[RchTop]

Hi

I was using my new oscilloscope to look at the heater (6.3v) AC signal
in a simple 12AX7 into a 6V6 SE design guitar amp.

Next thing I know I can smell buring and the ground lead of the probe
is starting to melt.

I turn everything off and barely salvage the scope lead (the ground
lead plastic coating almost melted off, but the main part of the scope
was ok)

I had the scope probe connected like this:

Probe (+ve end) on one side of the 6.3v winding and the ground lead
(-ve end) on the other side of the 6.3v winding.

Anyone know why it would have gotten so hot?

Perhaps I am using it incorrectly.

I am now scared to use it in case I melt or blow it up.

Any help would be appreciated.

Rchtop

[Phil Allison]

"RchTop" wrote in message
oups.com...


** Groper ALERT !!!!!


I was using my new oscilloscope to look at the heater (6.3v) AC signal
in a simple 12AX7 into a 6V6 SE design guitar amp.

Next thing I know I can smell buring and the ground lead of the probe
is starting to melt.

I turn everything off and barely salvage the scope lead (the ground
lead plastic coating almost melted off, but the main part of the scope
was ok)

I had the scope probe connected like this:

Probe (+ve end) on one side of the 6.3v winding and the ground lead
(-ve end) on the other side of the 6.3v winding.

Anyone know why it would have gotten so hot?

Perhaps I am using it incorrectly.

I am now scared to use it in case I melt or blow it up.



** Err - your scope is grounded at the power outlet and SO is the earth
clip on the probe - hence all readings with your scope are RELATIVE to
earth.

That ground clip must not be connected to a source of AC or DC current which
is ALSO ground referenced as the heater supply is in that tube amp - bet
there is a centre connection going to ground.

Just attach the clip to chassis ground or zero volts on the device's PSU in
future.




......... Phil

[EJP]

RchTop wrote:
I had the scope probe connected like this:

Probe (+ve end) on one side of the 6.3v winding and the ground lead
(-ve end) on the other side of the 6.3v winding.

Never connect the ground side of a scope lead to anything except ground.
That way short circuits lie ....

[Phil Allison]

"Andre"


! Never connect the ground side of a scope _mains_ lead to anything....

Andre Schmeets


** This sounds like * VERY BAD * advice.

A non-grounded scope is a *lethal weapon* sitting on your bench.





........ Phil

[Andre]

EJP wrote:
RchTop wrote:

I had the scope probe connected like this:

Probe (+ve end) on one side of the 6.3v winding and the ground lead
(-ve end) on the other side of the 6.3v winding.




! Never connect the ground side of a scope _mains_ lead to anything....

Andre Schmeets

[[email protected]]

Phil Allison wrote:
"Andre"


! Never connect the ground side of a scope _mains_ lead to anything....

Andre Schmeets


** This sounds like * VERY BAD * advice.

Generically lifting the ground of a scope is indeed a Bad Thing.

Much better example advice is to use, say, a differential probe (if you
can afford one!) or two channels in difference mode (even these
approaches have their disadvantages and limitations.)

When working with high-current supplies there are very real dangers
associated with the "safety ground" on test equipment. The current of a
filament transformer for a big rig can, for example, easily melt the
ground wiring inside the test equipment or inside the wall, which is
usually only sized for AC fault currents (say 15 or 20Amps). This is
particularly nasty because everything may seem to work afterwards but
you are left with NO ground protection.

A non-grounded scope is a *lethal weapon* sitting on your bench.

We have lots of similarly lethal weapons all over our benches, for the
most part, so I'm not fundamentally opposed to isolating ground to a
scope when done wisely and safely.

Tim.

[Phil Allison]

! Never connect the ground side of a scope _mains_ lead to anything....

Andre Schmeets


** This sounds like * VERY BAD * advice.

A non-grounded scope is a *lethal weapon* sitting on your bench.


We have lots of similarly lethal weapons all over our benches,



** Who is this " we " - white man ????

I don't - nor does *any* tech I know.



for the
most part, so I'm not fundamentally opposed to isolating ground to a
scope when done wisely and safely.


** There is no possible way to do that.

Floating an earthed scope is Dead, Bloody Dangerous !!!!!

It is essential that the metal case and BNC connectors etc remain at ground
potential & so cannot become a source of lethal voltage.






