Date   

Re: Strange 7912AD *EMERGENCY POST*

Ashton Brown <ashtonb@...>
 

Laurent Lamesch wrote:

dhuster@pb.k12.mo.us wrote:

...

And regarding nuclear research, I remember a field engineer telling
me about selling a lot of transient digitizers to the nuclear
research community. They'd put a TD down a hole with a bomb with the
cabling leading to the blockhouse a couple of miles away. They'd
blow up the bomb and the TD would send the signal out of all the
stuff they were monitoring -- about 1�s before it went into total
meltdown -- and then in the blockhouse monitoring station, they'd
wait for the signal to show up and then after it was captured, high-
speed clamps shut the lines down so the the massive EMP that was
right on the tail of the data didn't totally destroy all the
monitoring equipment. But the poor transient digitizers .... they
got to make one and only one measurement in their entire lives before
that serial number ceased to exist. Danged expensive probe!

Dean
Concerning 'strange' uses of TDs: I have a problem with a 7912AD
which apparantly has been used in the Sandia National Labs (it has
a Sandia cal sticker from 1993). While repairing the power supply,
I got some fine light brown dust present in the supply on my fingers.
After some minutes I had the impression that the dust warmed my
fingers up, I also had a salty taste in my mouth after working on
the supply. I let the TD run for some time with the case open, and
the TD's fan obviously spread some of that dust inside the room I
normally work in. During the weeks which followed, after being some
hours in the same room, I got a slight headache and nausea unless
I opened the door for letting fresh air in.

The problem is that I neither know if this dust is bad for my health,
nor what to do to find out what the dust is. Does anyone have a clue
what it might be, or has anyone ever seen something similar?

Laurent Lamesch

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Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
I'll try the e-mail response this time; can't get to Yahoo at moment -
and post this later, if it doesn't show up on web:

WHERE is ".lu" ??

RUN, do not walk - to somewhere local where you can borrow a geiger
counter. If you can't find one, I can send you a Monitor4, about the
size of a calculator -- but that will take DAYS - depending upon where
.lu IS. If there is a Radiation exposure .org nearby or even many miles
away: CALL THEM NOW !!!

SWAB your entire body with damp paper towels and put these in Ziplock
bag. Have your family (?) do likewise - it may be a false alarm and
your symptoms (of flu, etc) merely coincidence.. but the salty taste is
hardly likely from 'flu'.

SAVE all dust in a Ziplock bag. *BAG that counter* and maybe tape the
door to that room SHUT, pending more INFORMATION. I spent one career in
physics research / accelerators: you are describing symptoms of a
possibly Bad emitter of betas and gammas - IF>> alphas also are present:

HOPE you did not touch your tongue, eyes with your dusty fingers..
Outside body, alphas are not much of a problem; typ. a piece of paper
will shield from their also massively *greater ionizing power*: they are
Helium nuclei, after all = Heavy.

This is an EMERGENCY SITUATION, IMO and from what you said. I will cc:
this to your e-mail as well as the forum. E-mail me for a phone
exchange, when you get this. Sounds as if you are unaware of some
radiation basics, which you next need to find out.

SAVE everything you had that equipment around since purchase - packing,
RECEIPTS etc - IF your instinct is right and the symptoms too - someone
has made an utterly UNACCEPTABLE ERROR, beginning with SANDIA LABS, who
may be paying your air fare for decontamination. They may be NEXT place
you call, after local help...

In haste,

Ashton
ex- Lawrence Berkeley Lab.


Re: Strange 7912AD

Stan or Patricia Griffiths <w7ni@...>
 

If you know someone with a geiger counter, it might be a good idea to go over
that instrument with it . . . just as a precaution, you understand. This is
a serious suggestion.

Stan
w7ni@easystreet.com

Laurent Lamesch wrote:

dhuster@pb.k12.mo.us wrote:

...

And regarding nuclear research, I remember a field engineer telling
me about selling a lot of transient digitizers to the nuclear
research community. They'd put a TD down a hole with a bomb with the
cabling leading to the blockhouse a couple of miles away. They'd
blow up the bomb and the TD would send the signal out of all the
stuff they were monitoring -- about 1�s before it went into total
meltdown -- and then in the blockhouse monitoring station, they'd
wait for the signal to show up and then after it was captured, high-
speed clamps shut the lines down so the the massive EMP that was
right on the tail of the data didn't totally destroy all the
monitoring equipment. But the poor transient digitizers .... they
got to make one and only one measurement in their entire lives before
that serial number ceased to exist. Danged expensive probe!

