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Discussion Starter · #1 ·
While we wait for JVC to come up with some permanent fixes for the ailing 30k, I thought it might be fun for the more adventurous members to search for some solutions on our own. I'm not suggesting we redesign the machine, but rather to search for good user tactics, work-arounds, and maintenance procedures that will keep the 30k pixel free.


I'll start things off with some observations about the pinch roller. One of my older 30k's (Japan version) started showing some signs of decline, and head cleaning wasn't bringing it back to life like it should. As an experiment I replaced the pinch roller, and got some slight improvement, but what I discovered about the pinch roller is more interesting: the torsion spring, that sets the tension of the roller against the tape and capstan, scrapes against the pinch roller arm and eventually wears a groove in the arm. As the groove deepens, the pinch roller pressure could increase in an unpredictable manner.


A few photos might help. Click on the photos to enlarge.
http://home.earthlink.net/~rogercc/_uimages/dh30000/pinchroller/prnormal.jpg http://home.earthlink.net/~rogercc/_...prnormaltn.jpg fig 1 http://home.earthlink.net/~rogercc/_uimages/dh30000/pinchroller/prcompressed.jpg http://home.earthlink.net/~rogercc/_...mpressedtn.jpg fig 2

Fig 1 shows the pinch roller arm in the undeflected position it normally occupies when there is no tape in the machine. Fig 2 shows the arm deflected (manually with a pair of pliers) to the position it would occupy if a tape were inserted. Of course, the lower supporting arm swivels to the left to bring the roller into contact with the tape and capstan, but the pinch roller arm deflects as shown.


Notice the heavy black spring wire that scrapes on the top of the pinch roller arm where the "Lub here" arrow head is pointed. A black smudge is already visible, and this is a new arm that's only been actuated a few times.


The next photo shows the old pinch roller arm, with a about a hundred hours of use.
http://home.earthlink.net/~rogercc/_uimages/dh30000/pinchroller/wearpatch.JPG http://home.earthlink.net/~rogercc/_...earpatchtn.jpg fig 3

A closer look at the wear patch shows that it has worn through the plating into the base metal of the arm and shows signs of galling against the spring. As a result, the pinch roller arm would not deflect smoothly, and unpredictable pressure would be applied against the tape and capstan.


There are a couple of important points here. If you decide to do your own pinch roller replacement it is essential that you apply a good moly grease to this wear point, and to the under side of the arm as well. Notice also, that wear at this point is not a function of hours of use, but instead a function of the number of tape insertions and the number of FF/REW operations.


So, what can be done about this problem besides replacing the pinch roller arm and lubing it properly? A better lub?... chrome plate the arm?... insert a hard skid plate under the spring?


Put on your Thinking Caps.
 

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Hi Roger,


I was about to post something about the pinch roller when I saw your thread, so here it is.


I have one of my four decks which needs the PR cleaned every 2 tapes! It's my most recent 35000, with only 100 hours under the hood.


I rubbed the farn ducking thing with alcohol 10 times already, but after one play, the pixels come back. Even just after cleaning, I have one or two freeze frame every hour.


I thought that this could be caused by the PR not having enough grip when it starts to get dirty, and I decided to try to add some grip.


I took a piece of thin sandpaper, and rubbed the PR vertically, the idea being to make thin grooves perpendicular to the tape movement.


I cleaned then the PR with alcohol VERY thoroughly, to be sure no piece of sand remained on it, which would ruin the heads at the first use.


The question then was: would this damage the tape? I made a 2 minutes recording, played it, went back to the start in fast backward mode, played it again, and so on 20 times.


The 20th play was still perfect, no drops. So the tape was not damaged, at least not in a meaningful way.


So far, I played 2 entire tapes without problems. Will it last? We'll now next week when I'll have watched enough tapes...
 

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Roger,


Many thanks for bringing this information to the forefront. This would seem to be consistent with observed performance in my case.


You said you replaced your pinch roller and got some slight improvement, which indicates your problem wasn't completely solved. Please elaborate.


--Jerome
 

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Wow It sure does seem like the PR may in fact not be the problem as Roger pointed out. Of course it becomes the problem.


I suspect that not using FF or Rewind will add alot of life to this unit. It certainly seems like this piece needs hardened.


Is there anyway to find out what material is used.


We could machine a piece in our shop, but that would be ultra expensive. I'm wandering what material they are using and if it could be heat treated.


If someone knows where to get the piece and if it can be heat treated I could probably have a couple done for people to test.


Roger it seems your sanding the PR compensated for the increased pressure on it


Someone needs to get to JVC with this info. Problem is all machines would need to be recalled and parts replaced.
 

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I forwarded this thread to Marek at JVC. VERY informative.
 

