Date   

Re: Digest Number 1327

Ben Torre <btorre@...>
 

At 01:19 PM 12/2/04, you wrote:
always think "is that safe?".
I'd be thinking of my German-descent dentist too much. <ba-bump>

Seriously folks, all of the stuff being mentioned here I heard before from my long-retired dad who was a broadcasting chief engineer. It really is good practice and has saved my own silly posterior several times.

Lesson learned from experience: the second you take electricity for granted, you get bit by it.


Re: Critical of Tektronix (was Tek 570 curve-tracer)

Dave Wise
 

Good point Stefan. I've only used it a couple of times,
with my Weller WTCP whose tips seem almost indestructible.

Dave Wise

-----Original Message-----
From: Stefan Trethan [mailto:stefan_trethan@gmx.at]
Sent: Thursday, December 02, 2004 12:06 PM
To: TekScopes@yahoogroups.com
Subject: Re: [TekScopes] Re: Critical of Tektronix (was Tek 570
curve-tracer)



On Thu, 2 Dec 2004 10:26:57 -0800, David Wise
<david_wise@phoenix.com>
wrote:

Sorry if it's been mentioned before, but aspirin is a pretty
good varnish remover. It's the acid. Lay the wire on an
aspirin tablet, hold your breath, and heat with a soldering iron.
The varnish should disappear quickly. Now wash off the acid
residue, and you're ready to tin the wire.

Dave Wise

Do you know if that will eat away half my iron tip's plating?
I wonder about that a bit.. perhaps better use a old tip for
the stunt..

ST


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Re: Critical of Tektronix (was Tek 570 curve-tracer)

stefan_trethan
 

On Thu, 2 Dec 2004 10:26:57 -0800, David Wise <david_wise@phoenix.com> wrote:

Sorry if it's been mentioned before, but aspirin is a pretty
good varnish remover. It's the acid. Lay the wire on an
aspirin tablet, hold your breath, and heat with a soldering iron.
The varnish should disappear quickly. Now wash off the acid
residue, and you're ready to tin the wire.

Dave Wise

Do you know if that will eat away half my iron tip's plating?
I wonder about that a bit.. perhaps better use a old tip for the stunt..

ST


Re: Electrical safety - was Nuvistor type 8058 + New tube tester

stefan_trethan
 

On Thu, 2 Dec 2004 19:33:31 -0000, Jim Beacon <jim@g1jbg.co.uk> wrote:

It is common practice in the UK construction industry, where power tools are rquired to be 110V, fed via a centre tapped isolation transformer, with the centre tap of the secondary earthed. The maximum voltage to earth is then 55V, which is considered a "safe" low voltage in the UK regs.

Jim.

That's what i was thinking of. As David says in the other post it isn't done more often 'cause not enough die. But if you have a isolation transformer already (which is needed for this fun) you can simply leave
it floating for test bench use and have one touch "free" without harm. parasitive currents probably make it more reasonable to earth the center tap in the construction industry stuff (where you have long lines etc.).


thank you guys also for the CDC report which gave some numbers.


ST


Re: OT: Electrical safety - was Nuvistor type 8058 + New tube tester

david@...
 

Here is an exert from a paper on the Center for Disease Control
website entitled EPIDEMIOLOGY OF ELECTROCUTION FATALITIES :

http://www.cdc.gov/niosh/elecepid.html
Thanks for the data.

Looking at the pie chart, there were a total of 25 "Electrocution
Incidents" involving 110-120V over the period 1982-1994, or just over 2
per year.

To put that in perspective, we have about 50 lightning deaths per year in
the US.


Re: Electrical safety - was Nuvistor type 8058 + New tube tester

scoper796 <tekscopes@...>
 

Here is an exert from a paper on the Center for Disease Control
website entitled EPIDEMIOLOGY OF ELECTROCUTION FATALITIES :

http://www.cdc.gov/niosh/elecepid.html


"Two hundred twenty-one (99%) of the incidents involved alternating
current (AC). One incident involved direct current (DC). Two
incidents involved AC arcs. Of the 221 AC electrocutions, 74 (33%)
involved less than 600 volts and 147 (66%) involved 600 volts or
more. The number of electrocutions by voltage level is listed in
Figures 9 and 10. Forty (54%) of the lower-voltage electrocutions
involved household current of 120 to 240 volts. Manufacturing
companies accounted for 40 (54%) of the lower-voltage incidents. This
is particularly disturbing due to safety features such as electrical
safety interlocks, emergency stop devices, and electrical guarding
inherently designed into manufacturing equipment."