Dean
Concerning 'strange' uses of TDs: I have a problem with a 7912AD
which apparantly has been used in the Sandia National Labs (it has
a Sandia cal sticker from 1993). While repairing the power supply,
I got some fine light brown dust present in the supply on my fingers.
After some minutes I had the impression that the dust warmed my
fingers up, I also had a salty taste in my mouth after working on
the supply. I let the TD run for some time with the case open, and
the TD's fan obviously spread some of that dust inside the room I
normally work in. During the weeks which followed, after being some
hours in the same room, I got a slight headache and nausea unless
I opened the door for letting fresh air in.

The problem is that I neither know if this dust is bad for my health,
nor what to do to find out what the dust is. Does anyone have a clue
what it might be, or has anyone ever seen something similar?

Laurent Lamesch

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TekScopes-unsubscribe@egroups.com



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Re: Looking for 465B parts

Andrew Campbell <service@...>
 

Hi Don,

The Service Manual for the TAS465 is part number 070-8524-01. I have a copy
of one in my workshop (not for sale).

The only problem being is that I live in Sydney, Australia.

Best Regards,

Andrew Campbell

-----Original Message-----
From: donlcramer@cs.com [mailto:donlcramer@cs.com]
Sent: 08 May, 2001 02:12
To: TekScopes@yahoogroups.com
Subject: [TekScopes] Looking for 465B parts


Hello all,

My first post to this very interesting newsgroup, so I hope this message
makes it out ok.

I would like to acquire any of the following parts for a standard 465B. My
scope was rescued from the dumpster (!) and is completely refurbished save
one each from this list:

PN 131-1428-00 CONTACT,ELEC:GROUNDING CLIP Bottom board HV shield
to "can" contact.
PN 352-0263-00 HLDR,POUCH ASSY: Blue plastic piece at
the front top of the "can".
PN 378-0044-01 FILTER ELEM,AIR:2.5 X 2.5 X 0.25 Air filter element.

The plastic pouch holder piece is the most important to me. Anyone out
there parting out a 465B, perhaps with an otherwise unuseable can?

Next question has to do with a different animal altogether, a Tek TAS 465.
I will probably regret combining these two instruments in one email due to
the confusion over the shared numeric designator. I have acquired (another
"free to a good home") broken TAS 465 100MHz 2ch analog scope and with it
came an instruction manual (070-8523-03). This manual has very limited
service info. I would like to confirm if a separate service manual exists?
Would anyone have one to sell? I've tried the usual manual sources (except
Tek). The serial number on this scope is BR10900. I know that sounds odd,
but that's what is on the label. Would anyone also know what "BR"
signifies in the serial number? Perhaps it wasn't made in Beaverton....

Thank you.

Don


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TekScopes-unsubscribe@egroups.com



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Strange 7912AD (Was: 465 Scan Expansion Mesh)

Laurent Lamesch <jlamesch@...>
 

dhuster@pb.k12.mo.us wrote:

...

And regarding nuclear research, I remember a field engineer telling
me about selling a lot of transient digitizers to the nuclear
research community. They'd put a TD down a hole with a bomb with the
cabling leading to the blockhouse a couple of miles away. They'd
blow up the bomb and the TD would send the signal out of all the
stuff they were monitoring -- about 1�s before it went into total
meltdown -- and then in the blockhouse monitoring station, they'd
wait for the signal to show up and then after it was captured, high-
speed clamps shut the lines down so the the massive EMP that was
right on the tail of the data didn't totally destroy all the
monitoring equipment. But the poor transient digitizers .... they
got to make one and only one measurement in their entire lives before
that serial number ceased to exist. Danged expensive probe!

