Topics

475 With a bowed display. . . .Ideas?


Michael W. Lynch
 

On Fri, Aug 14, 2020 at 07:38 AM, Jim Hall wrote:


Michael,

I'm glad that I'm not the only one with the blue-box illness. I've had a 465
in my workshop for 20 years with the intention of getting it working.  I bid
on several units on eBay this year and was surprised to win all the bids.
Thus, with the knowledge from the postings on this group and manuals from
Artek, I now have 9 working scopes (465 and 475). Is there a cure for this
addition?
Jim.
I fear that the only sure cure is death.

--
Michael Lynch
Dardanelle, AR


Paul Amaranth
 

On Fri, Aug 14, 2020 at 01:59:38PM +0100, Tom Gardner wrote:
I'm glad that I'm not the only one with the blue-box illness. I've had a 465 in my workshop for 20 years with the intention of getting it working.  I bid on several units on eBay this year and was surprised to win all the bids. Thus, with the knowledge from the postings on this group and manuals from Artek, I now have 9 working scopes (465 and 475). Is there a cure for this addition?
Yes, but it is worse than the disease.

Start by reading *only* the first three posts on this page (including the acronyms)
https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg1114480/#msg1114480
*and nothing else*

Then look at the page and viewing count, and weep.
Ha, I had never looked at the start of that thread. The problem is that
the "problem" is not restricted to scopes, or Tek or whatever. Got
convinced to buy an electronic load the other week from reading that
thread. Also ended up with a couple of pieces of nixie gear that
was just too cool not to own.

It's also the entry path into time or volt nuttery. Down that rabbit
hole you could end up with your own hydrogen maser or two. I suppose
we should count ourselves lucky.

Did anyone see my post on selling 11 of my Tek scopes? Don't all rush
in at once.

Paul

--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix/Linux - We don't do windows


Tom Gardner
 

On 14/08/20 13:38, Jim Hall wrote:
On 8/13/2020 9:17 AM, Michael W. Lynch via groups.io wrote:

On Mon, Aug 10, 2020 at 11:58 AM, Tom Gardner wrote:


I went and picked up a CRT, and the bloke let me have a decent deal on a
485
that took a long time to startup first thing in the morning. Locating
the
dubious startup electrolytic fixed the problem, but lead to the
problem of
buying more duff scopes :(

Tom,

Laughing here at reading this. Almost exactly how I got into the
same predicament here. Some people say you smoke crack one time and you
are hooked and people like us fix one scope and we are hooked, we cannot
stop buying old blue boxes with a whole bunch of little knobs and switches
on the front.
Michael,

I'm glad that I'm not the only one with the blue-box illness. I've had a 465 in my workshop for 20 years with the intention of getting it working.  I bid on several units on eBay this year and was surprised to win all the bids. Thus, with the knowledge from the postings on this group and manuals from Artek, I now have 9 working scopes (465 and 475). Is there a cure for this addition?
Yes, but it is worse than the disease.

Start by reading *only* the first three posts on this page (including the acronyms)
https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg1114480/#msg1114480
*and nothing else*

Then look at the page and viewing count, and weep.


Jim Hall
 

On 8/13/2020 9:17 AM, Michael W. Lynch via groups.io wrote:


On Mon, Aug 10, 2020 at 11:58 AM, Tom Gardner wrote:


I went and picked up a CRT, and the bloke let me have a decent deal on a
485
that took a long time to startup first thing in the morning. Locating
the
dubious startup electrolytic fixed the problem, but lead to the
problem of
buying more duff scopes :(

Tom,

Laughing here at reading this. Almost exactly how I got into the
same predicament here. Some people say you smoke crack one time and you
are hooked and people like us fix one scope and we are hooked, we cannot
stop buying old blue boxes with a whole bunch of little knobs and switches
on the front.
Michael,

I'm glad that I'm not the only one with the blue-box illness. I've had a 465 in my workshop for 20 years with the intention of getting it working.  I bid on several units on eBay this year and was surprised to win all the bids. Thus, with the knowledge from the postings on this group and manuals from Artek, I now have 9 working scopes (465 and 475). Is there a cure for this addition?