"Improperly installed or damaged equipment can be responsible for
occupational electrocutions in a variety of ways. The most frequently
cited OSHA electrical regulation is improper grounding of equipment
or electrical circuitry. If the frame of a piece of electrical
equipment or machinery does not have a grounding conductor attaching
the frame to ground, as required to divert dangerous fault current to
ground, and an electrical fault occurs, anyone touching that frame
and any other object at ground potential would receive an electrical
shock. Should a fault occur with a grounding conductor present, the
circuit would open or trip as an alert that a problem existed, except
in high-resistance grounding applications. Damaged guards can expose
workers to energized conductors in proximity to their work areas.
Additionally, damaged extension cords or extension cords with their
ground prong removed can expose workers to the danger of
electrocution.

Failure to maintain a continuous path to ground can expose entire
electrical systems to damage and can expose the structures within
which they are housed and workers within these structures to
electrical and fire hazards.

For example, many electrical systems are installed in a manner that
allows a structure's water pipes or other conductive conduit to serve
as a continuous path to ground in compliance with the NEC. However,
FACE investigations have identified cases of electrocution or fire as
a result of an interruption in a continuous path to ground. During
renovation or repair activities, conductive components may be
replaced by nonconductive components such as PVC pipe, which will
interrupt the path to ground. This may result in fire due to the
intense overheating of components of the electrical system.
Additionally, workers contacting improperly grounded components while
being at ground potential would be exposed to electric shock."


Larry Christopher



--- In TekScopes@yahoogroups.com, david@s... wrote:
stefan_trethan@g... (Stefan Trethan) wrote:
I wonder if 110V is as dangerous, i mean if one would use a
transformer
with grounded center tap you would only have 55V to earth at all
times,
which is not more than the 50V considered safe. Tht might be an
option
for you US guys, is that done in labs? why not? I know it wouldn't
work
with 3-ph but for single ph situation?
This is done sometimes in recording studios (and maybe
by "audiophiles")
to solve intractable hum problems. A Google search for "balanced AC
power" will turn up some equipment. I haven't heard of it being
done for
safety purposes, probably because it's expensive and very few
people are
injured by 120VAC in a lab setting.


Re: Electrical safety - was Nuvistor type 8058 + New tube tester

jim_beacon2000
 

It is common practice in the UK construction industry, where power tools are rquired to be 110V, fed via a centre tapped isolation transformer, with the centre tap of the secondary earthed. The maximum voltage to earth is then 55V, which is considered a "safe" low voltage in the UK regs.

Jim.

----- Original Message -----
From: david@slack.com
To: TekScopes@yahoogroups.com
Sent: Thursday, December 02, 2004 7:21 PM
Subject: [TekScopes] Re: Electrical safety - was Nuvistor type 8058 + New tube tester


stefan_trethan@gmx.at (Stefan Trethan) wrote:
>I wonder if 110V is as dangerous, i mean if one would use a transformer
>with grounded center tap you would only have 55V to earth at all times,
>which is not more than the 50V considered safe. Tht might be an option
>for you US guys, is that done in labs? why not? I know it wouldn't work
>with 3-ph but for single ph situation?

This is done sometimes in recording studios (and maybe by "audiophiles")
to solve intractable hum problems. A Google search for "balanced AC
power" will turn up some equipment. I haven't heard of it being done for
safety purposes, probably because it's expensive and very few people are
injured by 120VAC in a lab setting.


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Re: Electrical safety - was Nuvistor type 8058 + New tube tester

david@...
 

stefan_trethan@gmx.at (Stefan Trethan) wrote:
I wonder if 110V is as dangerous, i mean if one would use a transformer
with grounded center tap you would only have 55V to earth at all times,
which is not more than the 50V considered safe. Tht might be an option
for you US guys, is that done in labs? why not? I know it wouldn't work
with 3-ph but for single ph situation?
This is done sometimes in recording studios (and maybe by "audiophiles")
to solve intractable hum problems. A Google search for "balanced AC
power" will turn up some equipment. I haven't heard of it being done for
safety purposes, probably because it's expensive and very few people are
injured by 120VAC in a lab setting.


