Date   
Re: A Question For The Group

Craig Sawyers <c.sawyers@...>
 

I'm thnking now, would it be more accurate and easier to simulate a
10X scope probe and of course not use the 50 ohm termination. I'm not
real happy with the waveform I'm getting right now with the TI
device. It's not an accurate reproduction at the higher frequencies,
I think because of the 10X attenuation circuit leading into the input
of the device.
The thing to do is use a probe adaptor. Tek used to supply these with some
of their probes. Looks like a little BNC, but the receptacle takes the
probe tip. You solder the centre pin to the signal, and the outer to the
ground plane (you've got one of those - right?). When you plug the scope
probe in, there are virtually no additional errors arising from tip grabber
and ground clip inductance, and you get a very clean signal.

You can do the same thing with a FET probe too, and reduce the loading to
one or two pF.

If the circuit has to look into 50 ohms, load the circuit locally with a
50-ohm resistor (a surface mount component connected between the IC pin and
ground plane is ideal), then probe the circuit as above.

Craig

Re: Oil Filled Capacitors

Craig Sawyers <c.sawyers@...>
 

Corona discharge would be pretty hard to induce at 200 Vac. You would have
to hit frequency around cap's resonance
That reminds me of another failure mechanism - acoustic. Try the following
experiment. Make a simple power amp for square waves with a couple of
transistors or FETS, driving +/- 30V (say). Connect capacitor from output
to low impedance load to get a reasonable current flowing. Now sweep an
audio generator.

Many capacitors howl like a banshee at particular frequencies where the
internal mechanics resonate. These are usually ones where the windings
inside are relatively "loose". Very tightly wound capacitors are very
quiet - but there are some real shocks out there when you try the experiment
(like some respected 10kV polypropylene which were more like a loudspeaker
than a capacitor).

Needless to say, such mechanical vibration does nothing to help the
reliability of the capacitor.

Craig

Re: 7d01 with df1 garbled display

Miroslav Pokorni
 

Hello Zenith,

Yes, you are absolutely right. Those low-pressure tin-to-tin contacts tend
to fail over time due to oxidation. It is only 'gas tight' and noble metal
contacts that make reliable sockets. I do not quite understand how a
combination of tin plate and gold works, but it does. Over past twenty years
there were number of attacks on tin plate to gold contact, about every four
to five years and then it turns out that arguments are short on substance
and whole thing gets dropped quietly. Usually, argument runs that gold and
tin in contact would cause fretting corrosion of tin. The last three
instances that story was flogged, it came out of AMP, I guess someone in
their metallurgical department is pursuing the line of fretting corrosion.
Is it not funny that AMP is one of few companies that have been pushing for
tin plated edge connectors? The last instance of gold to tin controversy
that I know of was around 1997 or 98, when Intel issued statement that
warranty on their motherboards was void if gold plated SIMMs were used in
it. I was working for a memory company and we had to contend with it,
because there were customers who would demand gold plating and then others
who were heeding Intel's edict. We requested supporting documentation from
Intel and sure enough, they sent us an article published by an AMP's
metallurgist. Knowing that it was just another tack of an old theme, company
decided to disregard Intel's notice and prepared a letter for customers who
expressed concern, explaining the previous history and seesaw of tin to
noble metal contact. Intel's notice was on their web site and their
marketing was aggressively pursuing the matter through trade magazines, but
after couple of months whole thing was quietly dropped. The first hint was
that notice was removed from web site.

As for flat cable, would you please describe that connector and cable more
closely so that we can identify it. I am guessing that brand was Spectra
Strip, a division of Amphenol: connector was black body and cable was color
coded; I believe that Spectra Strip had color coding of flat cable
trademarked, because no one else was using that for quite long time, just
about right timing for trade mark to expire. Spectra Strip thought that they
were smarter than rest of the bunch and they just about sunk because of it;
good thing was that Amphenol was doing real well and could cart them for
awhile.
Gold price of $800/oz brought grief to all of us and Insulation Displacement
Connectors (IDC) seem to have been hit harder then others. Their problem was
that cable part of connector did not have enough strength to live through
insulation displacement and still exert enough pressure to form gas tight
contact. The T & B made a name in IDCs, and I hope fortune, with their tulip
contact. The insulation displacement part of that contact looked like the
tulip flower, with four edges pressing into the wire and it relied solely on
metal to exert pressure on wire, unlike other connectors (Spectra Strip, 3M,
Berg) which relied on plastic body to support cutting edges of contacts. In
first iteration, all those other companies changed contact to have four
points to cut into wire, but cutting surfaces were highly cantilevered, so
not enough force was supplied by metal. It was the next iteration when all
of them got it right and it was only rarely, when someone tried to re-use
connector or did not use right tool for assembly, that problem reappeared. I
guess, since that time there were always batches when material was not quite
right, like GM putting out a batch of cars with gear in transmission which
skipped heat treating.

