D.G. Nova update (boo f'ing hoo)

[Tom Jennings]

The DG drives have the same system, a N.O. relay with a huge cap
yanks the linear motor home, should power fail. ANd there's the
write current interlocks too (probably all std for this type of
drive).


On Fri, 1 Apr 2005, jim stephens wrote:

> Date: Fri, 01 Apr 2005 09:51:13 -0800
> From: jim stephens <jwstephens at msm.umr.edu>
> To: General Discussion:  On-Topic Posts Only <cctech at classiccmp.org> ;
> Subject: Re: D.G. Nova update (boo f'ing hoo)
> 
> In the Western Dynax variety of these drives, there was a signal
> called "funul" which was "function unload".
>
> When a power supply was sensed to be out of spec, or any other
> malfunction was detected, such as an out of range seek attempt,
> funul would be pulled to kill any write current.
>
> The heads would then have a connection made to a set of capacitors
> which had sufficent energy to retract them very quickly (faster velocity
>
> than a regular seek) back to the unload stops.
>
> This ensured an unload when the power cable was pulled.
>
> I had occasions where the heads were energized when the unload
> happened and you could see dead sectors in a spiral all across many
> tracks down to track 0, as the heads unloaded.
>
> If you can run a verify program, and see this sort of thing, just a
> sector
> or two / track, you may have had this happen.
>
> On our drives there was a few gates that could fail to cause this to
> happen.
>
> Jim
>
> Tom Jennings wrote:
>
>> Last week, in the middle of debugging Kermit (and making headway)
>> the 6070 disk dropped dead (I think the technical word for it is
>> 'sh*t the bed').
>
> <snip>
>