Hello,

I have an old rear projection television that I would like to take
apart and use the frame for another project. The television has not
been plugged in since the year 2000. Do I still need to discharge
capacitors even though it hasn't seen AC in 4 years? Could anyone
tell me how long it would take on average for the caps to discharge
by themselves?

Thanks in advance.

"Steve" wrote in message
news
Hello,

I have an old rear projection television that I would like to take
apart and use the frame for another project. The television has not
been plugged in since the year 2000. Do I still need to discharge
capacitors even though it hasn't seen AC in 4 years?

YES

Could anyone
tell me how long it would take on average for the caps to discharge
by themselves?

it dosent matter assume they are charged just as you should assume a gun is
loaded when you handel it.


Thanks in advance.


never trust a bleeder resistor... it could be open

On Wed, 25 Aug 2004 12:12:46 +0000, Ross Herbert wrote:

On Wed, 25 Aug 2004 02:05:03 -0400, "Tim Perry"
wrote:

|
|"Steve" wrote in message
|news | Hello,
|
| I have an old rear projection television that I would like to take
| apart and use the frame for another project. The television has not
| been plugged in since the year 2000. Do I still need to discharge
| capacitors even though it hasn't seen AC in 4 years?
|
|YES

And here I was thinking this was a troll......

Tell me, how can any charge storage device (capacitor) or aquadag
coating on a tube retain a charge when not having been powered up for
4 years? Must be some magic new dielectric I haven't heard about, or
the air is awfully dry.

Personally, I wouldn't bother about charged capacitors causing
problems after a week of not having been powered up, but I would still
short the aquadag coating on the tube just to be sure. After 2 weeks I
wouldn't even bother about that.


|
| Could anyone
| tell me how long it would take on average for the caps to discharge
| by themselves?
|
|it dosent matter assume they are charged just as you should assume a gun is
|loaded when you handel it.
|
|
| Thanks in advance.
|
|
|never trust a bleeder resistor... it could be open
|

If you were referring to me as a troll, I really hope I didn't come
across as that way. I was looking for serious advice.

Actually after that period of time you probably will not have any problem
disassembling the set.
Be advised that the tubes are high vacuum devices and can implode if
handled improperly. Use extreme care in disposing and handling of these
particular items. BTW it may be necessary to have them properly disposed of
because or environmental laws in effect there in Canada. You may need to
contact your local DPW department and ask the about correct manner as to
resolving that problem.
I personally just go in with a set of dikes and cut the cables, inclusive
of the HV leads to the crts and have at it when trashing one of these. You
can always have a service company come out and remove the guts from the unit
but they will charge for a service call and labour to do so.
Something to comtemplate over a bottle of Labats Blue, Eh!! Or even an
imported Fosters; Cheers Gov, hopefully you get this resolved.
"Steve" wrote in message
news
On Wed, 25 Aug 2004 12:12:46 +0000, Ross Herbert wrote:

On Wed, 25 Aug 2004 02:05:03 -0400, "Tim Perry"
wrote:

|
|"Steve" wrote in message
|news | Hello,
|
| I have an old rear projection television that I would like to take
| apart and use the frame for another project. The television has not
| been plugged in since the year 2000. Do I still need to discharge
| capacitors even though it hasn't seen AC in 4 years?
|
|YES

And here I was thinking this was a troll......

Tell me, how can any charge storage device (capacitor) or aquadag
coating on a tube retain a charge when not having been powered up for
4 years? Must be some magic new dielectric I haven't heard about, or
the air is awfully dry.

Personally, I wouldn't bother about charged capacitors causing
problems after a week of not having been powered up, but I would still
short the aquadag coating on the tube just to be sure. After 2 weeks I
wouldn't even bother about that.


|
| Could anyone
| tell me how long it would take on average for the caps to discharge
| by themselves?
|
|it dosent matter assume they are charged just as you should assume a
gun is
|loaded when you handel it.
|
|
| Thanks in advance.
|
|
|never trust a bleeder resistor... it could be open
|

If you were referring to me as a troll, I really hope I didn't come
across as that way. I was looking for serious advice.

