Date   

Re: Encouraging beginners: What are we accomplishing?

Reginald Beardsley
 

It's a lot easier to fix a scope if you have a working scope. I bought a 60 MHz dual trace Dumont 1062 from Tucker in Dallas around 1990 for $300+. About a week after the 30 day warranty expired the horizontal section died.

Not realizing at the time I could have traced the sweep circuit using just the vertical channel it sat for some time until a traded a pair of 141 MB ESDI drives for a wonky 465. It worked just well enough that I was able to fix the Dumont after which I fixed the 465.

I'd never done this level of repair before. I just kept plugging away after work each evening until I got them going. That said, I did have a wide range of experience repairing things, so I had learned the important part, the thought process. And I had repaired my Heathkit IO-18 when a shorted cap blew up a pair of rectifier tubes. Before I got that all I had was a VOM and DMM which I used to fix stereo gear I fished out of the trash and sold.

I think it should be pointed out that the more you know, the less you need in the way of test gear. I did not read the 475 thread because i have no experience with a 475. Did anyone suggest using a blocking capacitor to measure the ripple on the +50 V line with a DMM? In short, was he told how to make the needed tests with the equipment he had available?

Reg


Re: Encouraging beginners: What are we accomplishing?

 

Hi Roy,

I understand where you are coming from with your post.
I also followed initially the thread started bu ciclista41@ with "475 questions", and I answered some of them.
I was not the only one, other members made their contribution too.

What discouraged me of continuing was the concern of all what could go wrong with an inexpert ciclista repairing the complex scope,
and also the fact that many good intentioned contributors with different ideas would only create confusion.

I looked at his thread just now, and it seems that ciclista41 is still struggling with the low voltage supply, the +50V, while asking himself why nothing right appears on the screen.
I truly wish that he finds one component that fixes his +50V, and then all the other supplies fall automatically in line, and then maybe... maybe he gets some sign that the scope is alive.
If this is not the case, it hurts me to think of his disappointment, and all his efforts that will not have been successful. So I hope for some good luck!

It is much easier to advise, to help a person who is more expert, perhaps at the same level or above one's level, who is simply missing some particular experience one can provide. Not missing a complete education in electronics.
It would also be easier if a person like ciclista41 starts off with a project that is less complex, (although, what is more simple than a linear power supply?)

I pass no judgment of your opinion and that of other members including myself. Things are what they are. And there is no doubt that we all have plenty of good will !

Ernesto


Re: 475 questions

ciclista41@...
 

Hi Eric!

Thanks for your suggestions. Just like your advice to ask a million questions, I appreciate as much input as I can get. I look forward to sharing in the satisfaction you obviously enjoy from having restored one of these scopes!

Bruce

On Wed, May 27, 2020 at 05:41 AM, Eric wrote:


I have some things to add given that I was in a similar position
recently but with a 485.

Go glacerly slow. There are some parts in these wonderful instruments
that you will not be able to replace if they get zapped. And you can zap
things with static / probing

Spend LOTS of time with the schematic especially in the theory of
operation section. Tek wrote some of the best technical manuals out there

Practice your soldering skill NOT on the 475 get a few soldering
projects and build them up soldering is 30% knowledge and 70% feel / Art
you just have to do it.. A Lot

DO NOT use a cheap iron. Minimum recommendation here is a Hakko 888D or
equivalent from a different vender. The last thing you want to do is
over heat a trace and de-laminate it from the board. Due to poor
temperature regulation or long dwell time.

It took me 8 months to fully restore my first 485, but mine was hacked
up pretty good by the previous owner. Lots of pots were replaced with
fixed resisters.

If you going to Calibrate/align the scope you will need to know some
high voltage probing -4000 Vdc will blow your meter input with out the
proper tools.

Proceed with caution and ask a million questions. It is better to ask
then to lose a hybrid that you cant replace.

Good luck I look forward to hearing about your success


Eric

On 5/27/2020 4:14 AM, David C. Partridge wrote:
I found that by searching "neon bulb oscilloscope", I found this:
https://en.wikipedia.org/wiki/Pearson%E2%80%93Anson_effect
So the bulbs are used as an oscillator
I don't believe so. IIRC the neons in the 475 are in the EHT supply
circuit and are effectively over-voltage spark gaps.

To add to this discussion - replace nothing until you know it is causing a
fault especially if you have limited soldering skills.

David




Re: Encouraging beginners: What are we accomplishing?

Siggi
 

On Wed, May 27, 2020 at 3:26 PM James Theonas via groups.io <jamestheonas=
yahoo.com@groups.io> wrote:

In any case as a noob as I consider myself (my first true oscilloscope)
this group came through for me in flying colors or colours (depends on
where your from) and I am very grateful for its existence and everyone here!
Looks like my first post on here was back in 2014 (
https://groups.io/g/TekScopes/message/103234), and it was a very similar
story back then. Without the help and encouragement of this group, I would
never have had the courage to tackle the repair of my beautiful old 2467.
Over time I even gathered together the gear to properly calibrate the old
girl, and went through the calibration process.


Re: Encouraging beginners: What are we accomplishing?

