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This is extremely helpful stuff, Karl. Many thanks. 

I'll see if I can do some tests on another machine and get a more precise 
sense of just what's going on. Not sure just yet if I should take on the 
task of cleaning it myself, but it's great to have such a precise account of 
how to do so. We've been quite successful in doing DAT transfers on our 
Tascam machine for a while now, with the rare glitchy cassettes (most of 
them about 20 years old) having only very isolated, relatively minor 
problems. But with the error rates going up noticeably lately, it does sound 
like the problem has become something with the machine. Should we have to 
invest in a new machine I'll take a look at the Sony PCM-R500 first, since 
you and Shai both put in a good word for it.

I'd be interested in hearing any more DAT adventure stories as well, since 
it sounds like a lot of places are migrating material off of DAT nowadays. 

Cheers,

Brian

 
----------------------------
Brian Carpenter
Mellon Digital Audio Technician
 
American Philosophical Society
105 South Fifth Street
Philadelphia, PA  19106-3386
(215) 440-3418


 
-----Original Message-----
From: Karl Fitzke <[log in to unmask]>
To: [log in to unmask]
Date: Thu, 13 May 2010 09:51:57 -0400
Subject: Re: [ARSCLIST] DAT glitches


Brian,

We routinely and very successfully use the Sony PCM-R500 machines here 
at the Lab of Ornithology for DAT transfers.  And we have a few  
Panasonic SV-3800 machines as well, which have an error count reporting 
mode that offers some more insight into what is going on with problem 
tape.  There is also a physical mod of the Sony remote control (drill a 
hole in it) that enables you to push a button and get error counts of 
some kind with those machines too, but I'd have to dig more info up on 
that, not having made use of that myself yet.

By the way, I am an audio engineer and technician here at the Cornell 
Lab of Ornithology's Macaulay Library of Natural Sounds, responsible for 
maintaining our DAT machines, Studer A820's, DAWs, and the rest. 

As Shai said, trying another DAT player can be telling.  Just 
keep in mind that anything that may have caused a tape that to clog one 
machine's head may leave you cleaning more than one machine (getting 
ahead of myself here).  It's a judgment call and hard to tell you the 
best course of action in your situation.

And as someone already said, if the recorder was out of spec, it can be 
a lifesaver to have it around for playback, which may be the only 
machine a tape will have any hope of playing back properly on.  This 
recently happened to us when someone brought us quite a bit of Mini-DV 
video that just wouldn't play back properly here.  Our faces went white 
because it was reportedly really great program material and the audio 
was constantly glitching.  Thankfully they recordist was able to send us 
the original camcorder and we got a good transfer in the end.  This is 
another reason to get stuff transfered or at least auditioned as soon as 
possible instead of sitting it on a shelf for years and years and 
missing an opportunity to get good stuff - the reason calibration 
standards came about in the first place.  But I digress.

As Jerry said, sometimes the dry cleaning tape will not get the job 
done.  The error rate may even be high enough to cause a machine to 
squelch it's output for some period of time.   But getting inside the 
machine and cleaning the drum heads with a swab quite often clears up 
any problems we are having.  So I'm optimistic you will have success 
with having your cleaned if necessary. 

All machines are not designed the same, i.e. some are easier to swab 
than others.  And yes, it is supposedly very easy to damage the heads, 
and I can see why (but thankfully I haven't learned the hard way - 
yet).  And more importantly, you risk electrical shock if not in the 
habit of making sure the unit is not plugged into the wall when you are 
working on it with the cover off.  If you have any doubt about damaging 
the unit or yourself, don't do it yourself.  Not worth it.