........ Phil

[Sander deWaal]

Andre said:


! Never connect the ground side of a scope _mains_ lead to anything....


Dangerous, as other posters observed.

Using an isolation transformer for the DUT is the safe way to go.

--
"All amps sound alike, but some sound more alike than others".

[Andre]

Phil Allison wrote:
"Andre"


! Never connect the ground side of a scope _mains_ lead to anything....

Andre Schmeets



** This sounds like * VERY BAD * advice.

A non-grounded scope is a *lethal weapon* sitting on your bench.





....... Phil



Who is using a scope.
I am doing this for my daily job.
I open up apparatus to repair it and
build apparatus.
I'm constantly manouvering at and around
parts connected to mains voltage and here
in Europe that is ...........230 Volt....
Whoeh !

115 Volt is a safetyvoltage for childrens toys.
*lethal weapon*

And then;
You cannot disconnect the earth-lead of the
probe.
Measuring v.s. mains-ground as reference gives
results that are useless ( if you get a
readout at all )

The apparatus to be measured is a given thing.
You cannot alter it in order to measure it.

So, there are two ways left.

One- is applying an isolationtransformer for
your complete lab.
Meaning one that can deliver a minimum of 1000 VA (Watt)
and has a realy high isolation for safety and
for minimising capacitive coupling wich could
again disturb your measurement.
This is the expensive way.

Two- is disconnecting the ground-lead of the
scope's mains-cord. You see it done everywhere.
Therefore.
Know what you are doing.
Work carefully.

Andre Schmeets

[Phil Allison]

"Andre"
Phil Allison wrote:
"Andre"


! Never connect the ground side of a scope _mains_ lead to anything....

Andre Schmeets


** This sounds like * VERY BAD * advice.

A non-grounded scope is a *lethal weapon* sitting on your bench.



Who is using a scope.


** Read your own bloody words - ****WIT.

" ! Never connect the ground side of a scope _mains_ lead to anything.... "


115 Volt is a safetyvoltage for childrens toys.


** WHAT AN INSANE LIE !!!!!!!!!!!


Two- is disconnecting the ground-lead of the
scope's mains-cord. You see it done everywhere.


** WHAT A BLATANT LIE !!

I sincerely hope doing it KILLS an arrogant, reckless asshole like YOU !





........ Phil

[Andre]

Phil Allison wrote:
"Andre"

Phil Allison wrote:

"Andre"


! Never connect the ground side of a scope _mains_ lead to anything....

Andre Schmeets


** This sounds like * VERY BAD * advice.

A non-grounded scope is a *lethal weapon* sitting on your bench.



Who is using a scope.

For getting a better view on the personality of Mr. Allison I have
hereby distilled his reaction to my message.


** Read your own bloody words - ****WIT.

** WHAT AN INSANE LIE !!!!!!!!!!!

** WHAT A BLATANT LIE !!

I sincerely hope doing it KILLS an arrogant, reckless asshole like YOU !

....... Phil

For a long time I have been wondering from what side all that
off-topic shouting and hate came in RAT. Now I know.

Andre Schmeets

[Phil Allison]

"Andre"


** Will someone track down and *deal* with this criminal wog pile of ****
ASAP.






......... Phil

[Sander deWaal]

Andre said:

Phil Allison wrote:
"Andre" wrote:


! Never connect the ground side of a scope _mains_ lead to anything....


** This sounds like * VERY BAD * advice.

A non-grounded scope is a *lethal weapon* sitting on your bench.


Agreed.


Who is using a scope.
I am doing this for my daily job.
I open up apparatus to repair it and
build apparatus.
I'm constantly manouvering at and around
parts connected to mains voltage and here
in Europe that is ...........230 Volt....
Whoeh !


Advising someone (is the OP a newbie? I don't know) to do something
that may have lethal consequences, is dangerous and irresponsible.
I don't know you in person, your comment about lifting the ground off
your scope may have come from an old, experienced coot, who knows his
things and who knows what he's doing.
It may as well have come from an not entirely clueless noob, who knows
just enough to hand out dangerous advice to others.
Up until the comment below, it could have been both.


115 Volt is a safetyvoltage for childrens toys.
*lethal weapon*


Hold it right there.
Now I know that you're the noob and not the old tinkerer.

Didn't you know that not voltage, but * current* kills?
Depending on the skin resistance and the general health of the
subject, currents from a few mA can be lethal, especially when they're
going through the chest.

