Very high value resistors

[Ralph Mowery]

"George Herold" <gherold@teachspin.com> wrote in message
news:c5739a9f-a5a0-49a4-a648-3af0d6749356@googlegroups.com...

On Monday, April 11, 2016 at 5:18:59 PM UTC-4, Ian Field wrote:

Exotic chemicals and solvents are hard to come by in the UK - car spay
paint
thinners is less difficult to obtain.

It shifts rosin flux very well, but is destructive to some components.

Acetone is considered exotic? Here (in the US) we can walk into any
hardware
store and buy Acetone/ alcohols/ other stuff.

Many women use Acetone every day. It is often used to clean the nail polish
off.
I just bought some in a can at Walmart in the paint department, a store that
sells most everything including food.

 

[Phil Hobbs]

On 04/12/2016 10:29 AM, Ralph Mowery wrote:

"George Herold" <gherold@teachspin.com> wrote in message
news:c5739a9f-a5a0-49a4-a648-3af0d6749356@googlegroups.com...
On Monday, April 11, 2016 at 5:18:59 PM UTC-4, Ian Field wrote:

Exotic chemicals and solvents are hard to come by in the UK - car spay
paint
thinners is less difficult to obtain.

It shifts rosin flux very well, but is destructive to some components.

Acetone is considered exotic? Here (in the US) we can walk into any
hardware
store and buy Acetone/ alcohols/ other stuff.


Many women use Acetone every day. It is often used to clean the nail polish
off.
I just bought some in a can at Walmart in the paint department, a store that
sells most everything including food.

Nail polish remover is usually ethyl acetate nowadays, IIRC. They're
easy to distinguish by the smell.

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

 

[Ralph Mowery]

"Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message
news:570D1702.8050608@electrooptical.net...

Many women use Acetone every day. It is often used to clean the nail
polish
off.
I just bought some in a can at Walmart in the paint department, a store
that
sells most everything including food.


Nail polish remover is usually ethyl acetate nowadays, IIRC. They're
easy to distinguish by the smell.

I do have to admitt it has been a while from the last time I colored my
nails

They probably did change the the chemical, almost everything else that works
well has been changed.

 

[Phil Hobbs]

On 04/12/2016 10:13 AM, George Herold wrote:

On Monday, April 11, 2016 at 5:18:59 PM UTC-4, Ian Field wrote:
"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message
news:ug4ogbtiemmd4h6707o11n6ke2ekaa3j0l@4ax.com...
On Fri, 8 Apr 2016 22:21:54 +0000 (UTC), Cydrome Leader
presence@MUNGEpanix.com> wrote:

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
On 04/04/2016 12:08 PM, John Larkin wrote:
On Mon, 04 Apr 2016 13:05:43 GMT, N0Spam@daqarta.com (Bob Masta)
wrote:

On Sun, 03 Apr 2016 16:10:38 -0700, John Larkin
jjlarkin@highlandtechnology.com> wrote:

On Sun, 3 Apr 2016 20:07:14 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"Chris" <cbx@noreply.com> wrote in message
news:ndrgbj$tt0$6@dont-email.me...
It seems there are resistors around in the range of 50Gohm! Having
never
encountered anything beyond 10M., I never imagined there could be
such a
stratospheric value but apparently there is:

There's a small stash of 100M resistors in my collection.

For anything in the G Ohm range - you should probably check the
leakage
resistance of whatever PCB/substrate you're mounting it on.

At the very least, you'll need guard slots cut in any PCB around the
termination points.

Here's a small PCB deliberately glopped with rosin flux and
fingerprints.

https://dl.dropboxusercontent.com/u/53724080/Gear/Keithley/Leak_Gloppy_Flux.JPG

https://dl.dropboxusercontent.com/u/53724080/Gear/Keithley/Leak_Test.JPG


It's pinning the needle on the 1e14 ohm range.

1G is easy. Just don't use water soluble flux, or if you do, clean it
really good.