Subject: Re: Re: Electrical safety - was Nuvistor type 8058 + New tube tester

scoper796 <tekscopes@...>
 

To amplify, the center of the transformer is literally "grounded" at
the home. It is either attached to a water pipe, or sometimes to a
ground rod driven into the soil. All metal attached to the electrical
system i.e. outlet boxes, lamp stands, conduit, panels etc are also
wired to the ground in the house wiring. I am sure other countries
have a similiar arrangement. If there is a short inside a box or
panel, it simply blows the circuit breaker.

This is why it is important to carry this ground through to the
chassis of any equipment, including test equipment, that we are using
or working on. I have receicved many Tek scopes with the grounding
pin on the power cord cut off. This is an invitation to disaster. And
it may not be you, it could be a child or other family member who
didn't want to "die of electrocution," as someone tastelessly said.

Larry Christopher



--- In TekScopes@yahoogroups.com, Brooke Clarke <brooke@p...> wrote:
Hi Stefan:

The US mains electrical system for delivering electricity to single
family homes uses a transformer that converts the local distribution
A.C. voltage from say 4,000 volts to 220 VAC. The secondary of this
transformer is center tapped and 3 wires are run to the dwelling
unit. The third wire MUST be grounded. The purpose of this is to
protect against the problem of a primary to secondary short in the
transformer, which would otherwise supply 4,000 VAC to the dwelling.
The dwelling wiring can either be for 220 VAC or for 110 VAC. It's
good practice to try and balance the 110 VAC loads.

Have Fun,

Brooke Clarke, N6GCE
--
w/Java http://www.PRC68.com
w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml
http://www.precisionclock.com



Date: Thu, 02 Dec 2004 09:00:03 +0100
From: "Stefan Trethan" <stefan_trethan@g...>
Subject: Re: Re: Electrical safety - was Nuvistor type 8058 + New
tube tester

On Wed, 1 Dec 2004 16:07:13 -0800, Gary Allsebrook <regman10@c...>
wrote:



According to the Tektronix book "Biophysical Measurements",
published in
1970, 10-20mA is in the "cannot let go", 60Hz, arm to arm, shock
current
chart; 100mA - 3A, ventricular fibrillation and probable death.

It doesn't take a lot of current surprisingly.
That might well be. But the thing is that 200mA ground fault
protectors
don't work because
there are no 200mA flowing in normal situation arm-to-arm (small
point of
contact on one side).
Luckily by far not all encounters are deadly, just potentially
deadly, if
that wasn't the case
i wouldn't be typing here. (And probably some of you too). I wonder
if
110V is as dangerous,
i mean if one would use a transformer with grounded center tap you
would
only have 55V to earth
at all times, which is not more than the 50V considered safe.
Tht might be an option for you US guys, is that done in labs? why
not? I
know it wouldn't work
with 3-ph but for single ph situation?






Re: Critical of Tektronix (was Tek 570 curve-tracer)

Dave Wise
 

Yes, I save the aspirin trick for the tough ones.

Thanks,
Dave Wise

-----Original Message-----
From: Gary Allsebrook [mailto:regman10@comcast.net]
Sent: Thursday, December 02, 2004 10:55 AM
To: David Wise; scoper796; TekScopes@yahoogroups.com
Subject: RE: [TekScopes] Re: Critical of Tektronix (was Tek 570 curve-tracer)


Simply tinning the wire is usually a good varnish remover also. I use liquid rosin flux as an enhancer.


Subject: Re: Re: Electrical safety - was Nuvistor type 8058 + New tube tester

Brooke Clarke
 

Hi Stefan:

The US mains electrical system for delivering electricity to single family homes uses a transformer that converts the local distribution A.C. voltage from say 4,000 volts to 220 VAC. The secondary of this transformer is center tapped and 3 wires are run to the dwelling unit. The third wire MUST be grounded. The purpose of this is to protect against the problem of a primary to secondary short in the transformer, which would otherwise supply 4,000 VAC to the dwelling. The dwelling wiring can either be for 220 VAC or for 110 VAC. It's good practice to try and balance the 110 VAC loads.