Do you keep any toddlers around?
Or an ill relative? Keep them out of your workshop, for God's sake.

Comments like this on a worldwide forum only show your ignorance and
your irresponsibility.


Two- is disconnecting the ground-lead of the
scope's mains-cord. You see it done everywhere.
Therefore.
Know what you are doing.
Work carefully.


Yep, something the old coots know. Phil and I know that as well.
But how do you know the OP is experienced enough to understand the
dangers involved?

Granted, his initial problem would have occured with an isolation
transformer as well, since it was the large current from the heater
winding that let his ground wire melt.
But suppose he was measuring the heater voltage of a GZ34 with an
ungrounded scope and no isolation transformer?
Can you tell me what could have happened then, if he accidently
reached to his scope to adjust the timebase?
Or to his toddler, grabbing his father's arm while the other was
resting on a grounded water pipe?

All of these scenarios may seem farfetched, but who knows how many
people die each year because of lazyness or ignorance.

Know your responsibility, give out advice only when you know that it
is safe for a newbie to do.
Hundreds of people could read your advice here!

--
"All amps sound alike, but some sound more alike than others".

[Phil Allison]

"Andre"


** Will someone track down and *deal* with this criminal wog pile of ****
ASAP.






...... Phil

[Phil Allison]

"Rich ****head ****wit "



* * **** OFF IDIOT TROLL !!!!!!!!!!!!!!






......... Phil

[Andre]

Sander deWaal wrote:



Hold it right there.
Now I know that you're the noob and not the old tinkerer.

Didn't you know that not voltage, but * current* kills?

Yep, something the old coots know. Phil and I know that as well.

In the 50's and 60's there was a series of electronic books by
Aisberg, that were translated into other languages as well.
They were written around two characters,. ask-all and know-all

This n.g. is populated with know-all's waiting for an ask-all
to show up with a stupid question so they have an oppertunity
to spread their knowledge.

Ofcause all know-all's have different opinions on tricky questions.
And their ego's are so tensed it immediately starts a war,.
not looking to arguments but shouting.

Finally
Someone who is messing around inside a tube-amplifier probably
is very aware of the +Ub that is found there.
The ( chassis of the ) apparatus you are working on should be
grounded and your scope grounded to that.

There is allways a way to get defibrilated.

Andre Schmeets

[Phil Allison]

"Andre Schmeets CRIMINAL"



** You are the VILEST imaginable of all possible arseholes - Andre
Schmeets.


YOU do not gave a funking hoot if you ** KILL ** someone with your
criminally reckless advice.

I dearly hope someone tracks YOU down your home and *deals* with YOU like
the worthless piece of wog vermin you are.

It cannot be soon enough for me.







....... Phil

[Andre]

Phil Allison wrote:
"Andre"


** Will someone track down and *deal* with this criminal wog pile of ****
ASAP.

........ Phil


Your contribution as an original poster to this n.g. for the last two
months is limited to a posting on electrostatic speakers and
"Why We Should Ignore Bill Ramsay" off-topic as-well.

Personally, I could do without the contributions of someone who starts
shouting and cursing immediately. I think it's typical for the
less-educated.

But it seems that you own this news-group Mr Allison.
I let you have it, make friends, but please go out for a walk
in the fresh air from time to time.

Andre Schmeets

[Rich Sherman]

Coward
"Phil Allison" wrote in message
...

"Rich ****head ****wit "



* * **** OFF IDIOT TROLL !!!!!!!!!!!!!!






........ Phil

[Phil Allison]

"Rich ****head ****wit MORON "



* * **** OFF !!!!!!!!!!!!!!!!!!!



BLOODY IDIOT TROLL !!!!!!!!!!!!!!






......... Phil

[Sander deWaal]

"Phil Allison" said:


"Andre"

** Will someone track down and *deal* with this criminal wog pile of ****
ASAP.


http://www.hitmanpro.nl

Best thing: they do it for free!

--
"All amps sound alike, but some sound more alike than others".

[Sander deWaal]

Andre said:


In the 50's and 60's there was a series of electronic books by
Aisberg, that were translated into other languages as well.
They were written around two characters,. ask-all and know-all


Heh! You bet I know these books, they're on my bookshelf for many
years. Even taught my little cousin some tube-electronics ;-)


This n.g. is populated with know-all's waiting for an ask-all
to show up with a stupid question so they have an oppertunity
to spread their knowledge.


