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.
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.