Have Fun,

Brooke Clarke, N6GCE
--
w/Java http://www.PRC68.com
w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml
http://www.precisionclock.com



Date: Thu, 02 Dec 2004 09:00:03 +0100
From: "Stefan Trethan" <stefan_trethan@gmx.at>
Subject: Re: Re: Electrical safety - was Nuvistor type 8058 + New tube tester

On Wed, 1 Dec 2004 16:07:13 -0800, Gary Allsebrook <regman10@comcast.net>
wrote:



According to the Tektronix book "Biophysical Measurements", published in
1970, 10-20mA is in the "cannot let go", 60Hz, arm to arm, shock current
chart; 100mA - 3A, ventricular fibrillation and probable death.

It doesn't take a lot of current surprisingly.
That might well be. But the thing is that 200mA ground fault protectors
don't work because
there are no 200mA flowing in normal situation arm-to-arm (small point of
contact on one side).
Luckily by far not all encounters are deadly, just potentially deadly, if
that wasn't the case
i wouldn't be typing here. (And probably some of you too). I wonder if
110V is as dangerous,
i mean if one would use a transformer with grounded center tap you would
only have 55V to earth
at all times, which is not more than the 50V considered safe.
Tht might be an option for you US guys, is that done in labs? why not? I
know it wouldn't work
with 3-ph but for single ph situation?


Re: Critical of Tektronix (was Tek 570 curve-tracer)

regman10
 

Simply tinning the wire is usually a good varnish remover also. I use liquid
rosin flux as an enhancer.


Re: Nuvistor type 8058 + New tube tester

Denton, Adam (Exchange)
 

--- In TekScopes@yahoogroups.com, "Craig Sawyers" <c.sawyers@t...>
wrote:
=============================================
INSTRUCTION SHEET
TYPE 874-FBL BIAS INSERTION UNIT
Lengthy non-sequitor replies like this I find really annoying, far
more so than "off topic" threads. Why not remain silent if you've
nothing to add?

JMHO.

Adam


Re: Critical of Tektronix (was Tek 570 curve-tracer)

Dave Wise
 

From: scoper796 [mailto:tekscopes@telus.net]
[snip]
Yes, I know whereof you speak. In fact, I stopped buying 3A6 plug-
[snip]
little tiny wire is accessible, but I have had no luck getting the
varnish off it and soldering it. But that would work. I have bypassed
Sorry if it's been mentioned before, but aspirin is a pretty
good varnish remover. It's the acid. Lay the wire on an
aspirin tablet, hold your breath, and heat with a soldering iron.
The varnish should disappear quickly. Now wash off the acid
residue, and you're ready to tin the wire.

Dave Wise


Re: Critical of Tektronix (was Tek 570 curve-tracer)

scoper796 <tekscopes@...>
 

Hi John,

Yes, I know whereof you speak. In fact, I stopped buying 3A6 plug-
ins, even thogh it is the best amp for the 560 series, because it is
impossible to find out if they are broken before purchase. And of
course I don't know of any source for replacements. I think they are
made of the same material as the disappearing crt clamps.

As far as repairing them go, I have the following to offer. The
little tiny wire is accessible, but I have had no luck getting the
varnish off it and soldering it. But that would work. I have bypassed
the peaking coils altogether, and that worked, but I didn't measure
the frequency response afterwards.

I would disagree that this is a mistake on Tektronics part. I know
they had no idea this equipment would still be in-use 40 years or so
after production. Even so, I have a 555 that is indestructible and I
am sure will work fine for another 40 years.

Good luck.

Larry Christopher



--- In TekScopes@yahoogroups.com, "John Doran" <johnd@e...> wrote:
Howdy!



That German fellow's comments reminded me that, while I love

Tektronix and regard them highly, they have indeed done some
seriously
bone-headed things over the years.



For example, in the 3A1 and 3A6 plug-in amplifiers for the 560
series


Critical of Tektronix (was Tek 570 curve-tracer)

John Doran <johnd@...>
 

Howdy!



