Monitor discharge

[Halfgaar]

Hi list,

I'll be getting a monitor for repair today. The problem is a faulty signal
cable, or cable connection inside the monitor. I'll have to see if it's
fixable, that's not my question. My question is, do I have to discharge the
caps and tube for this? I don't like to get fried...

TIA

 

[Jerry G.]

It sounds like you are not a monitor repair technician. The answer is
depending on where you have to work in the monitor, and what you are doing
in the monitor. If you are not in the high voltage section, scan
amplifiers, CRT drive area, or main power supply, it should be safe.
Discharging caps is not always necessary, and can introduce other risks and
problems in itself. Proper handling, and procedures of doing the repairs
are what is important. We normally hardly ever discharge caps when working
on monitors.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


Hi list,

I'll be getting a monitor for repair today. The problem is a faulty signal
cable, or cable connection inside the monitor. I'll have to see if it's
fixable, that's not my question. My question is, do I have to discharge the
caps and tube for this? I don't like to get fried...

TIA

 

[Halfgaar]

It sounds like you are not a monitor repair technician. The answer is
depending on where you have to work in the monitor, and what you are doing
in the monitor. If you are not in the high voltage section, scan
amplifiers, CRT drive area, or main power supply, it should be safe.
Discharging caps is not always necessary, and can introduce other risks
and
problems in itself. Proper handling, and procedures of doing the repairs
are what is important. We normally hardly ever discharge caps when working
on monitors.

I am indeed not a monitor repair technician.

So when I for example only want to remove metal-oxide from the cable
connector at the inside of the monitor, it should be safe?

BTW, the problem is a picture that turns purple/green/whatever when you
wiggle the cable. So, I would guess this has nothing to do with high
voltage parts.

 

[red]

To be safe you may want to discharge. But sounds like you just need to
attach or repair the cable, which should be away from all the high voltage.

Dont die

 

[Jerry Greenberg]

It sounds like the cable end has to be redone over, or there is a bad
connection. You should not have any high voltage exposure where you
are working.

Jerry Greenberg
http://www.zoom-one.com

--

 

[Halfgaar]

It sounds like the cable end has to be redone over, or there is a bad
connection. You should not have any high voltage exposure where you
are working.

And are the high voltage parts in the open, can I touch them accidently?

 

[James Sweet]

And are the high voltage parts in the open, can I touch them accidently?

Not easily, just use common sense, and if you're still nervous and wanna be
extra careful, let the monitor sit for 24 hours so everything discharges.

 

[Jerry Greenberg]

This all depends on the layout design of the monitor, and how you are
going to work on it.

I never had a problem with this in servicing monitors. I hardly ever
had to discharge the power suppy caps.

If you start discharging circuits, this adds to the risk of doing some
types of damage.

To discharge caps, this should be done with a resistor at a safe
wattage rating and proper amount of omage. You want to have a
reasoble rate of discharge, but not overload the cap. Using a
screwdriver, or direct short accross caps is not good for them.

If you discharge caps, and slip with the lead or whatever, to some
other trace on the board, you can cause some damage to other
components.

The best way to work is to work around this.

--

I do not want to be abrubt or rude.

The bottom line is, if you are not used to this type of work, or have
formal training for it, then you should contract it out to someone who
is.


Jerry Greenberg

 

[Halfgaar]

Not easily, just use common sense, and if you're still nervous and wanna
be extra careful, let the monitor sit for 24 hours so everything
discharges.

Some say it takes days for the charge to dissapate, is 24 hours enough?

 

[Halfgaar]

I do not want to be abrubt or rude.

The bottom line is, if you are not used to this type of work, or have
formal training for it, then you should contract it out to someone who
is.

If it were a more than simple matter, I would. But a faulty cable.... I
think I can do that myself.

 

[James Sweet]

Some say it takes days for the charge to dissapate, is 24 hours enough?

--

I've repaired a lot of monitors, old B&W ones often lack a focus divider and
can store a charge on the tube for quite some time, but most will discharge
within minutes. There's no voodoo involved, just don't touch exposed
connections if you don't know what they are and you'll be fine.

 

[John Robertson]

www.flippers.com/vid-tips.html#discharge

John :-#)#

Some say it takes days for the charge to dissapate, is 24 hours enough?

(Please post followups or tech enquires to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

 

[Halfgaar]

I've repaired a lot of monitors, old B&W ones often lack a focus divider
and can store a charge on the tube for quite some time, but most will
discharge within minutes. There's no voodoo involved, just don't touch
exposed connections if you don't know what they are and you'll be fine.

Looking at the pictures John linked in his reply, it seems that the tube
casing itself can deliver a shock when touched, or am I missing something
here:

http://www.flippers.com/images/jan21_05.jpg

They're touching the tube with a screwdriver to connect is to something else
(through a 1 meg resistor). Does that mean you can get a shock by touching
the tube?

