Very high value resistors

"Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message
news:O96dnZ1TzpCi44_KnZ2dnUU7-IOdnZ2d@supernews.com...
On 04/16/2016 01:58 PM, Ian Field wrote:


"Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message
news:BcKdnVwN7oaO-ozKnZ2dnUU7-VGdnZ2d@supernews.com...
On 04/15/2016 04:43 PM, John Larkin wrote:
On Fri, 15 Apr 2016 21:27:47 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message
news:vjb0hbthji9jggq9v0sara39g976gbejl6@4ax.com...
On Thu, 14 Apr 2016 21:11:35 -0000 (UTC), Cursitor Doom
curd@notformail.com> wrote:

On Wed, 13 Apr 2016 11:14:03 -0700, John Larkin wrote:

When I was a kid, we could buy anything at a chemical supply store,
including crystalline iodine and pure ammonia. They knew what we
would
do with it.

I bought a big jug of nitrobenzine and made a Kerr cell. Might have
killed myself.

Yup, been there; done that. I made most of the naughty stuff
beginning
with "nitro-" by the time I was 15. Surprised I'm still here. But
that
was what boys of that age did back then and it wasn't the least bit
frowned upon.

We found a shopping bag full of shotgun shells in an abandoned house.
A basically unlimited supply of black powder. Fun summer!

And a local sign company used to give away used neon sign
transformers. I had a double-insulator 15KV one that I could barely
lift.

Pah - all the big kids are playing with surplus pole-pig transformers.

Big kids with pickup trucks?



Nah, pole pigs are 1600V->240V. Running one backwards from domestic
mains here would only get you 800V. Neon sign transformers are _way_
more fun.

Of course, if you're running your California Kilowatt rig, maybe. ;)

Cheers

Phil Hobbs

AFAICR: the UK buried cables go up to 33kV for light to medium industry
and 11kV for the small businesses and domestic substations.

But those aren't pole pigs. Substation gear is of another order.


But you'd need something bigger than a pickup + winch.

Rural is a little different, high enough voltage for overhead cables are
provided for farms and villages. We have pole transformers, but very
rarely in towns.

Lots are generally larger in towns here, so you can't really run 240V all
the way from the substation. In my neighbourhood the lots are about 1/2
acre, which is not at all unusual.

My town has a huge transformer direct off the 400kV pylons. The substations
are dotted around all over town, typically about the same footprint as an
old style phone box but not as tall, often 2 to an enclosure. around the
industrial estates they can be about the size of a van. The rural ones range
from not much bigger than a suitcase to pretty big, depending what they
serve. Some farms have a full on substation if they have a lot of grain
handling machinery.
 
On 04/16/2016 03:09 PM, Ian Field wrote:
"Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message
news:O96dnZ1TzpCi44_KnZ2dnUU7-IOdnZ2d@supernews.com...
On 04/16/2016 01:58 PM, Ian Field wrote:


"Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message
news:BcKdnVwN7oaO-ozKnZ2dnUU7-VGdnZ2d@supernews.com...
On 04/15/2016 04:43 PM, John Larkin wrote:
On Fri, 15 Apr 2016 21:27:47 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message
news:vjb0hbthji9jggq9v0sara39g976gbejl6@4ax.com...
On Thu, 14 Apr 2016 21:11:35 -0000 (UTC), Cursitor Doom
curd@notformail.com> wrote:

On Wed, 13 Apr 2016 11:14:03 -0700, John Larkin wrote:

When I was a kid, we could buy anything at a chemical supply
store,
including crystalline iodine and pure ammonia. They knew what we
would
do with it.

I bought a big jug of nitrobenzine and made a Kerr cell. Might
have
killed myself.

Yup, been there; done that. I made most of the naughty stuff
beginning
with "nitro-" by the time I was 15. Surprised I'm still here. But
that
was what boys of that age did back then and it wasn't the least bit
frowned upon.

We found a shopping bag full of shotgun shells in an abandoned
house.
A basically unlimited supply of black powder. Fun summer!

And a local sign company used to give away used neon sign
transformers. I had a double-insulator 15KV one that I could barely
lift.

Pah - all the big kids are playing with surplus pole-pig
transformers.

Big kids with pickup trucks?