Tom Gardner
 

On 13/08/20 15:17, Michael W. Lynch via groups.io wrote:
On Mon, Aug 10, 2020 at 11:58 AM, Tom Gardner wrote:

I went and picked up a CRT, and the bloke let me have a decent deal on a 485
that took a long time to startup first thing in the morning. Locating the
dubious startup electrolytic fixed the problem, but lead to the problem of
buying more duff scopes :(
Tom,

Laughing here at reading this. Almost exactly how I got into the same predicament here. Some people say you smoke crack one time and you are hooked and people like us fix one scope and we are hooked, we cannot stop buying old blue boxes with a whole bunch of little knobs and switches on the front.
I taught my daughter the concept of how you become a drunkard, i.e. one drink at a time.

I once asked people why I needed a fourth scope. There was only one justifiable answer: you must have four before you can have five :(


Michael W. Lynch
 

On Mon, Aug 10, 2020 at 03:01 PM, Chuck Harris wrote:


RATS!!!

-Chuck Harris
Chuck,

Yes, it SUCKS! When I heard that glass tinkle, my heart sank. If this was an old beater, it would not be so bad, but this is a very nice scope. I suppose that a good parts scope will turn up sooner or later. At least I am ready if that happens.

Appreciate all the advice that you provide.

Sincerely,

--
Michael Lynch
Dardanelle, AR


Michael W. Lynch
 

On Mon, Aug 10, 2020 at 11:58 AM, Tom Gardner wrote:


I went and picked up a CRT, and the bloke let me have a decent deal on a 485
that took a long time to startup first thing in the morning. Locating the
dubious startup electrolytic fixed the problem, but lead to the problem of
buying more duff scopes :(
Tom,

Laughing here at reading this. Almost exactly how I got into the same predicament here. Some people say you smoke crack one time and you are hooked and people like us fix one scope and we are hooked, we cannot stop buying old blue boxes with a whole bunch of little knobs and switches on the front.
--
Michael Lynch
Dardanelle, AR


Michael W. Lynch
 

On Mon, Aug 10, 2020 at 12:01 PM, <toby@...> wrote:


Aaarg, sorry, ignore my message about Sphere. It's sold.

There is one on ebay UK though:
https://www.ebay.ca/itm/154-0677-10-TEKTRONIX-CRT/264704023173

--Toby
Toby,

Yes, I found that one. Too rich for my blood. I will just lurk around until I find a parts scope. One of these will turn up sooner or later.

--
Michael Lynch
Dardanelle, AR


Chuck Harris
 

RATS!!!

-Chuck Harris

Michael W. Lynch via groups.io wrote:

All:

I went back and confirmed that the Geometry and Y Align controls were functioning correctly. Both circuits checked out good.

Reconfirmed all power supplies potentials and ripple.

Checked all physical connections to the CRT.

After that, the CRT needed to come out to see if steering magnets were used and had subsequently become dislodged (which was not the case).

Although I was holding out hope that physical damage to the CRT was not the cause, Chuck Harris hit the nail on the head with his first response to my inquiry.

Chuck Harris
Aug 8 #170283
Typically, when a proper application of the Geometry,
Focus, Astigmatism, Trace Rotation, and other affiliated
adjustments results in a screen that just doesn't look
as pretty as we would like, it means that there has been
an outside physical influence on the CRT (READ: OOPS! BANG!
$%^! & #!!*^! Why Me???)
Cause of Problem found, But problem not solved! After removing the CRT, I could detect the very faint "tinkle" of broken glass. Closer examination revealed that one of the the glass rods that supports for the Deflection plates and the geometry shield had been broken. this obviously skews the deflection plates and the geometry electrodes as well.

