[TechAssist] Re: JVC VCR HR-J420U acts like bad heads- but is it?
- From: "K Dinckan" <kdinckan@xxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Sat, 10 May 2003 03:41:47 -0700
check surface mount cap next to the capstain motor board.
Ken Dinckan
e-mail to : kdinckan@xxxxxxx
All TV&Appliance Service
2747 Roosevelt Street # B
Carlsbad CA 92008
Tel:(760)4341131
Fax:(760)4348856
----- 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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