Nah, pole pigs are 1600V->240V. Running one backwards from domestic
mains here would only get you 800V. Neon sign transformers are _way_
more fun.

Of course, if you're running your California Kilowatt rig, maybe. ;)

Cheers

Phil Hobbs

AFAICR: the UK buried cables go up to 33kV for light to medium industry
and 11kV for the small businesses and domestic substations.

But those aren't pole pigs. Substation gear is of another order.


But you'd need something bigger than a pickup + winch.

Rural is a little different, high enough voltage for overhead cables are
provided for farms and villages. We have pole transformers, but very
rarely in towns.

Lots are generally larger in towns here, so you can't really run 240V
all the way from the substation. In my neighbourhood the lots are
about 1/2 acre, which is not at all unusual.

My town has a huge transformer direct off the 400kV pylons. The
substations are dotted around all over town, typically about the same
footprint as an old style phone box but not as tall, often 2 to an
enclosure. around the industrial estates they can be about the size of a
van. The rural ones range from not much bigger than a suitcase to pretty
big, depending what they serve. Some farms have a full on substation if
they have a lot of grain handling machinery.

Your nomenclature is a bit different. Round here a substation is
something at least 100 feet square, with a serious fence around it to
discourage the stupid or suicidal.

Do they really have 11 kV -> 240V transformers randomly out in the field
with no fence?

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net
 
"Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message
news:RPKdnY0kYtL8Oo_KnZ2dnUU7-f2dnZ2d@supernews.com...
On 04/16/2016 03:09 PM, Ian Field wrote:


"Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message
news:O96dnZ1TzpCi44_KnZ2dnUU7-IOdnZ2d@supernews.com...
On 04/16/2016 01:58 PM, Ian Field wrote:


"Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message
news:BcKdnVwN7oaO-ozKnZ2dnUU7-VGdnZ2d@supernews.com...
On 04/15/2016 04:43 PM, John Larkin wrote:
On Fri, 15 Apr 2016 21:27:47 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message
news:vjb0hbthji9jggq9v0sara39g976gbejl6@4ax.com...
On Thu, 14 Apr 2016 21:11:35 -0000 (UTC), Cursitor Doom
curd@notformail.com> wrote:

On Wed, 13 Apr 2016 11:14:03 -0700, John Larkin wrote:

When I was a kid, we could buy anything at a chemical supply
store,
including crystalline iodine and pure ammonia. They knew what we
would
do with it.

I bought a big jug of nitrobenzine and made a Kerr cell. Might
have
killed myself.

Yup, been there; done that. I made most of the naughty stuff
beginning
with "nitro-" by the time I was 15. Surprised I'm still here. But
that
was what boys of that age did back then and it wasn't the least
bit
frowned upon.

We found a shopping bag full of shotgun shells in an abandoned
house.
A basically unlimited supply of black powder. Fun summer!

And a local sign company used to give away used neon sign
transformers. I had a double-insulator 15KV one that I could barely
lift.

Pah - all the big kids are playing with surplus pole-pig
transformers.

Big kids with pickup trucks?



Nah, pole pigs are 1600V->240V. Running one backwards from domestic
mains here would only get you 800V. Neon sign transformers are _way_
more fun.

Of course, if you're running your California Kilowatt rig, maybe. ;)

Cheers

Phil Hobbs

AFAICR: the UK buried cables go up to 33kV for light to medium industry
and 11kV for the small businesses and domestic substations.

But those aren't pole pigs. Substation gear is of another order.


But you'd need something bigger than a pickup + winch.

Rural is a little different, high enough voltage for overhead cables
are
provided for farms and villages. We have pole transformers, but very
rarely in towns.

Lots are generally larger in towns here, so you can't really run 240V
all the way from the substation. In my neighbourhood the lots are
about 1/2 acre, which is not at all unusual.

My town has a huge transformer direct off the 400kV pylons. The
substations are dotted around all over town, typically about the same
footprint as an old style phone box but not as tall, often 2 to an
enclosure. around the industrial estates they can be about the size of a
van. The rural ones range from not much bigger than a suitcase to pretty
big, depending what they serve. Some farms have a full on substation if
they have a lot of grain handling machinery.

Your nomenclature is a bit different. Round here a substation is
something at least 100 feet square, with a serious fence around it to
discourage the stupid or suicidal.