See the condition of the glass support rod in New photos at: https://groups.io/g/TekScopes/photo/251792/0

My next problem is that I do not have a replacement CRT. I was thinking (there I go again!) that I have one, but what I have available are a 154-0731-00 and a 154-0731-04 not the required 154-0677-10. So, I need to find a good CRT for this scope. This scope is too nice to just part out, but also worthless without a proper CRT.


Michael Lynch
Dardanelle, AR




Michael W. Lynch
 

Raymond,

I am not familiar at all with the 475. This is the first one that I have tried working on. I do have a perfectly functional 475A/DM44, but have not had to open it up at this point. I have heard about these"distributed plates" but never took the time to explore the theory behind them. I suppose that these higher speed scopes require them at the higher bandwidths which they are capable of displaying. Most of my work has been on slower scopes.

Thanks for taking the time to explain this to me. I will do some additional reading.

Sincerely,

--
Michael Lynch
Dardanelle, AR


 

On Mon, Aug 10, 2020 at 08:59 PM, Raymond Domp Frank wrote:


both "ends".
Trying to say here that there's an impedance matching terminator connecting the "far side" of the top plate and the "far side" of the bottom plate.

Raymond


 

On Mon, Aug 10, 2020 at 08:28 PM, Michael W. Lynch wrote:


Raymond,

Unfortunately, the 475 CRT has an extra set of pins on the side of the CRT,
which the 465 CRT lacks. The extra pins are adjacent to and aligned with the
Vertical Deflection plate pins. There is about 1 1/2 - 2 inches between the
two sets of pins (I did not measure, just from memory). So there are a total
of 4 pins on the side of the CRT, where the 465 only has 2 pins. The
Horizontal pins come in from the bottom exactly like the 465. Even though the
465 and 475 are similar, I am much more familiar with the 465 and it is not at
all clear in the schematic or the service manual what these pins do. I am
certainly not experienced enough to say what these are for. These two extra
pins do not show in the schematic, at least not that I can find. I don't want
to risk trying without those extra pins connected. This might damage the
scope, the CRT or worst of all both of them. Clearly different from the
465/465B CRT. Do you have any idea what these extra 2 pins might be for?
I'm not familiar with the CRT of the 475, I have to admit. The extra pins almost certainly are distributed plate connections. In general, there's just a terminator connected between both "ends". I didn't know the 475 had distributed vertical plates. The main idea of distributed plates is to make sure that those electrons that make up the beam at any moment, traveling from cathode to screen at a certain (limited) speed, aren't deflected first to one side then to the other by the same vertical plate('s charge) because they take time to pass the plate which sits along the beam's path for a "significant time". The distributed plate artificially lengthens the signal path and causes the applied signal to travel in parallel with the beam at the beam's speed toward the screen. Using very "short" vertical plates instead isn't an option because deflection sensitivity depends (a.o.) on the time that the charge of a plate works on the beam. You should be able to measure a DC connection between both ends of each distributed plate.

Raymond


Michael W. Lynch
 

On Mon, Aug 10, 2020 at 12:27 PM, Raymond Domp Frank wrote:


It might be worthwhile to check and see if one of your -0731's will do. The
'scopes are very alike, except for BW of course and ISTR that CRT's of
different models were used during the production life of the 465/475 series.
At least I'd think that they are pin compatible. ISTR that the expansion mesh
construction in the 465 was changed/improved at some stage but that's probably
just the -0x mod level in the -0731.
Possibly worth a try after establishing that nothing will blow up.
Raymond,

Unfortunately, the 475 CRT has an extra set of pins on the side of the CRT, which the 465 CRT lacks. The extra pins are adjacent to and aligned with the Vertical Deflection plate pins. There is about 1 1/2 - 2 inches between the two sets of pins (I did not measure, just from memory). So there are a total of 4 pins on the side of the CRT, where the 465 only has 2 pins. The Horizontal pins come in from the bottom exactly like the 465. Even though the 465 and 475 are similar, I am much more familiar with the 465 and it is not at all clear in the schematic or the service manual what these pins do. I am certainly not experienced enough to say what these are for. These two extra pins do not show in the schematic, at least not that I can find. I don't want to risk trying without those extra pins connected. This might damage the scope, the CRT or worst of all both of them. Clearly different from the 465/465B CRT. Do you have any idea what these extra 2 pins might be for?