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Discussion Starter · #7 ·
Quote:
Originally posted by robena
...I took a piece of thin sandpaper, and rubbed the PR vertically, the idea being to make thin grooves perpendicular to the tape movement...
Great idea, Robert. Let us know if freeze-free operation last longer now.


There are also chemicals that increase the tackiness of rubber. One is oil of wintergreen (methyl salicylate) but it smells awful. There are also some mixtures of oil of wintergreen with other sovents that are less smelly and work equally well. It could be another option if sanding doesn't last.
 

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Discussion Starter · #8 ·
Quote:
Originally posted by jsaliga
...You said you replaced your pinch roller and got some slight improvement, which indicates your problem wasn't completely solved...
Jerome,


I'm working at somewhat of a disadvantage because none of my machines are really that bad. I have discovered one tape, a recording of Harry Potter made on an HD1000 with TDK XP160 tape, that does not play well on my 30k's (but perfectly on all my HD1000's, of course). It has become a "test tape" that I use to check the condition of my 30k's. That's what I was using for my experiments with the pinch roller. My goal is to make that tape play perfectly using methods available to everyone here on the forum, rather than optimizing the machine using instruments. Replacing the pinch roller improved the playback of that tape from pixels every 10 seconds to pixels every minute or so, but I still have not found nirvana.


I think it's clear by now that there is more than one problem with the 30k. I'll be posting a bit more about the pinch roller, and then I'll bring up some other issues.
 

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Discussion Starter · #9 ·
Problem #1 is the pinch roller runs against the magnetic surface of the tape. We can't do anything about that. Problem #2 is the spring wearing against the arm. A good lubricant is probably the solution there.


Problem #3 is related to the cam that moves the pinch roller into and out of contact with the capstan. It doesn't have quite enough travel. As a consequence, the pinch roller sits too close to the speeding tape when retracted for FF/REW, and it barely compresses the tension spring when it's extended for play mode. It wouldn't take much to displace the roller slightly one way or the other, and either direction would result in bad things happening. If it is spaced away from the capstan too much then there would be plenty of clearance during FF/REW but not enough tension during playback. That might be Robert's (robena's) problem where he has to clean or roughen the roller to gain traction.


On the other hand if the roller is spaced too close it could brush against the tape during FF/REW. That might be Jerome's problem when he heard a squeaking sound from the pinch roller during rewind.


Again, some photos might help. Click on them to enlarge.
http://home.earthlink.net/~rogercc/_uimages/dh30000/pinchroller/prffopencass.jpg http://home.earthlink.net/~rogercc/_...opencasstn.jpg Fig 4 http://home.earthlink.net/~rogercc/_uimages/dh30000/pinchroller/prffstdcass.jpg http://home.earthlink.net/~rogercc/_...fstdcasstn.jpg Fig 5

Fig 4 is a close view of the pinch roller during rewind mode. I used a special cassette with no tape guard so that the tape path can be seen during operation. The tape is seen exactly edge-on, so it's hard to see, but the four arrow heads each touch the tape. You can see that the tape almost brushes against the roller, but in my case the roller does not turn.


Fig 5 is the same situation, but with a standard cassette in place. All you can see is the roller, but if you try this you'll be able to see easily whether your roller spins during FF or REW. Keep in mind that when you first put the recorder in rewind mode the roller stays in contact with the capstan for a few seconds before it retracts.


I should also point out that the Mits recorder uses a very similar transport mechanism, but the pinch roller retracts a good quarter inch from the tape during FF/REW.
 

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gridleak,


You should be charging JVC for these diagnostics. I hope this points JVC in the right direction toward a fix.
 

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Roger,

Quote:
Great idea, Robert. Let us know if freeze-free operation last longer now.
I watched 3 tapes since, and the freeze-frame problem has just disappeared.


I did not need to re-clean the tape path either, so sanding the pinch roller worked well with this unit.


I have another unit which needs frequent cleaning too, but sanding did not improve it. As we are all painfully aware now, there is no one miracle cure, but many different problems. I'll try your grease fix next time this second unit starts to act up.
 

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Quote:
Originally posted by robena
Roger,




I watched 3 tapes since, and the freeze-frame problem has just disappeared.


I did not need to re-clean the tape path either, so sanding the pinch roller worked well with this unit.


I have another unit which needs frequent cleaning too, but sanding did not improve it. As we are all painfully aware now, there is no one miracle cure, but many different problems. I'll try your grease fix next time this second unit starts to act up.
Would it be logical to assume then that removing the cassette prior to rewind and using a VHS tape rewinder would greatly reduce potential problems as well as wear and tear?
 

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Hello,


interesting findings here. I only run D-Theater tapes and I have had problems from day one. I have tapes that run almost ok (one or two drops) and I have tapes that are a plain pixel storm.