Do they really have 11 kV -> 240V transformers randomly out in the field
with no fence?

Only pole transformers may not necessarily have a fence. They're mostly in
sparsely populated areas.

A fair bit of industry takes 11kV from underground cables, a few heavier
industries take 33kV, Foundries with blast furnaces take too high voltage
for buried cables - probably 275kV. Around town distribution is probably
less than 11kV, but I don't know the figures. The lower the distribution
voltage - the more they have to spend on copper.
 
Phil Hobbs wrote:
On 04/04/2016 12:08 PM, John Larkin wrote:

Water-wash flux is evil. It can leave hygroscopic crud on and under
parts.

Sure is. So is garden-variety IPA solvent. In high-Z circuits, I
usually used guard traces top and bottom (with the solder mask
removed) and a slot under the photodiode and the feedback resistor
(and cap, if any). Being able to get solvent under the components
helps a lot with the 1/f noise and stability.

The popcorn noise you get from a board washed with drugstore IPA has
to be seen to be believed.

What about ethyl?
 
On Sunday, April 24, 2016 at 11:20:49 AM UTC-7, Tom Del Rosso wrote:
Phil Hobbs wrote:

The popcorn noise you get from a board washed with drugstore IPA has
to be seen to be believed.

What about ethyl?

Good with orange juice. Replace the stock with some drugstore IPA....
 
On Monday, April 25, 2016 at 10:04:59 AM UTC-4, Phil Hobbs wrote:
On 04/25/2016 08:05 AM, Bob Masta wrote:
On Sun, 24 Apr 2016 17:11:17 -0700 (PDT), whit3rd
whit3rd@gmail.com> wrote:

On Sunday, April 24, 2016 at 11:20:49 AM UTC-7, Tom Del Rosso wrote:
Phil Hobbs wrote:

The popcorn noise you get from a board washed with drugstore IPA has
to be seen to be believed.

What about ethyl?

Good with orange juice. Replace the stock with some drugstore IPA....

Then of course there is the IPA that already has ethyl
alcohol in it. It's in the drugstore, but it's over in the
Beer and Wine department... under India Pale Ale. I don't
suppose it's very good with orange juice, however. <g

If you go light on the OJ, the IPA makes a good chaser. ;)

Or a Shandy... (Something my wife might do.)

George H.
Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net
 
whit3rd wrote:
On Sunday, April 24, 2016 at 11:20:49 AM UTC-7, Tom Del Rosso wrote:
Phil Hobbs wrote:

The popcorn noise you get from a board washed with drugstore IPA has
to be seen to be believed.

What about ethyl?

Good with orange juice. Replace the stock with some drugstore
IPA....

My drugstore has both. What's it for? If IPA has water and maybe
mineral oil in it I wonder what's in the ethyl. I doubt it's pure.
 
On Sun, 24 Apr 2016 17:11:17 -0700 (PDT), whit3rd
<whit3rd@gmail.com> wrote:

On Sunday, April 24, 2016 at 11:20:49 AM UTC-7, Tom Del Rosso wrote:
Phil Hobbs wrote:

The popcorn noise you get from a board washed with drugstore IPA has
to be seen to be believed.

What about ethyl?

Good with orange juice. Replace the stock with some drugstore IPA....

Then of course there is the IPA that already has ethyl
alcohol in it. It's in the drugstore, but it's over in the
Beer and Wine department... under India Pale Ale. I don't
suppose it's very good with orange juice, however. <g>


Bob Masta

DAQARTA v9.20
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, Pitch Track, Pitch-to-MIDI
FREE 8-channel Signal Generator, DaqMusiq generator
Science with your sound card!
 
On 04/25/2016 07:17 AM, Tom Del Rosso wrote:
whit3rd wrote:
On Sunday, April 24, 2016 at 11:20:49 AM UTC-7, Tom Del Rosso wrote:
Phil Hobbs wrote:

The popcorn noise you get from a board washed with drugstore IPA has
to be seen to be believed.

What about ethyl?

Good with orange juice. Replace the stock with some drugstore
IPA....

My drugstore has both. What's it for? If IPA has water and maybe
mineral oil in it I wonder what's in the ethyl. I doubt it's pure.