Been a long time since I used anything in the 100 Meg range
or above, but I recall that there were a lot of recommended
precautions. One was to clean the glass body very carefully
(with alcohol, I think) to remove fingerprints which would
otherwise trap dust, which would then allow humidity to
cause a low-resistance shunt. You also want the body to be
elevated above the board surface for the same reason. I
also seem to recall something about teflon
mounts/feedthroughs at the lead ends, but I can't recall
exactly what that was supposed to do.


Sounds like urban myths. 100M is regular PC board turf, axial or
surface-mount parts. Fingerprints seem to have no effect in 1G ohm
circuits.

Glass resistors are overkill in the low Gohm range.

High voltage breakdown is another matter. Fingerprints and dust can
reduce breakover voltages, in the many-kilovolt domain.

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.

I'd believe it. The drugstore stuff I've used (lots of it over the years)
seems to have denaturing agents added or some other alcohols even though
it's not needed.

Optical cleaning grade IPA doesn't seem to have the other "stuff" in it.

On my bench, if I'm too lazy to take a board downstairs to the solvent
cleaner machine, I use acetone. Cleans rosin flux nicely.

Exotic chemicals and solvents are hard to come by in the UK - car spay paint
thinners is less difficult to obtain.

It shifts rosin flux very well, but is destructive to some components.

Acetone is considered exotic? Here (in the US) we can walk into any hardware
store and buy Acetone/ alcohols/ other stuff.

George H.

In the UK there's an apparently-serious effort to ban kitchen knives.
Obviously they believe they're too stupid to be trusted with 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

 

[John Larkin]

On Tue, 12 Apr 2016 07:13:39 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

On Monday, April 11, 2016 at 5:18:59 PM UTC-4, Ian Field wrote:
"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message
news:ug4ogbtiemmd4h6707o11n6ke2ekaa3j0l@4ax.com...
On Fri, 8 Apr 2016 22:21:54 +0000 (UTC), Cydrome Leader
presence@MUNGEpanix.com> wrote:

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
On 04/04/2016 12:08 PM, John Larkin wrote:
On Mon, 04 Apr 2016 13:05:43 GMT, N0Spam@daqarta.com (Bob Masta)
wrote:

On Sun, 03 Apr 2016 16:10:38 -0700, John Larkin
jjlarkin@highlandtechnology.com> wrote:

On Sun, 3 Apr 2016 20:07:14 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"Chris" <cbx@noreply.com> wrote in message
news:ndrgbj$tt0$6@dont-email.me...
It seems there are resistors around in the range of 50Gohm! Having
never
encountered anything beyond 10M., I never imagined there could be
such a
stratospheric value but apparently there is:

There's a small stash of 100M resistors in my collection.

For anything in the G Ohm range - you should probably check the
leakage
resistance of whatever PCB/substrate you're mounting it on.

At the very least, you'll need guard slots cut in any PCB around the
termination points.

Here's a small PCB deliberately glopped with rosin flux and
fingerprints.

https://dl.dropboxusercontent.com/u/53724080/Gear/Keithley/Leak_Gloppy_Flux.JPG

https://dl.dropboxusercontent.com/u/53724080/Gear/Keithley/Leak_Test.JPG


It's pinning the needle on the 1e14 ohm range.

1G is easy. Just don't use water soluble flux, or if you do, clean it
really good.

Been a long time since I used anything in the 100 Meg range
or above, but I recall that there were a lot of recommended
precautions. One was to clean the glass body very carefully
(with alcohol, I think) to remove fingerprints which would
otherwise trap dust, which would then allow humidity to
cause a low-resistance shunt. You also want the body to be
elevated above the board surface for the same reason. I
also seem to recall something about teflon
mounts/feedthroughs at the lead ends, but I can't recall
exactly what that was supposed to do.


Sounds like urban myths. 100M is regular PC board turf, axial or
surface-mount parts. Fingerprints seem to have no effect in 1G ohm
circuits.

Glass resistors are overkill in the low Gohm range.

High voltage breakdown is another matter. Fingerprints and dust can
reduce breakover voltages, in the many-kilovolt domain.

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.

I'd believe it. The drugstore stuff I've used (lots of it over the years)
seems to have denaturing agents added or some other alcohols even though
it's not needed.