James Theonas
 

Hi Friends (and I don't say this lightly)
I'm a noob at oscilloscopes as they have always been out of my reach to purchase. I have worked many years and mostly depended on my trusty Multimeter to get me by. I have finally got my self an Oscilloscope the 2465b and I am very happy with my purchase. I did however have to clean some contacts in the ch1 attenuator and literally had to take the thing apart! A little scary but with the help of this group I got through it! Oscilloscope is up and running and working great despite the thread I had opened going overboard about cleaning fluids and alcohol and even reaching moonshine and distilleries! Funny thing is I didn't use alcohol at all but used benzine and cotton to clean contacts! In any case as a noob as I consider myself (my first true oscilloscope) this group came through for me in flying colors or colours (depends on where your from) and I am very grateful for its existence and everyone here!
Dimitris Theonas

On Wednesday, May 27, 2020, 10:07:48 PM GMT+3, Roy Thistle <roy.thistle@mail.utoronto.ca> wrote:

On Wed, May 27, 2020 at 08:51 AM, stevenhorii wrote:


87% of all statistics are made up on the spot
Well, you can take the Bayesian approach... a subjective interpretation of probability models, with feedback training... it's as legit as the frequency approach.
But anyway... back to Tek.
Some great blow-back, and thoughtful comments from everyone, particularly from Chuck... who even though... if he is referring to my values, and my thinking, has got me completely wrong... Chuck provided some great incite into what makes "collectors" tick.... and perhaps what professional repairs cost in the U.S.A.
Again, I should mention, if you want to tell me what I think, just PM me... I read my email. Although, IMO, asking me is often far more elucidatiing.. I'll admit, mileage may vary.
Best regards and wishes.
All the best
Roy


Re: Encouraging beginners: What are we accomplishing?

Roy Thistle
 

On Wed, May 27, 2020 at 08:51 AM, stevenhorii wrote:


87% of all statistics are made up on the spot
Well, you can take the Bayesian approach... a subjective interpretation of probability models, with feedback training... it's as legit as the frequency approach.
But anyway... back to Tek.
Some great blow-back, and thoughtful comments from everyone, particularly from Chuck... who even though... if he is referring to my values, and my thinking, has got me completely wrong... Chuck provided some great incite into what makes "collectors" tick.... and perhaps what professional repairs cost in the U.S.A.
Again, I should mention, if you want to tell me what I think, just PM me... I read my email. Although, IMO, asking me is often far more elucidatiing.. I'll admit, mileage may vary.
Best regards and wishes.
All the best
Roy


Re: Encouraging beginners: What are we accomplishing?

Jeff Woolsey
 

On 5/27/20 7:08 AM, Jamie Ostrowski wrote:
Does anyone have any idea, statistically, of how many scopes die from
beginners trying to repair them verses those that die to tube harvesters or
relatives who have no interest in "Bob's" old scopes who send them to the
recycler?

As a single data point, I've killed [1] my 455 and resurrected a 2440. 
So I guess my net phosphor footprint is zero, for now.

[1] well, I expect it's repairable, but HV scares me, as it should.

--
Jeff Woolsey {{woolsey,jlw}@jlw,first.last@{gmail,jlw}}.com
Nature abhors straight antennas, clean lenses, and empty storage.
"Delete! Delete! OK!" -Dr. Bronner on disk space management
Card-sorting, Joel. -Crow on solitaire


Re: Encouraging beginners: What are we accomplishing?

Sean Turner
 

"What are we accomplishing"...quite simple really, keeping the hobby, and some of the highest quality stuff ever bestowed the label "Made in USA", alive! Newcomers are lifeblood, and sour old men scaring them away with rhetoric like post this accomplishes nothing positive. It's gatekeeping, pure and simple. Instead, why not pass on your knowledge and be happy in knowing that it isn't going to die when you do. Sorry to be blunt, but that's really important. Given proper care, a lot these Tek scopes will probably last several more decades in good service to the hobbyist, but only if younger folks have an appreciation for them and a desire to preserve them.

This is a fantastic group for preserving that knowledge base, and I thank Dennis for working hard to provide it and keep it that way.

Sean


Re: Encouraging beginners: What are we accomplishing?

stevenhorii
 

Sorry if a bit off topic -

"Statistics are like bikinis and Speedos; what they reveal is interesting
but what they conceal is vital."

SteveH




On Wed, May 27, 2020, 11:26 Michael W. Lynch via groups.io <mlynch003=
yahoo.com@groups.io> wrote:

LarryS 9:52am #167513
87% of all statistics are made up on the spot.
:-)

L.
Larry,

You made me laugh with this one! TRUTH!
--
Michael Lynch
Dardanelle, Arkansas




Re: Encouraging beginners: What are we accomplishing?

Michael W. Lynch
 

LarryS 9:52am #167513
87% of all statistics are made up on the spot.
:-)

L.
Larry,

You made me laugh with this one! TRUTH!
--
Michael Lynch
Dardanelle, Arkansas


Re: 475 questions

n4buq
 

I have hesitated to mention this as a possible approach to the filter caps in the 475 because:

1. I don't know for sure whether the layouts between the 465 and 475 are identical
2. The design is, well, a bit kludgy (if I do say so myself)

However, I thought I'd pass it along.