That German fellow's comments reminded me that, while I love

Tektronix and regard them highly, they have indeed done some seriously
bone-headed things over the years.



For example, in the 3A1 and 3A6 plug-in amplifiers for the 560 series
oscilloscopes, Tek had big, heavy rubber-covered resistors connected
directly to the fragile little terminals of plastic coil forms, with no
intermediate tie-points. I have one of each plug-in, and in each of
them the terminals have been snapped right off...



What was Tek thinking? ...Were they thinking?



I have not yet attempted to repair this damage; it looks tough.



-John


TDR plug-ins for 564 scopes

Tim Phillips <t.phillips@...>
 

Hi, All;
I notice on the cover of the TDR Measurement Concepts book
(up for auction you-know-where)
there are a couple of plug-ins, seemingly for the 564, that I
don't recognise. Were there special TDR plug-ins equivalent to
the 1S2 for this system?
regards
Tim P.


Re: Electrical safety - was Nuvistor type 8058 + New tube tester

Ahlbrecht, Andreas <ahlbra@...>
 

I think that specialized test equipment that deals with high power or high
voltage is intended for being used by trained people. If such equipment is
used by people 'not in the know', then they are in potential danger. That's
everyday life. Take a chain saw for example. A chain saw usually has one or
more facilities which are useless for sawing but solely deal with safety. (A
shield that prevents the operator from coming in contact with the chain for
example.) But still, you wouldn't let your three years old son use the saw,
right? Why wouldn't you? Because he doesn't know anything about the very
dangers involved and even if you would explain, he would not fully
understand. Common sense!!!

OTOH things of everyday life commonly taken for being safe can expose great
dangers. In our living room we have a light chain (correct term for 'many
bulbs on a string'?) which is sort of wound around our cupboard. Yesterday I
found one of my sons (one year old) standing in front of the cupboard,
playing with the bulbs. He was about to stick one of the bulbs into his
mouth. As I saw this I immediately pulled him away. My wife was astonished
until I explained her that the bulbs, although low voltage types, are not
mains insulated. I explained further what could have happened to our son if
he had bitten the bulb into pieces, replacing the bulb with his
tongue....... Much, VERY much more dangerous than a tube tester which is
being used by a trained person.

Just my two cents.

Andi


Re: Electrical safety - was Nuvistor type 8058 + New tube tester

stefan_trethan
 

On Wed, 1 Dec 2004 16:07:13 -0800, Gary Allsebrook <regman10@comcast.net> wrote:


According to the Tektronix book "Biophysical Measurements", published in
1970, 10-20mA is in the "cannot let go", 60Hz, arm to arm, shock current
chart; 100mA - 3A, ventricular fibrillation and probable death.

It doesn't take a lot of current surprisingly.
That might well be. But the thing is that 200mA ground fault protectors don't work because
there are no 200mA flowing in normal situation arm-to-arm (small point of contact on one side).
Luckily by far not all encounters are deadly, just potentially deadly, if that wasn't the case
i wouldn't be typing here. (And probably some of you too). I wonder if 110V is as dangerous,
i mean if one would use a transformer with grounded center tap you would only have 55V to earth
at all times, which is not more than the 50V considered safe.
Tht might be an option for you US guys, is that done in labs? why not? I know it wouldn't work
with 3-ph but for single ph situation?


ST


Re: Nuvistor type 8058 + New tube tester

John Miles <jmiles@...>
 

What a hideous design - especially the "basic"
version! It's
not portable, it undoubtledly has safety deficiencies as you note, it's
incredibly ugly, and worst of all it requires mutilating a
classic piece
of
vintage test equipment.

That's a pretty neat hack, actually. He claims it does not permanently
damage the Cardmatic (which I seriously doubt lives up to contemporary UL or
CE safety standards even without a large metal box wired to it).

Personally, I'd be tempted to build a self-contained unit with its own bank
of sockets using high-voltage IGBTs or a similar technology to do the
switching, but for his purposes and those of his customers it sounds like he
has arrived at a good working solution.

Maybe someday Ralph Nader's successors will manage to bubble-wrap the world,
perhaps with help from some of the others in this thread. I hope I've
already electrocuted myself by then.

-- john KE5FX

176701 - 176720 of 187083