JVC HR-S4600U SVHS recorder -- automatic tracking doesn't work quite right.

[larrymoencurly]

Is there a sensitivity adjustment for the auto tracking feature of a
JVC HR-S4600U SVHS VCR? Mine doesn't seem to adjust the tracking
enough, so when I play tapes made in two other VCRs I usually get
white streaks in the lower 2", unless I adjust the tracking manually.
The auto tracking is definitely working somewhat because the picture
improves a lot in the first two seconds of play.

Am I right to assume that auto tracking works by aiming for the lowest
rate of missing sync pulses or something? If so, why won't mine try
harder? Is there a threshhold adjustment or something?

 

[Asimov]

"larrymoencurly" bravely wrote to "All" (16 Aug 03 11:07:17)
--- on the topic of "JVC HR-S4600U SVHS recorder -- automatic tracking doesn't
work quite ri"

Do you know if the little smt 3.3uF tantalum lower drum motor capacitor
has been serviced? These commonly developed a high esr causing a noise
band and touchy tracking. It's in the JVC faq on Sam's site.

la> From: [email protected] (larrymoencurly)

la> Is there a sensitivity adjustment for the auto tracking feature of a
la> JVC HR-S4600U SVHS VCR? Mine doesn't seem to adjust the tracking
la> enough, so when I play tapes made in two other VCRs I usually get
la> white streaks in the lower 2", unless I adjust the tracking manually.
la> The auto tracking is definitely working somewhat because the picture
la> improves a lot in the first two seconds of play.

la> Am I right to assume that auto tracking works by aiming for the lowest
la> rate of missing sync pulses or something? If so, why won't mine try
la> harder? Is there a threshhold adjustment or something?


.... This message transmitted on 100% recycled photons.

 

[u1061771156]

Is there a sensitivity adjustment for the auto tracking feature of a
JVC HR-S4600U SVHS VCR? Mine doesn't seem to adjust the tracking
enough, so when I play tapes made in two other VCRs I usually get
white streaks in the lower 2", unless I adjust the tracking manually.
The auto tracking is definitely working somewhat because the picture
improves a lot in the first two seconds of play.

If the bottom degrades sooner than the rest, this may point towards the
tape path not being quite correct, in particular the exit roller guide.

Am I right to assume that auto tracking works by aiming for the lowest
rate of missing sync pulses or something? If so, why won't mine try
harder? Is there a threshhold adjustment or something?

I think they typically monitor the amplitude of one of the carriers
(HiFi audio is the best I think, if available, otherwise it would have
to drop back to video carrier). The micro effectively "watches the meter"
as it twiddles the tracking and chooses what it thinks is an optimal
point. It will use the average across the picture, so if it drops out
top or bottom before the middle, then the adjustment is at best an
approximation.

Mike.

 

[u1061771156]

"larrymoencurly" bravely wrote to "All" (16 Aug 03 11:07:17)
--- on the topic of "JVC HR-S4600U SVHS recorder -- automatic tracking doesn't
work quite ri"

Do you know if the little smt 3.3uF tantalum lower drum motor capacitor
has been serviced? These commonly developed a high esr causing a noise
band and touchy tracking. It's in the JVC faq on Sam's site.

That cap is used to sense the head position modulo the number of poles (8?)
Finer head position is sensed by a different wiggly trace on the motor PCB
which doesn't use the 3.3uF cap. So when it fails, the machine intermittently
gets the head position radically wrong, and one gets wide noise bars with
sharp boundaries. I don't think it can cause a minor tracking problem like
this poster has.

Still worth replacing this cap while one has the machine apart, of course,
as it will fail sooner or later...

Mike.

 

[WEBPA]

That cap is used to sense the head position modulo the number of poles (8?)
Finer head position is sensed by a different wiggly trace on the motor PCB
which doesn't use the 3.3uF cap. So when it fails, the machine intermittently
gets the head position radically wrong, and one gets wide noise bars with
sharp boundaries. I don't think it can cause a minor tracking problem like
this poster has.

Still worth replacing this cap while one has the machine apart, of course,
as it will fail sooner or later...

Mike.

On the other hand...

If the tapes in question were recorded in SLP (6-hours on a T120), then
interchangeability problems are to be expected. That's because the VHS
standard does not promise SLP interchangeability. Tweaking tape path alignments
among the machines involved may or may not help.

webpa