[TechAssist] Re: JVC VCR HR-J420U acts like bad heads- but is it?
- From: "J Silverman" <greentron@xxxxxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Thu, 8 May 2003 13:43:39 -0400
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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