Dean
Concerning 'strange' uses of TDs: I have a problem with a 7912AD
which apparantly has been used in the Sandia National Labs (it has
a Sandia cal sticker from 1993). While repairing the power supply,
I got some fine light brown dust present in the supply on my fingers.
After some minutes I had the impression that the dust warmed my
fingers up, I also had a salty taste in my mouth after working on
the supply. I let the TD run for some time with the case open, and
the TD's fan obviously spread some of that dust inside the room I
normally work in. During the weeks which followed, after being some
hours in the same room, I got a slight headache and nausea unless
I opened the door for letting fresh air in.

The problem is that I neither know if this dust is bad for my health,
nor what to do to find out what the dust is. Does anyone have a clue
what it might be, or has anyone ever seen something similar?

Laurent Lamesch


Looking for 465B parts

donlcramer@...
 

Hello all,

My first post to this very interesting newsgroup, so I hope this message
makes it out ok.

I would like to acquire any of the following parts for a standard 465B. My
scope was rescued from the dumpster (!) and is completely refurbished save
one each from this list:

PN 131-1428-00 CONTACT,ELEC:GROUNDING CLIP Bottom board HV shield
to "can" contact.
PN 352-0263-00 HLDR,POUCH ASSY: Blue plastic piece at
the front top of the "can".
PN 378-0044-01 FILTER ELEM,AIR:2.5 X 2.5 X 0.25 Air filter element.

The plastic pouch holder piece is the most important to me. Anyone out
there parting out a 465B, perhaps with an otherwise unuseable can?

Next question has to do with a different animal altogether, a Tek TAS 465.
I will probably regret combining these two instruments in one email due to
the confusion over the shared numeric designator. I have acquired (another
"free to a good home") broken TAS 465 100MHz 2ch analog scope and with it
came an instruction manual (070-8523-03). This manual has very limited
service info. I would like to confirm if a separate service manual exists?
Would anyone have one to sell? I've tried the usual manual sources (except
Tek). The serial number on this scope is BR10900. I know that sounds odd,
but that's what is on the label. Would anyone also know what "BR"
signifies in the serial number? Perhaps it wasn't made in Beaverton....

Thank you.

Don


Hi All,

service@...
 

Hi All,

My name is Andrew Campbell and I live in Sydney, Australia.

I am an ex-Tektronix employee (Feb this year) and I am now working
for another company. I'm into repairing and calibrating 'old' tek
scopes.

Great to finally find a discussion list, hopefully I'll be of some
help to someone out there and that there are some of you that may be
able to help me.

Look forward to being part of this group.

Regards,

Andrew


Tek P6451 data probes

Phil (VA3UX) <phil@...>
 

Can anybody accomodate Curt ? (see below).

Please reply directly to him.

Phil

Date: Thu, 03 May 2001 15:31:22 -0700
From: Curtis Wheeler <curtw.curtw@verizon.net>
X-Mailer: Mozilla 4.7 [en]C-PBI-NC404 (Win98; U)
X-Accept-Language: en
To: phil@vaxxine.com
Subject: Tek P6451 data probes

Hi. I have 8 perfect Tek P6451 data probes to sell or exchange for
perfect P6452
probes. Thanks. Curt Wheeler


Re: 465 Scan Expansion Mesh

Stan or Patricia Griffiths <w7ni@...>
 

And regarding nuclear research, I remember a field engineer telling
me about selling a lot of transient digitizers to the nuclear
research community. They'd put a TD down a hole with a bomb with the
cabling leading to the blockhouse a couple of miles away. They'd
blow up the bomb and the TD would send the signal out of all the
stuff they were monitoring -- about 1�s before it went into total
meltdown -- and then in the blockhouse monitoring station, they'd
wait for the signal to show up and then after it was captured, high-
speed clamps shut the lines down so the the massive EMP that was
right on the tail of the data didn't totally destroy all the
monitoring equipment. But the poor transient digitizers .... they
got to make one and only one measurement in their entire lives before
that serial number ceased to exist. Danged expensive probe!

Dean
Yes, I think a lot of 519 scopes suffered a similar nuclear fate. In those
cases, they used polaroid cameras on them and the scopes and cameras were not
exactly melted down . . . just radiated so intensely that they were too "hot"
for anyone to use. As I understand it, some guy in a protective suit would
go rescue the exposed film and they would bury the scopes and cameras. Those
were "one-shot" deals, too. There are some pretty pristine 519's in a vault
somewhere . . .

