Common Maxtor MFM drive failure mode -- any ideas?

[tony duell]

>
> 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