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> An increasing failure rate is a symptom of electrostatic discharge
> damage.  If I recall correctly, the original ESD event can make a
> hole in a gate that later changes behaviour as a result of thermal
> cycling.

To re-cap

Card has two files, File1 and File2 which are played alternately
about a second apart. File1 plays perfectly, despite the failures
mentioned previously. File2 is deteriorating (not necessarily in
content but in what is presented to the dsPIC's DAC)

In today's episode of CSI:New Lynn

I hope you can follow this -

Instead of alternating I first tried continuous File1. Sounds OK
every time. Then continuous File2. Terribly noisy every time

Made a copy of Files 1 & 2, which are still on the card, and
accessed them as File3 and File4. This test was done before
modifying the PIC code to read the full 32-bit cluster address.

This meant that that File3 and File4 were actually played as
snippets of another file, because their true addresses are way
up at the 0x001d0000 cluster. Previously they had been at
0x00008500. The snippets played are from a file which also
has a 0x0000 high word. This file does not have any unwanted
noise when played.

The snippet played as File3 sounds OK, the snippet played as
File4 has a click in it. Not nearly as bad as the deteriorating
one but audible, and also consistent. Tried the continuous thing
as above, File3 always good, File4 always clicky

Modified the PIC code to read the full cluster address. File3 and
File4 are now played as they should be, which is copies of the
originals, from another part of the card.

Basically, original File2 played from 0x8500 is bad. The copy,
File4, played from 0x001d0000 seems OK

So far, no card failure (3 hours in), no noise, nothing unexpected

I wonder then if I just got "lucky" and File2 happened to be
sitting in a weak part of the card

I'll have to leave this running for a while, maybe a couple of days,
to see if anything does happen. Which I really really hope doesn't

Joe


-----
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2015.0.5863 / Virus Database: 4321/9425 - Release Date: 03/31/15

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