I guess, in this instance you can not blame Tektronix accountants for trying
to unreasonably pinch few pennies, not that I would put that past them. The
whole IDC industry went to selective gold plating, whatever marketing name
they gave to it, so getting full gold plating without custom order was just
not possible ever since it became clear that gold price was to stay high.

Regards

Miroslav Pokorni

----- Original Message -----
From: "zenith5106" <zenith@...>
To: "Miroslav Pokorni" <mpokorni2000@...>
Sent: Thursday, May 29, 2003 9:38 AM
Subject: Re: 7d01 with df1 garbled display


Miroslav,
I won't argue with you on that but I'm pretty sure age is also a
factor. The way the contacts were designed in combination with low
tension it was easy for dirt it enter or more likely oxide to build
up between the contacts an IC pin.
While we're at the topic there were another similar source of
intermittent faults. I guess at about the same time as the TI sockets
Tek was trying to save money on the ribbon cable connectors that were
in virtually every instruments. They used to be all gold plated but
they changed it to be goldplated only at the contact areas and the
rest of the connector had some other cheaper plating. I think the
name of the connectors were "spot on gold" or "spot of gold". They
also were susceptable to oxide building up at the point it had been
crimped to the cable. If you carefully wiggle intermittent cable you
can watch the fault come and go. A simple solution is to carefully
solder the cable to the connector. They can be identified by color,
compared to a real gold connector they were much more pale in color.
The bottom line is, if you have an intermittent instrument which
contains these sockets and/or the these ribbon cables they should be
the prime suspects.
/Zenith

--- In TekScopes@..., "Miroslav Pokorni"
<mpokorni2000@y...> wrote:
Hello Zenith,

Those sockets that you showed in picture look like famous TI
sockets that
wicked up flux and got fouled up. In most cases, they would be a
problem
from the start, on production line. Later on, TI tried to correct
problem by
placing a rectangular piece of paper of some kind at the bottom of
the
socket. The paper was pierced to let pins through and idea was that
paper
would hug outside surfaces of pin and keep flux from wicking. That
was
improvement, but was not good enough and that socket died. The AMP
had a
cheap socket, but they learned from TI's experience. Pin in AMP's
socket was
going all the way up the socket and was bent down to form one side
of
contact with IC and then was bent upward again to make the other
side of
contact. With such a pin flux would wick up the pin but could not
reach
contact area.

Regards

Miroslav Pokorni

----- Original Message -----
From: "zenith5106" <zenith@t...>
To: <TekScopes@...>
Sent: Wednesday, May 28, 2003 12:10 PM
Subject: [TekScopes] Re: 7d01 with df1 garbled display


--- In TekScopes@..., Joshua Van Tol <josh@s...>
wrote:
I've got a 7D01 with a DF1 data formatter that exhibits the
following
symptoms:

On power up, all the front panel lights come on. Sometimes most
of
them
come on and then a few seconds later the rest come on.
When the display comes up, it's all garbled. Usually a whole
screen
of
the same character.

Any ideas what this might be? I'm thinking the processor is
either
resetting, or reading incorrect data from its ROM.
---
Miroslav is right. The IC sockets on early 7D01's were really
bad. If
I remember correctly they were Texas brand and type C95. They were
installed in many Tek instruments at the time but seemed to create
the most problems in 7D01. The 7D01 problems were so severe that
Tek
even replaced several of the boards on warranty. It could be
easily
identified by its unique profile, looking at the short end. I put
a
picture at http://w1.871.telia.com/~u87138090/TexasC95.jpg if
anybody
is interested. Another problem with early 7D01's was that the
cursor
switch and position pots were very sensitve to even small static
discharge which would cause the instrument to reset when the knobs
were touched by the operator. This was later corrected with a new
type of pots with grounded shafts.
/Zenith

Re: Oil Filled Capacitors

Miroslav Pokorni
 

I wonder whether they talk when you squeeze them?

Regards

Miroslav Pokorni

----- Original Message -----
From: "Rolynn Prechtl K7DFW" <k7dfw@...>
To: <TekScopes@...>
Sent: Thursday, May 29, 2003 2:59 PM
Subject: Re: [TekScopes] Re: Oil Filled Capacitors




Hi, I am a high voltage power supply and I can shed some light on oil
filled capacitors.


I'll be dipped!