Pictured in this album is an implementation of a separate circuit board that provides that ability to use common snap-in caps as replacements. My intent for this was to make it possible to replace those caps again (should it every become necessary) without further desoldering/soldering on the main board.

https://groups.io/g/TekScopes/album?id=64929

There are small disc adapters that do somewhat the same thing (I have some); however, if a future cap replacement becomes necessary, I'm not sure it is possible to do that without removing the disc which, of course, involves solder work on the main board.

Maybe one day I'll afford a snazzy desoldering tool which would probably (certainly?) make that part much easier for me but, for those large can connections, it's not fun with a 25-year-old Radio Shack solder sucker. The can, itself, is a rather large heat sink/spreader which further complicates that process.

Anyway, FYI.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "VK1GVC" <vk1gvc@iinet.net.au>
To: TekScopes@groups.io
Sent: Wednesday, May 27, 2020 9:40:45 AM
Subject: Re: [TekScopes] 475 questions

Bruce, I treat tantalums like I treat people - assume they have good
intentions unless I learn otherwise.  If you remove lots of them without
reasonable suspicion then you'll probably do more damage than good as
Eric has warned.  As tantalums usually fail to a short circuit, a
failed/shorted tantalum will pull down the voltage at that point to
close to zero and this will/should be straighforward to find - later.
At this stage, if I haven't missed any key points, you've found 2
sick/dead capacitors in the +50V supply which MAY be the cause of all
the wrong voltages you've measured in the low voltage power supply
section.  So replace those caps first, then adjust all of the LV power
supply to meet calibrations specs and see what happens.  You might have
a working scope if luck is very much with you, or you might be one step
on a long journey towards that goal.

And when you replace the tantalum which lost a leg, make sure you
install the new one with the right polarity.  Tantalums don't like
reverse voltage and they can get hot, emit smoke and explode.  I've seen
it happen when a workmate powered up some newly assembled eqpt for the
first time and heard a hissing sound so he bent down for a better look.
A cylindrical metal tube type tantalum then exploded and flew off the
PCB, burning itself onto the side of his neck. Very painful ... and the
language was terrible.  And very lucky he didn't get hit in an eye.

BTW here's a different type of tantalum which I don't think has been
mentioned yet - see the colourful little blob in the lower left of the
picture at this link:
https://groups.io/g/TekScopes/photo/12901/22?p=Name,,475,20,1,0,0

It has a black top, brown middle and green bottom ... the colours are a
derivative of the resistor colour code and I think there's a spot on one
side too.  Much better dressed than a plain boring tantalum!

Graham

On 27/05/2020 3:28 pm, ciclista41 via groups.io wrote:
Graham,

Well, my scope is peppered with the kind in the photo. Maybe they
re-spec'ed the caps later in production, or maybe the US Army bought
enough in their contract with Tek that they were able to spec what they
wanted. Mine is from November of 1982, if the date code on the AC power
cord box inside the case just above the transformer is original.

I went ahead and pulled the two tantalums out of the circuit to measure
them. I broke a lead off the first one, pulling too hard. Because I only
have access from the top of this A7 board unless I remove it, which I
don't want to do, my solder sucker wasn't able to slide over the clipped
end of the leads, and I had to just use a sharp tip on my iron. Did much
better on the second one, which came out easily by that second method. I
then used the sucker to remove the remaining solder from the holes in the
board for when I replace the broken one.

Yes, you were right to question my belief that they were bad. Out of
circuit, they both tested well within the green on my ESR tester. So much
for being able to reliably test capacitors in circuit with that thing.
They weren't even close to being in spec when tested with it in circuit.
I was thinking that these dipped tantalums were generally bad in boards
this old based on numerous threads in this forum and others saying how
often these were bad. Some said they routinely replace them all when they
see them in a scope of this era. I have tested dozens on this board and
only found about a handful that this tester considered bad. So,
considering that these two were among the worst that I tested in circuit,
I decided to pull them, as they'd be less easily accessible later when the
A8 board is back in place.

So this makes me question whether the tantalums in this board are among the
infamous ones. I hope not, obviously. Your statement that my photo
showed what looked like a very '80's tantalum made me think maybe the
infamous ones are some earlier 60's or 70's version. How can I know,
other than pulling them all? At this point, I don't see the point of
pulling any of them unless they show up as faulty later, when there is a
trace on the scope and I can run it through its paces and make sure it's
working as it should.

Speaking of working as it should, Tektronics calls for several specialized
calibration tools in the manual. If the scope is running well, with no
serious issues other than calibration, can it be calibrated without
resorting to the purchase of such tools? I briefly noted some shops
wanting a couple of hundred dollars to calibrate a scope. Definitely
don't want to do that! If I thought I had to have someone else calibrate
it, I probably wouldn't have taken on the project and just invested in a
new digital scope.

Bruce

On Tue, May 26, 2020 at 09:09 PM, VK1GVC wrote:

Bruce, the link to the pics on TekScopes worked for me and that
capacitor looks very 1980's tantalum as Michael confirmed in a later 475
manual and the Tek Common Parts manual.  Ceramics of that era were
commonly flat circular disks, very different from what you have.