But this is what I do.  I unplug the machine first, and place it on a 
clean and organized bench surface, to avoid injury.  I then open up the 
machine.  Then I double check that the unit is unplugged.  Now I swab as 
Jerry suggested can be done.  It is important to use a chamois swab 
dipped in 99.9%  Isopropyl Alcohol (no cotton swabs or anything else 
likely to snag on the heads and/or leave material behind, either of 
which could damage to the heads).  I lightly rest the tip of the chamois 
swab on the head at an angle and gingerly turn the head counterclockwise 
a few times (viewed from above, which is no different than it's regular 
direction of rotation).  Imagine the angle I just mentioned by pointing 
the swab tip tangentially in the direction of the head rotation and then 
moving it 50-70 degrees so from this position (90 degrees, for example, 
would be radially oriented with the center of the head, perpendicular to 
the head surface in other words).  The point of my doing this is to 
avoid risk of digging into the head, as might easily happen if the swab 
was pointing into the direction of head travel.  Then put it all 
together again and try things out using a known good tape for starters, 
and then proceed to your original suspect tape if all is well.

A couple of times I've had to do the above procedure two and even three 
times before error rates with my known good tape returned to normally 
expected and correctable levels.  As you might imagine, the original 
problem tape had really clogged up the heads.

I'm interested in hearing other people's experience too.  I love how the 
Listserve makes us all smarter.

Karl Fitzke




Jerry Hartke wrote:
> You may be experiencing head clogs with material from the tape embedded in 
a
> head gap. When severe, there is no solution for this other than to replace
> the head or the drive.
>
> An experienced technician may be able to access the head and carefully 
swab
> the gaps with a swab dipped in ethyl alcohol, but there is also a risk of
> permanently damaging the head when this is done.
>
> This is not a firm diagnosis -  just a possibility, but such clogs are not
> uncommon. They can occur during normal use or when a tape has been run 
back
> and forth many times over the same area, causing debris to pile up at each
> end, and then clogging the head when the usage area is extended.
>
> Jerry
> Media Sciences, Inc.
>
>   
>> -----Original Message-----
>> From: Association for Recorded Sound Discussion List
>> [mailto:[log in to unmask]] On Behalf Of Brian Carpenter
>> Sent: Wednesday, May 12, 2010 3:17 PM
>> To: [log in to unmask]
>> Subject: [ARSCLIST] DAT glitches
>>
>> Recently I was reviewing some WAV files that I created from DAT and
>> noticed
>> a handful of glitches here and there that were clearly digital in origin,
>> rather than from the original analog tapes that had been transferred to
>> DAT.
>> After doing a retake or two, I discovered that some glitches remained,
>> occurring in the same places on both the old and new WAV file, while
>> others
>> were no longer there in the new one. So, since these errors didn't appear
>> random, it seemed to me they must be caused by physical blemishes on
>> particular spots on the tapes, rather than by a dirty head on the machine
>> (a
>> Tascam DA-20 MKII). But after having made a few hundred hours of WAVs 
from
>> DATs, the glitch problem had only recently started showing up. The newer
>> the
>> files, the more common the glitches. Anyway, long story short, I 
purchased
>> a
>> DAT cleaning cassette just in case, ran it in the machine one time,
>> following the instructions exactly, and then actually had more glitches
>> showing up, even on tapes that had zero errors when I first did them. I
>> did
>> a second cleaning run, found fewer glitches afterwards, but still more
>> than
>> originally. Since running the cleaning cassette more than 2 or 3 times in
>> a
>> short period is a bad idea, I'm told, does anyone have any suggestons on
>> how
>> to address this kind of problem?  Any input would be very helpful.  
Thanks
>> very much.
>>
>>
>>
>>
>> ----------------------------
>> Brian Carpenter
>> Mellon Digital Audio Technician
>>
>> American Philosophical Society
>> 105 South Fifth Street
>> Philadelphia, PA  19106-3386
>> (215) 440-3418
>>     

-- 

Karl Fitzke
Assistant Audio Engineer
Macaulay Library
Cornell Lab of Ornithology
159 Sapsucker Woods Road
Ithaca, NY 14850

607-254-1100

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