I've worked on a few of these critters but never had one talk to me, much
less send an email.

What will they think of next?

K7DFW

..._._

Re: Oil Filled Capacitors

Miroslav Pokorni
 

Yes, Morris, you are right, I did not consider that an area where there is a
transition between air and high dielectric constant material makes for some
very ugly field distribution. However, that is at the fringes of the cap,
not between 'plates' of it.

Your reply made me go and look up dielectric constants, what I should have
done in the first place. Paper shows values between 3.3 and 3.7, while oils
that are used for caps, chlorinated phenyls and naphthalenes (trade names
HB-40 Oil, Pyranol 1476, Arochlor 1260, Halowax Oil 1000), are between 2.6
and 5.0. There is not much disparity there, ratio is less than 1:2, so there
would not be much of electric field change going from solid paper particles
to liquid oil, at least not between plates in an oil field cap. On the
fringes of a cap, oil is held between dielectric layers by capillary action
so there is a continuity of dielectric there. Besides, applicable to both,
inter-plate and on fringes, oil being liquid and remaining so, is kind of
self-healing, through diffusion.

Looking at the dielectric constant of most frequently used plastic foil
materials, (polyethylene, polypropylene and polystyrene), there is nothing
dramatic, they are bunched at 2.4. The only other common capacitor
dielectric material, polycarbonate, stands at 3.2. These are not quite the
values that would make field discontinuity which might lead to local corona.

So, I guess, that corona stuff at 200 Vac is an artifact of Wima's marketing
department. I was aware that Wima was trying to tell world that there is no
such a thing as Wima when it comes to line voltage caps, but Taiwanese seem
to have held pretty good.

Regards

Miroslav Pokorni

----- Original Message -----

From: "Morris Odell" <morriso@...>
To: <TekScopes@...>
Sent: Thursday, May 29, 2003 11:15 PM
Subject: RE: [TekScopes] Re: Oil Filled Capacitors


Miroslav wrote:

Corona discharge would be pretty hard to induce at 200 Vac. You would
have
to hit frequency around cap's resonance, but then Q factor would be quite
miserable, so there would not be much of voltage amplification.
I can see that if you are getting corona, that can ruin a day for a high
voltage power supply, like yourself. Corona would cause impedance of a cap
to drop to next to zero and burn everythin in the path, it is just that
you
need pretty high voltage for that.

I am a high voltage power supply and I can shed some light on oil
filled capacitors.

The challenge in capacitor design is to make an A.C. cpacitor that
is
free from corona.

<snip>

I'm pretty sure the power supply was talking about corona initially on a
pretty small scale. It's well known that the voltage stress across
insulating voids is higher than that across a corresponding volume of
insulator due to the distribution of the electric field between areas of
different dielectric constant. The problem would be worse for AC because
of
the changing field - perhaps due to dielectric loss effects too. Once a
micro corona develops it would lead to local destruction and eventually
failure of the entire unit. One of the reasons for impregnating the
dielectric with oil is to fill the voids and prevent this from happening.
I
suppose the oil would really be the dielectric and the cellulose fibres of
the paper merely a carrier/spacer.

Plastic film dielectrics don't have the porous structure of paper with its
inherent voids and so doesn't need to be impregnated. I suppose you can
think of plastic films as "solid oil" anyway.

Morris

Re: Oil Filled Capacitors

Miroslav Pokorni
 

I guess, it does not help, but then everything has a resonant frequency. The
only way to cope with it, if you can not avoid operating at that frequency,
is to make cap mechanically lossy so that Q factor is down in mud.

Possibly, this acoustical phenomena, together with high current through cap,
made resonant power supplies pretty much disappear. The last one that I have
seen was a Hewlett Packard unit that used a cap branded with their name,
what I guess was a custom cap.

There seems to be no such a thing as a simple component, there is only the
simple demand.

Regards

Miroslav Pokorni

----- Original Message -----
From: "Craig Sawyers" <c.sawyers@...>
To: "TekScopes" <TekScopes@...>
Sent: Friday, May 30, 2003 12:27 AM
Subject: RE: [TekScopes] Re: Oil Filled Capacitors


Corona discharge would be pretty hard to induce at 200 Vac. You would
have
to hit frequency around cap's resonance
That reminds me of another failure mechanism - acoustic. Try the
following
experiment. Make a simple power amp for square waves with a couple of
transistors or FETS, driving +/- 30V (say). Connect capacitor from output
to low impedance load to get a reasonable current flowing. Now sweep an
audio generator.