Stan
w7ni@easystreet.com


Re: Tek 7904 Display Problem

patrick_vandenberghe@...
 

--- In TekScopes@y..., "Don Crano" <donc@s...> wrote:
Hi All

My old faithful 7904 has started to have a little problem with the
display.

It will run for hours or days with no problem. Then it will start
to drift
the display up and down, this is the trace/s and readouts as well.
Note this
is not on oscillation up and down. It will shift up for awhile,
then drop
down lower then it should be for awhile. I am talking about a 1/2
CM or so.
Everything is always on screen, it just gets annoying after awhile.

I found I can turn off the readouts and it will stop. Turn the
readouts back
on, and it will be fine again for a few hours or days.
Hello Don,

I had this problem. It turned out to be the channel switch hybrid
U625 (part nr. 1555-0060). This is located on a 'mezzanine' PCB
behind the two vertical plugins.
Some other sources mentioned the two 1W metal film resistors on the
vertical amplifier.

hope this helps

Patrick


Re: 465 Scan Expansion Mesh

John Rehwinkel <spam@...>
 

Yes, I put some of that mesh under a regular optical microscope here
and found the same thing you did . . . it is etched rather than woven.
I was surprised to discover that . . .
I have a friend who has an electron microscope -- if anyone cares to
lend me a bit of mesh, I'd be glad to get pictures of it and post
them. Naturally, I'd return the mesh too if you like.

-- John Rehwinkel KG4L
spam@fgm.com


Re: 465 Scan Expansion Mesh

dhuster@...
 

Stan,

Yeah, try to get most people to agree that the addition of the engine
computer on a car was a step forward. I think the step forward was
the fact that I have yet to not have a computerized car start within
2-3 seconds whether the temperature was -10°F or +110°F. The step
backward is how, with so many vehicles being produced that (1)
manufacturers over the world haven't settled on a common computer
platform and (2) that to replace one costs as much as my full-blown
home computer. I think the latter is simply because the
manufacturers have us poor consumers by the kahoonies and know it.

And back to the mesh vs. other methods. Not only can one compare
meshless CRTs from the 1960's to the 465/475 and now to the digital
scopes, but look at the digital scope displays. They're going to be
limited not only because of the ±1 digit bobble, but because of the
finite resolution of an LCD or a tri-color CRT dot pitch. No point
in using ADCs with resolution better than the display resolution
unless you have a method of "magnifying" the vertical and/or
horizontal to take advantage of the increase ADC resolution. I've
not looked up the LCD and color CRT specs to see where the two
resolutions converge. Might be interesting! It's an issue not
unlike having a 4-1/2 digit DMM display and only 0.5% accuracy on DCV
and 1% accuracy on ACV.

By the way, I had forgotten about the phosphor change. The P31 is
more durable, that's for sure. I have seen a few P11's that were
wrecked on 7904's and 485's that were being used for nuclear research
out in Amarillo. They were always set up with a camera (obviously,
with a P11) waiting for a single-shot event with the intensities
cranked up to max. They were a BIG market for the 7104 in the OKC
field office.

And regarding nuclear research, I remember a field engineer telling
me about selling a lot of transient digitizers to the nuclear
research community. They'd put a TD down a hole with a bomb with the
cabling leading to the blockhouse a couple of miles away. They'd
blow up the bomb and the TD would send the signal out of all the
stuff they were monitoring -- about 1µs before it went into total
meltdown -- and then in the blockhouse monitoring station, they'd
wait for the signal to show up and then after it was captured, high-
speed clamps shut the lines down so the the massive EMP that was
right on the tail of the data didn't totally destroy all the
monitoring equipment. But the poor transient digitizers .... they
got to make one and only one measurement in their entire lives before
that serial number ceased to exist. Danged expensive probe!

Dean


Re: 465 Scan Expansion Mesh

Stan or Patricia Griffiths <w7ni@...>
 

dhuster@pb.k12.mo.us wrote:

And Stan, I don't know that I agree 100% about the mesh being a bad
deal compared to what the 535 had. I've never seen a burned CRT in a
scope with a mesh and you can't say that about the old ones. The
mesh diffused the beam enough that the CRT was pretty burn
resistant. To me, the �1 digit bobble of a digital scope is far
worse to look at than the fuzzy trace of a 465.

