How fix lines on CRT from signal lead ?

[Jon D]

My 17 inch CRT sometimes gets ...

light-colored horizontal lines
a couple of inches above the bottom of the screen
usually just one or two of these
the picture size too *sometimes* seems to get a tiny bit smaller
when these lines are present.

I have tracked this down to the signal lead going from PC to monitor.

This d*mn lead seems quite sensitive because slight kinks and bends
in the lead can create this effect. So can gently moving the plug as
it goes into the video card. Why can't they design a better lead
than this? It is already the most inflexible lead on my whole
system!

MY QUESTION IS ... is this lead usually as sensitive as this or is it
related to the design of my particular monitor and PC interface.

Can I do anything to improve the situation? I have lowered the
screen refresh rate a bit but that doesn't seem to have help.

Is there a "magic bullet" like something to clip onto the leqad or
some screening.

Changing the lead means some tricky messing around inside the monitor
to terminate the leads it in the screened cage sitting on the cathode
parts of the CRT itself.

Any ideas?

Jon


[Please don't say buy a secondhand 17inch monitor for next to nothing
because cleaning it and dusting out its internals to sharpen up the
image and all that stuff takes time, and so does fetching a checking
over monitors which turn out to be crap.]

 

[Rod Speed]

My 17 inch CRT sometimes gets ...

light-colored horizontal lines
a couple of inches above the bottom of the screen
usually just one or two of these
the picture size too *sometimes* seems to get a tiny bit smaller
when these lines are present.

I have tracked this down to the signal lead going from PC to monitor.

They can fail.

This d*mn lead seems quite sensitive because slight
kinks and bends in the lead can create this effect.

You only get that if its got a break in the wire or at the connector.

So can gently moving the plug as it goes into the video card.

Likely thats where the problem is.

Why can't they design a better lead than this?

They can, you dont see that with most CRTs.

It is already the most inflexible lead on my whole system!

Because its got the most wires in it.

MY QUESTION IS ... is this lead usually as sensitive as this

Nope, most CRTs dont behave like that.

or is it related to the design of my particular monitor and PC interface.

Not the design, the actual implementation of the cable/connector.

Can I do anything to improve the situation?

Yes, replace the cable and connector if you dont get that
effect with a different CRT. If you do, its the video card.

I have lowered the screen refresh rate
a bit but that doesn't seem to have help.

Yeah, wont make any difference.

Is there a "magic bullet" like something to
clip onto the leqad or some screening.

The problem is a physical break in the cable/connector.

Changing the lead means some tricky messing around
inside the monitor to terminate the leads it in the screened
cage sitting on the cathode parts of the CRT itself.

Yeah, tho you can find that the break is actually in
the connector itself, or even just a broken pin there.

Any ideas?

Replace it with a 19" CRT.

[Please don't say buy a secondhand 17inch monitor for next
to nothing because cleaning it and dusting out its internals to
sharpen up the image and all that stuff takes time, and so does
fetching a checking over monitors which turn out to be crap.]

Then buy a new one.

 

[Michael Kennedy]

[Please don't say buy a secondhand 17inch monitor for next
to nothing because cleaning it and dusting out its internals to
sharpen up the image and all that stuff takes time, and so does
fetching a checking over monitors which turn out to be crap.]

Then buy a new one.

Or don't do anything at all..

 

[johns]

You probably have corroded solder connections
where that pc board hooks to the input cable.
Very common in old crts. Sounds like you also
have a flyback going bad. Time for new monitor.

johns

 

[lsmartino]

johns ha escrito:

You probably have corroded solder connections
where that pc board hooks to the input cable.
Very common in old crts. Sounds like you also
have a flyback going bad. Time for new monitor.

johns

Please explain how a bad flyback can cause the fault described by the
original poster.

 

[johns]

Please explain how a bad flyback can cause the fault described by the
original poster.

Picture size .. blooming .. is caused by high
voltage changing. Generally when the solder
joints start going, it occurs across all the power
handling connections, and at the flyback. Also,
the electrolytics tend to crap out and lose their
capacitance .. even to dead shorts. I've been
into lots of crts where all I did was touch up
solder connections and replace electrolytics
.... and the thing ran fine. Of course that did not
fix the gassy crt which starts the picture to
blur. TRUTH: I've had people come in and say
"just make it work. I'll pay the cost. I like my
crt". So, I clean it ... resolder a bunch of
points .. replace horizontal output transistor
.... replace flyback ... run tube through phosphor
restore and degauss ... set flyback focus ..
dark level ... remove and test all the big
electrolytics, and replace a bunch of them
.... replace the the transistor amps and current
limit resistors on the crt board ... put it back
together and clean the case and screen to
nearly new ... and charge the lady 3 hours
labor at $65 per hour plus parts .. and hope
to heaven that the 90 day warranty holds

johns

 

[meow2222]

My 17 inch CRT sometimes gets ...

light-colored horizontal lines
a couple of inches above the bottom of the screen
usually just one or two of these
the picture size too *sometimes* seems to get a tiny bit smaller
when these lines are present.