Roger re testing in place - very problematic.  Best to remove them to
eliminate any ambiguity and as you have reported success in desoldering
then that's the best option while you have access.  BTW I'm curious to
know why you *believe* that they are faulty - mere suspicion based on
type and age, or something else?

You quoted your post of 22 May to Harvey a few minutes ago in which you
sought advice about what can and cannot be substituted when replacing
1982 components in 2020.  Has that qn been answered to your satisfaction
or is it still a live issue?  The short answer is: it depends.  The long
answer really has to address a specific component in a specific
application.  But the laws of physics haven't changed a lot in the last
40 years so there is almost certainly something out there which can be
bought/found/made/adapted or cajoled to do the job.  If you need a 1amp
400V rectifier diode then a IN4004 of the 70's or 80's is just the same
as one from the factory today.  If you need a very specific high-spec
module made for or by Tek for a very challenging application 40 years
ago and now out of production ... oh dear, you've got a problem.
Fortunately we now have TekScopes, some wikis, eBay and of course the WWW.

Graham

On 27/05/2020 1:24 pm, ciclista41 via groups.io wrote:
Hi Graham,

I posted a photo of the C1091 tantalum, along with the plaque stuck to
the
back of my scope here:
https://groups.io/g/TekScopes/album?id=247625&p=Created,,,20,2,0,0

Bruce


--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus





Re: Encouraging beginners: What are we accomplishing?

toby@...
 

On 2020-05-27 10:08 AM, Jamie Ostrowski wrote:
Does anyone have any idea, statistically, of how many scopes die from
beginners trying to repair them verses those that die to tube harvesters or
relatives who have no interest in "Bob's" old scopes who send them to the
recycler?

Thanks Chuck, Jamie, Larry and others for your posts on this.

As a relative "beginner" in scope repair I could not say enough good
things about the encouragement and wisdom available in this mailing list
from those with great experience.

Last week I brought a 602 XY back to life with some trivial repairs.
Gaining confidence for another more challenging 602 on the bench now.
And a few more Teks waiting.

I often skim threads like the 475 thread for hints and warnings I can
use. I feel very lucky to have this list as a resource. Keep it up!

--Toby



On Wed, May 27, 2020 at 8:42 AM LarryS <vision1@southwind.net> wrote:

In answer to your question, ANY time you bring in fresh blood, it's better
for everyone. Every time. No exceptions. A rising tide floats all boats.
...
Anyway, help every newb you can. If they want to try their hand, the
answer is NEVER "let someone else do it". They're gonna do it wrong. Just
as wrong as you and I used to do stuff. The sooner they learn to do it
right, the sooner everything gets better.

L.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Roy
Thistle
Sent: Tuesday, May 26, 2020 10:52 PM
To: TekScopes@groups.io
Subject: [TekScopes] Encouraging beginners: What are we accomplishing?

Hi all TekScopers:
Reading through a long thread, recently posted, caused me to wonder.. just
what are TekScopers accomplishing with threads like this... ...
Roy








Re: Encouraging beginners: What are we accomplishing?

David Hallam
 

Sorry about all the partial posts.  It seems as if Thunderbird was saving parts of my draft and sending them when I stopped typing.

David
KW4DH

On 5/27/2020 10:33 AM, David Hallam wrote:
I will put in my 2 cents worth here.  I have a 465, and it had been in storage for about 2 years.  It wasn't working when I got it out to use.  Have owned it for about 7 years using in my trouble shooting and repair work.  The scope's case never been off.  I am a complete novice when it comes to SS electronics.  I have been a ham for a long time and have used, repaired, and home brewed tube type transmitters, receivers, and accessories.  With the help I got on TekScopes2, I was able to quickly locate and fix the problem with my scope.  I always welcome knowledgeable help from anyone.

David
KW4DH

On 5/27/2020 1:14 AM, Jim Ford wrote:
I agree with you, John.  At first I was dismayed at Bruce's many posts, but then I thought, hey, I have no experience with the 475 and no interest in one, so I'll just delete the darn posts! Simple as that!

Bruce, knock yourself out!  Post as much as you need to to get the information you need to fix your scope.  Good luck!

Jim Ford


Re: Encouraging beginners: What are we accomplishing?

LarryS <vision1@...>
 

87% of all statistics are made up on the spot.
:-)

L.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Jamie Ostrowski
Sent: Wednesday, May 27, 2020 9:09 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Encouraging beginners: What are we accomplishing?

Does anyone have any idea, statistically, of how many scopes die from beginners trying to repair them verses those that die to tube harvesters or relatives who have no interest in "Bob's" old scopes who send them to the recycler?



On Wed, May 27, 2020 at 8:42 AM LarryS <vision1@southwind.net> wrote:

In answer to your question, ANY time you bring in fresh blood, it's
better for everyone. Every time. No exceptions. A rising tide floats all boats.

Right now, Harley Davidson is facing 'massive restructuring'. Why?
Their rider base is literally dying off.
I'm involved in several other hobbies and pursuits where young blood
is not entering. They are dying. And with it comes a similar
intellectual cannibalism.

