Re: Question: EMI Shielding for IDE cables

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Date: Thu, 19 Aug 2004 22:50:03 -0700

It would be better to ground it, of course, but you would still get some
shielding from just wrapping it in the tape.

"blue" <user@host.com> wrote in message
news:Bj2Vc.432417$rCA1.312815@news01.bloor.is.net.cable.rogers.com...
> Thanks for the replies,
> I am using new aftermarket power supplies (thermaltake 480W). I've dealt
> with power supply problems with hard drives (long ago in the past), and
the
> symptoms don't fit my current situation. Drives are always detected in
bios,
> drives always spin up properly, drives are always accessible through os.
>
> The reason why I think it is interference of some sort:
> I did some checking of a bunch of corrupt files in a hex editor. I
actually
> had chunks of text from other text files. So data got scrambled up during
> read/writes to the drives.
> Switching to a shorter cable to do data recovery also meant unscrewing the
> drive from the bay, and just sitting it in the chassis next to the ide
> controller plug. This moved the drive away from the power cabling. Also,
> when doing recovery, I removed the rack chassis from the rack. With this
> done, I did some file copying tests to see if I was still getting
> corruption, and I did not. The same tests, with long ide cables, and the
> drive mounted in the bay, gave corruption errors. Test file was a large
rar
> archive set, test was a sfv file check.
> I am using flat ribbon IDE cables, 80 conductor / 40 pin. I understand
that
> the second connector is a ground, which should eliminate cable crosstalk.
> But I do believe that my problem is actual RF or EMI interference.
> I need to use longer cables because of the chassis layout - 24" - 36". It
> would seem to be quite easy to shield the rounded cables from EMI with
some
> aluminum tape, I just don't really know what I need to consider. An EMI
> shield doesn't really make sense to me without a ground. And, is aluminum
> muffler tape the right stuff to use?
>
> I am definitey paranoid of data corruption now - the amount of data I lost
> was crazy. I could have never imagined losing a full terabyte of data all
at
> once..
>
> Thanks,
> Keith
> creekchubbAThotmailDOTcom (replace AT with @, and DOT with .)
>
> "Kevin Kilzer" <kkilzer.remove.this@mindspring.com> wrote in message
> news:u998i0hfhq9083gij1i4mqftqnb1cinc9e@4ax.com...
> > On Thu, 19 Aug 2004 02:41:40 GMT, "blue" <user@host.com> wrote:
> >
> > >(Long story)
> > >I am having problems with hard drive data corruption.
> > >I have recently rebuilt some of my computers in rackmount casings.
After
> > >running them for a few weeks, I noticed that all of my files were
> becoming
> > >corrupted. I have 4 x 160GB + 4 x 120GB hard drives where this is
> becoming a
> > >problem. 2 of the drives lost their partition tables and became
> completely
> > >useless.
> > >I made valiant efforts to recover and preserve my data, but I have
> basically
> > >given up.
> > >
> > >After much investigation, I suspect the cause for these problems to be
> > >related to my IDE cables.
> > >1. With the chassis layout, the power supply is located at the front of
> the
> > >case, leaving an AC power cable running directly under the hard drive
> bays
> > >and the ide cables.
> > >2. The rack itself houses 6 computers, 2 UPS, 2 power bars, and about
> 10-15
> > >other devices (modems, switches, etc), so I expect that there is quite
a
> bit
> > >of interference here.
> > >3. I am using flat ribbon 24" and 36" IDE cables, because shorter
cables
> > >will not reach from the drive bays to the ide controller connectors.
> > >4. All drives are running ATA100
> > >
> > >When doing data recovery, I removed the drives from the cages and ran
> short,
> > ><18" ribbon cables. This seemed to greatly reduce the incidence of new
> data
> > >corruption.
> > >
> > >I have recovered whatever I could from the drives. They are now all
> freshly
> > >formatted and repartitioned. Because of the problems I have had, I am
> afraid
> > >to use them for anything.
> > >
> > >I truly do believe that the IDE cables are my problem. I ordered a
bunch
> of
> > >rounded 36" ide cables, but when I got them, I realized they have no
> > >shielding at all (I thought the point of rounding a cable was to put a
> > >shielding around it!).
> > >
> > >I expect that shielding these cables may help fix my problems. I am
> looking
> > >for any advice on doing this. I initially thought I'd just get some
> aluminum
> > >muffler tape from the auto parts store, and wrap the cables, but I'm
not
> too
> > >sure.
> > >- Do I need to put a ground wire onto the shield? I think it would make
> > >sense to have a drain on one end of the shield and attach it to the
> chassis
> > >- Should I put one of those ferrite clamp shields on the ide cables?
> > >- Should I put one of those ferrite clamp shields on the internal AC
> power
> > >cable?
> > >
> > >I also think it would be smart to wrap any shielding in an insulating
> > >material, like electrical tape or something. But when electrical tape
> heats
> > >up, the adhesive makes everything gooey. I don't know if I can fit heat
> > >shrink tubing over the connectors. Any other ideas?
> > >
> > >Thanks for making it to the end of this long email!
> > >Keith
> > >creekchubbAThotmailDOTcom (replace AT with @, and DOT with .)
> > >
> >
> > It is unlikely that shielding is the culprit, and more likely that
> > grounding or other power supply issues is the problem.
> >
> > By reducing the cable length, you have actually reduced the need for
> > good grounding. The suggestion by tempus fugit that 80-pin cables is
> > right-on, since those cables are required for proper ATA100 operation.
> > They provide 40 additional ground wires in each cable (which is not
> > quite the same as shielding). Standard ATA cables have only 5 or 6
> > ground conductors.
> >
> > You should also check the quality of the cabling in the power
> > connections. If you changed cases, I assume you also changed power
> > supplies and likewise the distibution of power. Watch out for those
> > "Y" cables in the power supply -- the standard ATA power connector is
> > notorious for getting bent out of shape if they are plugged/unplugged
> > a number of times.
> >
> > Kevin
> >
>
>

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