Many capacitors howl like a banshee at particular frequencies where the
internal mechanics resonate. These are usually ones where the windings
inside are relatively "loose". Very tightly wound capacitors are very
quiet - but there are some real shocks out there when you try the
experiment
(like some respected 10kV polypropylene which were more like a loudspeaker
than a capacitor).

Needless to say, such mechanical vibration does nothing to help the
reliability of the capacitor.

Craig

Looking for Tek Veterans

Phil T. <phil@...>
 

Gents,

I received the following e-mail from a Tek veteran. Please reply directly
to Robert if you "qualify".

Thanks...Phil


X-RCPT-To: <phil@...>
From: "Robert Nagler" <nagler-r@...>
To: <phil@...>
Date: Thu, 29 May 2003 12:19:58 +0200

I was in training in Beaverton in 1961 had a great time in Oregon.
Later worked in Tek Canada and for the Tek rep in Israel.
Now I am retired.
Would like to correspond with Tek vets by e-mail
Robert Nagler
nagler-r@...

---
Incoming mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.483 / Virus Database: 279 - Release Date: 5/19/2003


----------


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.483 / Virus Database: 279 - Release Date: 5/19/2003

(No subject)

Robert Nagler <nagler-r@...>
 

Does anybody have the e-mail address of Paul Whitlock.
Beaverton training class 1961?????

Re: 7d01 with df1 garbled display

zenith5106 <zenith@...>
 

Miroslav,

Actually I think the contacts in the TI sockets were gold plated but
it didn't seem to help in this case. See
http://w1.871.telia.com/~u87138090/TexasC95a.jpg . The flat cables I
mentioned are the standard ones you'll find everywhere in older Tek
equipment. I put a picture at
http://w1.871.telia.com/~u87138090/Flatcable.jpg but it is very
difficult to visualize the difference with a picture. You'd really
need to see them both in real life and compare. The green is the bad
one and the blue is OK. When they were new the bad ones had a much
more pale goldish color and over the years they turned darker but
still different from a good ones which stay golden.
/Zenith

--- In TekScopes@..., "Miroslav Pokorni"
<mpokorni2000@y...> wrote:
Hello Zenith,

Yes, you are absolutely right. Those low-pressure tin-to-tin
contacts tend
to fail over time due to oxidation. It is only 'gas tight' and
noble metal
contacts that make reliable sockets. I do not quite understand how a
combination of tin plate and gold works, but it does. Over past
twenty years
there were number of attacks on tin plate to gold contact, about
every four
to five years and then it turns out that arguments are short on
substance
and whole thing gets dropped quietly. Usually, argument runs that
gold and
tin in contact would cause fretting corrosion of tin. The last three
instances that story was flogged, it came out of AMP, I guess
someone in
their metallurgical department is pursuing the line of fretting
corrosion.
Is it not funny that AMP is one of few companies that have been
pushing for
tin plated edge connectors? The last instance of gold to tin
controversy
that I know of was around 1997 or 98, when Intel issued statement
that
warranty on their motherboards was void if gold plated SIMMs were
used in
it. I was working for a memory company and we had to contend with
it,
because there were customers who would demand gold plating and then
others
who were heeding Intel's edict. We requested supporting
documentation from
Intel and sure enough, they sent us an article published by an AMP's
metallurgist. Knowing that it was just another tack of an old
theme, company
decided to disregard Intel's notice and prepared a letter for
customers who
expressed concern, explaining the previous history and seesaw of
tin to
noble metal contact. Intel's notice was on their web site and their
marketing was aggressively pursuing the matter through trade
magazines, but
after couple of months whole thing was quietly dropped. The first
hint was
that notice was removed from web site.

As for flat cable, would you please describe that connector and
cable more
closely so that we can identify it. I am guessing that brand was
Spectra
Strip, a division of Amphenol: connector was black body and cable
was color
coded; I believe that Spectra Strip had color coding of flat cable
trademarked, because no one else was using that for quite long
time, just
about right timing for trade mark to expire. Spectra Strip thought
that they
were smarter than rest of the bunch and they just about sunk
because of it;
good thing was that Amphenol was doing real well and could cart
them for
awhile.
Gold price of $800/oz brought grief to all of us and Insulation
Displacement
Connectors (IDC) seem to have been hit harder then others. Their
problem was
that cable part of connector did not have enough strength to live
through
insulation displacement and still exert enough pressure to form gas
tight
contact. The T & B made a name in IDCs, and I hope fortune, with
their tulip
contact. The insulation displacement part of that contact looked
like the
tulip flower, with four edges pressing into the wire and it relied
solely on
metal to exert pressure on wire, unlike other connectors (Spectra
Strip, 3M,
Berg) which relied on plastic body to support cutting edges of
contacts. In
first iteration, all those other companies changed contact to have
four
points to cut into wire, but cutting surfaces were highly
cantilevered, so
not enough force was supplied by metal. It was the next iteration
when all
of them got it right and it was only rarely, when someone tried to
re-use
connector or did not use right tool for assembly, that problem
reappeared. I
guess, since that time there were always batches when material was
not quite
right, like GM putting out a batch of cars with gear in
transmission which
skipped heat treating.