No doubt.


Ofcause all know-all's have different opinions on tricky questions.
And their ego's are so tensed it immediately starts a war,.
not looking to arguments but shouting.


No doubt.


Finally
Someone who is messing around inside a tube-amplifier probably
is very aware of the +Ub that is found there.


You assume wrong, my friend.
I used to think like that, but judging from the strange questions that
pop up from time to time, one has to be extremely careful in what
advice to give, and how to say it.

Call me an idealist, but I think the "know-alls" of this NG have a
responsibility towards the newcomers.


The ( chassis of the ) apparatus you are working on should be
grounded and your scope grounded to that.


If you add an isolation transformer to supply the mains to the DUT, I
agree, and this is how it should be done.
(You and I both know that experienced servicemen sometimes "forget" to
ground their scope, but let's not go there) ;-)


There is allways a way to get defibrilated.


Yep, but if it can be easily avoided, please do so.

--
"All amps sound alike, but some sound more alike than others".

[Patrick Turner]

Phil Allison wrote:

"Andre Schmeets CRIMINAL"

** You are the VILEST imaginable of all possible arseholes - Andre
Schmeets.

YOU do not gave a funking hoot if you ** KILL ** someone with your
criminally reckless advice.

I dearly hope someone tracks YOU down your home and *deals* with YOU like
the worthless piece of wog vermin you are.

It cannot be soon enough for me.

...... Phil

But Phil, you are inciting others to an act of violence outside the rule of law.

Now you have been one moan and groan when someone says some *******
should go around to your place for a game of baseball at 3AM.

But here you are saying some ******* should go around to Schmeetsie's place and
teach him a lesson.

Methinks all you really need to say is why the advice he gives is wrong,
and you post would be all the more effective.

Patrick Turner.

[Patrick Turner]

Andre wrote:

Phil Allison wrote:
"Andre"


** Will someone track down and *deal* with this criminal wog pile of ****
ASAP.

........ Phil

Your contribution as an original poster to this n.g. for the last two
months is limited to a posting on electrostatic speakers and
"Why We Should Ignore Bill Ramsay" off-topic as-well.

Personally, I could do without the contributions of someone who starts
shouting and cursing immediately. I think it's typical for the
less-educated.

But it seems that you own this news-group Mr Allison.
I let you have it, make friends, but please go out for a walk
in the fresh air from time to time.

Andre Schmeets

Nobody owns the news group except all of us.
We all make it what it is. Sometimes its placid, calm and rational, other days
its like a lunatic assylum. That's life as we know it on this planet.

Some doctors of electronics such as Allison don't always have a nice webside
manner
on many days.

Could you guess what it was that made the man so cranky?

If it was some technical issue where you think you are correct,
then maybe you should explain why in greater detail.

Patrick Turner.

[Rich Sherman]

" ** Does nothing for ground loop hums - you ****ing dimwit.

** Inspect all your stools for worms and maggots as well ????

** So where DO you **** yourself - Nick ????

** Can I tell you most sincerely, Nick the Anonymous EE puke - that you
remind me of the vilest sort of human garbage that university faculties
defecate out into the world.