Since I'm usually only stuffing and testing one or two of each board, I
just use the same solvent I use for optics: HPLC-grade methanol. (Or at
least it was HPLC grade before I put it in a Nalgene wash bottle.) ;)

That and a toothbrush seem to work fine, as long as there are slots
under the super-high-Z parts, and guard traces sprinkled appropriately
(with the solder mask removed, of course).

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net
 
On 04/25/2016 08:05 AM, Bob Masta wrote:
On Sun, 24 Apr 2016 17:11:17 -0700 (PDT), whit3rd
whit3rd@gmail.com> wrote:

On Sunday, April 24, 2016 at 11:20:49 AM UTC-7, Tom Del Rosso wrote:
Phil Hobbs wrote:

The popcorn noise you get from a board washed with drugstore IPA has
to be seen to be believed.

What about ethyl?

Good with orange juice. Replace the stock with some drugstore IPA....

Then of course there is the IPA that already has ethyl
alcohol in it. It's in the drugstore, but it's over in the
Beer and Wine department... under India Pale Ale. I don't
suppose it's very good with orange juice, however. <g

If you go light on the OJ, the IPA makes a good chaser. ;)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net
 
On 04/25/2016 10:18 AM, George Herold wrote:
On Monday, April 25, 2016 at 10:04:59 AM UTC-4, Phil Hobbs wrote:
On 04/25/2016 08:05 AM, Bob Masta wrote:
On Sun, 24 Apr 2016 17:11:17 -0700 (PDT), whit3rd
whit3rd@gmail.com> wrote:

On Sunday, April 24, 2016 at 11:20:49 AM UTC-7, Tom Del Rosso wrote:
Phil Hobbs wrote:

The popcorn noise you get from a board washed with drugstore IPA has
to be seen to be believed.

What about ethyl?

Good with orange juice. Replace the stock with some drugstore IPA....

Then of course there is the IPA that already has ethyl
alcohol in it. It's in the drugstore, but it's over in the
Beer and Wine department... under India Pale Ale. I don't
suppose it's very good with orange juice, however. <g

If you go light on the OJ, the IPA makes a good chaser. ;)

Or a Shandy... (Something my wife might do.)

George H.

John Stuart Mill / Of his own free will / on half a pint of shandy/ was
particularly ill/ ....

Cheers

Phil "Not as fond of his dram as Thomas" Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net
 
On Monday, April 25, 2016 at 7:04:09 AM UTC-7, Phil Hobbs wrote:

Since I'm usually only stuffing and testing one or two of each board, I
just use the same solvent I use for optics: HPLC-grade methanol. (Or at
least it was HPLC grade before I put it in a Nalgene wash bottle.) ;)

I recall little humming dehumidifiers in the basement of Physics Hall,
where the astronomers were redistilling their alcohol by evaporating from
a pan (below boiling temperature) and wafting the vapor over cold coils to
condense. Their concern was with cost, of course. No ethanol involved.
No tax issues, either. Honest.

If you heat to boiling, the bubbles burst and create droplets of impure solvent, which
gets into the output. So, they didn't do that.
 
On Tuesday, April 26, 2016 at 11:39:24 AM UTC-4, Phil Hobbs wrote:
On 04/25/2016 05:11 PM, whit3rd wrote:
On Monday, April 25, 2016 at 7:04:09 AM UTC-7, Phil Hobbs wrote:

Since I'm usually only stuffing and testing one or two of each board, I
just use the same solvent I use for optics: HPLC-grade methanol. (Or at
least it was HPLC grade before I put it in a Nalgene wash bottle.) ;)

I recall little humming dehumidifiers in the basement of Physics Hall,
where the astronomers were redistilling their alcohol by evaporating from
a pan (below boiling temperature) and wafting the vapor over cold coils to
condense. Their concern was with cost, of course. No ethanol involved.
No tax issues, either. Honest.

Cleaning up denatured ethanol is a pain, and so not worthwhile when
Polmos is $17/litre retail.
Why is denatured alcohol a pain to clean up?
(are you worried about absorbing the methanol?)

So you Polmos, to clean your circuit boards?

George H.

(My liqueur-making spies tell me that
Polmost rectified spirit is much better than Everclear. I've never done
an A/B test myself.) ;)

If you heat to boiling, the bubbles burst and create droplets of impure solvent, which
gets into the output. So, they didn't do that.