As any discipline dies, like analog scopes, the entry price will be
lower and lower. Soon, for rummage sale prices, the once-crown-jewel
pieces become affordable. In 1983, how many 60s fastback Mustangs
were parked behind gas station garages (remember those?) and could be
had for a couple hundred? Many were chopped and otherwise brutalized
in ways I can't describe. But such is the price. Today, they're
worth more than most people's financials.

There were many thousands of units produced of scopes and cars and
organs and everything else. Some will live nice lives and some will
die horrible deaths and grownups understand this. I've been the
careless kid and the fastidious curator, but at both extremes I remembered the Prime Directive:
this thing is MINE, not yours. If you're worried about it, you can
buy it from me and store it away. If not, tough.

If we want a growing following, then we have to let the newbs make
their mistakes and learn as we did - yes, even on top tier equipment.
If it grows enough, someday my old junk might be worth as much as I
think it is now. If not, someone will speak poorly of me as they
shovel it all out into a dumpster after my demise.

Besides, if it tracks like everything else, one day some others will
join your song and these units will skyrocket - at least temporarily.
I own a Hammond console. In 1988, it was dumpster fodder. By 2010, it was $10K.
Today, it's maybe $4k. These things have a cycle and scopes are
certainly no exception.

Anyway, help every newb you can. If they want to try their hand, the
answer is NEVER "let someone else do it". They're gonna do it wrong.
Just as wrong as you and I used to do stuff. The sooner they learn to
do it right, the sooner everything gets better.

L.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
Roy Thistle
Sent: Tuesday, May 26, 2020 10:52 PM
To: TekScopes@groups.io
Subject: [TekScopes] Encouraging beginners: What are we accomplishing?

Hi all TekScopers:
Reading through a long thread, recently posted, caused me to wonder..
just what are TekScopers accomplishing with threads like this... and
why are we encouraging someone who is "... new to electronics..." to
dig into a 475?... one of the most complex, and compact, analog
instruments ever designed.
I suppose.. in consideration... Michael discouraged the use of a Mr.
Carlson super Weller-kluge special, on the 475's pcb(s)... but, ya know...
somewhere the thread... the 475 owner hints he paid 20.00 for 475?,
and he's also got a nonworking? PM3218 too.
So why didn't someone just recommend/... right off the bat... to take
the
475 to someone who knows what they are doing... drop another 100.00 on
it... and then he'd have one of the best scopes ever made.
Or alternatively... and better... just start in on the PM3218...itself
a very fine instrument, with a double insulated power supply... and
way overkill, for a beginner.
Look, I'm not unsympathetic... it's just that...too often.. after
parting with some scarce cash... or finding some Tek picked apart in a
basement somewhere, where its been languishing for a generation...I've
witnessed the havoc wreaked by someone trying to "fix" them.
If you want to call me a dumb ass... for thinking this way... well fine...
just PM me to do it. I can't promise I'll reply to that... but, I'll
read your message.
Best regards and wishes.
Roy







Re: 475 questions

VK1GVC
 

Bruce, I treat tantalums like I treat people - assume they have good intentions unless I learn otherwise.  If you remove lots of them without reasonable suspicion then you'll probably do more damage than good as Eric has warned.  As tantalums usually fail to a short circuit, a failed/shorted tantalum will pull down the voltage at that point to close to zero and this will/should be straighforward to find - later.  At this stage, if I haven't missed any key points, you've found 2 sick/dead capacitors in the +50V supply which MAY be the cause of all the wrong voltages you've measured in the low voltage power supply section.  So replace those caps first, then adjust all of the LV power supply to meet calibrations specs and see what happens.  You might have a working scope if luck is very much with you, or you might be one step on a long journey towards that goal.

And when you replace the tantalum which lost a leg, make sure you install the new one with the right polarity.  Tantalums don't like reverse voltage and they can get hot, emit smoke and explode.  I've seen it happen when a workmate powered up some newly assembled eqpt for the first time and heard a hissing sound so he bent down for a better look.  A cylindrical metal tube type tantalum then exploded and flew off the PCB, burning itself onto the side of his neck. Very painful ... and the language was terrible.  And very lucky he didn't get hit in an eye.

BTW here's a different type of tantalum which I don't think has been mentioned yet - see the colourful little blob in the lower left of the picture at this link:
https://groups.io/g/TekScopes/photo/12901/22?p=Name,,475,20,1,0,0

It has a black top, brown middle and green bottom ... the colours are a derivative of the resistor colour code and I think there's a spot on one side too.  Much better dressed than a plain boring tantalum!

Graham

On 27/05/2020 3:28 pm, ciclista41 via groups.io wrote:
Graham,

Well, my scope is peppered with the kind in the photo. Maybe they re-spec'ed the caps later in production, or maybe the US Army bought enough in their contract with Tek that they were able to spec what they wanted. Mine is from November of 1982, if the date code on the AC power cord box inside the case just above the transformer is original.