I guess, in this instance you can not blame Tektronix accountants
for trying
to unreasonably pinch few pennies, not that I would put that past
them. The
whole IDC industry went to selective gold plating, whatever
marketing name
they gave to it, so getting full gold plating without custom order
was just
not possible ever since it became clear that gold price was to stay
high.

Regards

Miroslav Pokorni


----- Original Message -----
From: "zenith5106" <zenith@t...>
To: "Miroslav Pokorni" <mpokorni2000@y...>
Sent: Thursday, May 29, 2003 9:38 AM
Subject: Re: 7d01 with df1 garbled display


Miroslav,
I won't argue with you on that but I'm pretty sure age is also a
factor. The way the contacts were designed in combination with low
tension it was easy for dirt it enter or more likely oxide to
build
up between the contacts an IC pin.
While we're at the topic there were another similar source of
intermittent faults. I guess at about the same time as the TI
sockets
Tek was trying to save money on the ribbon cable connectors that
were
in virtually every instruments. They used to be all gold plated
but
they changed it to be goldplated only at the contact areas and the
rest of the connector had some other cheaper plating. I think the
name of the connectors were "spot on gold" or "spot of gold". They
also were susceptable to oxide building up at the point it had
been
crimped to the cable. If you carefully wiggle intermittent cable
you
can watch the fault come and go. A simple solution is to carefully
solder the cable to the connector. They can be identified by
color,
compared to a real gold connector they were much more pale in
color.
The bottom line is, if you have an intermittent instrument which
contains these sockets and/or the these ribbon cables they should
be
the prime suspects.
/Zenith

--- In TekScopes@..., "Miroslav Pokorni"
<mpokorni2000@y...> wrote:
Hello Zenith,

Those sockets that you showed in picture look like famous TI
sockets that
wicked up flux and got fouled up. In most cases, they would be a
problem
from the start, on production line. Later on, TI tried to
correct
problem by
placing a rectangular piece of paper of some kind at the bottom
of
the
socket. The paper was pierced to let pins through and idea was
that
paper
would hug outside surfaces of pin and keep flux from wicking.
That
was
improvement, but was not good enough and that socket died. The
AMP
had a
cheap socket, but they learned from TI's experience. Pin in
AMP's
socket was
going all the way up the socket and was bent down to form one
side
of
contact with IC and then was bent upward again to make the other
side of
contact. With such a pin flux would wick up the pin but could
not
reach
contact area.

Regards

Miroslav Pokorni

----- Original Message -----
From: "zenith5106" <zenith@t...>
To: <TekScopes@...>
Sent: Wednesday, May 28, 2003 12:10 PM
Subject: [TekScopes] Re: 7d01 with df1 garbled display


--- In TekScopes@..., Joshua Van Tol <josh@s...>
wrote:
I've got a 7D01 with a DF1 data formatter that exhibits the
following
symptoms:

On power up, all the front panel lights come on. Sometimes
most
of
them
come on and then a few seconds later the rest come on.
When the display comes up, it's all garbled. Usually a whole
screen
of
the same character.

Any ideas what this might be? I'm thinking the processor is
either
resetting, or reading incorrect data from its ROM.
---
Miroslav is right. The IC sockets on early 7D01's were really
bad. If
I remember correctly they were Texas brand and type C95. They
were
installed in many Tek instruments at the time but seemed to
create
the most problems in 7D01. The 7D01 problems were so severe
that
Tek
even replaced several of the boards on warranty. It could be
easily
identified by its unique profile, looking at the short end. I
put
a
picture at http://w1.871.telia.com/~u87138090/TexasC95.jpg if
anybody
is interested. Another problem with early 7D01's was that the
cursor
switch and position pots were very sensitve to even small
static
discharge which would cause the instrument to reset when the
knobs
were touched by the operator. This was later corrected with a
new
type of pots with grounded shafts.
/Zenith

Re: 7d01 with df1 garbled display

Craig Sawyers <c.sawyers@...>
 

The flat cables I
mentioned are the standard ones you'll find everywhere in older Tek
equipment. I put a picture at
http://w1.871.telia.com/~u87138090/Flatcable.jpg but it is very
difficult to visualize the difference with a picture. You'd really
need to see them both in real life and compare. The green is the bad
one and the blue is OK.
This is very reminiscent of the problem with one design of connector that
Lucas invented for Jaguar in the 1970s. The idea was that the cables were
crimped into either bullets or sockets, and these were assembled into an
array held in place by a moulded rubber housing.

