Date   
Re: Capacitors Question?

Mlynch001
 

Chuck,
As I understand the issue, it is ALL capacitors in almost all equipment manufactured in late 80's to early 90's, I have seen video of destroyed boards in various types of equipment, including TEKTRONIX Scopes, with leaky SMD electrolytic caps. I was concerned enough that I took my machine apart and gave it a good going over. Regardless, the boards look great and solder joints in my machine are shiny, like chrome. They are really nice, with no sign of even the slightest corrosion. I looked them over with a Magnifying glass and a good strong light. This made me feel really good about the machine. Also the fact that this is a fairly late version of the TDS460A series, probably cannot hurt. I appreciate all the advice and guidance.

Tek 7623A - Inverted and compressed Horizontal only from TB (was 7623A + 7A26 + 7B53)

Fabio Trevisan
 
Edited

Hello guys,
After having purchased that of my previous topic (see subject), and initially discussed its issues, I'll separate now the topics.
Here, I focus on the rather funny behavior of the Horizontal axis... as follows:
1. It's compressed... Full sweep covers only about 3.5 divisions.
2. It moves backwards (right to left)
3. Problem doesn't affect readout (readout is correctly spanning the whole screen width and it's not inverted).

What is already checked / ruled out:
a. It's not the TB plugin... I have 2 TBs (of which, one wasn't working initially, but I found what was wrong with it), and both exhibits the same behavior, leading me to conclude that the problem is in the mainframe hor. amplifier.
b. Pressing x10 on the plugin, makes the sweep extends beyond screen, which leads to conclude that the Hor. amplifier is well capable of the output voltage span.
c. Either at x1 or at X10, the sweep is linear... (although compressed)
b. I already checked the harmonica connector P501 going into the A6 HOR. AMP. board and it's not inverted. Damn! I could bet it was it... But not!
c. I already removed and re-seated the Hor. Channel Switcher IC (U510). The socket is the dreaded Texas, but it doesn't seem there's a bad contact issue here (U510 pins are gold plated).

What has been already advised and I`m pending to check:
a. L.V. Power supply voltages and ripple. I know, that should have been my first stop.. but as soon as i opened it, I found the FAN was stuck (dried out, sticky oil) so I fixed that ahead of everything else.
b. Probing around the Horizontal Channel switcher IC (U510) and check if all voltages are present.

QUESTIONS:
=> What is the nominal deflection factor of the 7000 series mainframe inputs (Diff Volt / Div. of deflection). I tried to find it on the specs, but it only says a blunt: "Compatible with all 7000 series plug-in units"
=> Is this IC 155-0022-00 a common failure?

I am posting pictures under title Tek7623a B060527...
https://groups.io/g/TekScopes/album?id=35474

Thanks for any advice and Rgrds,

Fabio

Re: What calibration items to buy.

Harvey White
 

On Tue, 6 Mar 2018 16:32:03 -0500, you wrote:

Close, but how about this scenario:
I'll guess.

I have a 5-1/2 dig DMM (dc) with 200mv low range.
OK, then LSD displayed = 10 uv.

I have a voltage ref standard with 1uv resolution.
Got one of them, too.
I know the std is good in the 10uv slot but may be off in the 1mv.
Then anything involving that digit is suspect, which carries over to
the next digit in what I'd say is a possible 1 digit error.
Can I calibrate the DMM to it’s full spec?
I'd say no. The last digit is uncertain (could be anything), which I
think could cause the next digit (100 uv) to be off by one.
Or am I missing something.
What if the DMM was 2v low range?
And 5 1/2 digits the lsb is 100 uv, see above with uncertainty about
the 100 uv digit.

Note I don’t need to prove cal to anyone but myself.
Well, that's what I think will happen. Let's see if I got it right.

Harvey


Sent from kjo iPhone


Re: SG505 THD issues

Craig Sawyers <c.sawyers@...>
 

I don't think so. By subterfuge I can get it to measure .0008%, at 100kHz with tiltering, as the
AA501
only goes up to 300kHz. Dennis' statement is further evidence.

But I am going to revisit the AA501's calibration, as there is a 3HD adjustment that I've never
made.
Well yes - if you filter of course you are going to see a lower reading, as you will if you use
weighting.

The numbers I quoted were straight from the AA501 manual. But if you think that your SG505's are
misbehaving nonetheless then so be it.

You'll know for certain if you knock up a twin-T passive filter at say 1kHz (or any other frequency
that takes your fancy) and look at the harmonics on a spectrum analyser. But that is the only way you
will know, because any other way will just give a system level measurement (i.e. of the SG505 and
AA501 taken together)

Craig

Re: What calibration items to buy.