"Ross Herbert" bravely wrote to "All" (25 Aug 04 12:12:46)
--- on the heady topic of " Television discharge question"

RH From: Ross Herbert

RH On Wed, 25 Aug 2004 02:05:03 -0400, "Tim Perry"
RH wrote:

RH |
RH |"Steve" wrote in message
RH |news | Hello,
|
| I have an old rear projection television that I would like to take
| apart and use the frame for another project. The television has not
| been plugged in since the year 2000. Do I still need to discharge
| capacitors even though it hasn't seen AC in 4 years?
RH |
RH |YES

RH And here I was thinking this was a troll......

RH Tell me, how can any charge storage device (capacitor) or aquadag
RH coating on a tube retain a charge when not having been powered up for
RH 4 years? Must be some magic new dielectric I haven't heard about, or
RH the air is awfully dry.


PURISTS!

The "YES" reply is in practice wrong, maybe even a little ignorant?
Realize, the crt glass has some leakage on the order of 10^14 ohms.
Say we have an aquadag capacitance of 0.005uF, then the time constant
is 500,000 seconds. Assuming 5 time constants for a nearly full
discharge this is 2,500,000 seconds or about 1 month. Clearly after 4
years there is practically no charge left.

A+s+i+m+o+v

.... High voltage can give a dangerously uncomfortable discharge.

"Ross Herbert" bravely wrote to "All" (26 Aug 04 04:31:20)
--- on the heady topic of " Television discharge question"

RH From: Ross Herbert

RH |Realize, the crt glass has some leakage on the order of 10^14 ohms.
RH |discharge this is 2,500,000 seconds or about 1 month. Clearly after 4
RH |years there is practically no charge left.

RH The actual time will depend on;

RH a) moisture content of the atmosphere
RH b) conductivity to chassis

RH In practical situations it won't take anywhere near this estimated
RH maximum to self discharge to a safe level.


Yes, even dry air is about 100 times more conductive than glass but
this neglects that the circuit wiring and anode boot insulate the air
path. The remaining path, assuming the focus divider is open circuit,
is via the HV rectifier but its leakage is of the same order as glass.
So then that could double the speed of the discharge. Okay, 2 weeks?!

A+s+i+m+o+v

.... I know flyback, ultor, and 47 other dangerous words.

Gentelman, question was not "theoretecly how long will a HV cap hold a
charge" it was "Do I still need to discharge
capacitors even though it hasn't seen AC in 4 years?" which i interpreted
as: "i don't know what i am doing so how do i do this safely?"

when working with old HV electronics never assume. tie a conductor to the
chassies and use it to touch everything.

dont even assume that it hasen't been plugged in in 4 years.

im recomending you follow basic safety procedures.

we can guess that 'probably' every thing is discharged and 'maybe' the
safety bleeders are intact.... but do you want to find out the hard way that
someone guessed wrong?

On Fri, 27 Aug 2004 03:06:14 +0000, Ross Herbert wrote:

On Thu, 26 Aug 2004 21:37:40 -0400, "Tim Perry"
wrote:

|Gentelman, question was not "theoretecly how long will a HV cap hold a
|charge" it was "Do I still need to discharge
| capacitors even though it hasn't seen AC in 4 years?" which i interpreted
|as: "i don't know what i am doing so how do i do this safely?"
|
|when working with old HV electronics never assume. tie a conductor to the
|chassies and use it to touch everything.
|
|dont even assume that it hasen't been plugged in in 4 years.
|
|im recomending you follow basic safety procedures.
|
|we can guess that 'probably' every thing is discharged and 'maybe' the
|safety bleeders are intact.... but do you want to find out the hard way that
|someone guessed wrong?
|

All good advice for those cases where you don't know for a fact how
long since a TV has not been powered up. In the Op's case he KNOWS for
a fact that the TV hasn't seen power for 4 years.

which i interpreted
|as: "i don't know what i am doing so how do i do this safely?"

You are correct. I've never discharged a television before and was
wondering how to do it safely. I've had the television since it was
bought new and know for a fact the last time it was plugged in was
in early 2000. Thank you all for your input, I will be calling a
service company to dismantle it and dispose of the guts.