Optical cleaning grade IPA doesn't seem to have the other "stuff" in it.

On my bench, if I'm too lazy to take a board downstairs to the solvent
cleaner machine, I use acetone. Cleans rosin flux nicely.

Exotic chemicals and solvents are hard to come by in the UK - car spay paint
thinners is less difficult to obtain.

It shifts rosin flux very well, but is destructive to some components.

Acetone is considered exotic? Here (in the US) we can walk into any hardware
store and buy Acetone/ alcohols/ other stuff.

George H.

Acetone is one of the ingredients in TATP, “the mother of Satan”.

We can get it by the gallon in most any hardware store.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

On Tue, 12 Apr 2016 13:11:14 -0700, John Larkin
<jjlarkin@highlandtechnology.com> wrote:

On Tue, 12 Apr 2016 07:13:39 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Monday, April 11, 2016 at 5:18:59 PM UTC-4, Ian Field wrote:
"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message
news:ug4ogbtiemmd4h6707o11n6ke2ekaa3j0l@4ax.com...
On Fri, 8 Apr 2016 22:21:54 +0000 (UTC), Cydrome Leader
presence@MUNGEpanix.com> wrote:

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
On 04/04/2016 12:08 PM, John Larkin wrote:
On Mon, 04 Apr 2016 13:05:43 GMT, N0Spam@daqarta.com (Bob Masta)
wrote:

On Sun, 03 Apr 2016 16:10:38 -0700, John Larkin
jjlarkin@highlandtechnology.com> wrote:

On Sun, 3 Apr 2016 20:07:14 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"Chris" <cbx@noreply.com> wrote in message
news:ndrgbj$tt0$6@dont-email.me...
It seems there are resistors around in the range of 50Gohm! Having
never
encountered anything beyond 10M., I never imagined there could be
such a
stratospheric value but apparently there is:

There's a small stash of 100M resistors in my collection.

For anything in the G Ohm range - you should probably check the
leakage
resistance of whatever PCB/substrate you're mounting it on.

At the very least, you'll need guard slots cut in any PCB around the
termination points.

Here's a small PCB deliberately glopped with rosin flux and
fingerprints.

https://dl.dropboxusercontent.com/u/53724080/Gear/Keithley/Leak_Gloppy_Flux.JPG

https://dl.dropboxusercontent.com/u/53724080/Gear/Keithley/Leak_Test.JPG


It's pinning the needle on the 1e14 ohm range.

1G is easy. Just don't use water soluble flux, or if you do, clean it
really good.

Been a long time since I used anything in the 100 Meg range
or above, but I recall that there were a lot of recommended
precautions. One was to clean the glass body very carefully
(with alcohol, I think) to remove fingerprints which would
otherwise trap dust, which would then allow humidity to
cause a low-resistance shunt. You also want the body to be
elevated above the board surface for the same reason. I
also seem to recall something about teflon
mounts/feedthroughs at the lead ends, but I can't recall
exactly what that was supposed to do.


Sounds like urban myths. 100M is regular PC board turf, axial or
surface-mount parts. Fingerprints seem to have no effect in 1G ohm
circuits.

Glass resistors are overkill in the low Gohm range.

High voltage breakdown is another matter. Fingerprints and dust can
reduce breakover voltages, in the many-kilovolt domain.

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.

I'd believe it. The drugstore stuff I've used (lots of it over the years)
seems to have denaturing agents added or some other alcohols even though
it's not needed.

Optical cleaning grade IPA doesn't seem to have the other "stuff" in it.

On my bench, if I'm too lazy to take a board downstairs to the solvent
cleaner machine, I use acetone. Cleans rosin flux nicely.

Exotic chemicals and solvents are hard to come by in the UK - car spay paint
thinners is less difficult to obtain.

It shifts rosin flux very well, but is destructive to some components.

Acetone is considered exotic? Here (in the US) we can walk into any hardware
store and buy Acetone/ alcohols/ other stuff.

George H.

Acetone is one of the ingredients in TATP, “the mother of Satan”.

We can get it by the gallon in most any hardware store.