** You have not got a single *sincere* bone in your thick, Neanderthal head.

** YOU are the ** DESPERATE** ****wit looking to do the work or a lowly wire
tugger to feed yourself - not me.

** **** you - you top posting, evil, **** for brains prick.

** That you are an insane, evil piece of sub human vermin is abundantly
clear.

** Well, one thing is for sure, a know nothing arsehole like YOU is not a
real EE.

** If a bus or AIDS does not get you first.

** You are a truly an EVIL piece of garbage - go rot in HELL.

** My comment was about THIS scenario - not your one ****head.

** Then you really are a complete ****wit.

** **** you ****head.

** Sure - so a pompous, control freak arsehole like you can lord it all over
the poor sods

** The topic was "electronic circuit design " - you lying, criminal piece of
****.

** Shame it has had no such effect on an anonymous lump of excrement like
you.

** Yes it is - you brainless arse pedlar.

** Yep. Definately a arse peddling faggot.

** DSE staff are expected to control any abuse - you dopey wog ****wit.

** Right - your Adelaide ISP proves what a scary ape man POS wop your are.

** Like the anal, pedantic, stinking prick that he is he has no idea what
ordinary words mean.

** It is not an "argument" you tedious ****wit - it is a simple fact and is
quoted in the maker's specs.

** SO ****ING WHAT ??????

** **** off you PITA ******.

** **** off moron.

** .... is a lying, criminal ****.

** So ****wits in company are more credible than lone ****wits ????

** That was your own remark - ****head.

** No test of any kind was possible at the time - as you well know, you
****ing LIAR !!!

** No relevance to your ****ing idiot claims about me.

** Go get stuffed you schizoid moron.

*** Tell them you are an autistic ****wit and that seeing missing letters
and typos causes you NIGHTMARES !!! ***

** Go get ****ed you asinine Grease Monkey.

** Hey, aus.hi-fi's regular arse peddler is back.

** Shame that lying cutns like you will not post under the words you allude
to.

** Find where I said otherwise - you lying arsehole.

** Spoils the shark's fun - you asinine pig.

** Totally WRONG - as usual from this thick as a plank ****head.

** Here it is you SNIPPING MANIAC !!!!!!!!!!!!!!!!!!!!!!!

*** SEE IT NOW - ****HEAD ???? ***

** Tell me yours - you dumb ****.

** It creates a non standard music CD - ****head.

** Call them what you like - dickhead.

** **** off back to your ????? pals at RAO - you psychopathic freak.

** To making a music CD that complies with the standard of course -
****head.

** Listen you raving MORONIC PIG - facts are just facts, it does NOT matter
who the hell "cares" !!!

** What seems to you to be the case is YOUR defective brain's problem and
only more evidence of how ****ING ASININE you are !!!

** The ones that come back are the problem - ****head.

** No legally valid reason is not the same as no reason at all - you
autistic ****head.

** How is the weather on Mars today - ****head ?

** Psycho - Autistic - Paranoid - Schizo - Turd

** The ****head is YOU - bitch face.

* Listen to this very carefully arsehole - go get ****ed.

** You are an insane, audiophool ****wit - right ?

** You do suffer from *queer * masturbation fantasies.

** Those were your words - you dumb ****HEAD !!!!!!!!!!!!!!!!!!!!

** You are definitely no * READER * - you posturing pile of insanity.

** The demented arsehole still cannot read :

** Are you so *** ****ING DUMB YOU CANNOT READ *** !!!!!!!!!!!!!!!

** It is exactly what you just wrote you ****ING LIAR !!!!!!!!!!!!!!!

** I have yet to see you prove even **ONE** of you utterly INSANE assertions
about anything - you genetically defective ****head.

** No relevance to your ****ing idiot claims about me.

** No test of any kind was possible at the time - as you well know, you
****ing LIAR !!!

** That wild assertion is totally ****ing absurd - as per usual for Trevor
the ****wit.

** That wild assertion is totally ****ing absurd - as per usual for Trevor
the Masturbating ****wit.

( The rest of this cretinous ****wit's pig ignorant opinions got flushed
down the dunny.)"

"Phil Allison" wrote in message
...
"Rich ****head ****wit MORON "



* * **** OFF !!!!!!!!!!!!!!!!!!!



BLOODY IDIOT TROLL !!!!!!!!!!!!!!






........ Phil

[Jon Yaeger]

Phil Allison's report card:


Electrical Engineering A
Plays well with Others F-


;-)

[Prune]

A lot of time you can float ground partially, without fully
disconnecting it, say using chains of diodes or high power zeners, so if
the potential you're floating to exceeds what you expect, it can pass
and hopefully blow the fuse.


wrote in
:

On Tue, 18 Jul 2006 23:29:57 +1000, "Phil Allison"
wrote:




! Never connect the ground side of a scope _mains_ lead to
anything....

Andre Schmeets


** This sounds like * VERY BAD * advice.

A non-grounded scope is a *lethal weapon* sitting on your bench.


We have lots of similarly lethal weapons all over our benches,



** Who is this " we " - white man ????

I don't - nor does *any* tech I know.



for the
most part, so I'm not fundamentally opposed to isolating ground to a
scope when done wisely and safely.


** There is no possible way to do that.

Floating an earthed scope is Dead, Bloody Dangerous !!!!!

It is essential that the metal case and BNC connectors etc remain at
ground potential & so cannot become a source of lethal voltage.






....... Phil




Phil is right.

