[TechAssist] Re: Sony HK short

This is a copy form a Manual I have for SONY RA4 chassis.
I hope it will render a few tips:

IK/AKB
Overview
When troubleshooting a blanking problem, you must first understand the
video drive and IK blanking circuit and how they interrelate. Second, by
applying the troubleshooting techniques in this book you can determine if 
blanking is caused by the video drive circuit or the IK.
Video Drive.The RGB video signals exit IC511 Video Processor at pins 35, 37 
and 39. The RGB signals pass through buffers and enter the CR board at 
CN7101.
The G and B signals are sent to their respective C boards. Each of these
signals are input to their respective Video Out IC, then amplified and 
output to the cathode of their tube.

IK
The purpose of the AKB or IK circuit is to keep the picture?s white balance 
correct by controlling the bias or input level at the picture tubes cathode.
When serial data is present at the IC511 Video Processor, the IK circuit
begins operation. Three pulses are output during vertical blanking, one
at each of the RGB outputs. These pulses turn the tubes fully on. The
beam current is sensed at pin 5 of each Video Out and applied to the IK
buffer. This signal is sent to IC511/41 IK In, which is the reference return 
for the loop. The RGB output voltage levels are determined by this input. If 
the voltages of the pulses returned are not within a certain window, the 
video signal will be blanked. Internally these three pulses are applied to 
their own sample and hold circuit. They all contain an external capacitor, 
which is connected to pins 36, 38 and 40 respectively. The voltage at these 
pins corresponds to the efficiency of each cathode. The more current drawn, 
the lower the voltage output at the sample and hold capacitors.
This differs from previous models.
When a normally working set is first turned ON, the Timer LED blinks for
approximately 8 to 10 seconds. This is because IC511 Video Processor
is holding the data bus in a busy state. When the voltages at IC511/36,
38 and 40 are between 2.5 and 6 volts, the IC511 Video Processor will
signal the micro that it is no longer in a busy state and unblank the set. 
When IC511 unblanks the video, it outputs RGB of approximately 2 Vp-p from 
pins 35, 37 and 39. If there is a problem, the Timer LED will flash five 
times in accordance with the Self-Diagnostic function. As an example, if the 
red tube were drawing no current, IC7101/5 would fall to
about 2 volts. This would cause the voltage at IC511/36 to rise to around 
6.5 volts. These voltages are indications that the red tube is not drawing 
enough current.
Troubleshooting
The first thing that must be determined is if the problem is with the video 
drive or the IK return. There are several ways to determine if the IK pulse 
is driving the tube. The quickest way is to take a mirror and place it at
about a 45-degree angle above and behind the tube and look for a bright
horizontal line at the bottom of the tube (this would be at the top of the 
mirror). Remember the IK pulse is done during vertical blanking, so although 
it cannot be seen on the screen, it can be seen in the tube. If one of the 
lines is missing or is significantly dimmer than the other two, that color 
has the problem. Check the color?s output from the Video Processor to decide 
if it or the video drive circuit is at fault. If the video drive circuit is 
at fault, the IK pulse can be followed to signal trace the circuit.
If all three lines can be seen, then you can check the sample and hold
voltages at IC301/19, 21 and 23 to see if the IK pulses are being 
returned.These voltages are normally around 4 Vdc, but any voltage between 
2.5
and 6 volts should not cause blanking. If all three lines are seen and the 
S/H voltages are correct, suspect the IC511 Video Processor. However, when 
one of the S/H voltages is incorrect, there are a few possibilities:
The screen control could be mis-adjusted. Simply turn the screen adjustment 
up or down. If this is the problem, the set should unblank before the 
adjustment brings the tube to retrace. If the voltage at Q501/B is not 
within the levels mentioned above, there could be a problem with that 
picture tube or its biasing. The voltage at Q501/B depends on the voltages 
output by each pin 5 on the video drive IC?s.