I have tracked this down to the signal lead going from PC to monitor.

This d*mn lead seems quite sensitive because slight kinks and bends
in the lead can create this effect. So can gently moving the plug as
it goes into the video card. Why can't they design a better lead
than this? It is already the most inflexible lead on my whole
system!

MY QUESTION IS ... is this lead usually as sensitive as this or is it
related to the design of my particular monitor and PC interface.

Can I do anything to improve the situation? I have lowered the
screen refresh rate a bit but that doesn't seem to have help.

Is there a "magic bullet" like something to clip onto the leqad or
some screening.

Changing the lead means some tricky messing around inside the monitor
to terminate the leads it in the screened cage sitting on the cathode
parts of the CRT itself.

Any ideas?

Jon

Sounds like a flyback problem, but it might just be a poor connection
on the sync pulse line. Prodding should lead you to see where its most
sensitive, and thus where the probelm is. Typically its cable ends or
connectors.

The good news is this fault is likely non-fatal. Having retrace lines
scattered over the screen doesnt exactly make it look better, but it
means you can wait to see if it goes bad, and if it does find a monitor
then.


NT

 

[Rod Speed]

Picture size .. blooming .. is caused by high voltage changing.

Yes, but you havent established that the real reason
for the picture size changing is because the monitor
is getting confused by the obvious glitches on the
cable into changing the screen mode etc.

Generally when the solder joints start going,
it occurs across all the power handling connections,

Oh bullshit. You only get bad joints where large components are
soldered onto the pcb and they start to fail due to thermal cycling.

and at the flyback.

Utterly mangled all over again. Flybacks fail quite differently.

Also, the electrolytics tend to crap out and
lose their capacitance .. even to dead shorts.

No evidence of that in the symptoms the OP mentioned.

I've been into lots of crts where all I did was
touch up solder connections and replace
electrolytics ... and the thing ran fine.

Sure, but that doesnt appear to be the OP's problem
given that its so sensitive to the video cable.

Of course that did not fix the gassy
crt which starts the picture to blur.

TRUTH: I've had people come in and say
"just make it work. I'll pay the cost. I like my
crt". So, I clean it ... resolder a bunch of
points .. replace horizontal output transistor
... replace flyback ... run tube through phosphor
restore and degauss ... set flyback focus ..
dark level ... remove and test all the big
electrolytics, and replace a bunch of them
... replace the the transistor amps and current
limit resistors on the crt board ... put it back
together and clean the case and screen to
nearly new ... and charge the lady 3 hours
labor at $65 per hour plus parts .. and hope
to heaven that the 90 day warranty holds

Irrelevant to what the OP's symptoms indicate.

 

[Rod Speed]

Sounds like a flyback problem,

Nope, doesnt explain the sensitivity to the video cable.

 

[lsmartino]

Rod Speed ha escrito:

Nope, doesnt explain the sensitivity to the video cable.

That´s exactly what I thought. A bad flyback will not worsen or
improve by "wiggling" the VGA cable of the monitor. In other words, if
the fault dissapears by wiggling the VGA cable, that rules out the
flyback and other components of the monitor.

 

[lsmartino]

johns ha escrito:

Picture size .. blooming .. is caused by high
voltage changing.

True, but high voltage changes can be caused by a number of other
things, not just the flyback.

Generally when the solder
joints start going, it occurs across all the power
handling connections, and at the flyback.

OK, but that can be solved by simply resoldering the faulty joints. No
need to blame the flyback on that, or to replace it blindly.

Also,
the electrolytics tend to crap out and lose their
capacitance .. even to dead shorts.

Bad electrolytics in the PSU can be the origin of the high voltage
changes.

I've been
into lots of crts where all I did was touch up
solder connections and replace electrolytics
... and the thing ran fine. Of course that did not
fix the gassy crt which starts the picture to
blur. TRUTH: I've had people come in and say
"just make it work. I'll pay the cost. I like my
crt". So, I clean it ... resolder a bunch of
points .. replace horizontal output transistor
... replace flyback ... run tube through phosphor
restore and degauss ... set flyback focus ..
dark level ... remove and test all the big
electrolytics, and replace a bunch of them
... replace the the transistor amps and current
limit resistors on the crt board ...