--
Michael Lynch
Dardanelle, AR


 

On Mon, Aug 10, 2020 at 06:57 PM, <toby@...> wrote:


My next problem is that I do not have a replacement CRT. I was thinking (there
I go again!) that I have one, but what I have available are a 154-0731-00 and
a 154-0731-04 not the required 154-0677-10. So, I need to find a good CRT for
this scope. This scope is too nice to just part out, but also worthless
without a proper CRT.
It might be worthwhile to check and see if one of your -0731's will do. The 'scopes are very alike, except for BW of course and ISTR that CRT's of different models were used during the production life of the 465/475 series. At least I'd think that they are pin compatible. ISTR that the expansion mesh construction in the 465 was changed/improved at some stage but that's probably just the -0x mod level in the -0731.
Possibly worth a try after establishing that nothing will blow up.
An example of Tek's CRT selection but "the other way around" is the CRT Tek used in the 24XX series: The same CRT model could be found in digitizing 'scopes (2430..2440), where a BW of a few MHz was enough and in 150..400 MHz 2445..2465 models. So, distributed plates (HF feature) in a 'scope where only a few MHz is needed (2430..2440)! Economies of scale probably were behind that decision.

Raymond


toby@...
 

On 2020-08-10 12:25 p.m., Michael W. Lynch via groups.io wrote:
All:
...
My next problem is that I do not have a replacement CRT. I was thinking (there I go again!) that I have one, but what I have available are a 154-0731-00 and a 154-0731-04 not the required 154-0677-10. So, I need to find a good CRT for this scope. This scope is too nice to just part out, but also worthless without a proper CRT.
Aaarg, sorry, ignore my message about Sphere. It's sold.

There is one on ebay UK though:
https://www.ebay.ca/itm/154-0677-10-TEKTRONIX-CRT/264704023173

--Toby



Michael Lynch
Dardanelle, AR



Tom Gardner
 

On 10/08/20 17:25, Michael W. Lynch via groups.io wrote:
Cause of Problem found, But problem not solved! After removing the CRT, I could detect the very faint "tinkle" of broken glass. Closer examination revealed that one of the the glass rods that supports for the Deflection plates and the geometry shield had been broken. this obviously skews the deflection plates and the geometry electrodes as well.
See the condition of the glass support rod in New photos at: https://groups.io/g/TekScopes/photo/251792/0
My first scope repair, a 465, took a similarly long time. The scope was doing a passable imitation of a torch, which I eventually traced to a broken grid weld, see https://entertaininghacks.files.wordpress.com/2016/03/crtgrid.jpg I learned a lot in that process :)

I went and picked up a CRT, and the bloke let me have a decent deal on a 485 that took a long time to startup first thing in the morning. Locating the dubious startup electrolytic fixed the problem, but lead to the problem of buying more duff scopes :(


toby@...
 

On 2020-08-10 12:25 p.m., Michael W. Lynch via groups.io wrote:
...
My next problem is that I do not have a replacement CRT. I was thinking (there I go again!) that I have one, but what I have available are a 154-0731-00 and a 154-0731-04 not the required 154-0677-10. So, I need to find a good CRT for this scope. This scope is too nice to just part out, but also worthless without a proper CRT.

Hi,

Sphere lists one. https://www.sphere.bc.ca/test/tek-crts.html

--Toby




Michael Lynch
Dardanelle, AR



Michael W. Lynch
 

All:

I went back and confirmed that the Geometry and Y Align controls were functioning correctly. Both circuits checked out good.

Reconfirmed all power supplies potentials and ripple.

Checked all physical connections to the CRT.

After that, the CRT needed to come out to see if steering magnets were used and had subsequently become dislodged (which was not the case).

Although I was holding out hope that physical damage to the CRT was not the cause, Chuck Harris hit the nail on the head with his first response to my inquiry.