I had heard that TATP is fairly easy to make and hard to detect (at
least with conventional sniffers) because it is not a nitrogen based
explosive. So I looked it up and found it is pretty easy to make. No
free lunch though. As easy as it is to make it is even easier for it
to explode. Good thing too. I hope lots of it explodes in the faces of
those who would use it to hurt or kill people.
Eric

 

[Ian Field]

"George Herold" <gherold@teachspin.com> wrote in message
news:c5739a9f-a5a0-49a4-a648-3af0d6749356@googlegroups.com...

On Monday, April 11, 2016 at 5:18:59 PM UTC-4, Ian Field wrote:
"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message
news:ug4ogbtiemmd4h6707o11n6ke2ekaa3j0l@4ax.com...
On Fri, 8 Apr 2016 22:21:54 +0000 (UTC), Cydrome Leader
presence@MUNGEpanix.com> wrote:

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
On 04/04/2016 12:08 PM, John Larkin wrote:
On Mon, 04 Apr 2016 13:05:43 GMT, N0Spam@daqarta.com (Bob Masta)
wrote:

On Sun, 03 Apr 2016 16:10:38 -0700, John Larkin
jjlarkin@highlandtechnology.com> wrote:

On Sun, 3 Apr 2016 20:07:14 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"Chris" <cbx@noreply.com> wrote in message
news:ndrgbj$tt0$6@dont-email.me...
It seems there are resistors around in the range of 50Gohm!
Having
never
encountered anything beyond 10M., I never imagined there could
be
such a
stratospheric value but apparently there is:

There's a small stash of 100M resistors in my collection.

For anything in the G Ohm range - you should probably check the
leakage
resistance of whatever PCB/substrate you're mounting it on.

At the very least, you'll need guard slots cut in any PCB around
the
termination points.

Here's a small PCB deliberately glopped with rosin flux and
fingerprints.

https://dl.dropboxusercontent.com/u/53724080/Gear/Keithley/Leak_Gloppy_Flux.JPG

https://dl.dropboxusercontent.com/u/53724080/Gear/Keithley/Leak_Test.JPG


It's pinning the needle on the 1e14 ohm range.

1G is easy. Just don't use water soluble flux, or if you do, clean
it
really good.

Been a long time since I used anything in the 100 Meg range
or above, but I recall that there were a lot of recommended
precautions. One was to clean the glass body very carefully
(with alcohol, I think) to remove fingerprints which would
otherwise trap dust, which would then allow humidity to
cause a low-resistance shunt. You also want the body to be
elevated above the board surface for the same reason. I
also seem to recall something about teflon
mounts/feedthroughs at the lead ends, but I can't recall
exactly what that was supposed to do.


Sounds like urban myths. 100M is regular PC board turf, axial or
surface-mount parts. Fingerprints seem to have no effect in 1G ohm
circuits.

Glass resistors are overkill in the low Gohm range.

High voltage breakdown is another matter. Fingerprints and dust can
reduce breakover voltages, in the many-kilovolt domain.

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.

I'd believe it. The drugstore stuff I've used (lots of it over the
years)
seems to have denaturing agents added or some other alcohols even
though
it's not needed.

Optical cleaning grade IPA doesn't seem to have the other "stuff" in
it.

On my bench, if I'm too lazy to take a board downstairs to the solvent
cleaner machine, I use acetone. Cleans rosin flux nicely.

Exotic chemicals and solvents are hard to come by in the UK - car spay
paint
thinners is less difficult to obtain.

It shifts rosin flux very well, but is destructive to some components.

Acetone is considered exotic? Here (in the US) we can walk into any
hardware
store and buy Acetone/ alcohols/ other stuff.

They won't even let us have tincture of iodine antiseptic in case we make
our own ammonium-iodide toy snappers.

 

[Ian Field]

"Cursitor Doom" <curd@notformail.com> wrote in message
news:nej0te$l2v$2@dont-email.me...

On Tue, 12 Apr 2016 07:13:39 -0700, George Herold wrote:

Acetone is considered exotic? Here (in the US) we can walk into any
hardware store and buy Acetone/ alcohols/ other stuff.

