[TechAssist] Re: JVC VCR HR-J420U acts like bad heads- but is it?
- From: Gary McCartney <gary@xxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Sat, 10 May 2003 19:10:23 -0400
I ran out of time to work on the VCR and returned it to the customer.
Thanks for all the good suggestions from everyone.
Gary McCartney
McCartney Electronics
7134 Fife Rd, RR 7
Guelph Ontario Canada N1H 6J4
Fax: (519)821-1530
email: gary (at) number63.ca
K Dinckan wrote:
>
> check surface mount cap next to the capstain motor board.
> Ken Dinckan
>
> e-mail to : kdinckan@xxxxxxx
>
> All TV&Appliance Service
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> ----- Original Message -----
> From: "Gary McCartney" <gary@xxxxxxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Thursday, May 08, 2003 7:13 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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