Sony GDM F520 CRT Monitor

[Scrim]

I finally took the cover off my F520 monitor to see if I can fix its
intermittent blurred picture fault, but, of course, now it won't do it!
Meanwhile, I've noticed something strange and would appreciate some advice:

Included amongst the components on the small PCB mounted on the end of the
CRT are (what look exactly like) four wire ended neon lamps. I don't have
much CRT experience, but still, was surprised to see these. The service
manual refers to them as SG001 to SG301. For example, "SG001 1-519-422-11
SPARK GAP". Anyway, I haven't seen any light up, but they all have very dark
glass envelopes from internal electrode evaporation.
Can anyone:
Tell me what these Neon Bulbs are for?
If there condition indicates a fault (possibly related to the intermittent
blur fault)?
If I can/should replace them with regular neon bulbs?

Thanks,

Scrim

 

[[email protected]]

I finally took the cover off my F520 monitor to see if I can fix its
intermittent blurred picture fault, but, of course, now it won't do it!
Meanwhile, I've noticed something strange and would appreciate some advice:

Included amongst the components on the small PCB mounted on the end of the
CRT are (what look exactly like) four wire ended neon lamps. I don't have
much CRT experience, but still, was surprised to see these. The service
manual refers to them as SG001 to SG301. For example, "SG001 1-519-422-11
SPARK GAP". Anyway, I haven't seen any light up, but they all have very dark
glass envelopes from internal electrode evaporation.
Can anyone:
Tell me what these Neon Bulbs are for?
If there condition indicates a fault (possibly related to the intermittent
blur fault)?
If I can/should replace them with regular neon bulbs?

Thanks,

Scrim

The neons are the backup system. If the main CRT fails, these will
display enough basic characters to enable you to sort it out. Conceived
in the days of DOS, theyre less well suited to modern graphic displays,
but you can reboot into dos and sort your computer from there.

Intermittent blurring is nearly always due to focus voltage variation,
which is nearly always due to arcing somewhere in the focus voltage
line.


NT

 

[Homer J Simpson]

Included amongst the components on the small PCB mounted on the end of the
CRT are (what look exactly like) four wire ended neon lamps. I don't have
much CRT experience, but still, was surprised to see these. The service
manual refers to them as SG001 to SG301. For example, "SG001 1-519-422-11
SPARK GAP". Anyway, I haven't seen any light up, but they all have very
dark glass envelopes from internal electrode evaporation.
Can anyone:
Tell me what these Neon Bulbs are for?

They are spark gaps.

 

[[email protected]]

They are spark gaps.

Seems a bit strange they all have darkened glass.


NT

 

[Scrim]

Seems a bit strange they all have darkened glass.


NT

Thanks for your thoughts folks.
The service manual is here:
http://www.eserviceinfo.com/downloadsm/17886/Sony_GDM-F520.html

You can see the 'neons' or Spark Gaps at the top right of the diagram on
page 30, located around the CRT base.

Before I took the case off, when I had the intermittent blur problem with
this monitor, occasionally I'd hear an electrical discharge (crack!) and the
focus would recover or at least change.
Googling I've found this, which was posted at this newsgroup earlier this
year:
http://groups.google.com/group/sci....ed+glass+bulb."&rnum=1&hl=en#225f9ba99b385945

This certainly sounds similar to what I'm describing, although another model
is involved.

Any further advice gratefully received,

Scrim

 

[Andy Cuffe]

Seems a bit strange they all have darkened glass.


NT

Those have darkened glass even when they are new.

I've seen a LOT of flat CRT Sony monitors with bad CRTs that cause
arcing and loss, or change of focus.
Andy Cuffe

[email protected]

 

[Scrim]

Those have darkened glass even when they are new.

I've seen a LOT of flat CRT Sony monitors with bad CRTs that cause
arcing and loss, or change of focus.
Andy Cuffe

[email protected]

Hi Andy,
Thanks a lot for the info about the 'Neon' spark gaps having a dark coating
from new. I wouldn't have considered that possibility.
The intermittent blur seems to have stopped for now, but I always got the
impression it was worse in cold weather. My hope was that if it turned out
to be the tube I might help it with a bit of carefully placed thermal
insulation.

Scrim

 

[[email protected]]

Hi Andy,
Thanks a lot for the info about the 'Neon' spark gaps having a dark coating
from new. I wouldn't have considered that possibility.
The intermittent blur seems to have stopped for now, but I always got the
impression it was worse in cold weather. My hope was that if it turned out
to be the tube I might help it with a bit of carefully placed thermal
insulation.

Scrim

not a chance. If the tube's arcing you might be able to clear the short
- you might even fix it with just flicking the neck if youre lucky.
Just dont break it or all hell will break loose.


