I've been hunting down several problems with a Sharp Image 429-DS-SY monitor
(Dual-scan 15k/25k monitor with Sony Trinitron tube used in video games, mfg
1998). I've totally recapped (the lytics) and replaced a diode in the power
supply that had opened up. I'm so close to wrapping it up, yet keep running
up against a wall with the last few issues.

Schematic: http://www.sharpimage.net/images/schematicD.pdf

In my latest saga, I've got a compressed right edge of the picture. From
everything that I know, this indicates that there's not enough current. I
would guess that perhaps it's a snubber cap issue, but I'm at a loss looking
at the schematic which caps to suspect (I don't have values onhand to
substitute each one). Further confusing to me is the E/W correction
components (most of the stuff I work on are much simpler devices).

Next, there's a twitching of the image. Maybe 1 or 2 twitches (horizontal
size appears to increase for a fraction of a second) every couple of
seconds, sometimes a longer interval of a steady image. For this, I would
suspect cold solder, but I've touched up just about every solder joint and
still haven't found it. Could this be a component issue?

And finally, sometimes on cold start, the pincushion is really bad--as if
it's non-existant, and there's a really bad hourglass effect (looking at a
convergence grid pattern). Pulling out the freeze spray doesn't allow me to
locate the fault once the monitor warms up and the pattern returns to
normal. Again, I'm suspecting cold solder could be the culprit.

Any tips or pointers for identifying cold solder joints? I've tried tapping
and using a toothbrush, but no luck.

The freeze spray hit a component that has become thermo sensitive, if
something changed with the action of the spray going on it. Locate and
change that component, and you will have that fault fixed. You may find a
number of components that have become thermo sensitive with age.

--

Jerry G.
==========================


"Jason F" wrote in message
...
I've been hunting down several problems with a Sharp Image 429-DS-SY monitor
(Dual-scan 15k/25k monitor with Sony Trinitron tube used in video games, mfg
1998). I've totally recapped (the lytics) and replaced a diode in the power
supply that had opened up. I'm so close to wrapping it up, yet keep running
up against a wall with the last few issues.

Schematic: http://www.sharpimage.net/images/schematicD.pdf

In my latest saga, I've got a compressed right edge of the picture. From
everything that I know, this indicates that there's not enough current. I
would guess that perhaps it's a snubber cap issue, but I'm at a loss looking
at the schematic which caps to suspect (I don't have values onhand to
substitute each one). Further confusing to me is the E/W correction
components (most of the stuff I work on are much simpler devices).

Next, there's a twitching of the image. Maybe 1 or 2 twitches (horizontal
size appears to increase for a fraction of a second) every couple of
seconds, sometimes a longer interval of a steady image. For this, I would
suspect cold solder, but I've touched up just about every solder joint and
still haven't found it. Could this be a component issue?

And finally, sometimes on cold start, the pincushion is really bad--as if
it's non-existant, and there's a really bad hourglass effect (looking at a
convergence grid pattern). Pulling out the freeze spray doesn't allow me to
locate the fault once the monitor warms up and the pattern returns to
normal. Again, I'm suspecting cold solder could be the culprit.

Any tips or pointers for identifying cold solder joints? I've tried tapping
and using a toothbrush, but no luck.

"Jason F" wrote in message
...
I've been hunting down several problems with a Sharp Image 429-DS-SY
monitor
(Dual-scan 15k/25k monitor with Sony Trinitron tube used in video games,
mfg
1998). I've totally recapped (the lytics) and replaced a diode in the
power
supply that had opened up. I'm so close to wrapping it up, yet keep
running
up against a wall with the last few issues.

Schematic: http://www.sharpimage.net/images/schematicD.pdf

In my latest saga, I've got a compressed right edge of the picture. From
everything that I know, this indicates that there's not enough current. I
would guess that perhaps it's a snubber cap issue, but I'm at a loss
looking
at the schematic which caps to suspect (I don't have values onhand to
substitute each one). Further confusing to me is the E/W correction
components (most of the stuff I work on are much simpler devices).

