Maker Pro
Maker Pro

Repairing monitors

R

rpcarnell

Jan 1, 1970
0
Hello,

I am an electrical engineer, and I know exactly how computer monitors
work, and I know how televisions work as well.

Thing is I have never repaired a television or computer monitor while
having it on and plugged. I just can't risk it. I never learned how
to do it.

Any book that covers the safety issues regarding this kind of
technology?
 
rpcarnell said:
I am an electrical engineer, and I know exactly how computer monitors
work, and I know how televisions work as well.
Thing is I have never repaired a television or computer monitor while
having it on and plugged. I just can't risk it. I never learned how
to do it.
Any book that covers the safety issues regarding this kind of
technology?

Are we talking CRT, Plasma, LCD, .. ?

As for CRT:
Keep the left hand in your pocket such that hazardous voltage may not pass
through your heart. Beware of things that may explode and threaten eyevision.
Common sense goes a far way however..
You could use some kind of insulating gloves to prevent some hazards.
There is also lot of toxic chemicals inside in the form of flame retardants.
 
L

Luhan

Jan 1, 1970
0
As for CRT:
Keep the left hand in your pocket such that hazardous voltage may not pass
through your heart. Beware of things that may explode and threaten eyevision.
Common sense goes a far way however..
You could use some kind of insulating gloves to prevent some hazards.
There is also lot of toxic chemicals inside in the form of flame retardants.

Good advice. Also, I like to run a GFI on my bench outlet that powers
whatever I am working on - could be a lifesaver.

Luhan Monat (luhanxmonat-at-yahoo^dot^com)
http://members.cox.net/berniekm/
"Reality: what a concept!"
 
R

Rich Grise

Jan 1, 1970
0
Hello,

I am an electrical engineer, and I know exactly how computer monitors
work, and I know how televisions work as well.

Thing is I have never repaired a television or computer monitor while
having it on and plugged. I just can't risk it. I never learned how
to do it.

Any book that covers the safety issues regarding this kind of
technology?

Get a heavy clip lead, and ground one end to the main chassis, which
should be in common with the outside coating of the CRT. Clip it to
a small screwdriver, and poke the screwdriver under the HV cap, until
you feel it in physical contact with the HV contact, then leave it there.

There's also 200-300V "B+", used for deflection amps and focus and so on,
use the usual precautions around them.

The safest thing to do, of course, is to have somebody else fix them. ;-)

Good Luck!
Rich
 
S

scada

Jan 1, 1970
0
rpcarnell said:
Hello,

I am an electrical engineer, and I know exactly how computer monitors
work, and I know how televisions work as well.

Thing is I have never repaired a television or computer monitor while
having it on and plugged. I just can't risk it. I never learned how
to do it.

Any book that covers the safety issues regarding this kind of
technology?

With the set off!
Use a clip lead connected to a flat blade screwdriver on one end, connect
the other end to the "Daq". The Daq is a wire surounding the area of the CRT
usualy suspended by springs. Push the blade of the screwdriver under the
Anode cap (high voltage to CRT) you should hear a snap indicating the HV is
discharged. Do this even if the set has been off for hours, days, months,
etc... The CRT has a large capacitance that stores leathal high voltage! and
yes it will recharge itself!

Testing with set on:
Use an isolation transformer to power the unit. This will protect you the
unit, & test equipment! Be aware of high voltages at the power supply and
the flyback (HV) transformer and surrounded area. Tread safely - good
luck...
 
L

Luhan

Jan 1, 1970
0
scada said:
Use a clip lead connected to a flat blade screwdriver on one end, connect
the other end to the "Daq". The Daq is a wire surounding the area of the CRT
usualy suspended by springs. Push the blade of the screwdriver under the
Anode cap (high voltage to CRT) you should hear a snap indicating the HV is
discharged. Do this even if the set has been off for hours, days, months,
etc...

I needed to move a picture tube that had been sitting (by itself) in
our basement for over a year. Just for yacks, I did the
clip-lead-to-the-pins clipped to a screwdriver. It drew a half inch
arc off the anode connection!!!

Luhan Monat (luhanxmonat-at-yahoo^dot^com)
http://members.cox.net/berniekm/
"Reality: what a concept!"
 
R

rpcarnell

Jan 1, 1970
0
What about putting a piece of plywood on the floor and standing on it?
Someone recommended that.

And what kind of gloves should I wear? Cotton maybe?
 
P

Phil Allison

Jan 1, 1970
0
"rpcarnell"
What about putting a piece of plywood on the floor and standing on it?
Someone recommended that.


** Completely asinine advice.

Chassis parts of a TV set or monitor are at earth potential while other
parts are at lethal voltages.

Put one hand on each - get a massive shock right through the heart.

And what kind of gloves should I wear? Cotton maybe?


** Even more asinine.

Provides no reliable shock protection and PREVENTS you from handling small
parts successfully.

A clueless Googlegroper and blatant LIAR like you needs to keep right away
from TVs and monitors .



........ Phil
 
N

Nico Coesel

Jan 1, 1970
0
scada said:
With the set off!
Use a clip lead connected to a flat blade screwdriver on one end, connect
the other end to the "Daq". The Daq is a wire surounding the area of the CRT
usualy suspended by springs. Push the blade of the screwdriver under the
Anode cap (high voltage to CRT) you should hear a snap indicating the HV is
discharged. Do this even if the set has been off for hours, days, months,
etc... The CRT has a large capacitance that stores leathal high voltage! and
yes it will recharge itself!

My advice: Don't discharge the CRT unless you have to remove the
high-voltage section. Just leave the cap in place. It provides enough
protection. Discharging the CRT just adds extra unnecessary risc to
the job.
 
D

Don Lancaster

Jan 1, 1970
0
Phil said:
Chassis parts of a TV set or monitor are at earth potential while other
parts are at lethal voltages.

Not even wrong.

Many early tv sets and some earlier monitors were hot chassis designs.

As of course, were the overwhelming majority of lower cost am radios.

They simply hoped the cheater cord interlock and the knobs stayed in
place. There were very few complaints from the fatalities themselves.


--
Many thanks,

Don Lancaster voice phone: (928)428-4073
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
rss: http://www.tinaja.com/whtnu.xml email: [email protected]

Please visit my GURU's LAIR web site at http://www.tinaja.com
 
P

Phil Allison

Jan 1, 1970
0
"Don Lancaster"
Not even wrong.


** True for the vast majority of TV and monitors in service.

Note, my comment above is written in the present tense.

Many early tv sets and some earlier monitors were hot chassis designs.


** Still a few hot chassis TV colour sets about - mainly in the smaller tube
sizes. They can be VERY hard to spot sometimes, particularly if of "double
insulated" construction ( ie with no supply earth wire).

A 12 inch, GE brand set I own, made by Thomson in Thailand, is just such a
beast.

There are NO printed warnings and the metal antenna plug goes directly into
the tuner module - so it must be an earthed chassis set - right ??

Wrong !!

Close examination of the co-axial antenna socket reveals small, white
plastic ring around the middle and an ohm meter test shows no continuity
from the outer part to the tuner module box.

Arrrrghhhh !!

The antenna socket contains a hidden isolation balun -

the WHOLE DAMN SET was live at 240 volts !!


As of course, were the overwhelming majority of lower cost am radios.


** That means tube sets, all well over 40 years old.





........ Phil
 
Top