I went ahead and pulled the two tantalums out of the circuit to measure them. I broke a lead off the first one, pulling too hard. Because I only have access from the top of this A7 board unless I remove it, which I don't want to do, my solder sucker wasn't able to slide over the clipped end of the leads, and I had to just use a sharp tip on my iron. Did much better on the second one, which came out easily by that second method. I then used the sucker to remove the remaining solder from the holes in the board for when I replace the broken one.

Yes, you were right to question my belief that they were bad. Out of circuit, they both tested well within the green on my ESR tester. So much for being able to reliably test capacitors in circuit with that thing. They weren't even close to being in spec when tested with it in circuit. I was thinking that these dipped tantalums were generally bad in boards this old based on numerous threads in this forum and others saying how often these were bad. Some said they routinely replace them all when they see them in a scope of this era. I have tested dozens on this board and only found about a handful that this tester considered bad. So, considering that these two were among the worst that I tested in circuit, I decided to pull them, as they'd be less easily accessible later when the A8 board is back in place.

So this makes me question whether the tantalums in this board are among the infamous ones. I hope not, obviously. Your statement that my photo showed what looked like a very '80's tantalum made me think maybe the infamous ones are some earlier 60's or 70's version. How can I know, other than pulling them all? At this point, I don't see the point of pulling any of them unless they show up as faulty later, when there is a trace on the scope and I can run it through its paces and make sure it's working as it should.

Speaking of working as it should, Tektronics calls for several specialized calibration tools in the manual. If the scope is running well, with no serious issues other than calibration, can it be calibrated without resorting to the purchase of such tools? I briefly noted some shops wanting a couple of hundred dollars to calibrate a scope. Definitely don't want to do that! If I thought I had to have someone else calibrate it, I probably wouldn't have taken on the project and just invested in a new digital scope.

Bruce

On Tue, May 26, 2020 at 09:09 PM, VK1GVC wrote:

Bruce, the link to the pics on TekScopes worked for me and that
capacitor looks very 1980's tantalum as Michael confirmed in a later 475
manual and the Tek Common Parts manual.  Ceramics of that era were
commonly flat circular disks, very different from what you have.

Roger re testing in place - very problematic.  Best to remove them to
eliminate any ambiguity and as you have reported success in desoldering
then that's the best option while you have access.  BTW I'm curious to
know why you *believe* that they are faulty - mere suspicion based on
type and age, or something else?

You quoted your post of 22 May to Harvey a few minutes ago in which you
sought advice about what can and cannot be substituted when replacing
1982 components in 2020.  Has that qn been answered to your satisfaction
or is it still a live issue?  The short answer is: it depends.  The long
answer really has to address a specific component in a specific
application.  But the laws of physics haven't changed a lot in the last
40 years so there is almost certainly something out there which can be
bought/found/made/adapted or cajoled to do the job.  If you need a 1amp
400V rectifier diode then a IN4004 of the 70's or 80's is just the same
as one from the factory today.  If you need a very specific high-spec
module made for or by Tek for a very challenging application 40 years
ago and now out of production ... oh dear, you've got a problem.
Fortunately we now have TekScopes, some wikis, eBay and of course the WWW.

Graham

On 27/05/2020 1:24 pm, ciclista41 via groups.io wrote:
Hi Graham,

I posted a photo of the C1091 tantalum, along with the plaque stuck to the
back of my scope here:
https://groups.io/g/TekScopes/album?id=247625&p=Created,,,20,2,0,0

Bruce


--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus


Re: Encouraging beginners: What are we accomplishing?

David Hallam
 

I will put in my 2 cents worth here.  I have a 465, and it had been in storage for about 2 years.  It wasn't working when I got it out to use.  Have owned it for about 7 years using in my trouble shooting and repair work.  The scope's case never been off.  I am a complete novice when it comes to SS electronics.  I have been a ham for a long time and have used, repaired, and home brewed tube type transmitters, receivers, and accessories.  With the help I got on TekScopes2, I was able to quickly locate and fix the problem with my scope.  I always welcome knowledgeable help from anyone.

David
KW4DH

On 5/27/2020 1:14 AM, Jim Ford wrote:
I agree with you, John.  At first I was dismayed at Bruce's many posts, but then I thought, hey, I have no experience with the 475 and no interest in one, so I'll just delete the darn posts! Simple as that!

Bruce, knock yourself out!  Post as much as you need to to get the information you need to fix your scope.  Good luck!

Jim Ford


Re: Encouraging beginners: What are we accomplishing?

Chuck Harris <cfharris@...>
 

Hi John,

I have to set the record straight.

Dennis did not jump on me for describing a way of using
an oscilloscope to measure ESR. Quite the opposite, he
even tried to help with my poorly received ascii art
attempt at displaying a schematic... Curses foiled by
groups.io's website's mandatory proportional type font,
and their overzealous period police!

If anything, I jumped on Dennis, as I think we should be
able to discuss such things on this group without fear of
reprisal. But perhaps not to the exclusion of talking
about scopes.

And, it is way off to spend time plotting how we can get
some cantankerous old fool that designed his own ESR meter
to let us copy his design and sell it among ourselves...

Dennis and I are good friends. There really was no jumping
going on here...

