| Attached here is a customer description of an RA73 failure situation
they are experiencing. Does it sound like it is related to the
reversed capacitor scenario described in this string???
Any/all help appreciated,
Randy
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We have two DEC 7000 Model 630 (3 CPU's) AXP Computers at the site.
Each computer has eight RA73 disks (@2.0 GB) and two RA72 disks (@1.0 GB).
While the computers were being staged here in the USA (before shipment to
Hong Kong in May 1995), three of the RA73's failed; these were replaced by
DEC USA under warranty. Since they've been powered up and running in the
field (only since May 1996), four of the RA73's have failed; in fact, a fifth
one is now failing. This failure rate seems excessively high to us.
It seems that the "ECM Board" of the disk drive is most prone to
failure, not the mechanical drive itself. (Hmmm, that's certainly counter-
intuitive.) DEC Hong Kong went to site, replaced the ECM board on a few of
these, and shipped one of the bad ones back to us. It's a DEC P/N 5421396.
On the same side of the ECM board as the power input connector, there is a
small toroidal transformer (L2). This transformer appears to be burned.
Our electronics guys, while admittedly not familiar with DEC circuit
boards, surmise that this transformer is being used in a "chopper" circuit to
provide a different voltage on the board. They don't believe that this
transformer caused the failure, but rather that this is a symptom of the real
failure, whatever it is. It doesn't seem that fluctuations of the AC power
source, whether present or not, would cause such a problem on this board. I
believe that the disks are fed DC from the Alpha power supply. (Is that
correct?) What do your technical support people say about the relative
reliability of this drive? What is your observed MTBF for this drive?
In summary, we can't escape the nagging suspicion that there's a
design flaw in this drive, which is causing these high failure rates that we
are seeing. We are pglanning to go to the site during the week of 17 FEB 97
to replace some of the disks, but we'd like an answer from DEC well before
then.
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