Kevin Oconnor
 

Close, but how about this scenario:
I have a 5-1/2 dig DMM (dc) with 200mv low range.
I have a voltage ref standard with 1uv resolution.
I know the std is good in the 10uv slot but may be off in the 1mv.
Can I calibrate the DMM to it’s full spec?
Or am I missing something.
What if the DMM was 2v low range?
Note I don’t need to prove cal to anyone but myself.

Sent from kjo iPhone

Re: OT: Homebrew scanning electron microscopes

Chuck Harris
 

Think of the STM as being more like dragging a phonograph
needle over the atoms in the surface of a material. The
STM needle doesn't actually touch, but comes as close as
possible to touching without actually doing so. it can
see the actual atoms in a gold object.

-Chuck Harris

Brad Thompson wrote:

Hello--

Apropos of an earlier discussion, I came across the following web page:

http://www.opencircuits.com/Atomic_microscope

Very interesting, and no need for a high vacuum(?).

73--

Brad AA1IP

Re: Capacitors Question?

Dave Casey
 

What about the many SMD electrolytics which are just radial electrolytics
anchored in a base with their leads bent over and cut really short?

Dave Casey

On Tue, Mar 6, 2018 at 3:25 PM, Chuck Harris <cfharris@...> wrote:

Not to put too fine a point on my nitpicking, but
AFAIK, the capacitor plague applied only to radial
leaded, low ESR electrolytic capacitors, not to
SMD electrolytic capacitors.

The problem mostly appeared on computer motherboards,
and on graphics cards. The electrolyte would etch
through the factory applied anodize coating, which
was the capacitor's dielectric. When this dielectric
layer was thin enough, the leakage current the capacitor
drew would climb, and the capacitor would get hot.

The heat made the electrolyte boil, and the cap would
blow out its bottom rubber plug, leaving the cap all
akimbo, or it would "dome up" the the explosion relief
on the top, or sides, of the capacitor.

-Chuck Harris

Dennis Tillman W7PF wrote:
Hi Michael,

Don't do anything until you read this article which explains the problem
in detail:
https://en.wikipedia.org/wiki/Capacitor_plague

Dennis Tillman W7PF


-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
Chuck Harris
Sent: Tuesday, March 06, 2018 11:26 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Capacitors Question?

The problem will never really be completely solved, as long as
manufacture involves putting a plastic/rubber sealed, liquid filled,
component into an oven heated to soldering temperatures as a means
soldering its leads to the board. You are heating up a lot of things that
don't want to be heated up, just to solder a couple of tiny little tabs to
the board. Heat them a little too hot, or a little too long (same thing),
and the seal will be damaged, and won't keep the electrolyte inside of the
capacitor.



Re: Wanted: Tek 503

Ronald Carlson
 

blockquote, div.yahoo_quoted { margin-left: 0 !important; border-left:1px #715FFA solid !important; padding-left:1ex !important; background-color:white !important; } Harvey,
I'll check the specs, might just work. Back to you in a bit. 
Ron

On Tuesday, March 6, 2018, 2:14 PM, Harvey White <madyn@...> wrote:

On Tue, 6 Mar 2018 20:09:11 +0000 (UTC), you wrote:

Would an RM504 do?  I've got one I've been saving to send to a good home.
My understanding is that some of the very first *digital* computers also had scopes on them.  I cannot now find the reference but in one early tube-based computer, the CRT displayed an analog rendition of the address on the vertical axis and an analog rendition of the program counter on the horizontal axis.   IF there program got stuck in an infinite loop, it would end up literally drawing a loop on the CRT.
The HP 1600/1601 logic analyzer would do much the same.  Not sure
about the Tek 308. (much later vintage).

Most of the early hardware was considered unreliable enough that there
was considerable diagnostic software/equipment built into the project.
It was at a level where the basic processor functionality could be
checked.

Harvey



Dan

    On Friday, March 2, 2018, 12:25:12 AM EST, Ronald Carlson <ronald.carlson.54@...> wrote:

Anyone have a Tek 503 that's looking for a new home?

The 503's specs fit nicely as an output display for an analog computer project I'm working on.  Or, perhaps there's a better, newer model the group could recommend?  The identical low frequency response horiz and vert amplifiers with a square display make it initially an interesting option.

TIA, Ron




Re: Capacitors Question?

Chuck Harris
 

Not to put too fine a point on my nitpicking, but
AFAIK, the capacitor plague applied only to radial
leaded, low ESR electrolytic capacitors, not to
SMD electrolytic capacitors.

The problem mostly appeared on computer motherboards,
and on graphics cards. The electrolyte would etch
through the factory applied anodize coating, which
was the capacitor's dielectric. When this dielectric
layer was thin enough, the leakage current the capacitor
drew would climb, and the capacitor would get hot.

