[TV] Re: Sony KV35S65 SAMS 4699

["lynnslb" <lynnslb@xxxxxxxxxxxxx>]

Note I have copied the following from the Nesda Website.
http://www.nesda-ohio.com I have not included the pictures from the site. Go
there to see them. However you will have to signup for membership to login
and see the whole article.

I have posted this before as a troubleshooting
aid. It should explain what is
happening.
I don't have the manual in front of me
so this may be a little generic. The IK
circuit sends out a 100% white pulse
during the vertical blanking interval.
There is a pulse for red then green and
lastly blue. Each pulse is on a different
scan line. The IK circuit then matrixes
them together, amplifies the 3 pulses and
send it back to the jungle IC.
Using a scope with delayed sweep or set
at the vertical rate and expended 10X you
should be able to see the 3 pulses at the
IK output from the CRT board and
note that the amplitude will grow or
shrink depending on the screen setting.
If one color is missing then you have
an amp circuit problem for that color.
If none of the pulses are there and
they go in from the jungle IC then
look for a bad IK amp transistor.
If the pulses are there but do not vary
with changing screen voltage the feedback
to the jungle IC or the IC itself is
bad Some times the jungle IC has small
Mylar caps off of it and if there they
have been known to short. Sometimes
the caps are built into the jungle IC and
can still short.
Many times the IK circuit just goes out
of tolerance meaning the current drawn
by one crt is no longer within acceptable
range and the picture is blanked.
If this is the case then increasing the
screen voltage will solve, for a while,
the complaint.
Daniel Mundy, CET®/CSM
HiFi Buys a Tweeters Etc. Company
Atlanta, GA 30331
Sony IK Circuit... Explained by Dan Mundy, CET/CSM
See The Next Three Pages
To Bypass This Circuit
For Test Purposes
DISCLAIMER
Information presented here is derived from
many sources and is believed to be correct
at time of printing. We make no guarantee,
express or implied of the accuracy, efficacy,
or safety of any of the techniques
published. It is not intended to replace
Manufacturer's Recommendations or
good Safety and Troubleshooting
practices.
Use at your own Risk. The Speaker, its
Writers and Staff, and Nesda of Ohio
assume NO responsibility for damage to
persons or property as a result of any
information printed herein.
Opinions stated are those of the author and
not the Nesda of Ohio Newsletter. Opinions
stated are believed to be true, and are
offered in the spirit of helping other
servicers but may have no basis in fact.
Sony television sets of recent years
(1994-95 & more) contain circuits which
monitor the current of the CRT cathodes.
The microprocessor in combination
with the "jungle" chip and a series of
transistors and other components in the
circuits corresponding to the three cathodes,
then automatically adjust the bias of
each individual gun to compensate for
Kinescope aging.
Unfortunately for the owner, they also
will blank the picture when the Kine
slumps too low. Some tech's have been
able to "Rejuvinate" the Kine & restore
performance, while others have wondered
if there was a way to bypass that IK
circuit. That answer has been always
been "NO" --- Until now.
Jorge Miret, of J.C.Electronic Repairs in
Puerto Rico has discovered a circuit
modification which will allow a bypass of
that circuit. It is found on a Spanish-
Language website
www.comunidadelectronicos.com/
articulos/IK.htm
which makes it a bit tough on us Gringo's,
but "not to worry". Google, the ever helpful
search engine is capable of translating,
as you've learned in another article
published within the pages of "The
Speaker".
Following is a machine-translation of that
webpage, aided by your reporter where
necessary.
A diagram of the circuit modification is
provided. It involves cutting a trace and
the addition of 3 diodes.
Translation for Gringo's:
Following is a brief description of the
Operation of the IK circuit. From each
output of the Jungle Chip (R, G, B) exits
a pulse, three pulses in all, one to cathode
of the Kine. These pulses are at the horizontal
sweep rate, so that it activates
during the exploration of a line. These
lines are not visible in the screen, since
they are sent during the beginning of the
"vertical sweeping", in the area of
"blanking", but they can be seen in the
overscanned part of the screen if the
vertical height (VSIZ) in the Menu is
reduced slightly. This circuit, besides to
verify the correct operation of the CRT,
allows to make automatic adjustments
within the IC jungle, to compensate the
small differences of emission between the
cathodes and to maintain the correct color
of the image. The current of the cathodes
is detected by 3 Detector circuits put in
between the exciting amplifiers and
each one of the cathodes. These circuits,
send a signal, proportional to the current
of each one of the cathodes, to a IK
Buffer circuit, from where they are sent to
the jungle chip. In many equipment these
circuits are formed by discrete components
(transistors, diodes, resistance, etc.)
but in more recent models, all the exciting
stage of the CRT and the components of
IK circuit are included in a single
integrated circuit like the TDA6108.
Almost from the moment at which the
equipment is ignited, the "jungle" chip
sends the respective pulses to each one of
the output pins, while it maintains a "cut"
or "muting" of video (black screen). As
the cathodes reach the temperature necessary
to emit electrons, the current of such,
generates in the respective detector circuits,
a pulse similar to the applied one
and whose amplitude is proportional to
the current of the cathode. To see the
image on the screen, When the pulses in
the IK circuit reach certain amplitude, the
"cut" of video is deactivated and the image
appears. The lack of video (black
screen), in these TV Sony, sometimes
causes confusion between the technicians,
because when not having an output of
signal from the jungle chip, tend to
suppose that the problem is in the Jungle
Chip.