On Thu, 26 Aug 2004 21:37:40 -0400, "Tim Perry"
wrote:

Gentelman, question was not "theoretecly how long will a HV cap hold a
charge" it was "Do I still need to discharge
capacitors even though it hasn't seen AC in 4 years?" which i interpreted
as: "i don't know what i am doing so how do i do this safely?"

when working with old HV electronics never assume. tie a conductor to the
chassies and use it to touch everything.

Like a screwdriver w/clip lead to chassis? Or a test light? Any
recommendations for "discharge devices?"


__________________
Note: To reply, replace the word 'spam' embedded in return address with 'mail'.
N37.3 W122.0

I don't know the original question, but pretty much sitting overnight will
discharge the HV or filter caps. Sitting longer than a couple days=no charge
left.

"RonKZ650" wrote in message
...
I don't know the original question, but pretty much sitting overnight will
discharge the HV or filter caps. Sitting longer than a couple days=no
charge
left.

Usually a few minutes is enough to discharge it, however that's no reason
not to manually discharge it no matter how long it's been sitting. It may
have been off for 10 years, but like a gun, always treat it as if it's
loaded.

Lets hope nobody decided to plug the set in without you knowing!

"Art" wrote in message
...
Actually after that period of time you probably will not have any problem
disassembling the set.
Be advised that the tubes are high vacuum devices and can implode if
handled improperly. Use extreme care in disposing and handling of these
particular items. BTW it may be necessary to have them properly disposed
of
because or environmental laws in effect there in Canada. You may need to
contact your local DPW department and ask the about correct manner as to
resolving that problem.
I personally just go in with a set of dikes and cut the cables, inclusive
of the HV leads to the crts and have at it when trashing one of these.
You
can always have a service company come out and remove the guts from the
unit
but they will charge for a service call and labour to do so.
Something to comtemplate over a bottle of Labats Blue, Eh!! Or even an
imported Fosters; Cheers Gov, hopefully you get this resolved.
"Steve" wrote in message
news
On Wed, 25 Aug 2004 12:12:46 +0000, Ross Herbert wrote:

On Wed, 25 Aug 2004 02:05:03 -0400, "Tim Perry"
wrote:

|
|"Steve" wrote in message
|news | Hello,
|
| I have an old rear projection television that I would like to take
| apart and use the frame for another project. The television has not
| been plugged in since the year 2000. Do I still need to discharge
| capacitors even though it hasn't seen AC in 4 years?
|
|YES

And here I was thinking this was a troll......

Tell me, how can any charge storage device (capacitor) or aquadag
coating on a tube retain a charge when not having been powered up for
4 years? Must be some magic new dielectric I haven't heard about, or
the air is awfully dry.

Personally, I wouldn't bother about charged capacitors causing
problems after a week of not having been powered up, but I would still
short the aquadag coating on the tube just to be sure. After 2 weeks I
wouldn't even bother about that.


|
| Could anyone
| tell me how long it would take on average for the caps to discharge
| by themselves?
|
|it dosent matter assume they are charged just as you should assume a
gun is
|loaded when you handel it.
|
|
| Thanks in advance.
|
|
|never trust a bleeder resistor... it could be open
|

If you were referring to me as a troll, I really hope I didn't come
across as that way. I was looking for serious advice.

To be perfectly honest, sitting overnight is ample time to discharge 99.999% of
caps or CRTs. I'd say 4 years you're relatively safe.
Ron

Did you ever try to remove the anode cap from a CRT on a set that has been
sitting for a week, and you didn't discharge it? There are some models that
are designed to slowly discharge on their own, but not all of them. If not,
try it, and let me know how you feel after!

After several months, I have been zapped from anode caps. This is because
the source DC resistance is extremely high in some of these sets.

As for the power supply, after about 2 to 3 days, I would say it will be
safe, because there are other components connected to the caps, and they
have resistive characteristics. Some of the manufactures have a bleeder
resistor built in for the main filter caps. But, I would not trust this
without first checking this out.

