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Subject:  Fixed Tape Crinkle by cleaning off scum
Date: Sat, 11 Dec 1999 22:23:21 -0800
To: TRV900@onelist.com
From: Jerry Anderson (jranders at adobe com)

I thought I had found something of a cure by slamming the tape down on a hard surface to be sure it was not sticking inside the cassette before rewinding. My email about that procedure is here.

Tonight I accidentally recorded to the very end of the tape. I spent about an hour trying to rewind the tape. Every couple of seconds I would hear the tape crinkling, and after a few episode of crinkling the camera would jam with an error code and I would remove the battery for 20 seconds then start in again. This time I got it rewound to about 35 minutes and it was still crinkling. Slamming down the tape on a hard surface didn't help. I tried using the Sony DV cleaning tape but that didn't help.

I remembered that someone had written that they had taken their TRV900 in for repair and been told by Sony that the camera needed cleaning because the tape rollers had excessive tape residue build-up that had formed a sticky scum. I think there was also something about the heat that is generated in the camera being a problem.

Perhaps it was softening the tape binding adhesive and melting a tiny bit of it onto the tape rollers where it became a sticky glue waiting to grab the tape during rewind.

I removed the tape and looked at the rollers under bright light. Sure enough, there was a very thin brown ring around the inner end of the capstan motor spindle. (I think that's what I was looking at!) Using a cotton swab Q-tip dipped in 91% Isopropyl alcohol I carefully rubbed off the brown ring, and I cleaned the pinch roller and other rollers and guides as best as I could for good measure. (There isn't much room to get at them.) I was careful not to touch the large recording head.

I waited a minute to be sure the alcohol was dry and put my troublesome tape back in and now it rewound without problem. Just for good measure I fast-forwarded to the end again and rewound without problem. I put in another partially recorded tape and fast-forwarded to the end and then rewound without problem.

I hope this cures the problem for a while. From now on I plan to carry alcohol and cotton swabs with me, and clean the inner works every few tapes. Hope this works. Give it a try, yourself, if you are having this problem.

I'm sure none of this is approved of under the Sony warranty but my camera is long out of warranty and I didn't see what harm it could do.

[...] I'm sure that rubbing alcohol and Q-tips are not the ideal materials for cleaning but I was desperate and I have used that combination to clean the capstan and pinch rollers of audio tape recorders for many years without apparent damage. Perhaps someone can also suggest something better than Q-tips. The clearance for getting into the tape well and cleaning the parts  is very tight.

My theory here is that the tape capstan motor generates quite a bit of heat after extended running and the heat is transmitted through the capstan to the tape. The heat will be greatest at the end of the capstan nearest the motor since the rubber pinch roller and the tape will dissipate heat as it moves out the length of the capstan. The inner end of the capstan is where the brown ring was observed.

The heat is just enough to melt microscopic traces of the adhesive onto the capstan itself. Over time the adhesive builds up until it forms a sticky scum at the inner end of the capstan and causes the tape to skew off its proper path during rewinding. This causes the crinkle.

The length of time the camera is in continuous usage would help determine how fast the scum would build up because a cold capstan would cause little adhesive to come off and a hot capstan would cause a lot.

Other problems could also be a misalignment of the various tape guides and incorrect tensioning of the tape hub spindles, but those will require a qualified repair shop.

I hope some other brave souls who have started to encounter the tape crinkle problem will give this cleaning method a try to find out if we are on to something.

[J.Anderson, update 12/14/99] Although I have not used it heavily in the last few days, my camera is still working like a champ ever since its cleaning with NO new tape crinkling.

Experts caution against using cotton swabs because stray cotton threads left behind could cause damage if they reach the video head, for example. There are low- or no-lint foam tipped cleaning swabs sold by A/V stores, Radio Shack etc. which would be safer to use. For instance Radio Shack #44-1001 ultrathin foam cleaning swabs. RS #44-1113 A/V head cleaning solvent "leaves no residue behind" according to the catalog. The VCR cleaning section of the Repair FAQ suggests lint-free cloth, chamois swabs and 99% isopropyl alcohol, among other things. Rubbing alcohol contains some fraction of water which may leave more residue. The service manual for this tape drive specifies "super fine applicator" (NIPPON APPLICATOR P752D) and "cleaning fluid" (Y-2031-001-0) for cleaning the tape path, for what it's worth. (After disassembling the unit, the video head is cleaned with a special cleaning cloth while being hand-rotated counterclockwise. It can be damaged easily, and I don't suggest touching it.)

Jerry's experience suggests that in his case, the problem was tape residue. It may also be that there is more than one cause or contributing factor to tape crinkles. Some people have reported the problem showing up almost immediately, whereas it seems these deposits would take time to accumulate. Another user on the TRV900 list, Henri, suggests the root cause of crinkling is back tension, spindle height, wobble and alignment problems, and that other MiniDV and DV tape transports don't suffer this problem.

I understand that the normal service procedure in the case of a reported tape crinkle is to clean the capstan and adjacent tape guide, re-align or replace the tapeguide if misaligned, replace the pinch roller if necessary, and check tape tension, possibly replacing the reel tables (supporting tape hubs) if necessary.

-john beale 12/12/99

Subject: Tape Crinkle and Isopropyl Alcohol
From: "HB & Emilio Trampuz" (Starbright compuserve com)

I always keep a bottle of 91% pure Isopropyl alcohol at hand (both as a first-aid disinfectant and for cleaning electronic equipment such as audio-cassette players and camcorders). I get it at the local pharmacy. In case it's of any help, the particular brand I get is:

PUREPAC Isopropyl alcohol (91% by volume, azeotropic)
Distributed by:
Purepac Pharmaceutical Co.
Division of Kalipharma Inc.
Elizabeth, NJ 07207
U.S.A.

Emilio

Subject: Re: trv900 tape problem
From: (bob at abctaxi com) (bob bryce)
Date: Feb. 9 2000
Newsgroups: rec.video.desktop

>> "bob bryce" wrote 
> I have a trv900 that is causing me big grief.  I regularly get tape
> crease problems when I rewind 60dv tapes.  This seems only to happen
> when I rewind from the end of the tape.  any other victims?  I suspect
> that the guides may be the culprits.  I've shot a lot a tape on this
> unit but it's less than a year old.  Any suggestions.

Well upon reading John Beale's info on his trv900 page, I noticed that my
capstan roller pin had the same build up as the gentleman pointed out in
his article/photoshop enhanced picture, exactly the same!  After a good
cleaning it appears the problem is gone!  The theory is that because there
is so much torque on the tape when it is in the last 5 min stage (smaller
reel diameter on takeup and larger dia on feed reel) that the build up goo
catches the edge of the tape while in rewind (maybe due to gumming up while
tape screams by, heating up the peg making the goo sticky??)  This theory
is also confirmed by how the tape is creased, looks like the top edge was
getting pulled along faster than the bottom (couldnt keep up).  I just
removed the tape eject cover and cleaned (very carefully) with cleaner and
lint free swab.

Many thanks to John beale and the contributing authors on his excellent web
page.  BTW.  I bought the trv900 based on a quality comparaison chart from
John's page.  Keep up the good work.

bb