I decided to make things worse in order to check the pinch roller issue : Backdraft is one of the few tapes that runs ok. I touched the pinch roller so that the rubber is contaminated with fat from my skin ( I do wash my fingers ). I also touched the capstan. That was all in order to reduce grip a little and guess what : Backdraft is even worse than my worst D-Theater tape now. Glitches over glitches and pixels all over the place. Now I will head to the town and get some cleaning stuff in order to "repair" the pinch roller.


Question : can it be that the tape material that JVS uses has various qualities and hence different thickness or grip or is it all the same stuff ?


Regards,

Andreas
 

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Andreas,


I don't know if that was wise. The pinch roller is in contact with the magnetic side of the tape. Your experiment could have contaminated your tape.


--Jerome
 

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Quote:
Originally posted by Andreas Griess
Hello,


interesting findings here. I only run D-Theater tapes and I have had problems from day one. I have tapes that run almost ok (one or two drops) and I have tapes that are a plain pixel storm.


I decided to make things worse in order to check the pinch roller issue : Backdraft is one of the few tapes that runs ok. I touched the pinch roller so that the rubber is contaminated with fat from my skin ( I do wash my fingers ). I also touched the capstan. That was all in order to reduce grip a little and guess what : Backdraft is even worse than my worst D-Theater tape now. Glitches over glitches and pixels all over the place. Now I will head to the town and get some cleaning stuff in order to "repair" the pinch roller.


Question : can it be that the tape material that JVS uses has various qualities and hence different thickness or grip or is it all the same stuff ?


Regards,

Andreas
I have a number of D-VHS tapes that playback perfectly except one. Took that one back to exchange it and the new tape played perfectly. So, in my case it is not the machine that had problem but THAT particular tape which I exchanged.


My machine with a little less than 300 hours of use is running perfectly.
 

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Quote:
Originally posted by jsaliga
Andreas,


I don't know if that was wise.
Jerome,


it certainly is not wise to do that but there is no other way to verify this issue. I am risking a tape worth 30 Dollars or so. If I send in the player the transportation costs is a multiple of that tape.


Regards,

Andreas
 

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Quote:
Originally posted by SARHENTO So, in my case it is not the machine that had problem but THAT particular tape which I exchanged.


. [/b]
I have 8 tapes and only 2 are running just ok. Oh wait a minute, now it is only one.


Regards,

Andreas
 

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Discussion Starter · #18 ·
Quote:
Originally posted by Andreas Griess
...I touched the pinch roller so that the rubber is contaminated with fat from my skin ( I do wash my fingers ). I also touched the capstan. That was all in order to reduce grip a little and guess what : Backdraft is even worse than my worst D-Theater tape now...
Wow, Andreas, thanks for that. It really shows how easy it is to upset the stability of the pinch roller/capstan system. It also ties in with my next post describing pinch roller problem #4.


Regarding your tape question: there are definite differences between tape brands, and some brands seem to work better in the 30k than others. But it's a difficult subject to deal with because I suspect that switching around between brands can have bad effects too.


All the Dtheater tapes I've looked at seem to be 0.7 mil tape, regardless of the length of the movie. The brand is probably JVC, but I have no way of checking.
 

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Roger,


the DF-300 and DF-420 D-VHS tapes from JVC look to be identical to the tapes D-Theater is recorded on, the tape material seems to be of the same thickness as in the D-theater tapes, too.


Oliver Klohs
 

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Quote:
Originally posted by gridleak

It really shows how easy it is to upset the stability of the pinch roller/capstan system.

Yes, this seems to be a very weak point of the design. I have cleaned the tape path with alcohol today (I mean alcohol was used for cleaning not for putting me into clean mode). I cleaned all metal items that come in touch with the tape. This includes the capstan. Unbelievable how dirty this stuff was. The capstan itself had so much dirt on it that it was almost gray.


I cleaned the pinch roller and it was very dirty as well. Backdraft is now working again. That's a clear evidence that the pinchroller is quite problematic.


Enthusiastic as I was I tried XMen, but this did fail with pixels. I will get the oil of wintergreen today and then I will work on the pinchroller surface again.


Probably the head has a lot dirt on it as well. I have a dry cleaning tape but I think I will try a wet cleaning first. Any suggestion on how to do this safely in order to protect the head as much as possible ?


The fact that the capstan is so dirty after having played just a few tapes means that the backside of the tape collects a lot of dirt as well and when it is on the spool, the backside comes in touch with data side which will then be contaminated and probably makes problems later on the head.


Is there anything available that cleans tapes ? Something like a rewinder with a wet cleaner for front and back sides of the tapes ?


Regards,

Andreas
 
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