In theory, a good cap can hold the charge for a long time. I have charged up
caps to several hundred volts, and the next day when I checked them with my
DVM, there was still too much for comfort.

Considering the natural leakage in the caps of any device, after about a
week or so, they should normally be discharged. When I work on anything that
uses voltages in excess of about 50 Volts, I check with a DVM first before
my hands go in to it. If I have to, I find a way to discharge the voltage
that is present, or I work in a fashion where I don't have to be directly
handling the components at their leads.

Normally when I work on these sets, I check to see if the caps are charged.
If so, I have a 20 Watt 220 ohm resistor with a set of leads that I put
across the main caps for a few seconds to discharge them. I am concerned
about the main electrolytic caps that are holding at least a few hundred
volts.

In many of the switching supplies, depending on the design, they self
discharge across the other resistive components anyways. I found that after
about a few minutes or so, they are very safe to handle.

The best way to work is with caution.



--

Jerry G.
======


"RonKZ650" wrote in message
...
To be perfectly honest, sitting overnight is ample time to discharge 99.999%
of
caps or CRTs. I'd say 4 years you're relatively safe.
Ron

Did you ever try to remove the anode cap from a CRT on a set that has been
sitting for a week, and you didn't discharge it? There are some models that
are designed to slowly discharge on their own, but not all of them. If not,
try it, and let me know how you feel after!

Interesting, I can say I've been in the business for 27 yrs and have never once
been shocked off a tube that has sat overnight, regardless of whether it has a
bleeder resistor in the design or not. I've been mighty lucky all these years I
guess :-)

i fined it safer to dispose of old tubes
is to snip of the nipple on the end of the
tubes neck under the crt board, there wil be a plastic
keyway over the pins on tube remove it
gently or cutt into the plastic end between the
pins.
where protection goggles and wrap some
rags around the neck on the tube before you
do this.
after that you move it around without
it inploding.

"Peter Kolbe" wrote in message
...
Lets hope nobody decided to plug the set in without you knowing!

"Art" wrote in message
...
Actually after that period of time you probably will not have any
problem
disassembling the set.
Be advised that the tubes are high vacuum devices and can implode if
handled improperly. Use extreme care in disposing and handling of these
particular items. BTW it may be necessary to have them properly disposed
of
because or environmental laws in effect there in Canada. You may need to
contact your local DPW department and ask the about correct manner as to
resolving that problem.
I personally just go in with a set of dikes and cut the cables,
inclusive
of the HV leads to the crts and have at it when trashing one of these.
You
can always have a service company come out and remove the guts from the
unit
but they will charge for a service call and labour to do so.
Something to comtemplate over a bottle of Labats Blue, Eh!! Or even an
imported Fosters; Cheers Gov, hopefully you get this resolved.
"Steve" wrote in message
news
On Wed, 25 Aug 2004 12:12:46 +0000, Ross Herbert wrote:

On Wed, 25 Aug 2004 02:05:03 -0400, "Tim Perry"
wrote:

|
|"Steve" wrote in message
|news | Hello,
|
| I have an old rear projection television that I would like to take
| apart and use the frame for another project. The television has
not
| been plugged in since the year 2000. Do I still need to discharge
| capacitors even though it hasn't seen AC in 4 years?
|
|YES

And here I was thinking this was a troll......

Tell me, how can any charge storage device (capacitor) or aquadag
coating on a tube retain a charge when not having been powered up for
4 years? Must be some magic new dielectric I haven't heard about, or
the air is awfully dry.

Personally, I wouldn't bother about charged capacitors causing
problems after a week of not having been powered up, but I would
still
short the aquadag coating on the tube just to be sure. After 2 weeks
I
wouldn't even bother about that.


|
| Could anyone
| tell me how long it would take on average for the caps to
discharge
| by themselves?
|
|it dosent matter assume they are charged just as you should assume a
gun is
|loaded when you handel it.
|
|
| Thanks in advance.
|
|
|never trust a bleeder resistor... it could be open
|

If you were referring to me as a troll, I really hope I didn't come
across as that way. I was looking for serious advice.