-Chuck Harris

John Crighton wrote:

Hello Roy,

I am really surprised at you of all people sounding like a wet blanket.

The owner of this tekscope group told you in no uncertain terms if you
want to talk about ESR Meters to go and form your own group. Which
to your credit you did just that.  I also did not like the way that the owner
of this group, Dennis Tillman, jumped on Mr Chuck Harris for describing
how to use an oscilloscope with a function generator to check capacitors
for value and ESR. Shutting someone up for describing how to use an
oscilloscope on an oscilloscope group is to me just plain crazy.
Those are rules that you have to obey, like them or not.


Re: Encouraging beginners: What are we accomplishing?

Jamie Ostrowski
 

Does anyone have any idea, statistically, of how many scopes die from
beginners trying to repair them verses those that die to tube harvesters or
relatives who have no interest in "Bob's" old scopes who send them to the
recycler?

On Wed, May 27, 2020 at 8:42 AM LarryS <vision1@southwind.net> wrote:

In answer to your question, ANY time you bring in fresh blood, it's better
for everyone. Every time. No exceptions. A rising tide floats all boats.

Right now, Harley Davidson is facing 'massive restructuring'. Why? Their
rider base is literally dying off.
I'm involved in several other hobbies and pursuits where young blood is
not entering. They are dying. And with it comes a similar intellectual
cannibalism.

As any discipline dies, like analog scopes, the entry price will be lower
and lower. Soon, for rummage sale prices, the once-crown-jewel pieces
become affordable. In 1983, how many 60s fastback Mustangs were parked
behind gas station garages (remember those?) and could be had for a couple
hundred? Many were chopped and otherwise brutalized in ways I can't
describe. But such is the price. Today, they're worth more than most
people's financials.

There were many thousands of units produced of scopes and cars and organs
and everything else. Some will live nice lives and some will die horrible
deaths and grownups understand this. I've been the careless kid and the
fastidious curator, but at both extremes I remembered the Prime Directive:
this thing is MINE, not yours. If you're worried about it, you can buy it
from me and store it away. If not, tough.

If we want a growing following, then we have to let the newbs make their
mistakes and learn as we did - yes, even on top tier equipment. If it
grows enough, someday my old junk might be worth as much as I think it is
now. If not, someone will speak poorly of me as they shovel it all out
into a dumpster after my demise.

Besides, if it tracks like everything else, one day some others will join
your song and these units will skyrocket - at least temporarily. I own a
Hammond console. In 1988, it was dumpster fodder. By 2010, it was $10K.
Today, it's maybe $4k. These things have a cycle and scopes are certainly
no exception.

Anyway, help every newb you can. If they want to try their hand, the
answer is NEVER "let someone else do it". They're gonna do it wrong. Just
as wrong as you and I used to do stuff. The sooner they learn to do it
right, the sooner everything gets better.

L.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Roy
Thistle
Sent: Tuesday, May 26, 2020 10:52 PM
To: TekScopes@groups.io
Subject: [TekScopes] Encouraging beginners: What are we accomplishing?

Hi all TekScopers:
Reading through a long thread, recently posted, caused me to wonder.. just
what are TekScopers accomplishing with threads like this... and why are we
encouraging someone who is "... new to electronics..." to dig into a
475?... one of the most complex, and compact, analog instruments ever
designed.
I suppose.. in consideration... Michael discouraged the use of a Mr.
Carlson super Weller-kluge special, on the 475's pcb(s)... but, ya know...
somewhere the thread... the 475 owner hints he paid 20.00 for 475?, and
he's also got a nonworking? PM3218 too.
So why didn't someone just recommend/... right off the bat... to take the
475 to someone who knows what they are doing... drop another 100.00 on
it... and then he'd have one of the best scopes ever made.
Or alternatively... and better... just start in on the PM3218...itself a
very fine instrument, with a double insulated power supply... and way
overkill, for a beginner.
Look, I'm not unsympathetic... it's just that...too often.. after parting
with some scarce cash... or finding some Tek picked apart in a basement
somewhere, where its been languishing for a generation...I've witnessed the
havoc wreaked by someone trying to "fix" them.
If you want to call me a dumb ass... for thinking this way... well fine...
just PM me to do it. I can't promise I'll reply to that... but, I'll read
your message.
Best regards and wishes.
Roy







Re: Encouraging beginners: What are we accomplishing?

Chuck Harris <cfharris@...>
 

Hi Roy,

I guess the first thing is that tektronix made these scopes to
be reparable by their customers. That is why they made available
such detailed manuals for their scopes.

I am pretty sure they figured that if the customer was not
up to the challenge, the high price of replacing the scope if
they failed, would discourage unqualified repairs. And, for those
who would not be discouraged, they had a school for turning
unqualified repairmen into repairmen.

A major point that everyone should realize is these scopes are
scrap in as far as the commercial market goes. That is why they
are in the hands of novice owners. If the novice owner botches
the repair, it just moves a little closer to the scrap bin.

Every major collector's field has this debate at some point.

I have heard the museum guys argue the point successfully in front
of legislatures that metal detectorists should be jailed for
disturbing as yet unknown archeological digs with their explorations.