Now although nominally gas tight, they progressively fail. Some stay OK,
but at random contacts can measure an ohm or two - upwards to open circuit.
This can be disastrous with ampere currents in automotive circuits. Because
housing is a moulded block around contacts it is impossible to solder the
crimp area - so the only way to solve the problem is to chop off the old
mating pair and replace with a good quality modern locking connector.

The failure mechanism might be to do with compounds in the rubber slowly
oxidising the copper, or it could be heat and humidity - or a combination.
Whatever, it is a sod to find (like the tek crimp problem).

Craig

Re: P/N for Tek 336 CRT

zenith5106 <zenith@...>
 

--- In TekScopes@..., "adibene" <i2phd@w...> wrote:
Does anybody know the P/N of the CRT used in the Tek 336 scope ?
I have already checked the
http://www.reprise.com/host/tektronix/home/default.asp
site, but the 336 is declared there as unknown.

Thanks

Alberto I2PHD
----
The 336 CRT is 154-0866-00 and was not used in any other scope.
/Zenith

Re: 7d01 with df1 garbled display

Miroslav Pokorni
 

Who was Lucas? Was that not British God of Darkness?

Regards

Miroslav Pokorni

----- Original Message -----
From: "Craig Sawyers" <c.sawyers@...>
To: <TekScopes@...>
Sent: Friday, May 30, 2003 11:34 AM
Subject: RE: [TekScopes] Re: 7d01 with df1 garbled display


The flat cables I
mentioned are the standard ones you'll find everywhere in older Tek
equipment. I put a picture at
http://w1.871.telia.com/~u87138090/Flatcable.jpg but it is very
difficult to visualize the difference with a picture. You'd really
need to see them both in real life and compare. The green is the bad
one and the blue is OK.
This is very reminiscent of the problem with one design of connector that
Lucas invented for Jaguar in the 1970s. The idea was that the cables were
crimped into either bullets or sockets, and these were assembled into an
array held in place by a moulded rubber housing.

Now although nominally gas tight, they progressively fail. Some stay OK,
but at random contacts can measure an ohm or two - upwards to open
circuit.
This can be disastrous with ampere currents in automotive circuits.
Because
housing is a moulded block around contacts it is impossible to solder the
crimp area - so the only way to solve the problem is to chop off the old
mating pair and replace with a good quality modern locking connector.

The failure mechanism might be to do with compounds in the rubber slowly
oxidising the copper, or it could be heat and humidity - or a combination.
Whatever, it is a sod to find (like the tek crimp problem).

Craig

Re: Oil Filled Capacitors

Stan & Patricia Griffiths <w7ni@...>
 

At least one of the caps in that auction is a Tek timing capacitor and I am
not sure Tek ever used oil in those or not. I never took one apart.

I have sometimes referred to "Black Beauty" caps as oil caps since the
actually have oil in them. Technically they may be "dry paper, treated with
oil" but there is so much oil in them that it often leaks out by the wire
seals and gets all over the outside of the cap and sometimes drips onto the
instrument chassis. It is hard for me to think of that as a "dry" cap . . .

Stan
w7ni@...

----- Original Message -----
From: "Miroslav Pokorni" <mpokorni2000@...>
To: <TekScopes@...>
Sent: Wednesday, May 28, 2003 10:14 PM
Subject: [TekScopes] Oil Filled Capacitors


In several instances of discussion on this forum paper caps were called
'oil
caps'. In last case that I remember, Don wrote back and pointed out that
those caps were actually paper, treated with oil but dry paper caps. There
is an auction on e bay for several oil caps with pretty good picture of
them; address is:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2534602284&category=4662

As picture shows, oil caps are enclosed in steel case, to contain oil, and
usual purpose of those caps is phase correction (or motor start), where
considerable current is drawn through the cap.

Regards

Miroslav Pokorni






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Re: Oil Filled Capacitors

eboytoronto
 

Hi,
I am not really a high voltage power supply !!

I am a high voltage power supply engineer. I work for CPI designing power supplies for Medical X-ray generators. These are up to 100kW, 150kV and 1000mA.
Some of my work can be seen at www.cpii.com/cmp
These incidently use resonant technology.

I learned about the corona effects from a company called ASC. This company was TRW. They make and have made many custom capacitors for HP, Tek, Varian, Fluke etc. They are generally white wrap and fill construction.

