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ARSCLIST  September 2018

ARSCLIST September 2018

Subject:

Re: very strange/unique decay found on u-matic

From:

lists <[log in to unmask]>

Reply-To:

Association for Recorded Sound Discussion List <[log in to unmask]>

Date:

Tue, 11 Sep 2018 15:01:34 -0400

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (143 lines)

Thanks all for the great ideas.

Left in a machine is unlikely as the heavy damage to the tape surface, itself, occurs only where the tape is under the access door and where it bends around the plastic guides in the cassette.  It does not extend far enough into the wrap to account for the tape length necessary for it to exposed in the machine over the playback/record heads.  The damage observed is consistent with it happening while the tape was rewound/retracted into the shell.

Extended exposure to sunlight is a possibility, but- the parts that are decayed are inside the shell.  The outside of the shell shows no evidence of extended sun exposure and, for the parts that decayed to have been affected by sunlight, the tape access door would have had to have been left propped open for an extended time.  While this is possible, it would be a very, very  strange thing to do.  It also does not explain the corrosion on the screws or inside the tape door.  Sunlight doesn't, generally, cause this sort of metal corrosion.  A weird option but possible.

Could it have been re-shelled? This is a cassette structure where the manufacturer decided to use custom molded plastic pieces for the door lock mechanism and the guides instead of using any metal.  While it is sometimes possible to swap metal guides and pieces of door lock mechanisms between different kinds/brands of 3/4" cassettes, the molded plastic used in this cassette only fit in this specific brand/era of cassette.  If the tape was swapped into the exact same type of cassette, you need these specific pieces.  If they were missing in the new cassette shell and the chemical damage to these pieces on the original was not yet evident , they could have reused the  pieces from the original. This, actually, could explain the observed damage.  If whatever affected the original only contacted the front of the cassette and didn't penetrate far enough to contaminate the hubs inside, and some parts (the guides, door lock mechanism and screws) from the original (contaminated) cassette were reused in the new shell- and the contamination on the tape resulted in damage to the inside of the tape access door in the new cassette over time, the observed damage would be consistent.

Of course, the client claims that nothing ever happened to the tape and it was never re-shelled.  But they may not know, or remember, what happened 34 years ago.  At least this scenario could explain the anomalies.  If it is what happened, I wonder what kind of contamination could result in little or no "obvious"  visible damage at the time it occurred but eventually damage the plastic parts to near destruction. Chlorine is a possibility but, could enough chlorine remain on/in the plastic pieces to destroy them over a period of years?  And what sort of numbskull would reuse contaminated parts?

 I don’t think this scenario is likely but it is the only scenario, so far, that even comes close to being consistent with the observed damage.  There is, of course, one BIG flaw in this scenario.  There is another piece of plastic on the cassette that is badly decayed.  The red “record button” in the bottom of the cassette has decayed so badly that it has turned “pink” and fractured into pieces.  Someone might put contaminated pieces into a new cassette shell, if necessary, but no one is going to swap a contaminated record button into a new shell on a “master” tape.  Nope.  Don’t buy it.  Oh well, back to square one.  I can’t explain the damage pattern.  It is just too strange.

Thanks, again.


Peter Brothers
SPECS BROS., LLC
973-777-5055
[log in to unmask]
Audio and video restoration and re-mastering since 1983




-----Original Message-----
From: Association for Recorded Sound Discussion List [mailto:[log in to unmask]] On Behalf Of John Haley
Sent: Tuesday, September 11, 2018 12:48 AM
To: [log in to unmask]
Subject: Re: [ARSCLIST] very strange/unique decay found on u-matic

Peter,

Keep in mind that the U-Matic machine pulls the tape fairly far out of the shell when it loads it, winding it around the heads inside.  This happens more than with, say, a VCR tape.  As you know, the U-Matic mechanism has a zillion moving parts inside, and the machine I had (before I tossed it) would jam easily.  I used to keep the top cover off for this reason, so I could poke around inside to make it load and unload right.  Perhaps with this tape, the machine it was in got jammed with the tape loaded and it remained that way for a long period of time, thus holding open the door and exposing the tape guides (if they are near the opening), and the part of the tape that was outside the shell wound around the heads, to whatever did the damage.  That would be demonstrated if the remaining tape wound on the
reels inside is undamaged.   Alternatively, I suppose the tape might have
been somehow removed from a jammed machine but not wound back into the shell, with the tape laying around outside the shell, with the door somehow being held open.