Dean
Hi Dean,

It is great to hear other opinions and views on this sort of thing especially
from someone who was as close to the situation as you have been.

I suspect the difference in burned phosphors was due to the change from P2 to
P31 for a standard phosphor in most general purpose scopes. Both of those
phosphors look very much alike to the eye, being blue-green in color. I
think that phoshor change took place about 1965 or so. Scopes shipped before
that time with P2 phosphors where MUCH easier to burn . . . I don't think I
have ever seen a CRT with a mesh and P2 at the same time . . .

Yes, I put some of that mesh under a regular optical microscope here and
found the same thing you did . . . it is etched rather than woven. I was
surprised to discover that . . .

Whether the fuzzy trace was a bad tradeoff or not is another one of those
opinion issues. I just talked to one guy who told me he could see stuff
(tiny wrinkles) in the trace of a 454 that just are not there in the display
of the same signal on a 475, even though the 475 has 50 MHz more bandwidth
and a much larger screen. The position I am coming from is that I was a
Sales Engineer for Tek at the time mesh CRT's were introduced and I can tell
you that MANY customers noticed the difference and were not pleased . . .
they always expected the new model to be better, in every respect, than the
one it replaced, sort of like cars. Well, they aren't always better in
performance. Sometimes they are better in price, instead. Sort of like cars
. . .

Stan
w7ni@easystreet.com


TEK 2230 Power UP and Service manual

Don Crano <donc@...>
 

Does anyone happen to have a Service Manual for the Tek 2230, they would
like to sell?

And does anyone know what the power up error:
CDT : uncaled : min = 84
might be about.


Thanks in advance!

Don


Re: 465 Scan Expansion Mesh

dhuster@...
 

I believe you're right, Stan. I'd heard both explanations.
Actually, the geometry story doesn't pan out well if you've ever seen
one of the guns outside of the jug. the mesh is hemispherical in
shape. If it dealt with geometry, I'd expect an odd shape to
compensate for the extremes of the rectangular screen. For those who
have never seen one, it is interesting. Very, very delicate, and so
fine that when you hold it up to the light, it's like a diffraction
grating, splitting the light up into different colors. It's also so
fine that it will hold water. One little puff of air and you dimple
it permanently. I send a piece of a mesh to friend Dale Johnson
(used to work for Tek in the Dallas Service center, but at the time
was working for a company that serviced scanning electron
microscopes. He put the piece of mesh under a scope and the view was
really interesting. It's quiet obvious that it's etched and not a
woven screen that one first envisions. I don't know whatever
happened to the Polaroid of that scan that I had. It should would
make for an interesting post, but that was 25 years ago!

Sometimes, during manufacturing, a little dirt gets inside the jug
and finds its way to the mesh. The resulting display is a small spot
on the CRT that just can't be illuminated by the beam because of the
shadow effect it creates. I was rather irritated one time when a new
465B came in with that exact problem and the factory wasn't going to
honor a warranty replacement of the jug because it was "still within
all specifications of CRT anomolies". I put myself in the customer's
shoes and decided that I wouldn't put up with a something like that
in the windshield of a new car. Why should the customer put up with
a manufacturing defectlike that in his $3500 scope? We replaced the
CRT anyway and shoved the old one down factory's throat. Tek was
starting to change from a very customer-oriented organization to a
very money-conscious outfit.

And Stan, I don't know that I agree 100% about the mesh being a bad
deal compared to what the 535 had. I've never seen a burned CRT in a
scope with a mesh and you can't say that about the old ones. The
mesh diffused the beam enough that the CRT was pretty burn
resistant. To me, the ±1 digit bobble of a digital scope is far
worse to look at than the fuzzy trace of a 465.

Dean


Tek 2230 Digital scope options

vincent coppola
 

Does anyone know where I can pick up the GPIB OPT 10 for the Tek 2230
or the RS232 option?
Thanks,
Vince Coppola


Re: Tek 7904 Display Problem

Don Crano <donc@...>
 

Hi Mark,

Yeah I remember posting a list of the YaHoo groups I belong to.