NT

 

[[email protected]]

To keep the strike voltage up?

NT

 

[Homer J Simpson]

To keep the strike voltage up?

Could be. And maybe to avoid scaring the purchasers.

 

[[email protected]]

Could be. And maybe to avoid scaring the purchasers.

good point. I guess thats why they dont use mercury fill then

NT

 

[Andy Cuffe]

Hi Andy,
Thanks a lot for the info about the 'Neon' spark gaps having a dark coating
from new. I wouldn't have considered that possibility.
The intermittent blur seems to have stopped for now, but I always got the
impression it was worse in cold weather. My hope was that if it turned out
to be the tube I might help it with a bit of carefully placed thermal
insulation.

Scrim

I used a 21" Sony for quite a while with a CRT that was acting like
yours. It was ok most of the time, but would occasionally act up for
between a few seconds and a few minutes. Eventually it settled down
to the point where it would only act up every few weeks. After about
a year I found a broken non-Sony monitor with the same Sony CRT and
did a swap. It never acted up again.
Andy Cuffe

[email protected]

 

[James Sweet]

Thanks for your thoughts folks.
The service manual is here:
http://www.eserviceinfo.com/downloadsm/17886/Sony_GDM-F520.html

You can see the 'neons' or Spark Gaps at the top right of the diagram on
page 30, located around the CRT base.

Before I took the case off, when I had the intermittent blur problem with
this monitor, occasionally I'd hear an electrical discharge (crack!) and the
focus would recover or at least change.
Googling I've found this, which was posted at this newsgroup earlier this
year:
http://groups.google.com/group/sci....ed+glass+bulb."&rnum=1&hl=en#225f9ba99b385945

This certainly sounds similar to what I'm describing, although another model
is involved.

Any further advice gratefully received,

Scrim

My G520 loses focus occasionally too and a power cycle fixes it. I got
rid of a similar model last year that would do the same thing, been
doing it for years and hasn't gotten any more frequent. Someone told me
it was a fault within the CRTs.

 

[James Sweet]

To keep the strike voltage up?

It's part of the processing when they make it. Neon lamps are driven
hard for a time to cook impurities out of the electrodes, the spark gaps
are probably cooked a bit harder to get a uniform striking voltage.

 

[Scrim]

My G520 loses focus occasionally too and a power cycle fixes it. I got rid
of a similar model last year that would do the same thing, been doing it
for years and hasn't gotten any more frequent. Someone told me it was a
fault within the CRTs.

Thanks for the help so far.
The intermittent fault has finally shown up again, perhaps because of the
colder weather last night.

First it blurred: I started prodding around in the back with a long glass
rod. I tried tapping the tube, tube end pcb, focus leads and the focus
adjust side of flyback transformer unit, to no avail.
The blurred focus cleared itself after a while, but later there were a
series of pops from the back accompanied by momentary collapses of the
screens image. I have no idea where the pops came from. If I knew this was
an insoluble tube problem I'd just give up, but, at best, this is such a
good monitor I'm still holding out for the chance it's reparable.
Any ideas how I could pin down the problem or eliminate any suspects?
Thanks

Scrim

 

[Mike]

To keep the strike voltage up?

The strike voltage changes if light gets to them?

I wonder if that explains why a neon (integral resistor) fitted in a piece
of equipment here flickers intermittently when it's in the dark, but
lights reliably when illumination falls on it.

This is not a wind-up!

At first it seemed that it only flickered when the fluorescent light in
the room was turned off, which led to thoughts of some bizarre wiring
related error ... but then it turned out that it also responded to
torchlight ... so light was the common factor.

Never seen it before on any other neons, so it might be just a marginal
one!

 

[Andy Cuffe]

First it blurred: I started prodding around in the back with a long glass
rod. I tried tapping the tube, tube end pcb, focus leads and the focus
adjust side of flyback transformer unit, to no avail.
The blurred focus cleared itself after a while, but later there were a
series of pops from the back accompanied by momentary collapses of the
screens image. I have no idea where the pops came from. If I knew this was
an insoluble tube problem I'd just give up, but, at best, this is such a
good monitor I'm still holding out for the chance it's reparable.
Any ideas how I could pin down the problem or eliminate any suspects?
Thanks

Scrim

The only real other possibility is the flyback. Unfortunately, that's
a pretty expensive part to replace on a long shot. It's also worth
checking for signs of arcing in the CRT socket.

Andy Cuffe

[email protected]

 

[Scrim]

The only real other possibility is the flyback. Unfortunately, that's
a pretty expensive part to replace on a long shot. It's also worth
checking for signs of arcing in the CRT socket.

Andy Cuffe

[email protected]

OK, Thanks Andy and everyone else for the help,

Scrim