NOVA4 6070 disk booboo

From: Jay West <jwest_at_classiccmp.org>
Date: Wed Feb 2 14:06:19 2005

You wrote....
> Reassembled, READY, spinup, brush, head load.... CRASH. Top
> surface of the fixed disk unmistakably crashed.
>
> While I had the dust cover off the first time I did look at the
> heads and the platter surfaces. I didn't clean the heads
Almost always the problem is failure to completely clean the drive; heads,
airfilter and ducts, all platters (both surfaces)... you've got to
disassemble the platters, clean and buff them, clean the head armature, ALL
internal cavities, etc. Yes, it could be a pre-existing crash. The above
would have caught that ;) To clean an unknown HP 7906 drive for example,
takes me a good 5+ days solid before even looking at mechanics, then
electronics. You can't be too anal or thorough about this. One spec of dust
is all it needs to poof. Working under an extremely bright light will
educate on just how much dust is floating in the air :)

> Knowing that the platter was trashed, I took off the dust cover,
> cleaned the platter with a new pad, and felt for large bumps, and
> ran the READY sequence again. Crashed two more times then I
> stopped.
Yeah, I bet it did ;) Don't clean the platter in place, too hard to do a
good job and buff it. Remove the platter. Also break out a dial test
indicator and measure the runout/flatness (which you have to do when you
replace it anyways).

> It suuuuure looks like the platters on the removable cartridge are
> physically the same as the fixed platter; and since I have two
> spare (three total) carts I may attempt surgery.
The key of course if is there is a designated servo platter, or if the drive
uses a glass reticule with cylinder markings on it and an optical system. I
can't speak for other drives, but at least on the 7905/7906 - the servo
platter is actually a completely different magnetic coating from the data
platters. You can see the difference when you get a good look at the
platter. Servo head is different too. On the HP 7900A, the removable and
fixed platters are identical (optical type drive).

I should buy stock in Kim-Wipes :>

Jay
Received on Wed Feb 02 2005 - 14:06:19 GMT