I have all kinds of junk on my bench, going back even to the stone
age, lots of 2-prong cords and cords missing the ground pin - but I
have all my stuff bonded chassis to chassis with good wire. AND I test
the integrity of the ground every now and then, I even ran a dedicated
AC wire and breaker for my bench. (this old house has no ground in
most wires.) I keep a supply of alligators to clip on all the chassis.

Sometimes you can float the ground of certain equipment that you are
testing, but you gots to know what you are doing! Don't make it a
habit with regular electronic gear.

After you've seen fat blue sparks between your variac and the chassis
it's sitting on, you'll be much more careful! Bond everything!

[Andre Jute]

Sander deWaal wrote:
Andre said:

This n.g. is populated with know-all's waiting for an ask-all
to show up with a stupid question so they have an oppertunity
to spread their knowledge.

No doubt.

In the sixth post in this thread, Tim who writes in as shoppa, said,

"Generically lifting the ground of a scope is indeed a Bad Thing."

I wrote a note telling Tim he should have stopped there, and begging
everyone not to confuse the issue for newbies. I trashed it because I
knew that the usual RAT scum piling in would do more harm than good.

The issue with HT on a public forum is never what experts can or cannot
do, but what a total innocent *must* do with his first DVM or scope, or
even his wirecutters (I learned the hard way to discharge caps before
cutting the wires -- I could have lost an eye from melted pieces of my
expensive wirecutters flying around).

Ofcause all know-all's have different opinions on tricky questions.
And their ego's are so tensed it immediately starts a war,.
not looking to arguments but shouting.

No doubt.

Andre Smeets may be sensitive here but he is in the wrong. He shouldn't
have turned this particular matter into a flame war. Too much hangs on
it for personalities to intrude.

Finally
Someone who is messing around inside a tube-amplifier probably
is very aware of the +Ub that is found there.

You assume wrong, my friend.
I used to think like that, but judging from the strange questions that
pop up from time to time, one has to be extremely careful in what
advice to give, and how to say it.

After I reviewed some kits and published some of my own circuits I had
the mail I received analyzed and then sent out a questionaire. Most of
the kit builders and guys who built my designs from scratch -- were
building their first amp, with their first DMM and their first
soldering iron and their first scope...

Call me an idealist, but I think the "know-alls" of this NG have a
responsibility towards the newcomers.

Goddamn right. And the first responsibility is to ensure that they
don't electrocute themselves or burn their families in their homes.

Complication snipped.

There is allways a way to get defibrilated.

Yep, but if it can be easily avoided, please do so.

I've had no problem with Andre Smeets, in fact he seems a good guy. But
I was appalled when I read that, and again when I read his ignorant and
reckless remarks about 115 v 230V. How childish can you get? That sort
of faux bravado, standing on Google year after year, to be singled out
by the seach engine without our reservations anywhere in sight, will
sooner or later kill some newbie.

--
"All amps sound alike, but some sound more alike than others".

Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

[Phil Allison]

"Rick ****head = ****wit MORON "


* * **** OFF RICK !!!!!!!!!!!!!!!!



BLOODY IDIOT TROLL !!!!!!!!!!!!!!






......... Phil

[zack]

phil, goto a museum ******

"Phil Allison" wrote in message
...

"Rick ****head = ****wit MORON "


* * **** OFF RICK !!!!!!!!!!!!!!!!



BLOODY IDIOT TROLL !!!!!!!!!!!!!!






........ Phil

[Prune]

"zack" wrote in news:44bf29d7$0$22361$afc38c87
@news.optusnet.com.au:
phil, goto a museum ******

ROFLLMAO

[zack]

were do you go to get the codes for ng's
LOL meens lough etc.

"RchTop" wrote in message
oups.com...
Hi

I was using my new oscilloscope to look at the heater (6.3v) AC signal
in a simple 12AX7 into a 6V6 SE design guitar amp.

Next thing I know I can smell buring and the ground lead of the probe
is starting to melt.

I turn everything off and barely salvage the scope lead (the ground
lead plastic coating almost melted off, but the main part of the scope
was ok)

I had the scope probe connected like this:

Probe (+ve end) on one side of the 6.3v winding and the ground lead
(-ve end) on the other side of the 6.3v winding.

Anyone know why it would have gotten so hot?

Perhaps I am using it incorrectly.

I am now scared to use it in case I melt or blow it up.

Any help would be appreciated.