 

[James Sweet]

Looking at the pictures John linked in his reply, it seems that the tube
casing itself can deliver a shock when touched, or am I missing something
here:

http://www.flippers.com/images/jan21_05.jpg

They're touching the tube with a screwdriver to connect is to something else
(through a 1 meg resistor). Does that mean you can get a shock by touching
the tube?

--

In the picture he's getting ready to poke the screwdriver under the suction
cup looking anode cap, the contact this covers is what you discharge, most
people get all nervous when doing this and expect a big bang, but are
dissapointed when nothing happens or worst case a small static zap sound.

 

[Halfgaar]

In the picture he's getting ready to poke the screwdriver under the
suction cup looking anode cap, the contact this covers is what you
discharge, most people get all nervous when doing this and expect a big
bang, but are dissapointed when nothing happens or worst case a small
static zap sound.

Then it's OK. Thanks for all the info.

 

[Asimov]

"Halfgaar" bravely wrote to "All" (11 Dec 03 19:51:03)
--- on the heady topic of "Re: Monitor discharge"

They should put an NE-2 neon bulb across the resistor to protect it from
the high voltage spike. Otherwise the resistor may eventually open up
and leave the crt undischarged i.e. a latent unknown shock hazard.


Ha> From: Halfgaar <[email protected]>

I've repaired a lot of monitors, old B&W ones often lack a focus divider
and can store a charge on the tube for quite some time, but most will
discharge within minutes. There's no voodoo involved, just don't touch
exposed connections if you don't know what they are and you'll be fine.

Ha> Looking at the pictures John linked in his reply, it seems that the
Ha> tube casing itself can deliver a shock when touched, or am I missing
Ha> something here:

Ha> http://www.flippers.com/images/jan21_05.jpg

Ha> They're touching the tube with a screwdriver to connect is to
Ha> something else (through a 1 meg resistor). Does that mean you can get
Ha> a shock by touching the tube?

Ha> --
Ha> To send me, Halfgaar, email, remove remove from my email address.

.... Dunno if we'll get that past the CSA und UL 'owever.

 

[James Sweet]

"Halfgaar" bravely wrote to "All" (11 Dec 03 19:51:03)
--- on the heady topic of "Re: Monitor discharge"

They should put an NE-2 neon bulb across the resistor to protect it from
the high voltage spike. Otherwise the resistor may eventually open up
and leave the crt undischarged i.e. a latent unknown shock hazard.

I've never used a resistor, 10 years and dozens of monitors later I've never
had a problem. My advice, unless it's an irreplaceable antique, forget the
resistor and discharge it with a straight wire.

 

[Halfgaar]

I've never used a resistor, 10 years and dozens of monitors later I've
never had a problem. My advice, unless it's an irreplaceable antique,
forget the resistor and discharge it with a straight wire.

Why take the risk of having to replace an expensive component? What is the
problem with buying a resistor worth a few cents. Just discharge it with a
resistor, and after you're done, measure the resistor with an Ohm-meter to
be sure it hasn't been destroyed by any high voltage spike.

 

[Sam Goldwasser]

"Halfgaar" bravely wrote to "All" (11 Dec 03 19:51:03)
--- on the heady topic of "Re: Monitor discharge"

They should put an NE-2 neon bulb across the resistor to protect it from
the high voltage spike. Otherwise the resistor may eventually open up
and leave the crt undischarged i.e. a latent unknown shock hazard.

An NE2 drops only about 60 V so you've reduced the 25,000 V to 24,940 V.
In other words, the resistor now does almost nothing at all which defeats
its purpose. What you might want to do is put an NE2 in series with the
resistor so you will see a flash as the HV discharges.

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[Asimov]

"James Sweet" bravely wrote to "All" (13 Dec 03 11:27:53)
--- on the heady topic of "Re: Monitor discharge"

JS> Reply-To: "James Sweet" <[email protected]>
JS> message JS> "Halfgaar" bravely wrote to "All" (11 Dec 03 19:51:03)
JS> --- on the heady topic of "Re: Monitor discharge"

They should put an NE-2 neon bulb across the resistor to protect it from
the high voltage spike. Otherwise the resistor may eventually open up
and leave the crt undischarged i.e. a latent unknown shock hazard.

JS> I've never used a resistor, 10 years and dozens of monitors later I've
JS> never had a problem. My advice, unless it's an irreplaceable antique,
JS> forget the resistor and discharge it with a straight wire.

It is just a precaution in case the ground connection isn't 100% and/or
the current path takes it through a semiconductor junction or two.
But basically electromagnetic pollution is a thing to avoid on
principle. Less snow in the neighbor's tv and static on the radio is
reason enough why we should always buy resistive type spark plugs or
avoid making sparks in general. 10 years is a long time in dog years!


.... Gender is irrelevant. Resistance turns me on.