Chuck Harris
Aug 8 #170283
Typically, when a proper application of the Geometry,
Focus, Astigmatism, Trace Rotation, and other affiliated
adjustments results in a screen that just doesn't look
as pretty as we would like, it means that there has been
an outside physical influence on the CRT (READ: OOPS! BANG!
$%^! & #!!*^! Why Me???)
Cause of Problem found, But problem not solved! After removing the CRT, I could detect the very faint "tinkle" of broken glass. Closer examination revealed that one of the the glass rods that supports for the Deflection plates and the geometry shield had been broken. this obviously skews the deflection plates and the geometry electrodes as well.

See the condition of the glass support rod in New photos at: https://groups.io/g/TekScopes/photo/251792/0

My next problem is that I do not have a replacement CRT. I was thinking (there I go again!) that I have one, but what I have available are a 154-0731-00 and a 154-0731-04 not the required 154-0677-10. So, I need to find a good CRT for this scope. This scope is too nice to just part out, but also worthless without a proper CRT.


Michael Lynch
Dardanelle, AR


Chuck Harris
 

I don't think so, and here is why:

When the scope is exposed to a strong magnet,
the field lines extend in loops from N to S poles.
When those flux lines confront a magnetizable metal,
they are distorted and concentrated into that metal,
making for truly weird looking flux arrangements.

On screen, such magnetizations of the mumetal
shield, which really is the only magnetizable material
anywhere near the CRT will make beam deflections in
small areas. This typically shows up as a kink
somewhere on the screen, near one edge.

_____________

_____________

___________/\

____________/

A power supply regulation failure could cause a progressive
pinch of the screen width making a "keystone" shape.

-Chuck Harris

Keith wrote:

Just thinking out loud here - if a scope sat on a bench (or in storage) in one position for a long time near some relatively powerful fixed nearby magnetic field, (like a big permanent magnet loudspeaker assembly, etc.) I suppose it is possible for some nearby magnetic anomaly like that to gradually induce a very specific magnetism somewhere, leading to visible misalignment? Such an unwanted magnetic influence could produce a very specific distortion and it would seem reasonable for such an influence to be most obvious on traces out at the edges of the CRT.

Maybe you could try degaussing the shield around the CRT? You can borrow my degaussing tool if you want. Sometimes it is the simple stuff. PIA to remove the shield and separate from the CRT, but that is probably the safest way to do it. Of course you would first have to remove those steering magnets like someone mentioned, or the degaussing tool would ruin them. Of course this means even more fiddling, but hey...that’s why we do this hobby, right?

Also, maybe the shield has been damaged by some mishandling in the past? Tek says, and I quote

“CAUTION This Mumetal shield has been carefully annealed after fabrication. Any shock may destroy its magnetic shielding characteristics”

So obviously it is possible for them to go bonkers. Just a thought...

Cheers,
CBG




Keith
 

Just thinking out loud here - if a scope sat on a bench (or in storage) in one position for a long time near some relatively powerful fixed nearby magnetic field, (like a big permanent magnet loudspeaker assembly, etc.) I suppose it is possible for some nearby magnetic anomaly like that to gradually induce a very specific magnetism somewhere, leading to visible misalignment? Such an unwanted magnetic influence could produce a very specific distortion and it would seem reasonable for such an influence to be most obvious on traces out at the edges of the CRT.

Maybe you could try degaussing the shield around the CRT? You can borrow my degaussing tool if you want. Sometimes it is the simple stuff. PIA to remove the shield and separate from the CRT, but that is probably the safest way to do it. Of course you would first have to remove those steering magnets like someone mentioned, or the degaussing tool would ruin them. Of course this means even more fiddling, but hey...that’s why we do this hobby, right?

Also, maybe the shield has been damaged by some mishandling in the past? Tek says, and I quote

“CAUTION This Mumetal shield has been carefully annealed after fabrication. Any shock may destroy its magnetic shielding characteristics”

So obviously it is possible for them to go bonkers. Just a thought...

Cheers,
CBG