[TechAssist] Re: JVC VCR HR-J420U acts like bad heads- but is it?
- From: "Satguy" <satguy@xxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Thu, 8 May 2003 17:43:44 -0600
There is also a cap on the board that the video head is attached to on the
bottom side that goes bad an causes your problem. If this unit has one just
replace it, it is a pretty small one so be careful.hth
Shaun
Advanced Electronics
Fort Morgan, CO 80701
(970) 867-3124
satguy@xxxxxxxxxxxxx
----- Original Message -----
From: "J Silverman" <greentron@xxxxxxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Thursday, May 08, 2003 11:43 AM
Subject: [TechAssist] Re: JVC VCR HR-J420U acts like bad heads- but is it?
>
> You need to set the back tension to 30 grams since the back tension
affects
> the entire tape path, and have the tension arm position where it can move
> back and forth properly. If the auto tracking is on and the supply guide
> post height is wrong it will hunt. To tell if it is a tracking or capstan
> problem put it in pause and see if the envelope keeps changing.
> Jerry Silverman
> Greentron Inc
> 4 Newland Ave
> Greenville SC 29609
> 864 232 3889
> Fax 271 2080
> mailto:greentron@xxxxxxx
> ----- Original Message -----
> From: "Gary McCartney" <gary@xxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Thursday, May 08, 2003 10:13 AM
> Subject: [TechAssist] JVC VCR HR-J420U acts like bad heads- but is it?
>
>
> >
> > I have this JVC VCR model HR-J420U which shows a few lines across the
> > screen near the top during playback of some SP or EP speed tapes.
> >
> > Pulling the back tension post out further by hand would make the lines
> > go away but adjusting the arms position with it's set screw would only
> > result in a worse picture, never better.
> >
> > I scoped the RF envelope waveform and it didn't look very good, not
> > square at all. I set the tracking to manual and tried to align guide
> > posts so the envelope would be squared up. This seemed to work out ok
> > using my test alignment tape, but some other factory made tapes still
> > had the problem and some were even worse than before I made any
> > adjustments. Actually the envelope waveform is now fluctuating. It won't
> > stay the same shape while playing most tapes. It keeps gradually losing
> > the signal from the one head and getting it back again slowly, while the
> > other head goes from square waveform shape to oval shape. Hope I've
> > explained this ok. The control pulse appears to be stable at approx. 3V
> > p-p at C.P. test point, regardless of what tape I am playing.
> >
> > I removed the upper drum and checked for green corrosion at the base of
> > the post as was a problem with some JVC machines a few years ago. All
> > was clear. I also tried a new spring at the back tension arm but that
> > didn't help either. This problem seems to be worse on EP speed tapes.
> > Are my heads just too weak to lock in the RF signal or are there other
> > known conditions with these machines causing this type of fault?
> >
> > Thanks for any help.
> > --
> >
> >
> >
> >
> > Gary McCartney
> >
> > McCartney Electronics
> > 7134 Fife Rd, RR 7
> > Guelph Ontario Canada N1H 6J4
> > Fax: (519)821-1530
> > email: gary (at) number63.ca
> >
> >
>
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