Smart, if you have the time available. The other approach is to run the
vapour through a sufficiently fine filter. Ultrafilters down to 15 nm
pore size are readily available.

Interestingly, those ones are made by solvent-casting polyethersulphone
with a little water in the mix. It forms a foam whose pore size is a
very predictable function of the water content, and the matrix is pretty
inert, at least to polar solvents.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net
 
On 04/25/2016 05:11 PM, whit3rd wrote:
On Monday, April 25, 2016 at 7:04:09 AM UTC-7, Phil Hobbs wrote:

Since I'm usually only stuffing and testing one or two of each board, I
just use the same solvent I use for optics: HPLC-grade methanol. (Or at
least it was HPLC grade before I put it in a Nalgene wash bottle.) ;)

I recall little humming dehumidifiers in the basement of Physics Hall,
where the astronomers were redistilling their alcohol by evaporating from
a pan (below boiling temperature) and wafting the vapor over cold coils to
condense. Their concern was with cost, of course. No ethanol involved.
No tax issues, either. Honest.

Cleaning up denatured ethanol is a pain, and so not worthwhile when
Polmos is $17/litre retail. (My liqueur-making spies tell me that
Polmost rectified spirit is much better than Everclear. I've never done
an A/B test myself.) ;)
If you heat to boiling, the bubbles burst and create droplets of impure solvent, which
gets into the output. So, they didn't do that.

Smart, if you have the time available. The other approach is to run the
vapour through a sufficiently fine filter. Ultrafilters down to 15 nm
pore size are readily available.

Interestingly, those ones are made by solvent-casting polyethersulphone
with a little water in the mix. It forms a foam whose pore size is a
very predictable function of the water content, and the matrix is pretty
inert, at least to polar solvents.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net
 
On 04/26/2016 01:27 PM, George Herold wrote:
On Tuesday, April 26, 2016 at 11:39:24 AM UTC-4, Phil Hobbs wrote:
On 04/25/2016 05:11 PM, whit3rd wrote:
On Monday, April 25, 2016 at 7:04:09 AM UTC-7, Phil Hobbs wrote:

Since I'm usually only stuffing and testing one or two of each board, I
just use the same solvent I use for optics: HPLC-grade methanol. (Or at
least it was HPLC grade before I put it in a Nalgene wash bottle.) ;)

I recall little humming dehumidifiers in the basement of Physics Hall,
where the astronomers were redistilling their alcohol by evaporating from
a pan (below boiling temperature) and wafting the vapor over cold coils to
condense. Their concern was with cost, of course. No ethanol involved.
No tax issues, either. Honest.

Cleaning up denatured ethanol is a pain, and so not worthwhile when
Polmos is $17/litre retail.
Why is denatured alcohol a pain to clean up?
(are you worried about absorbing the methanol?)

"Clean up" as in "distill into pure ethanol". I was alluding to W's
reference to tax and ethanol.

So you Polmos, to clean your circuit boards?

Nope, 99.9+% methanol, about $60 for a 4-litre jug from Fisher
Scientific. I'd be quite unlikely to use anything with much water in
it, and I'm sure not using anything remotely resembling aqueous ammonia.

But all my boards are Sn63 with rosin flux. ("No clean" flux in leaded
solder paste is good old RMA.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net
 
On Tuesday, April 26, 2016 at 11:06:35 AM UTC-7, Phil Hobbs wrote:

On Monday, April 25, 2016 at 7:04:09 AM UTC-7, Phil Hobbs wrote:

Since I'm usually only stuffing and testing one or two of each board, I
just use the same solvent I use for optics: HPLC-grade methanol.

... I'd be quite unlikely to use anything with much water in
it, and I'm sure not using anything remotely resembling aqueous ammonia.

But all my boards are Sn63 with rosin flux.

If there's anything ionic to be removed, distilled water or water/alcohol azeotrope
(i.e. don't take water-removal steps on the solvent) should work better than
anhydrous solvent. The removal mechanism, diffusion, scales with square root
of time, so a wash ten times more effective than a ten-second rinse, takes a quarter
hour. Maybe that's why water-soluble flux (which is ionic) is antipreferred.
 

Welcome to EDABoard.com

Sponsor

Back
Top