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Track: mazdai1
Wu: Macros
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How to configure CVL for VCRs.
The material was prepared on the basis
the following materials
JVC - service manual video cassette
recorder HR-J227MS/J229EE
SAMSUNG - mechanical manual
DX7-A/DX7-AC,DX8-A/DX8-AC
AIWA - service manual video mechanism
D-27 ( apply to models VCR HV-FX22800
and up)
TOSHIBA - service manual video cassette
recorder V-405W
The main focus was on
next tbonpocam
1) setting up guide posts
2) settingSynchro heads
3) touched a little on tension issues
tapes
Issues were deliberately not addressed
stereo device settings, etc.
in this aria we are talking about two heads
devices, although everything that will be said
also applicable to higher classes
equipment.
Unfortunately, it is not possible
play back waveforms :(
To configure you will need
1) Oscilloscope with external input
scans. ->required
2) Test tape with recorded
signal. This signal, in the original
called stairsstep, in practice it is
black and white vertical stripes with
sound signal 6 kHz.
I have such test cassettes. Toshiba
uses the same thing, but with a sound signal
7 kHz.
A test cassette like this costs a lot
money. Of course it varies from company to company. But in
on average 50-100 bucks. You can get by
high-quality recording of any image,
with superimposed sound signal
"sine wave" 6-7kHz. The entry must be
made on a known working device.
3) Screwdriver with slots in the slot for
adjusting the height of the guide posts.
Imagination is in full swing here - everyone benefits from
ordinary otbeptok to pliers. But
better, of course, specialized
thing. Branded costs a lot. small,
crummy screwdriver from Samsung for
Setting up the stands in the camera costs 120
bucks.
When I saw her I was a little freaked out
didn't grab it - so much money for it
give away.
However, other companies are more liberal in
in terms of prices. Quince costs about 10
DEM.
4) To adjust the tape tension
you will need a corresponding cassette -
which measures tension. I won’t
mention the price so as not to irritate.
So let's get started.
1. Adjusting the height of the guides
racks
Ground the oscilloscope to ground
"VCR".
Probe nputkhem to point (ATTENTION)
frequency-modulated video signal.
If notscheme - it can be called: RV
FM, VIDEO ENV, RF RF, RF ENVELOPE....
External scan input to HEAD signal
SWITCH. If the signal cannot be found, then
connector from the video head amplifier
run the oscilloscope signal probe
represents a 25 hertz square wave.
So the input is to RF RF, and the scan is external
by HD SWITCH.
Should be visible on the oscilloscope screen
signal (oh how graphics are not enough).
The signal when the CVL is in good working order should
represent a continuous strip
high-frequency signal - ideally it
continuous and identical in scope.Span
it is usually 0.4-0.8 volts.
If the stands are not adjusted correctly
in height, then the signal will be
folds are observed, the signal will be
"hunch over" ...
If you set the scan to around 25
hertz, then cermehthoctb will be noticeable
signal.
Each segment represents
signal from one video head. Signal
HD SWITCH switching frequency 25
Hertz switches the output signal
pre-amplifier chips,
how do you ensure
continuity of video signal.
If it is contaminated from the heads, then this
is expressed in the fact that the scope of one of
segments, or rather every secondsegment will be sharply reduced by
compared to the neighboring one.
If the height is the height of the guide posts
strongly knocked down, then visually on the screen
TV will be visible multiple
horizontal noise stripes. Than
the more the altitude is reduced, the more
stripes On the oscilloscope, on the signal this
will manifest itself in frequent vertical
folds on the signal. If the height
slightly different from the nominal value, then
the signal will narrow at the edges of the segment.
If the signal narrows from the left edge
segment, then it is not adjusted in height
the left pillar, and the right side
signal - right pillar.
(Yes, I forgot to mention, all manuals
declare that already at this stage,
you need to disable automatic
tracking. We will follow the instructions
from above. Although when setting up the racks I
I don’t bother with this. But at
setting up the synchro head - strictly
necessarily. Disable tracking, and it
set by manual adjustment
maximum swing of the RF RF signal at
oscilloscope.)
By adjusting the height of the stands, achieve
maximum smooth signal throughout
segment.
If, despite all your efforts, you still don’t
managed to eliminate the gap between
segments, then the HEAD point is probably knocked down
SWITCH POINT.In other words, the exit
amplifier is switched not when
one video head starts reading
entry, and the other one leaves
contact with the tape, and
right at the moment
reading in the middle of reading a line.
On the TV screen in this case as
usually visible constant wide
horizontal noise band, although in
in some cases it may appear with
at intervals of about five seconds. B
In this case, the situation will be saved by a variable
resistor with the inscription HD SWITCH POINT.
As a rule, in modern devices it
it's called that. Dated before
inscription PG POS, PG MM. Twist it around
ensure there is no gap between
segments.
If the resistor is not found, then no luck.
Nowadays, more and more manufacturers are switching
to adjust SWITCH POINT from the remote control. U
SAMSUNG and JVC is a special service
remote control
In this case, the direct road to
authorized service center.
So, you have achieved a good signal.
Let me remind you that a good signal is
signal running in a straight line, without
dips, swing 0.4-0.8 volts.
The next stage is to adjust the height and
azimuth of the audio/sync head. This
configuration is easy. Oscilloscope probe
on the way outsound by bass and adjustment
screws on the audio/sync head pad
achieve maximum signal swing.
Now comes the most mysterious part -
answer to questions like “why is this there?”
big nut?"
Adjusting the phase of the clock signal (in
original A/C head phase (X-Value)-JVC)
Probe the oscilloscope back to the RF RF. Tape
with the stairsstep signal in mode
playback
(I hope you adjusted the struts
was it not done in stop mode? ;) )
Set manual tracking to medium
position.
What regulates the phase of the clock signal
is it a flare nut or something else that
moves a little (0.5 cm)
audio/sync head along the tape. Not
up/down, does not tilt it away
vertical, namely moves ALONG
ribbons. Gently making the movement
synchro head along the tape, achieve
maximum scope. Before we start
adjustments must be released
fixing screws, and then re-install them
tighten. From experience I can say that
sometimes I set the maximum signal to
oscilloscope, when transferring the device to
"pause" mode appears on the image
hindrance.
The phenomenon of this is not clear to me, but
The problem is usually solved with a small
right height deviationguide
racks from nominal. In the image
this has no effect, and the pause even
two-headed apparatus is obtained at
four-headed level.
Adjusting the belt tension.
Whoever has it, take the cassette out of their briefcases
for measuring belt tension. B apparatus
it and into the “playback” mode.
In a working machine, the tension value is
tape on the slave cassette deck
ranges from 35 to 48 grams/cm for JVC from
70 to 130 for SAMSUNG, from 45 to 95 for
TOSHIBA, 32-43 at AIWA
Well, that's probably all, it seems like the main thing
part is illuminated.
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