Hello,

I have a Sony Trinitron KV27S22 (December 1997). A couple of days ago, it
developed a picture problem. Rather than try to describe it, I have placed
the following photos on the web:

Image of color bars: Behaving OK -
http://www.enosoft.net/kv27s22/Bars%20-%20OK.JPG
Image of color bars: Exhibiting problem -
http://www.enosoft.net/kv27s22/Bars%20-%20Problem.JPG

The problem will set in anything from a few seconds to a few minutes after
cold-starting the set. The problem will persist for a few seconds before
the display completely disappears. Only a cold reset will restore the
image. Audio is fine.

I have done some troubleshooting and have narrowed the problem to what I
think is a capacitance issue. Using a painter's stick (wooden!), I tapped
the various components on the main board and found that the tapping could
induce the problem. However, if I hold the ground of the audio connectors,
the tapping does not create the problem. When the problem is present,
grabbing the ground of the audio connector clears the problem.

The most sensitive part of the board is shown at:

http://www.enosoft.net/kv27s22/Main%20Board%20(Part).JPG

I have a copy of the Sony service manual for this set but, before I merrily
begin replacing all the capacitors, I would like to know if anyone knows a
specific cause and/or that I am barking up the right tree.

Many thanks in advance,

John Miller.

Thanks for your quick reply.

I suspect a capacitance issue based on the problem not occurring (or even
reversing) when I touch a ground on the board (e.g., the audio input
ground). When tapping, there's no specific component that is most sensitive
and, if, instead of tapping, I apply a more constant force to the
components, I cannot reproduce the problem. I have disconnected and
reconnected all the connectors to the main board with no effect. I have
looked at the underside of the board with a magnifying lamp but couldn't
detect any obvious problems.

John.

wrote in message
oups.com...
How does tapping on the board narrow it down to a capacitance issue?

Any mechanical vibration testing that changes the symptom points to a
connection problem. It is possible, though highly unlikely, that the
leads to a capacitor have become partially disconnected internally.

I would start by a good visual going over with a light and magnifying
glass the solder connections on the bottom of the board.

John F Miller wrote:
Thanks for your quick reply.

I suspect a capacitance issue based on the problem not occurring (or even
reversing) when I touch a ground on the board (e.g., the audio input
ground). When tapping, there's no specific component that is most sensitive
and, if, instead of tapping, I apply a more constant force to the
components, I cannot reproduce the problem. I have disconnected and
reconnected all the connectors to the main board with no effect. I have
looked at the underside of the board with a magnifying lamp but couldn't
detect any obvious problems.

John.

wrote in message
oups.com...
How does tapping on the board narrow it down to a capacitance issue?

Any mechanical vibration testing that changes the symptom points to a
connection problem. It is possible, though highly unlikely, that the
leads to a capacitor have become partially disconnected internally.

I would start by a good visual going over with a light and magnifying
glass the solder connections on the bottom of the board.

Sonys from this period had a solder problem esp around the tuner and
tuner board. I repaired a few recently with this problem. Sam talks
about it he
http://www.eio.com/repairfaq/REPAIR/F_sonytune.html
Very careful inspection is a must. Some of the solder might have to be
sucked off and replaced. The bad joints have a frosted look with a
grainy look and sometimes veins running through them. I usually reheat
everything and resolder everything that looks bad. Quite tedious. Just
did an eMac with the same problem.
richard

Thanks! I will check that area very carefully.

John.


"spudnuty" wrote in message
oups.com...

John F Miller wrote:
Thanks for your quick reply.

I suspect a capacitance issue based on the problem not occurring (or even
reversing) when I touch a ground on the board (e.g., the audio input
ground). When tapping, there's no specific component that is most
sensitive
and, if, instead of tapping, I apply a more constant force to the
components, I cannot reproduce the problem. I have disconnected and
reconnected all the connectors to the main board with no effect. I have
looked at the underside of the board with a magnifying lamp but couldn't
detect any obvious problems.

John.

wrote in message
oups.com...
How does tapping on the board narrow it down to a capacitance issue?

Any mechanical vibration testing that changes the symptom points to a
connection problem. It is possible, though highly unlikely, that the
leads to a capacitor have become partially disconnected internally.

I would start by a good visual going over with a light and magnifying
glass the solder connections on the bottom of the board.

Sonys from this period had a solder problem esp around the tuner and
tuner board. I repaired a few recently with this problem. Sam talks
about it he
http://www.eio.com/repairfaq/REPAIR/F_sonytune.html
Very careful inspection is a must. Some of the solder might have to be
sucked off and replaced. The bad joints have a frosted look with a
grainy look and sometimes veins running through them. I usually reheat
everything and resolder everything that looks bad. Quite tedious. Just
did an eMac with the same problem.
richard

Resolder your vertical output IC561.

This will solve your problem.

Resolder the Horizontal Driver Transformer while your in there for good
preventive maintenance


--
==========================
Jeff Stielau
Shoreline Electronics Repair
344 East Main Street
Clinton,CT 06413
860-399-1861
860-664-3535 (fax)

========================

"John F Miller" johnATenosoft.net wrote in message
...
Hello,

I have a Sony Trinitron KV27S22 (December 1997). A couple of days ago, it
developed a picture problem. Rather than try to describe it, I have
placed the following photos on the web:

Image of color bars: Behaving OK -
http://www.enosoft.net/kv27s22/Bars%20-%20OK.JPG
Image of color bars: Exhibiting problem -
http://www.enosoft.net/kv27s22/Bars%20-%20Problem.JPG

The problem will set in anything from a few seconds to a few minutes after
cold-starting the set. The problem will persist for a few seconds before
the display completely disappears. Only a cold reset will restore the
image. Audio is fine.