I have heard warbird enthusiasts demand that warbird owners should be
jailed for flying (and occasionally crashing) the airplanes they saved
from oblivion, and own.

I have heard coin collectors cry when some amateur polishes some
marginally significant coin, ruining its value...

And, I have heard a very, very, few guys like you worry about the
damage a novice may do to a scope that you don't even want...

I guess we have reached the big time!

As for paying $100 for a repair... I repair scopes cheaply, and even
I won't work on a 475 for that little.

-Chuck Harris



Roy Thistle wrote:

Hi all TekScopers:
Reading through a long thread, recently posted, caused me to wonder.. just what are TekScopers accomplishing with threads like this... and why are we encouraging someone who is "... new to electronics..." to dig into a 475?... one of the most complex, and compact, analog instruments ever designed.
I suppose.. in consideration... Michael discouraged the use of a Mr. Carlson super Weller-kluge special, on the 475's pcb(s)... but, ya know... somewhere the thread... the 475 owner hints he paid 20.00 for 475?, and he's also got a nonworking? PM3218 too.
So why didn't someone just recommend/... right off the bat... to take the 475 to someone who knows what they are doing... drop another 100.00 on it... and then he'd have one of the best scopes ever made.
Or alternatively... and better... just start in on the PM3218...itself a very fine instrument, with a double insulated power supply... and way overkill, for a beginner.
Look, I'm not unsympathetic... it's just that...too often.. after parting with some scarce cash... or finding some Tek picked apart in a basement somewhere, where its been languishing for a generation...I've witnessed the havoc wreaked by someone trying to "fix" them.
If you want to call me a dumb ass... for thinking this way... well fine... just PM me to do it. I can't promise I'll reply to that... but, I'll read your message.
Best regards and wishes.
Roy




Re: Encouraging beginners: What are we accomplishing?

LarryS <vision1@...>
 

In answer to your question, ANY time you bring in fresh blood, it's better for everyone. Every time. No exceptions. A rising tide floats all boats.

Right now, Harley Davidson is facing 'massive restructuring'. Why? Their rider base is literally dying off.
I'm involved in several other hobbies and pursuits where young blood is not entering. They are dying. And with it comes a similar intellectual cannibalism.

As any discipline dies, like analog scopes, the entry price will be lower and lower. Soon, for rummage sale prices, the once-crown-jewel pieces become affordable. In 1983, how many 60s fastback Mustangs were parked behind gas station garages (remember those?) and could be had for a couple hundred? Many were chopped and otherwise brutalized in ways I can't describe. But such is the price. Today, they're worth more than most people's financials.

There were many thousands of units produced of scopes and cars and organs and everything else. Some will live nice lives and some will die horrible deaths and grownups understand this. I've been the careless kid and the fastidious curator, but at both extremes I remembered the Prime Directive: this thing is MINE, not yours. If you're worried about it, you can buy it from me and store it away. If not, tough.

If we want a growing following, then we have to let the newbs make their mistakes and learn as we did - yes, even on top tier equipment. If it grows enough, someday my old junk might be worth as much as I think it is now. If not, someone will speak poorly of me as they shovel it all out into a dumpster after my demise.

Besides, if it tracks like everything else, one day some others will join your song and these units will skyrocket - at least temporarily. I own a Hammond console. In 1988, it was dumpster fodder. By 2010, it was $10K. Today, it's maybe $4k. These things have a cycle and scopes are certainly no exception.

Anyway, help every newb you can. If they want to try their hand, the answer is NEVER "let someone else do it". They're gonna do it wrong. Just as wrong as you and I used to do stuff. The sooner they learn to do it right, the sooner everything gets better.

L.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Roy Thistle
Sent: Tuesday, May 26, 2020 10:52 PM
To: TekScopes@groups.io
Subject: [TekScopes] Encouraging beginners: What are we accomplishing?

Hi all TekScopers:
Reading through a long thread, recently posted, caused me to wonder.. just what are TekScopers accomplishing with threads like this... and why are we encouraging someone who is "... new to electronics..." to dig into a 475?... one of the most complex, and compact, analog instruments ever designed.
I suppose.. in consideration... Michael discouraged the use of a Mr. Carlson super Weller-kluge special, on the 475's pcb(s)... but, ya know... somewhere the thread... the 475 owner hints he paid 20.00 for 475?, and he's also got a nonworking? PM3218 too.
So why didn't someone just recommend/... right off the bat... to take the 475 to someone who knows what they are doing... drop another 100.00 on it... and then he'd have one of the best scopes ever made.
Or alternatively... and better... just start in on the PM3218...itself a very fine instrument, with a double insulated power supply... and way overkill, for a beginner.
Look, I'm not unsympathetic... it's just that...too often.. after parting with some scarce cash... or finding some Tek picked apart in a basement somewhere, where its been languishing for a generation...I've witnessed the havoc wreaked by someone trying to "fix" them.
If you want to call me a dumb ass... for thinking this way... well fine... just PM me to do it. I can't promise I'll reply to that... but, I'll read your message.
Best regards and wishes.
Roy

20761 - 20780 of 188141