They explained the corona effects in capacitors to me. They have an application note at:

http://www.ascapacitor.com/PDF/corona%20phenomena.pdf

Wima built their capacitors with two sections in series to help with the self-healing properties. When one of the sections arcs the other still presents impedance.

ASC has built some snubber capacitors for me that have four sections in series to obtain an a.c. rating of 800 v rms. The dc. rating of these was 1600 v.

As someone pointed out the corona arises because the electric field is not uniform in the area of a void or mismatched dielectric constants.

These comments on capacitors also apply to high voltage transformers. This why vacumn impregnating is used.

I have done some work with solid dielectric materials, potting, matching the dielectrics and preventing voids is quite a challenge.


Regards,


John Barnes

P.S. just got home from the Rochester Hamfest with a pile of 7K plugins to work on.

---------- Original Message ----------------------------------
From: "Miroslav Pokorni" <mpokorni2000@...>
Reply-To: "Miroslav Pokorni" <mpokorni2000@...>
Date: Fri, 30 May 2003 02:42:39 -0700

I guess, it does not help, but then everything has a resonant frequency. The
only way to cope with it, if you can not avoid operating at that frequency,
is to make cap mechanically lossy so that Q factor is down in mud.

Possibly, this acoustical phenomena, together with high current through cap,
made resonant power supplies pretty much disappear. The last one that I have
seen was a Hewlett Packard unit that used a cap branded with their name,
what I guess was a custom cap.

There seems to be no such a thing as a simple component, there is only the
simple demand.

Regards

Miroslav Pokorni

----- Original Message -----
From: "Craig Sawyers" <c.sawyers@...>
To: "TekScopes" <TekScopes@...>
Sent: Friday, May 30, 2003 12:27 AM
Subject: RE: [TekScopes] Re: Oil Filled Capacitors


Corona discharge would be pretty hard to induce at 200 Vac. You would
have
to hit frequency around cap's resonance
That reminds me of another failure mechanism - acoustic. Try the
following
experiment. Make a simple power amp for square waves with a couple of
transistors or FETS, driving +/- 30V (say). Connect capacitor from output
to low impedance load to get a reasonable current flowing. Now sweep an
audio generator.

Many capacitors howl like a banshee at particular frequencies where the
internal mechanics resonate. These are usually ones where the windings
inside are relatively "loose". Very tightly wound capacitors are very
quiet - but there are some real shocks out there when you try the
experiment
(like some respected 10kV polypropylene which were more like a loudspeaker
than a capacitor).

Needless to say, such mechanical vibration does nothing to help the
reliability of the capacitor.

Craig





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Re: Oil Filled Capacitors

Miroslav Pokorni
 

You surely fulled me, I thought you are a mutant power supply.
Thank you for lead on corona effects and new name of TRW capacitor division.
Would you happen to know what was name of that company before TRW bought
them; I do not think that division was home grown at TRW, they seemed to
preffer acquisitions.

Regards

Miroslav Pokorni

----- Original Message -----
From: "jbarnes" <jbarnes@...>
To: "TekScopes" <TekScopes@...>; "Craig Sawyers"
<c.sawyers@...>; "Miroslav Pokorni" <mpokorni2000@...>
Sent: Friday, May 30, 2003 4:43 PM
Subject: Re: [TekScopes] Re: Oil Filled Capacitors


Hi,
I am not really a high voltage power supply !!

I am a high voltage power supply engineer. I work for CPI designing power
supplies for Medical X-ray generators. These are up to 100kW, 150kV and
1000mA.
Some of my work can be seen at www.cpii.com/cmp
These incidently use resonant technology.

I learned about the corona effects from a company called ASC. This company
was TRW. They make and have made many custom capacitors for HP, Tek, Varian,
Fluke etc. They are generally white wrap and fill construction.

They explained the corona effects in capacitors to me. They have an
application note at:

http://www.ascapacitor.com/PDF/corona%20phenomena.pdf

Wima built their capacitors with two sections in series to help with the
self-healing properties. When one of the sections arcs the other still
presents impedance.

ASC has built some snubber capacitors for me that have four sections in
series to obtain an a.c. rating of 800 v rms. The dc. rating of these was
1600 v.

As someone pointed out the corona arises because the electric field is not
uniform in the area of a void or mismatched dielectric constants.

These comments on capacitors also apply to high voltage transformers. This
why vacumn impregnating is used.

I have done some work with solid dielectric materials, potting, matching
the dielectrics and preventing voids is quite a challenge.


Regards,


John Barnes

P.S. just got home from the Rochester Hamfest with a pile of 7K plugins to
work on.