When faced the repair of a recent TV that
presents absence of Video (black screen),
we must make the following steps: To
increase G2 screen voltage. If the screen
is illuminated with "raster" (swept) normal,
we can discard the possible problems
in the circuits of sweeping. (a defect
in the Vertical circuit, can cause the same
symptom) This also allows us to quickly
verify the necessary voltages for the
operation of the CRT (filament, anode,
G2). If these voltages are correct, is very
possible that the problem is in the Kine
drive amplifiers, in the CRT, or in the IK
circuit.
The next step, is to verify the state of the
CRT. If it has low emission in some of
the cathodes, or if it has some internal
short it can cause that IK circuit to stay in
"cut". For this it is advisable to use a Kine
Checker. If it is not had one, the following
verification can be made: With the
TV operating, momentarily place a 15 or
20K 2W resistor, between ground and
each one of the cathodes (KR, KG and
KB), one at a time. This will result in
the corresponding color illuminating
brightly. The intensity must be similar
when doing the test in the three cathodes.
If some of the colors does not appear or it
does in tenuous form, it indicated an exhausted
or defective CRT. (This is not a
very precise test. It is better to use a Kine
Checker, but nevertheless, this test could
aid to determine if some of the guns, is
defective or with very low emission).
To deactivate or "to deceive" the IK circuit
sometimes can be useful. The
circuit modification below will "deceive"
the IK circuit into deactivating the video
blockade that it causes. This can be done
by disconnecting the line of the IK buffer
and placing three diodes of the type
1N4148 between the pins of the integrated
jungle, as it is shown in the figure.
With this modification, the pulses from
the output of the jungle chip are
re-introduced into the IK line of the chip
which then deactivates the video
blockade, allowing the image to appear
on the screen. If the image does NOT
appear, and having made the verifications
given earlier, is possible that the integrated
jungle (or some component
associate) is defective.
Granted, The translation leaves a bit to be
desired (you should have tried reading it
before I "Helped" it along). I make no
claim to be a linguist- My parents never
even spoke Hungarian around me, but I
believe that this is more information than
we've ever seen about this IK circuit
before.
( Cont. Next Page )
Sony IK Circuit Bypass By Joe Sopko, CET
Contributed By Jorge Miret And Luis Alberto Tamiet
The article that you've just read was contributed
By Jorge Miret and appears to be
written by Luis Alberto Tamiet on the
website listed in the first paragraph. As
the entire site is in Spanish, I am not sure
of the actual author.
The Speaker would like to thank Both of
these Techs for adding to our store of
knowledge. Take the information for
what it's worth, I've not tried it, and
neither has the contributor so we can't
speak of it's efficacy from personal
experience. It is presented as another diagnostic
tool to determine whether the
blanking is caused by the jungle chip or
the kine.
Of course, no tech would ever leave
the bypass circuit in as a permanent
measure, nor would "The Speaker"
ever recommend a modification not
authorized by the manufacturer. If
you try this, we'd like to hear of your
experience and opinion as to it's
value.
See follow-up article
next page.
Author Joe Sopko
Tried This Procedure
Hey,
It Works !!
Recently, The Speaker printed an
article describing a procedure to bypass
the Sony IK circuit. The procedure came
from a Latin American site, and at the
time of printing we didn't know of anyone
who had actually tried it or if it was
actually effective...Heck, it took us long
enough just to translate the thing!
Subsequent to that time, a Sony
KV20S20 came into Consumer Service in
South Euclid Ohio with a Black Screen
(has sound). Turning up the Screen
Grid restored the picture, so it looked as
though this was a candidate to determine
the efficacy of that Bypass Mod. Seized
by the curiosity that marks all
technicians, I installed the components
mentioned in that article from The
Speaker.
As you can see in Figure 1, there are 3
diodes riding like an outrigger on the
Jungle Chip (CXA1870). Those 3 diodes
and a cut of a foil trace on the PCB are all
that the mod involves. Real Easy, Takes
only a couple of minutes. Figure 2 shows
how the diodes are connected schematically.
Be aware that there are different jungle
chips involved in different sony chassis.
Some use the CXA1465, and some use
the CXA1870 (and I have no doubt
that there are others, too). I have put the
affected pin numbers for these 2 chips in
figure 2 for your information. Also be
aware that a particular chassis may use
"either" of 2 chips. The chassis that I was
working with had
the PCB roadmapped for a 48 pin chip,
but actually had a 42 pin chip
installed. Needless to say, the pin markings
on the PCB's surface were
incorrect. (Tech's are nothing if not
adaptable)
I'm glad to report that the modification
performs as promised. BEFORE the
Mod, the picture would blank at the low
end of the screen control, would
reappear at mid to high range, and then
blank again at very high position of
the control. AFTER the Mod, The picture
was present throughout the entire
rotation of the screen control. I assume
that Sony's intent was to prevent a
poor picture from being seen as the kine
aged beyond limits. With this
modification, you can watch a crappy
picture throughout the entire range of
the control if you so desire.
Naturally, this procedure is
presented only as a Test procedure to
determine if the IK Blanking Circuit
is indeed keeping the picture from
appearing. No technician would
ever leave the mod in as a permanent
fix and The Speaker would never
recommend any procedure contrary
to the manufacturer's approved
practices.
Sony IK bypass, IT WORKS !! By: Joe Sopko CET
FIGURE 1
Photo by Flash Sopko with the new
NesdaOhio Digital Camera

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