I have done some troubleshooting and have narrowed the problem to what I
think is a capacitance issue. Using a painter's stick (wooden!), I tapped
the various components on the main board and found that the tapping could
induce the problem. However, if I hold the ground of the audio
connectors, the tapping does not create the problem. When the problem is
present, grabbing the ground of the audio connector clears the problem.

The most sensitive part of the board is shown at:

http://www.enosoft.net/kv27s22/Main%20Board%20(Part).JPG

I have a copy of the Sony service manual for this set but, before I
merrily begin replacing all the capacitors, I would like to know if anyone
knows a specific cause and/or that I am barking up the right tree.

Many thanks in advance,

John Miller.

Based on his description (problem shows for a while then screen disappears)
the protection circuitry is kicking in to blank the picture. A loose
connection (or bad solder joint) can definitely cause this. If not a solder
joint problem, it is doubtful that a component failure problem would allow
him to get a normal picture to submit.

I have a Sony KP-41T15 that has a similar "line paring" problem but in my
case there are faulty components in the vertical circuit as the problem
condition is continuous from when the set is turned on. The vertical
voltage feed to the jungle IC is twice what it should be (approx 3V versus
1.5V). I am suspecting the jungle IC as well but first I have to find the
problem components(s).

Bruce


"Shoreline Electronics" wrote in message
...
Resolder your vertical output IC561.

This will solve your problem.

Resolder the Horizontal Driver Transformer while your in there for good
preventive maintenance


--
==========================
Jeff Stielau
Shoreline Electronics Repair
344 East Main Street
Clinton,CT 06413
860-399-1861
860-664-3535 (fax)

========================

"John F Miller" johnATenosoft.net wrote in message
...
Hello,

I have a Sony Trinitron KV27S22 (December 1997). A couple of days ago,
it developed a picture problem. Rather than try to describe it, I have
placed the following photos on the web:

Image of color bars: Behaving OK -
http://www.enosoft.net/kv27s22/Bars%20-%20OK.JPG
Image of color bars: Exhibiting problem -
http://www.enosoft.net/kv27s22/Bars%20-%20Problem.JPG

The problem will set in anything from a few seconds to a few minutes
after cold-starting the set. The problem will persist for a few seconds
before the display completely disappears. Only a cold reset will restore
the image. Audio is fine.

I have done some troubleshooting and have narrowed the problem to what I
think is a capacitance issue. Using a painter's stick (wooden!), I
tapped the various components on the main board and found that the
tapping could induce the problem. However, if I hold the ground of the
audio connectors, the tapping does not create the problem. When the
problem is present, grabbing the ground of the audio connector clears the
problem.

The most sensitive part of the board is shown at:

http://www.enosoft.net/kv27s22/Main%20Board%20(Part).JPG

I have a copy of the Sony service manual for this set but, before I
merrily begin replacing all the capacitors, I would like to know if
anyone knows a specific cause and/or that I am barking up the right tree.

Many thanks in advance,

John Miller.

Thanks, Jeff!

I followed your suggestions yesterday and, after being on continuously for
more than 20 hours, the problem seems to have gone away.

Regards,

John.

--
John F. Miller
http://www.enosoft.net
high performance tools for music and video


"Shoreline Electronics" wrote in message
...
Resolder your vertical output IC561.

This will solve your problem.

Resolder the Horizontal Driver Transformer while your in there for good
preventive maintenance


--
==========================
Jeff Stielau
Shoreline Electronics Repair
344 East Main Street
Clinton,CT 06413
860-399-1861
860-664-3535 (fax)

========================

"John F Miller" johnATenosoft.net wrote in message
...
Hello,

I have a Sony Trinitron KV27S22 (December 1997). A couple of days ago,
it developed a picture problem. Rather than try to describe it, I have
placed the following photos on the web:

Image of color bars: Behaving OK -
http://www.enosoft.net/kv27s22/Bars%20-%20OK.JPG
Image of color bars: Exhibiting problem -
http://www.enosoft.net/kv27s22/Bars%20-%20Problem.JPG

The problem will set in anything from a few seconds to a few minutes
after cold-starting the set. The problem will persist for a few seconds
before the display completely disappears. Only a cold reset will restore
the image. Audio is fine.

I have done some troubleshooting and have narrowed the problem to what I
think is a capacitance issue. Using a painter's stick (wooden!), I
tapped the various components on the main board and found that the
tapping could induce the problem. However, if I hold the ground of the
audio connectors, the tapping does not create the problem. When the
problem is present, grabbing the ground of the audio connector clears the
problem.

The most sensitive part of the board is shown at:

http://www.enosoft.net/kv27s22/Main%20Board%20(Part).JPG

I have a copy of the Sony service manual for this set but, before I
merrily begin replacing all the capacitors, I would like to know if
anyone knows a specific cause and/or that I am barking up the right tree.

Many thanks in advance,

John Miller.