possible problem with Sony flat-face WEGA

[William Sommerwerck]

I'm posting this to see if anyone /knows/ the answer, or has a reasonable
suspicion. I do not want to initiate an interminable chain of speculation.

I own a 36" flat-face 400-series Sony WEGA IDTV and, yes, I have the service
manual. The set has gotten heavy use over the past decade; I often leave it
on when I go to bed. It wasn't cheap, and I'd like to get at least another
five years out of it. For a non-HD CRT set, it has an excellent picture,
especially with RGB signals from a DVD player.

When the set's turned on, the HV is apparently shut off, so that the CRT
heater has time to come to full temperature, to avoid stripping the cathode.
(This is speculation.) Though sound comes on almost immediately, it takes
about 10 seconds for the raster to appear.

Recently I've noticed "something new". For about two seconds after the
raster comes on, the black level is too light. You can see the image
"darkening" as the black level drops to its "correct" point. This occurs
only when the set is "cold"; cycling the power doesn't cause this.

I'm hoping someone will say "I've seen this. It's the ___________."
Troubleshooting this set won't be easy (if only because it's close to the
wall on a near-immovable stand). I don't want to tear into it until I'm
reasonably certain I can fix it on the first try.

Thanks in advance.

 

[Jeffrey Angus]

I own a 36" flat-face 400-series Sony WEGA IDTV and, yes, I have the service
manual.

Is that the same set you kept trying to give away on
rec.antique.radio+phono?

Jeff

 

[William Sommerwerck]

I own a 36" flat-face 400-series Sony WEGA IDTV

Is that the same set you kept trying to give away
on rec.antique.radio+phono?

Are you kidding? That was an NAD MR-20A with a failing focus system.

It is a classic set, and worth restoring -- if you can find the parts needed
(most likely a no-longer-available HOT system). If someone wants it, it's
theirs for the cost of shipping.

 

[Meat Plow]

I'm posting this to see if anyone /knows/ the answer, or has a
reasonable suspicion. I do not want to initiate an interminable chain of
speculation.

I own a 36" flat-face 400-series Sony WEGA IDTV and, yes, I have the
service manual. The set has gotten heavy use over the past decade; I
often leave it on when I go to bed. It wasn't cheap, and I'd like to get
at least another five years out of it. For a non-HD CRT set, it has an
excellent picture, especially with RGB signals from a DVD player.

When the set's turned on, the HV is apparently shut off, so that the CRT
heater has time to come to full temperature, to avoid stripping the
cathode. (This is speculation.) Though sound comes on almost
immediately, it takes about 10 seconds for the raster to appear.

Recently I've noticed "something new". For about two seconds after the
raster comes on, the black level is too light. You can see the image
"darkening" as the black level drops to its "correct" point. This occurs
only when the set is "cold"; cycling the power doesn't cause this.

I'm hoping someone will say "I've seen this. It's the ___________."
Troubleshooting this set won't be easy (if only because it's close to
the wall on a near-immovable stand). I don't want to tear into it until
I'm reasonably certain I can fix it on the first try.

Thanks in advance.

Wait until it is a problem that doesn't go away after 2 seconds.

 

[William Sommerwerck]

Wait until it's a problem that doesn't go away after 2 seconds.

In other words, wait until an "intermittent" becomes permanent.

Definitely common sense -- but I'd rather make an end run around the
problem.

 

[Meat Plow]

In other words, wait until an "intermittent" becomes permanent.

Definitely common sense -- but I'd rather make an end run around the
problem.

Good luck.

 

[Chuck]

I'm posting this to see if anyone /knows/ the answer, or has a reasonable
suspicion. I do not want to initiate an interminable chain of speculation.

I own a 36" flat-face 400-series Sony WEGA IDTV and, yes, I have the service
manual. The set has gotten heavy use over the past decade; I often leave it
on when I go to bed. It wasn't cheap, and I'd like to get at least another
five years out of it. For a non-HD CRT set, it has an excellent picture,
especially with RGB signals from a DVD player.

When the set's turned on, the HV is apparently shut off, so that the CRT
heater has time to come to full temperature, to avoid stripping the cathode.
(This is speculation.) Though sound comes on almost immediately, it takes
about 10 seconds for the raster to appear.

Recently I've noticed "something new". For about two seconds after the
raster comes on, the black level is too light. You can see the image
"darkening" as the black level drops to its "correct" point. This occurs
only when the set is "cold"; cycling the power doesn't cause this.

I'm hoping someone will say "I've seen this. It's the ___________."
Troubleshooting this set won't be easy (if only because it's close to the
wall on a near-immovable stand). I don't want to tear into it until I'm
reasonably certain I can fix it on the first try.

Thanks in advance.

William, the condition is usually caused by the crt cathode emission
becoming weaker. When the picture no longer comes on, adjusting the
screen control higher will allow the set to work for a few months to a
year more. Chuck

 

[William Sommerwerck]

The condition is usually caused by the CRT's cathode

emission becoming weaker. When the picture no longer
comes on, adjusting the screen control higher will allow
the set to work for a few months to a year more.

I kinda expected that. If you're correct, it looks like I won't get my
money's worth out of the set.

I wonder if anyone still makes CRT heater boosters. <grin> Remember those?

 

[William Sommerwerck]

If they use DC on the filament, check for a bad electrolyytic

in its power supply. I used to add a filament transformer to
series string TV sets with a dropping diode to power an 84
volt string of filaments. They barely lasted a year from new,
without the modification.

Well, this set's over 10 years old. I'll pull out the service manual and
give it a look.

 

[Chuck]

I kinda expected that. If you're correct, it looks like I won't get my
money's worth out of the set.

I wonder if anyone still makes CRT heater boosters. <grin> Remember those?

CRT brighteners are still available but I wouldn't go that route
until the screen control adjustment is no longer effective.

 

[William Sommerwerck]

The industrial Sonys do a very similar thing as the CRT

warms up. In those you're waiting for the beam current
feedback to get up to speed. Since you have the service
manual, is there anything in there about setting G2 by
monitoring a specific set of lines in the vertical interval?

I don't know; I haven't looked yet.

Is there any way to do that without reducing vertical scan?

 

[Meat Plow]

CRT brighteners are still available but I wouldn't go that route
until the screen control adjustment is no longer effective.

Once you need a filament booster it's time to get the good old Sencore
CR70 'Beam Builder' out of storage.

Or maybe just a bottle of Jim Beam?