There is still *something* very nasty that can be bought over the counter
in the UK and that is 99% pure sulphuric acid which is readily available
from plumbers merchants and DIY sheds like Homebase

A couple of years ago there was an "incident" at a block of flats - someone
had used H2SO4 as a sink unblocker, it had eaten through the pipes and run
through into the flat below. The fire service turned up complete with
hazardous materials unit.

When I tipped over my motorcycle battery, it took a fair bit of pleading
before the motorcycle shop parted with a liter of it.

 

[Ian Field]

<etpm@whidbey.com> wrote in message
news:htmqgb1ddehi54v4e9bhoe9g8r13su731k@4ax.com...

On Tue, 12 Apr 2016 13:11:14 -0700, John Larkin
jjlarkin@highlandtechnology.com> wrote:

On Tue, 12 Apr 2016 07:13:39 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Monday, April 11, 2016 at 5:18:59 PM UTC-4, Ian Field wrote:
"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message
news:ug4ogbtiemmd4h6707o11n6ke2ekaa3j0l@4ax.com...
On Fri, 8 Apr 2016 22:21:54 +0000 (UTC), Cydrome Leader
presence@MUNGEpanix.com> wrote:

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
On 04/04/2016 12:08 PM, John Larkin wrote:
On Mon, 04 Apr 2016 13:05:43 GMT, N0Spam@daqarta.com (Bob Masta)
wrote:

On Sun, 03 Apr 2016 16:10:38 -0700, John Larkin
jjlarkin@highlandtechnology.com> wrote:

On Sun, 3 Apr 2016 20:07:14 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"Chris" <cbx@noreply.com> wrote in message
news:ndrgbj$tt0$6@dont-email.me...
It seems there are resistors around in the range of 50Gohm!
Having
never
encountered anything beyond 10M., I never imagined there
could be
such a
stratospheric value but apparently there is:

There's a small stash of 100M resistors in my collection.

For anything in the G Ohm range - you should probably check the
leakage
resistance of whatever PCB/substrate you're mounting it on.

At the very least, you'll need guard slots cut in any PCB
around the
termination points.

Here's a small PCB deliberately glopped with rosin flux and
fingerprints.

https://dl.dropboxusercontent.com/u/53724080/Gear/Keithley/Leak_Gloppy_Flux.JPG

https://dl.dropboxusercontent.com/u/53724080/Gear/Keithley/Leak_Test.JPG


It's pinning the needle on the 1e14 ohm range.

1G is easy. Just don't use water soluble flux, or if you do,
clean it
really good.

Been a long time since I used anything in the 100 Meg range
or above, but I recall that there were a lot of recommended
precautions. One was to clean the glass body very carefully
(with alcohol, I think) to remove fingerprints which would
otherwise trap dust, which would then allow humidity to
cause a low-resistance shunt. You also want the body to be
elevated above the board surface for the same reason. I
also seem to recall something about teflon
mounts/feedthroughs at the lead ends, but I can't recall
exactly what that was supposed to do.


Sounds like urban myths. 100M is regular PC board turf, axial or
surface-mount parts. Fingerprints seem to have no effect in 1G ohm
circuits.

Glass resistors are overkill in the low Gohm range.

High voltage breakdown is another matter. Fingerprints and dust
can
reduce breakover voltages, in the many-kilovolt domain.

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.

I'd believe it. The drugstore stuff I've used (lots of it over the
years)
seems to have denaturing agents added or some other alcohols even
though
it's not needed.

Optical cleaning grade IPA doesn't seem to have the other "stuff" in
it.

On my bench, if I'm too lazy to take a board downstairs to the
solvent
cleaner machine, I use acetone. Cleans rosin flux nicely.

Exotic chemicals and solvents are hard to come by in the UK - car spay
paint
thinners is less difficult to obtain.

It shifts rosin flux very well, but is destructive to some components.

Acetone is considered exotic? Here (in the US) we can walk into any
hardware
store and buy Acetone/ alcohols/ other stuff.

George H.

Acetone is one of the ingredients in TATP, "the mother of Satan".

