24 Oct
2015
24 Oct
'15
4:36 p.m.
On 10/24/15 11:40 AM, tony duell wrote:
So, a quick update here (and some idiocy on my part):
I (carefully) opened up the Symbolics' XT-2190 and took a quick look;
the rubber bumper that Joseph mentioned (and it is rubber in this one --
my other opened drive has a plastic bumper) has started
crumbling/turning to goo. Portions of it had already chipped off. This
bumper acts as both the start and end stop for the head assembly.
I removed the remainder of it (it's held on with a circlip) and spun the
drive up (to see if they had just been stuck to the bumper) to the same
effect as before -- the heads recal and then it just buzzes. Then I
gave the heads a nudge just to see what would happen, and... they ran
off the end of the platters (no stop anymore) and well, I feel kinda
stupid. Sigh.
To add insult to injury, one of the heads is loose (the glue holding it
on dried up and it fell off after the impact of running off the platter)
so this drive is basically toast. At least now I can kind of see how
one takes this drive apart to remove the spindle; if I get overly
ambitious and find a working sacrificial XT2190 to start with I could
almost see myself doing a spindle replacement surgery to see if I can
recover the data.
I think I'll stick to solid state devices for awhile.
- Josh
That's
pretty much what I figured. I took a closer look at one of the
other dead XT2190s I have that I'd opened up to inspect awhile back and
there are a few ICs surface-mounted to the flat ribbon cable running to
the head assembly. I suppose it's likely that one of these has failed,
though actually repairing it would be a trick involving some very
careful disassembly in a very clean environment. (And a nonexistent
service manual.)
I have had (in other devices) dry joints on SMD devices on
flexiprints. But
resoldering them inside the HDA is not going to be easy...
Most likely those ICs are head switch/preamp devices and the servo head
preamplifier. They are very likely to be custom.
On older/larger drives (the sort of thing I am more likely to work on) the ICs were
often DIL packages on a normal PCB. Often you couldn't replace them without opening
the HDA :-(. Micropolis had a nice feature on the 1200 series (8" hard drives)
though --
the PCB was mounted over a hole in the HDA casing (obviously with a gasket). The heads
were wired to the inside face of the PCB, the cable to the logic board plugged into the
outside face. The ICs were plugged into turned pin sockets on the outside. So on that
drive you could field-replace them. They were custom chips, though. And of course you
couldn't replace soldered parts, like the decoupling capacitors as the solder joints
formed
part of the HDA seal...
-tony
- Josh