I know what you mean about the older scopes and their fine trace lines. My
old 453 is still on of my favorites, I can sync it on anything I feed into
it.<g> Under it sits a 475A with it's mixed mode delay is nice, but does
not have the fine trace of the ol 453. On a Tekmobile 3 I have the 7904,
with the two lower shelfs each holding a TM504A, and both fully loaded with
plug-ins. So it is my mobile work bench, I can take it any where around the
layout as need be.<g> I really do not have a count of the 7K and TM plug-ins
I have and what works and does not work. But I am sure I do not have them
all. Then on my bench I have a 2230 for what ever analog/digital I might
need.

Don

Remember Always Have Fun and Enjoy!,
Don Crano Akron, Oh NMRA #096211
mailto:donc@sssnet.com
Visit Model Railroading with DCC at:
http://pages.sssnet.com/donc/
Join Model Railroading with DCC Web Ring.

----- Original Message -----
From: Mark Gurries <gurriesm@macconnect.com>
To: <TekScopes@yahoogroups.com>
Sent: Thursday, April 19, 2001 6:12 PM
Subject: Re: [TekScopes] Tek 7904 Display Problem


BTW Hi Mark Gurries glad to see you on the list.
Hi Don.

Been watching the list for a while. It was from one of your email on the
DCC list that I learned about this list. Anyway...

I told Jim Williams here at Linear Tech about this list. (My Lab bench
is next to his.) But he is not one to use PC's. That Jim for ya. For
those who are not familiar with Jim, he is one of out treasured assets at
the company. Hi writes many application notes for our IC and tackling
problems and parts that cause most of us to glaze over our eyes in terms
of the accuracy or noise level requirements. Things like how do you
verify all 24 bits of a 24 bit DAC!

The trick around here to getting a Tek scope fixed and checked out by Jim
Williams is to get an old 500 or 400 series scope in the lab. Tell Jim
about it, and the fact that it does not work annoys Jim to no end.
Before you know it, he is digging into the scope and fixing everything.
Not that we cannot fix out own scopes mind you, but, Jim does a faster
and better job than anyone I know. It fun to watch him and of course you
learn along the way the history and debug tricks.

We have about every make of Tek scope at the company labs. We have lots
of 547's working in parallel with the latest Tek Scopes. We just got
around to setting up an old 556 dual beam on another engineers lab bench.
454's are another favorite. A few of the guys have 7K stuff like yours.
One of my employees has every 7K plug in made including some test
adapters if I recall correctly. It amazing to see the latest scopes
setup right next to an old classic. The biggest reason we like the old
400 and 500 series scopes is the very fine trace and excellent noise
floor. When Jim sets up his 556 with two 1A4 plugins showing 8 traces
that are all beautifully detailed (4 of the traces are on a different
time base to boot) published in a App note, we sometimes get letters and
calls about the scope photo alone! How did you do that?

We think that our lab is one of the biggest consumers of electricity in
Silicon Valley with all these Tube Tek scopes on and possibly the source
of all the blackouts here in California. We already went though one air
conditioner! ;-0


Best Regards,

Mark Gurries
gurriesm@macconnect.com

---------------------------------------------------------
Promotor of the DCC Standard for Model trains.
Model Railroad Club and NMRA DCC presentations are at:
http://www.falken.net/dave/svl
--------------------------------------------------------
Audio Enthusiast (Love SAE equipment)
http://members.ebay.com/aboutme/gurriesm/
http://www.wardsweb.org/audio/index_audio.html
----------------------------------------------------------


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Re: 465 Display Help Needed

Stan or Patricia Griffiths <w7ni@...>
 

CRT Mesh comment below:

dhuster@pb.k12.mo.us wrote:

A few comments on what has been offered so far.

The characteristic fuzziness of a 465/475 and 7K scopes over their
earlier cousins (and which apparently is NOT your problem since you
describe major "focus" problems) is due to the inclusion of a scan
expansion mesh within the jug through which the electron beam has to
pass, causing a small amount of beam scatter. The mesh is there to
improve geometry.
My understanding of the reason an expansion mesh was used in 465 and later
vintage tubes was really to improve the vertical and horizontal sensitivity
of the CRT such that expensive transistors would no longer be necessary in
the vertical and horizontal scope amplifiers. It was mostly a manufacturing
cost reduction measure with a spot size tradeoff. Not a good tradeoff, in my
opinion.