What a horrible format this was.  As you probably know, finding players now that work right is a challenge.  There can't be that many of them left in the world that work well.

Best,
John Haley


On Mon, Sep 10, 2018 at 11:12 PM, Corey Bailey <[log in to unmask]>
wrote:

> Hi Peter,
>
> Well, if it stumped you then, it stumped the wizard!
>
> Perhaps the client can shed some light on the situation (Storage 
> conditions, storage location, etc.) Or, perhaps the content on the 
> tape (If at all playable) can help.
>
> Please keep us posted,
>
> Corey
>
> Corey Bailey Audio Engineering
> www.baileyzone.net
>
>
> On 9/10/2018 3:14 PM, lists wrote:
>
>> Today I received a ¾” u-matic tape with the strangest damage I have 
>> ever seen and was wondering if anyone else had seen something similar 
>> or had an idea what might have caused it.
>>
>> We have processed nearly 500, 000 tapes and we do quite a lot of 
>> disaster recovery.  I have seen tapes that have been exposed to 
>> virtually every negative influence imaginable (and some not so 
>> imaginable) so I was quite surprised to see something totally new.
>>
>> The tape:
>>
>> The tape is a 3M UCA-60 from 1984.  The cassette and hubs are 
>> white(ish) plastic and the interior posts/guides and the door lock 
>> mechanism are made out of black plastic.  The access door is anodized black metal.
>>
>> The damage:
>>
>> The tape is entirely discolored where exposed. The discoloration is 
>> only near the edges a few wraps into the tape.  I have not spooled  
>> the entire tape yet to determine how far the discoloration continues.  
>> The metal cassette access door shows many small spots of corrosion on 
>> the inside of door where it would be closest to the tape.  There is 
>> no corrosion on the outside or the edges of the door. The tops of the 
>> metal screws on the back of the cassette are badly corroded.  The 
>> entirety of the black plastic tape guides and black plastic door lock 
>> mechanism are very brittle/damaged, to the point where they are 
>> falling apart and partially missing/destroyed.
>> There is no other indication of damage. The white plastic shell and 
>> tape hubs are intact and clean and the plastic slip pads inside the 
>> cassette are undamaged.  There is no staining, no warping, no 
>> breakage and no brittleness anywhere else. Whatever happened, only 
>> the exposed tape and the black plastic tape guides, the black plastic 
>> door lock, the inside of the metal access door and the metal screws 
>> were affected.  Everything else looks fine.
>>
>> The damage to the tape “could” be consistent with either exposure to 
>> liquid or heat,  but-  there is no staining anywhere or damage to the 
>> paper label to indicate liquid contamination and there is no 
>> brittleness or deformation/melting anywhere else to indicate exposure 
>> to high heat.  The overall damage is not really consistent with 
>> either liquid or high heat damage. I even considered the unlikely 
>> possibility that the tape was contaminated with some corrosive 
>> element during playback/rewind and the posts were damaged as the tape 
>> was wound into the cassette.  This could explain why plastic guides 
>> are nearly destroyed and the metal access door was only corroded 
>> inside, near the tape, and nowhere else.  This, unfortunately,  
>> doesn’t explain the corrosion on the screws and heavy damage to the 
>> plastic door lock mechanism, however, since neither of these parts 
>> ever touch the tape.  The plastic hub flange and slip pads inside the 
>> cassette, which do contact the tape, are also undamaged.
>>
>> Ok, how about some highly corrosive gas that reacts very aggressively 
>> with one specific type of plastic (the guides and door lock 
>> mechanism) and uncoated metal (the screws) but doesn’t react at all 
>> with any of the other plastics in the shell/ hubs/slip pads and/or 
>> with anodized metal and reacts differently with the plastics in the 
>> tape (or maybe the metal in the
>> tape?)
>> in such a way as to produce a byproduct that corrodes nearby anodized 
>> metal (the inside of the cassette door) but dissipates quickly (so 
>> the rest of the anodized cassette door is unaffected).  Sound crazy?  
>> Yes it does.  The damage is so very specific and selective that I 
>> can’t figure out what could have happened.
>>
>> Any ideas?  Magic?  Space aliens?
>>
>> A very perplexed
>>
>>
>> Peter Brothers
>> SPECS BROS., LLC
>> 973-777-5055
>> [log in to unmask]
>> Audio and video restoration and re-mastering since 1983
>>
>>
>>
>>
>

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