Again it will vary depending on the chassis but the basic principle
of operation remian the same.
I hope it will be of help.
Panday

From: "tomlee" <t8872695@xxxxxxxxxxxxx>
Reply-To: techassist@xxxxxxxxxxxxx
To: <techassist@xxxxxxxxxxxxx>
Subject: [TechAssist] Re: Sony  HK  short
Date: Sun, 30 Mar 2003 22:15:21 -0800


Sometimes we can find them at electronic surplus source. I have some prewire
of this type transformer those used in car amplifier. I did not test it yet.
Dang
TD electronics
----- Original Message -----
From: "Gary McCartney" <gary@xxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Sunday, March 30, 2003 9:34 PM
Subject: [TechAssist] Re: Sony HK short


 >
 > I just did one with the torroid core donut last week. Worked fine. The
 > best thing about it rather than using turns of wire around the flyback
 > core, is that you don't have to guess at how many turns to make the
 > proper filament voltage. Just wrap 5 turns around one side of the donut,
 > then 5 turns at the opposite side and you have a 1:1 ratio transformer.
 > Slice the traces to the heater pins on the CRT board and connect the
 > primary winding to the circuit traces and connect the secondary winding
 > to the heater pins. Done.
 >
 > Only problem is I don't know where to get any more torroid donuts with
 > the proper characteristics for this purpose.
 >
 >
 >
 >
 > Gary McCartney
 >
 > McCartney Electronics
 > 7134 Fife Rd, RR 7
 > Guelph Ontario Canada N1H 6J4
 > Fax: (519)821-1530
 > email: gary (at) number63.ca
 >
 >
 >
 >
 >
 >
 > tomlee wrote:
 > >
 > > I remember somebody said about the  small  ferite donut can do the
 > > job.Primary on one half .Secondary on the other half .
 > >  I think it is a good idea. I never try but I will do it when The fly
back
 > > does not have place to wind the
 > > wire.
 > > Dang
 > > TD electronics
 > > ----- Original Message -----
 > > From: "Kevin" <kevintv@xxxxxxx>
 > > To: <techassist@xxxxxxxxxxxxx>
 > > Sent: Sunday, March 30, 2003 1:28 PM
 > > Subject: [TechAssist] Re: Sony HK short
 > >
 > > >
 > > > Isolate the heater from ground.  There are a couple of ways to do
this.
 > > > The easiest way is to take an 18-22 gauge insulated wire and wrap the
 > > > middle of the wire 2 or 3 turns around the ferrite core of the 
flyback
 > > > and then solder one end to H1 and the other end to H2.  You should
 > > > measure the heater voltage before disconnecting the heater circuit
from
 > > > H1 and H2.  You may have to play with the gauge of wire and number of
 > > > turns to get it close to the original heater voltage.  Unless
something
 > > > else happens to the pix tube, this should be a permanent fix.
 > > >
 > > > The second way involves using a 120 volt to 6 volt transformer.  But
 > > > this way is more difficult because you have to have the type of
circuit
 > > > that has a relay that is activated by the micro and then the relay
turns
 > > > the set on.  Also the transformer costs more money than a piece of
wire.
 > > > The wire method also is easier to figure out (at least for me!)
 > > >
 > > > Kevin Wilks
 > > > Kevin's TV & Video Repair
 > > > Penticton BC Canada
 > > > kevintv@xxxxxxx
 > > >
 > > > -----Original Message-----
 > > > From: techassist-bounce@xxxxxxxxxxxxx
 > > > [mailto:techassist-bounce@xxxxxxxxxxxxx] On Behalf Of mark brock
 > > > Sent: Sunday, March 30, 2003 12:18 PM
 > > > To: techassist@xxxxxxxxxxxxx
 > > > Subject: [TechAssist] Sony HK short
 > > >
 > > >
 > > > I have a 35" Sony in with bright blue and retrace then shutdown,  I
find
 > > > 46
 > > > ohms from KB ( pin 10 ) to either  H1 or H2,  tried the hk short
removal
 > > > using hivoltage to G1 and G2 but no help,  since the short doesn't
 > > > involve
 > > > G1 and 2 should  I be arcing the H's or KB pins instead ?  may have 
to
 > > > try
 > > > the isolation procedure  if so,  is this put on the H1 and H2 either
or
 > > > both
 > > > or do I Isolate KB from the board ?   now are you as confused as I 
am,
 > > > I've
 > > > had good luck in past by using the G2 procedure,  anyway,  customer
 > > > won't do
 > > > the new tube thing but willing to spend a little on a short term fix 
?
 > > > sure
 > > > appreciate any clarification on this method.  thanks for all your 
help
 > > > brock
 > > > Brock Electronics
 > > > R.R.4 box 237
 > > > 5208  cr.3385
 > > > Independence Ks. 67301
 > > > 620-331-0235
 > > > fax  331-7191
 > > >
 > > > brock@xxxxxxx
 > > > mailto:brock@xxxxxxx
 > > > Zenith*Philips*Peavey*Fender*Crate
 > > > we work on all brands,makes,models
 > > > of anything that plugs in the wall
 > > >
 > > >
************************************************************************
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