We can get it by the gallon in most any hardware store.
I had heard that TATP is fairly easy to make and hard to detect (at
least with conventional sniffers) because it is not a nitrogen based
explosive. So I looked it up and found it is pretty easy to make. No
free lunch though. As easy as it is to make it is even easier for it
to explode. Good thing too. I hope lots of it explodes in the faces of
those who would use it to hurt or kill people.

Enterprise should be encouraged - especially selling dodgy detonators to
terrorists.

 

On Tue, 12 Apr 2016 22:05:50 +0100, "Ian Field"
<gangprobing.alien@ntlworld.com> wrote:

"George Herold" <gherold@teachspin.com> wrote in message
news:c5739a9f-a5a0-49a4-a648-3af0d6749356@googlegroups.com...
On Monday, April 11, 2016 at 5:18:59 PM UTC-4, Ian Field wrote:
"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message
news:ug4ogbtiemmd4h6707o11n6ke2ekaa3j0l@4ax.com...
On Fri, 8 Apr 2016 22:21:54 +0000 (UTC), Cydrome Leader
presence@MUNGEpanix.com> wrote:

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
On 04/04/2016 12:08 PM, John Larkin wrote:
On Mon, 04 Apr 2016 13:05:43 GMT, N0Spam@daqarta.com (Bob Masta)
wrote:

On Sun, 03 Apr 2016 16:10:38 -0700, John Larkin
jjlarkin@highlandtechnology.com> wrote:

On Sun, 3 Apr 2016 20:07:14 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"Chris" <cbx@noreply.com> wrote in message
news:ndrgbj$tt0$6@dont-email.me...
It seems there are resistors around in the range of 50Gohm!
Having
never
encountered anything beyond 10M., I never imagined there could
be
such a
stratospheric value but apparently there is:

There's a small stash of 100M resistors in my collection.

For anything in the G Ohm range - you should probably check the
leakage
resistance of whatever PCB/substrate you're mounting it on.

At the very least, you'll need guard slots cut in any PCB around
the
termination points.

Here's a small PCB deliberately glopped with rosin flux and
fingerprints.

https://dl.dropboxusercontent.com/u/53724080/Gear/Keithley/Leak_Gloppy_Flux.JPG

https://dl.dropboxusercontent.com/u/53724080/Gear/Keithley/Leak_Test.JPG


It's pinning the needle on the 1e14 ohm range.

1G is easy. Just don't use water soluble flux, or if you do, clean
it
really good.

Been a long time since I used anything in the 100 Meg range
or above, but I recall that there were a lot of recommended
precautions. One was to clean the glass body very carefully
(with alcohol, I think) to remove fingerprints which would
otherwise trap dust, which would then allow humidity to
cause a low-resistance shunt. You also want the body to be
elevated above the board surface for the same reason. I
also seem to recall something about teflon
mounts/feedthroughs at the lead ends, but I can't recall
exactly what that was supposed to do.


Sounds like urban myths. 100M is regular PC board turf, axial or
surface-mount parts. Fingerprints seem to have no effect in 1G ohm
circuits.

Glass resistors are overkill in the low Gohm range.

High voltage breakdown is another matter. Fingerprints and dust can
reduce breakover voltages, in the many-kilovolt domain.

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.

I'd believe it. The drugstore stuff I've used (lots of it over the
years)
seems to have denaturing agents added or some other alcohols even
though
it's not needed.

Optical cleaning grade IPA doesn't seem to have the other "stuff" in
it.

On my bench, if I'm too lazy to take a board downstairs to the solvent
cleaner machine, I use acetone. Cleans rosin flux nicely.

Exotic chemicals and solvents are hard to come by in the UK - car spay
paint
thinners is less difficult to obtain.

It shifts rosin flux very well, but is destructive to some components.

Acetone is considered exotic? Here (in the US) we can walk into any
hardware
store and buy Acetone/ alcohols/ other stuff.

They won't even let us have tincture of iodine antiseptic in case we make
our own ammonium-iodide toy snappers.