---------- Original Message ----------------------------------
From: "Miroslav Pokorni" <mpokorni2000@...>
Reply-To: "Miroslav Pokorni" <mpokorni2000@...>
Date: Fri, 30 May 2003 02:42:39 -0700

I guess, it does not help, but then everything has a resonant frequency.
The
only way to cope with it, if you can not avoid operating at that
frequency,
is to make cap mechanically lossy so that Q factor is down in mud.

Possibly, this acoustical phenomena, together with high current through
cap,
made resonant power supplies pretty much disappear. The last one that I
have
seen was a Hewlett Packard unit that used a cap branded with their name,
what I guess was a custom cap.

There seems to be no such a thing as a simple component, there is only
the
simple demand.

Regards

Miroslav Pokorni

----- Original Message -----
From: "Craig Sawyers" <c.sawyers@...>
To: "TekScopes" <TekScopes@...>
Sent: Friday, May 30, 2003 12:27 AM
Subject: RE: [TekScopes] Re: Oil Filled Capacitors


Corona discharge would be pretty hard to induce at 200 Vac. You would
have
to hit frequency around cap's resonance
That reminds me of another failure mechanism - acoustic. Try the
following
experiment. Make a simple power amp for square waves with a couple of
transistors or FETS, driving +/- 30V (say). Connect capacitor from
output
to low impedance load to get a reasonable current flowing. Now sweep
an
audio generator.

Many capacitors howl like a banshee at particular frequencies where the
internal mechanics resonate. These are usually ones where the windings
inside are relatively "loose". Very tightly wound capacitors are very
quiet - but there are some real shocks out there when you try the
experiment
(like some respected 10kV polypropylene which were more like a
loudspeaker
than a capacitor).

Needless to say, such mechanical vibration does nothing to help the
reliability of the capacitor.

Craig





Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/


Tek 2465* ?

kolesnik
 

Which of the 2465 models is most reliable or is there any difference?

tnx
hank wd5jfr

TEK 2445A - parts

Dragan Stojanovic <dragans@...>
 

Hello,

I have finally determined bad IC U800 on my TEK 2445A. Chip is not available
any more. Everything else is in "like new" condition.

Instead to throw it to trash I would like to sell parts on very popular
prices.

Regards,

Dragan

p.s. I'm located in Sweden

FOR "Dr M J Di Girolamo" DrD@adelpha.net RE: TEK 2445A - parts

Dragan Stojanovic <dragans@...>
 

Mail has returned. Sending you again via group. Sorry.



Hello Mike,

No, that's not me. I have been for the first time to USA, CA, just two weeks
ago. :-))

Regards,

Dragan (ex ET3YU) :-))





Hi. This is the qmail-send program at ian.ukinternetsites.com.

I'm afraid I wasn't able to deliver your message to the following addresses.

This is a permanent error; I've given up. Sorry it didn't work out.

<DrD@...>:

--- Below this line is a copy of the message.

Return-Path: <dragans@...>

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for <DrD@...>; Sat, 31 May 2003 20:04:21 +0200 (CEST)

From: "Dragan Stojanovic" <dragans@...>

To: "Dr M J Di Girolamo" DrD@...

Oil Filled Capacitors

daven9ooq <daven9ooq@...>
 

Hi All:
I been copying the mail and noted all the questions reguarding oil
filled capacitors, Transformers, and the like, Tek manufactured a lot
of their own parts. I been fortunate to have picked up the intermal
tek materials manual vol.3 1987 it's a very elaborate catalog listing
just about every material tektronix used in the manufacturing of
their test equipment. I thought I would list some of their lubricants
used for variouse purposes. I can't find any cross reference to what
materials were used for specific parts, But it does list very
specific charastics of just about every material used.

Beacon 325 grease..... used for switches
Dow corning 200..... silicone dielectric fluid
Dow corning 5 ......." "
Mobile oil type 45 Used for transformers
Lubriplate 14285 multipurpose lubricant
Lubriplate A type 105 " "
Thermalloy..... 251, and 249 Silicone grease for heatsinks
Ibm 23 grease............... general purpose.

Thease are just a few of the litings.
To clean cam switch contacts I'm told isoproply alcohol Wet heavy
card stock and carefully slide underneath the contacts untill clean
is the only recomended method as anything harsher may damage the
laminate.

hope this is helpful!
73's
Dave
N9OOQ

Source of connecters for 7L13 to TR502

Dave Henderson <nr1dx@...>
 

Anyone know a source for the 6 pin connectors that are used to connect the 7L13 spectrum analyzer to the TR502 tracking generator?

Dave