Rchtop

[Phil Allison]

"Prune" = a consummate IDIOT.


You know - for someone who uses the idiotic handle "prune", he has not
eaten too many.

Or he would not be so brim full of ****.






........ Phil

[Prune]

LOL Phil, try as you might, you can't **** me off. Lamers like you are
a dime a dozen.


"Phil Allison" wrote in news:4i8pcsF2m4pkU1
@individual.net:


"Prune" = a consummate IDIOT.


You know - for someone who uses the idiotic handle "prune", he has
not
eaten too many.

Or he would not be so brim full of ****.






....... Phil

[Phil Allison]

"Prune" = a consummate, audiophool IDIOT.


You know - for someone using the idiotic handle of "prune", he has never
eaten many.

Or he would not be soooooo Full of ****.


BTW:

Funny how " tubes " are such powerful ****wit magnets .






........ Phil

[zack]

never seen a 6PW7, full name for this vave
6PHIL******7 made by phil

"Phil Allison" wrote in message
...

"Prune" = a consummate, audiophool IDIOT.


You know - for someone using the idiotic handle of "prune", he has never
eaten many.

Or he would not be soooooo Full of ****.


BTW:

Funny how " tubes " are such powerful ****wit magnets .






....... Phil

[[email protected]]

Andre Jute wrote:
In the sixth post in this thread, Tim who writes in as shoppa, said,

"Generically lifting the ground of a scope is indeed a Bad Thing."

I wrote a note telling Tim he should have stopped there, and begging
everyone not to confuse the issue for newbies. I trashed it because I
knew that the usual RAT scum piling in would do more harm than good.

The issue with HT on a public forum is never what experts can or cannot
do

Assuming HT = High Tension:

What's ironic is that the original poster's ACTUAL problem had to do
with low voltage (3.15VAC to ground, as in a center-tapped filament
winding) and high current. Well, probably less than 10 amps nominal,
but with a short he may have been drawing 40 or 50 or more amps.

If the OP had grounded out the B+ supply, he would've had some bright
sparks and noise but NOT the silent melting and damage of the ground
wiring in his probe, in his scope, in the cord from the scope to the
wall, and in the ground wiring in his house's electrical system.

Tim.

[Phil Allison]

What's ironic is that the original poster's ACTUAL problem had to do
with low voltage ...


** The OP's problem was answered and gone long ago - you ****ing half-wit.

Go shove your BAD ADVICE where the sun don't shine !!!!

Go shove Andre Schmeets up there too.

I guarantee your ASS HOLE is big enough.




...... . Phil

[[email protected]]

Phil Allison wrote:

What's ironic is that the original poster's ACTUAL problem had to do
with low voltage ...


** The OP's problem was answered and gone long ago - you ****ing half-wit.

Go shove your BAD ADVICE where the sun don't shine !!!!

Go shove Andre Schmeets up there too.

I guarantee your ASS HOLE is big enough.

Phil,

While my anatomy is well-addressed in your reply, you seem to have
neglected my last name and racial heritage recently. I have high
expectations. Don't let me down!

Tim.

[Andre]

Andre Jute wrote:
Sander deWaal wrote:

Andre said:


The issue with HT on a public forum is never what experts can or cannot
do, but what a total innocent *must* do with his first DVM or scope, or
even his wirecutters

Let me explain my original thought:
Imagine measuring with a DVM... two leads, nothing else.
The ground of the DVM becomes the potential you connect it to.
But the DVM is isolated, double isolated.

When measuring with a scope the same principle would be ideal.
There are DVM/scope instruments, battery powered, isolated.
The real-world scope is mains-powered and not isolated.

The amplifier or whatever to be measured is connected to mains
as it should be, with ground.

Meanwhile I accidentally or intended touched the chassis of the amp...
It is grounded.

and here comes the tricky part, i admit.

and assume that the circuit 0 is tied to this chassis and go measuring
with the ground-wire of the probe tied to the 0 / ground / chassis
of the amp.

As long as I can rely on the scope not giving a failure of its own
I am safe.

When one ties the scope-probe-ground-wire to a mains-wire or +Ub
it is obvious he's asking for trouble.

Now could this be a startingpoint for a discussion.



I've had no problem with Andre Smeets, in fact he seems a good guy.

Indeed I try to be a good guy. Did send my apologies to the OP
for my postings might have been confusing to him.

Andre Schmeets