My dad told me how to make that when I was 14. Told me not to take it
to school. So I promptly did. Painted it on the almost black masonite
benches in jewelry class. Boy did I piss the teacher off.
Eric

 

[John Larkin]

On Tue, 12 Apr 2016 22:05:50 +0100, "Ian Field"
<gangprobing.alien@ntlworld.com> wrote:

"George Herold" <gherold@teachspin.com> wrote in message
news:c5739a9f-a5a0-49a4-a648-3af0d6749356@googlegroups.com...
On Monday, April 11, 2016 at 5:18:59 PM UTC-4, Ian Field wrote:
"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message
news:ug4ogbtiemmd4h6707o11n6ke2ekaa3j0l@4ax.com...
On Fri, 8 Apr 2016 22:21:54 +0000 (UTC), Cydrome Leader
presence@MUNGEpanix.com> wrote:

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
On 04/04/2016 12:08 PM, John Larkin wrote:
On Mon, 04 Apr 2016 13:05:43 GMT, N0Spam@daqarta.com (Bob Masta)
wrote:

On Sun, 03 Apr 2016 16:10:38 -0700, John Larkin
jjlarkin@highlandtechnology.com> wrote:

On Sun, 3 Apr 2016 20:07:14 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"Chris" <cbx@noreply.com> wrote in message
news:ndrgbj$tt0$6@dont-email.me...
It seems there are resistors around in the range of 50Gohm!
Having
never
encountered anything beyond 10M., I never imagined there could
be
such a
stratospheric value but apparently there is:

There's a small stash of 100M resistors in my collection.

For anything in the G Ohm range - you should probably check the
leakage
resistance of whatever PCB/substrate you're mounting it on.

At the very least, you'll need guard slots cut in any PCB around
the
termination points.

Here's a small PCB deliberately glopped with rosin flux and
fingerprints.

https://dl.dropboxusercontent.com/u/53724080/Gear/Keithley/Leak_Gloppy_Flux.JPG

https://dl.dropboxusercontent.com/u/53724080/Gear/Keithley/Leak_Test.JPG


It's pinning the needle on the 1e14 ohm range.

1G is easy. Just don't use water soluble flux, or if you do, clean
it
really good.

Been a long time since I used anything in the 100 Meg range
or above, but I recall that there were a lot of recommended
precautions. One was to clean the glass body very carefully
(with alcohol, I think) to remove fingerprints which would
otherwise trap dust, which would then allow humidity to
cause a low-resistance shunt. You also want the body to be
elevated above the board surface for the same reason. I
also seem to recall something about teflon
mounts/feedthroughs at the lead ends, but I can't recall
exactly what that was supposed to do.


Sounds like urban myths. 100M is regular PC board turf, axial or
surface-mount parts. Fingerprints seem to have no effect in 1G ohm
circuits.

Glass resistors are overkill in the low Gohm range.

High voltage breakdown is another matter. Fingerprints and dust can
reduce breakover voltages, in the many-kilovolt domain.

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.

I'd believe it. The drugstore stuff I've used (lots of it over the
years)
seems to have denaturing agents added or some other alcohols even
though
it's not needed.

Optical cleaning grade IPA doesn't seem to have the other "stuff" in
it.

On my bench, if I'm too lazy to take a board downstairs to the solvent
cleaner machine, I use acetone. Cleans rosin flux nicely.

Exotic chemicals and solvents are hard to come by in the UK - car spay
paint
thinners is less difficult to obtain.

It shifts rosin flux very well, but is destructive to some components.

Acetone is considered exotic? Here (in the US) we can walk into any
hardware
store and buy Acetone/ alcohols/ other stuff.

They won't even let us have tincture of iodine antiseptic in case we make
our own ammonium-iodide toy snappers.

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. I never realized it was so toxic until I read about an
(improbable) murder in a Nero Wolfe story.

https://en.wikipedia.org/wiki/Nitrobenzene#Safety


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Cursitor Doom]

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.

 

[Ian Field]

<etpm@whidbey.com> wrote in message
newsbvqgb56lkh89l6a13q7mvs9a10vpb7kbm@4ax.com...