Compare the output stages of the 547, 453, and 454 scopes to what you see in
the 465 and 475 and you will see what I am talking about.

Stan
w7ni@easystreet.com


Re: 465 Display Help Needed

dhuster@...
 

A few comments on what has been offered so far.

The characteristic fuzziness of a 465/475 and 7K scopes over their
earlier cousins (and which apparently is NOT your problem since you
describe major "focus" problems) is due to the inclusion of a scan
expansion mesh within the jug through which the electron beam has to
pass, causing a small amount of beam scatter. The mesh is there to
improve geometry.

If oscillations within the vertical system is the problem, then
inputting a sine wave will show a thicker trace at the peaks and a
thinner trace at the zero-crossing points. Also, you'll see the
signal from the vertical deflection plate pins on back to the source
of oscillation.

Open elements inside the jug can cause defocusing.

Don't forget that astigmatism and focus interact and one may be the
problem where the other is not. If you can "round up" an unfocused
stationary dot on the CRT with the astigmatism control, then focus is
your problem. If not, the astigmatism circuit may be at fault.

Make sure the LV power supplies are clean, correct and ripple-free.


Re: 465 Display Help Needed - another thought

Bill Wollam
 

--- In TekScopes@y..., ashtonb@j... wrote:
--- In TekScopes@y..., Kurt Graber <kurtg@s...> wrote:


billw101@a... wrote:

Hello, I have been pulling problems out of a 465 that I recently
acquired. The last remaining problem is the inability to get a
sharp
focus on the trace with any combination of intensity, focus or
astigmatism. I have checked everything in the CRT circuits with
the
exception of the high voltage, crt bias and cathode bias, until
I
get
the use of an HV probe. Can anyone tell me if I am looking in
the
right area or suggest any common failure modes? The low voltage
supplies all check good and noise free. Thanks for any help.
...........................................



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A common problem or failure is the opening of the voltage divider
circuit
that the focus and astig tap into.
I am unfamilier with your particular scope but the chances are
good
that one
of the resistors has opened up. I have seen many cases !!! you
don't
need a
HV probe , just take your meter and ohm them out. They will not
appear burned
but they have a tendancy to open up due to the high
voltage.......this will
cause an unsharp trace and many cases no trace at all (just a
haze)...Good
Luck
Another point: the 46x, 47x series just wasn't as sharp as the tube
scopes! or even and especially - the 454, 454A. Some engrs. think
the 454A best 150 MHz scope ever (2mV/DIV, all the delay
triggering)
or sometimes ~ 200 MHz if all went well on that assembly..

I can see the clear difference bewtween say, a 475A and the 454As
-
tiny wiggles just visible on 54-A disappear into the thick trace of
475 (or 465).

Just in case you're trying to do better than it Can!


Ashton
AShton, yes I have heard that same thing about the 465, however after
troubleshooting I am further able to describe the problem. The
transition of the trace either falling or rising is poorly defined
and instead of one sharp edge I see almost a centimeter of blur. I
have been through the video output amplifier from one end to the
other but I still have the symptom that any capacitance such as a
scope lead hung on either vertical deflection output causes the
amplifier to go into high freq. oscillation and the trace becomes a
fog. I will press on but there is definitely something wrong with
this thing.

Bill


Re: 465 Display Help Needed - another thought

Stan or Patricia Griffiths <w7ni@...>
 

billw101@aol.com wrote:

AShton, yes I have heard that same thing about the 465, however after
troubleshooting I am further able to describe the problem. The
transition of the trace either falling or rising is poorly defined
and instead of one sharp edge I see almost a centimeter of blur. I
have been through the video output amplifier from one end to the
other but I still have the symptom that any capacitance such as a
scope lead hung on either vertical deflection output causes the
amplifier to go into high freq. oscillation and the trace becomes a
fog. I will press on but there is definitely something wrong with
this thing.

Bill
Hi Bill,

I would take a close look at the input FET's to make sure they are the
original type. Sometimes they will short or open and the repair techinician
will use whatever FET is handy and not bother with the correct part. This
can cause all sorts of oscillation problems and stuff like you are seeing.

Stan
w7ni@easystreet.com

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