If so, it 
might explain why they seem tofail all too often over there.

I am sure you know the blower comes apart. After removing it (4 Allen 
screws hidden by the foam seal), you  can remove the ring under that seal 
(a few self-tapping screws), then the fan blades (Use a long hex key 
between the blades to undo the setscrew), and then seprate the motor from 
the fan housing (2 nuts). The motor itself comes apart by flicking off 
the clims and removing the end plate and rotor. But it is almost 
imposible to rewind it.

I mention this because when one ofmine failed, a friend gave me a faulty 
blower with good winidings and bad bearings. And of course I made one 
good one from the 2. 

If you can find a suitable motro, you could probably fit it to the 
housing and fit the fan blades. A motoe may be easier to find than an 
RK05 blower.

Of course all the screws are UNC sizes, you need imperial (inch-size) 
Allen keys and nutdrivers. But if you work on DEC stuff, you must have 
thsoe anyway.

> 
> >>
> >> 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.
> Of course, I *can* degauss the pack. The question is if I *must* degauss a pack before using it with 
> new track positions.

I think it;'s worth tryiong if you have a sutiable AC electromagnet.

> 
> > Do yuo have any more packs?
> Of course.
> 
> 
> > 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.
> If I had a degausser I'd immediately try it out.

What do you use to rease audio recording tapes?

-tony



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