On Tue, 12 Apr 2016 22:05:50 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"George Herold" <gherold@teachspin.com> wrote in message
news:c5739a9f-a5a0-49a4-a648-3af0d6749356@googlegroups.com...
On Monday, April 11, 2016 at 5:18:59 PM UTC-4, Ian Field wrote:
"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message
news:ug4ogbtiemmd4h6707o11n6ke2ekaa3j0l@4ax.com...
On Fri, 8 Apr 2016 22:21:54 +0000 (UTC), Cydrome Leader
presence@MUNGEpanix.com> wrote:

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
On 04/04/2016 12:08 PM, John Larkin wrote:
On Mon, 04 Apr 2016 13:05:43 GMT, N0Spam@daqarta.com (Bob Masta)
wrote:

On Sun, 03 Apr 2016 16:10:38 -0700, John Larkin
jjlarkin@highlandtechnology.com> wrote:

On Sun, 3 Apr 2016 20:07:14 +0100, "Ian Field"
gangprobing.alien@ntlworld.com> wrote:



"Chris" <cbx@noreply.com> wrote in message
news:ndrgbj$tt0$6@dont-email.me...
It seems there are resistors around in the range of 50Gohm!
Having
never
encountered anything beyond 10M., I never imagined there
could
be
such a
stratospheric value but apparently there is:

There's a small stash of 100M resistors in my collection.

For anything in the G Ohm range - you should probably check the
leakage
resistance of whatever PCB/substrate you're mounting it on.

At the very least, you'll need guard slots cut in any PCB
around
the
termination points.

Here's a small PCB deliberately glopped with rosin flux and
fingerprints.

https://dl.dropboxusercontent.com/u/53724080/Gear/Keithley/Leak_Gloppy_Flux.JPG

https://dl.dropboxusercontent.com/u/53724080/Gear/Keithley/Leak_Test.JPG


It's pinning the needle on the 1e14 ohm range.

1G is easy. Just don't use water soluble flux, or if you do,
clean
it
really good.

Been a long time since I used anything in the 100 Meg range
or above, but I recall that there were a lot of recommended
precautions. One was to clean the glass body very carefully
(with alcohol, I think) to remove fingerprints which would
otherwise trap dust, which would then allow humidity to
cause a low-resistance shunt. You also want the body to be
elevated above the board surface for the same reason. I
also seem to recall something about teflon
mounts/feedthroughs at the lead ends, but I can't recall
exactly what that was supposed to do.


Sounds like urban myths. 100M is regular PC board turf, axial or
surface-mount parts. Fingerprints seem to have no effect in 1G ohm
circuits.

Glass resistors are overkill in the low Gohm range.

High voltage breakdown is another matter. Fingerprints and dust
can
reduce breakover voltages, in the many-kilovolt domain.

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.

I'd believe it. The drugstore stuff I've used (lots of it over the
years)
seems to have denaturing agents added or some other alcohols even
though
it's not needed.

Optical cleaning grade IPA doesn't seem to have the other "stuff" in
it.

On my bench, if I'm too lazy to take a board downstairs to the
solvent
cleaner machine, I use acetone. Cleans rosin flux nicely.

Exotic chemicals and solvents are hard to come by in the UK - car spay
paint
thinners is less difficult to obtain.

It shifts rosin flux very well, but is destructive to some components.

Acetone is considered exotic? Here (in the US) we can walk into any
hardware
store and buy Acetone/ alcohols/ other stuff.

They won't even let us have tincture of iodine antiseptic in case we make
our own ammonium-iodide toy snappers.
My dad told me how to make that when I was 14. Told me not to take it
to school. So I promptly did. Painted it on the almost black masonite
benches in jewelry class. Boy did I piss the teacher off.

A wad of AI soaked cotton wool in every hole on the golf
course..............................

 

[John Larkin]

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.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Ian Field]

"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.

 

[John Larkin]

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?


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Ian Field]

"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message
news:jhk2hbdj85ttea8ambos917j1umubdb9jl@4ax.com...

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?

With a winch probably.................

 

[Phil Hobbs]

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

--
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

 

[Ian Field]

"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 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.

 

[Phil Hobbs]

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. Our mains distribution is done
by a 1.6 kV line at the top of the pole, with a couple of pole pigs per
block to generate 240V 2-phase.

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