Next, there's a twitching of the image. Maybe 1 or 2 twitches (horizontal
size appears to increase for a fraction of a second) every couple of
seconds, sometimes a longer interval of a steady image. For this, I would
suspect cold solder, but I've touched up just about every solder joint and
still haven't found it. Could this be a component issue?

And finally, sometimes on cold start, the pincushion is really bad--as if
it's non-existant, and there's a really bad hourglass effect (looking at a
convergence grid pattern). Pulling out the freeze spray doesn't allow me
to
locate the fault once the monitor warms up and the pattern returns to
normal. Again, I'm suspecting cold solder could be the culprit.

Any tips or pointers for identifying cold solder joints? I've tried
tapping
and using a toothbrush, but no luck.




Cold solder joints usually look dull and sometimes cracked. Start by
resoldering any capacitors and coils near the flyback, and then move on to
elsewhere.

Thanks for the reply, but perhaps I didn't articulate--I could not find a
component that would respond to the freeze spray, at least in the way that I
was expecting (total failure of the pincushion correction like when the
monitor starts from cold).

I did discover something this morning. If you refer to the schematics:

"Jerry G." wrote in message
...
The freeze spray hit a component that has become thermo sensitive, if
something changed with the action of the spray going on it. Locate and
change that component, and you will have that fault fixed. You may find a
number of components that have become thermo sensitive with age.

--

Jerry G.
==========================


"Jason F" wrote in message
...
I've been hunting down several problems with a Sharp Image 429-DS-SY
monitor
(Dual-scan 15k/25k monitor with Sony Trinitron tube used in video games,
mfg
1998). I've totally recapped (the lytics) and replaced a diode in the
power
supply that had opened up. I'm so close to wrapping it up, yet keep
running
up against a wall with the last few issues.

Schematic: http://www.sharpimage.net/images/schematicD.pdf

In my latest saga, I've got a compressed right edge of the picture. From
everything that I know, this indicates that there's not enough current. I
would guess that perhaps it's a snubber cap issue, but I'm at a loss
looking
at the schematic which caps to suspect (I don't have values onhand to
substitute each one). Further confusing to me is the E/W correction
components (most of the stuff I work on are much simpler devices).

Next, there's a twitching of the image. Maybe 1 or 2 twitches (horizontal
size appears to increase for a fraction of a second) every couple of
seconds, sometimes a longer interval of a steady image. For this, I would
suspect cold solder, but I've touched up just about every solder joint and
still haven't found it. Could this be a component issue?

And finally, sometimes on cold start, the pincushion is really bad--as if
it's non-existant, and there's a really bad hourglass effect (looking at a
convergence grid pattern). Pulling out the freeze spray doesn't allow me
to
locate the fault once the monitor warms up and the pattern returns to
normal. Again, I'm suspecting cold solder could be the culprit.

Any tips or pointers for identifying cold solder joints? I've tried
tapping
and using a toothbrush, but no luck.

Thanks for the reply, but perhaps I didn't articulate--I could not find a
component that would respond to the freeze spray, at least in the way that I
was expecting (total failure of the pincushion correction like when the
monitor starts from cold).

I did discover something this morning. If you refer to the schematics:

http://www.sharpimage.net/images/schematicD.pdf

When it's cold and the pincushion correction is not functioning, the
pincushion pot (VR901) acts exactly like the H-Size pot (VR902)--that is, it
makes the picture wider instead of correcting the pincushion. I'm not
familar with how the pincushion correction circuit works, but at this point,
I think I need to focus on the transistors nearest this pot:

Q901, Q902, Q903

Can someone offer an explaination of how the pincushion correction works
using this schematic?

"Jerry G." wrote in message
...
The freeze spray hit a component that has become thermo sensitive, if
something changed with the action of the spray going on it. Locate and
change that component, and you will have that fault fixed. You may find a
number of components that have become thermo sensitive with age.

--

Jerry G.