I don´t understand why do you replace the CRT drivers and the HOT if
they are OK. I can understand that part about replacing aged
electrolytics, redoing any stressed solder joints and restoring the
CRT... but why to replace transistors if they are ok?

 

[larry moe 'n curly]

My 17 inch CRT sometimes gets ...
light-colored horizontal lines
a couple of inches above the bottom of the screen
usually just one or two of these
the picture size too *sometimes* seems to get a tiny bit smaller
when these lines are present.

I have tracked this down to the signal lead going from PC to monitor.

This d*mn lead seems quite sensitive because slight kinks and bends
in the lead can create this effect.

I've never seen light-colored lines like that caused by a bad monitor
cable, which usually causes the color to be funny all over the screen
or change abruptly.

Please don't say buy a secondhand 17inch monitor for next to nothing

Buy? They're free.

because cleaning it and dusting out its internals to sharpen up the
image and all that stuff takes time,

How long can cleaning take? Almost every one I've found was very
clean.

How does cleaning the inside make the image sharper? There are 1-2
focus adjustments inside, but it takes just seconds to adjust each one.

 

[CBFalconer]

Rod Speed ha escrito:


That´s exactly what I thought. A bad flyback will not worsen or
improve by "wiggling" the VGA cable of the monitor. In other words,
if the fault dissapears by wiggling the VGA cable, that rules out
the flyback and other components of the monitor.

Wiggling the flyback can disturb the horizontal sync, which in turn
disturbs the HV, which in turn affects the picture size.

 

[mike.j.harvey]

because cleaning it and dusting out its internals to sharpen up the

image and all that stuff takes time,

The admission by the OP of being a troll, in plain sight, and nobody
noticed!

 

[Rod Speed]

The admission by the OP of being a troll, in plain sight, and nobody noticed!

Nothing to notice except you jumping at bogeymen.

 

[meow2222]

Nope, doesnt explain the sensitivity to the video cable.

sorry, I though it was obvious. Wiggling a thick fat cable will wiggle
the main pcb slightly, which may disturb any poor connection anywhere
on the board.


NT

 

[Rod Speed]

(e-mail address removed) wrote

Rod Speed wrote

sorry, I though it was obvious.

Never ever could bullshit its way out of a wet paper bag.

Wiggling a thick fat cable will wiggle the main pcb slightly,

Not if you only fiddle with the video card end it doesnt.

which may disturb any poor connection anywhere on the board.

Pity the FBT isnt even on that board.

 

[johns]

I don´t understand why do you replace the CRT drivers and the HOT if
they are OK. I can understand that part about replacing aged
electrolytics, redoing any stressed solder joints and restoring the
CRT... but why to replace transistors if they are ok?

Because you are in there. It takes bench time $$$$ just to
open the thing, and so you don't take chances on the HOT,
flyback, power electrolytics, CRT board adjustments .. esp
the driver transistors and current limit resistors. All of those
points "heat cycle" badly, and the solder joints crack. That
causes any movement of the video cable to wiggle those
bad joints and glitch the picture in a million ways. A bench
tech can't spend time diagnosing that stuff. I just shotgun
all the potentially weak areas and run a bench test for about
an hour to watch the video cycle. If it works ... start praying
for 90 days. Otherwise .. MAD BOSS ... mad mad Boss !
Something else .. all those parts run about $30 total on the
bill. Stupid not to replace them. More stupid is to repair the
thing at all, but that is not my option, and some customers
simply believe in maintaining their hardware.

johns

 

[johns]

Wiggling the cable wiggles the entire monitor.
What drives me crazy is to pick up the monitor
and carry it back to the test bench, and have it
run perfectly

johns

 

[lsmartino]

johns ha escrito:

Because you are in there. It takes bench time $$$$ just to
open the thing, and so you don't take chances on the HOT,
flyback, power electrolytics, CRT board adjustments .. esp
the driver transistors and current limit resistors. All of those
points "heat cycle" badly, and the solder joints crack.

Just resoldering the transistors will suffice. No need to replace them
blindly.

That
causes any movement of the video cable to wiggle those
bad joints and glitch the picture in a million ways. A bench
tech can't spend time diagnosing that stuff. I just shotgun
all the potentially weak areas and run a bench test for about
an hour to watch the video cycle. If it works ... start praying
for 90 days. Otherwise .. MAD BOSS ... mad mad Boss !
Something else .. all those parts run about $30 total on the
bill. Stupid not to replace them. More stupid is to repair the
thing at all, but that is not my option, and some customers
simply believe in maintaining their hardware.

I agree, trying to repair a computer monitor from 1994 is a waste of
money.