The heat made the electrolyte boil, and the cap would
blow out its bottom rubber plug, leaving the cap all
akimbo, or it would "dome up" the the explosion relief
on the top, or sides, of the capacitor.

-Chuck Harris

Dennis Tillman W7PF wrote:

Hi Michael,

Don't do anything until you read this article which explains the problem in detail:
https://en.wikipedia.org/wiki/Capacitor_plague

Dennis Tillman W7PF


-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Chuck Harris
Sent: Tuesday, March 06, 2018 11:26 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Capacitors Question?

The problem will never really be completely solved, as long as manufacture involves putting a plastic/rubber sealed, liquid filled, component into an oven heated to soldering temperatures as a means soldering its leads to the board. You are heating up a lot of things that don't want to be heated up, just to solder a couple of tiny little tabs to the board. Heat them a little too hot, or a little too long (same thing), and the seal will be damaged, and won't keep the electrolyte inside of the capacitor.

OT: Homebrew scanning electron microscopes

Brad Thompson <brad.thompson@...>
 

Hello--

Apropos of an earlier discussion, I came across the following web page:

http://www.opencircuits.com/Atomic_microscope

Very interesting, and no need for a high vacuum(?).

73--

Brad AA1IP

Re: SG505 THD issues

EJP
 

I don't think so. By subterfuge I can get it to measure .0008%, at 100kHz with tiltering, as the AA501 only goes up to 300kHz. Dennis' statement is further evidence.

But I am going to revisit the AA501's calibration, as there is a 3HD adjustment that I've never made.

Re: Wanted: Tek 503

toby@...
 

On 2018-03-06 3:09 PM, Daniel Koller via Groups.Io wrote:
Would an RM504 do?  I've got one I've been saving to send to a good home.
My understanding is that some of the very first *digital* computers also had scopes on them.  I cannot now find the reference but in one early tube-based computer, the CRT displayed an analog rendition of the address on the vertical axis and an analog rendition of the program counter on the horizontal axis.   IF there program got stuck in an infinite loop, it would end up literally drawing a loop on the CRT.
This is the case for the Royal McBee LGP-30, and several examples still
exist and operate.

https://www.youtube.com/watch?v=7WaYYNUCWMY - scope at e.g. 3:12

--Toby

Dan

On Friday, March 2, 2018, 12:25:12 AM EST, Ronald Carlson <ronald.carlson.54@...> wrote:

Anyone have a Tek 503 that's looking for a new home?

The 503's specs fit nicely as an output display for an analog computer project I'm working on.  Or, perhaps there's a better, newer model the group could recommend?  The identical low frequency response horiz and vert amplifiers with a square display make it initially an interesting option.

TIA, Ron





Re: Capacitors Question?

 

Hi Michael,

Don't do anything until you read this article which explains the problem in detail:
https://en.wikipedia.org/wiki/Capacitor_plague

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Chuck Harris
Sent: Tuesday, March 06, 2018 11:26 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Capacitors Question?

The problem will never really be completely solved, as long as manufacture involves putting a plastic/rubber sealed, liquid filled, component into an oven heated to soldering temperatures as a means soldering its leads to the board. You are heating up a lot of things that don't want to be heated up, just to solder a couple of tiny little tabs to the board. Heat them a little too hot, or a little too long (same thing), and the seal will be damaged, and won't keep the electrolyte inside of the capacitor.

However, you can be pretty confident that if the capacitor didn't start leaking electrolyte soon after it left the factory, it probably won't. The damage to the capacitors, if it is going to happen, starts right in the factory, not on your bench.

If your solder is shiny, and I do mean shiny, it is good.

-Chuck Harris

Mlynch001 wrote:
We all know the horror stories about the leaky capacitors in TEK Scopes. This may have been answered, however, I cannot find this in a search. I am thinking that the first Surface mounted caps were used in the late 80's and early 90's and these were the ones that had serious electrolyte leakage issues. My question is, about WHEN was this issue solved so that these types of caps were no longer a serious problem? I have a TDS460A that has an inspection date on the CRT of mid 1998 and the caps on the main board look beautiful. Solder joints are clean and bright, there is no apparent leakage or corrosion present. The scope works fine, so I do not want to mess with it unless it begins to exhibit problems.

Michael Lynch




--
Dennis Tillman W7PF
TekScopes Moderator

Re: Tek 2445B Focus Problem

Fabio Trevisan
 

Hello Peter,
My first scope was not a Tek (it was a Kenwood of the 80s) and, like some Teks, it has a feature that is known by the name "Auto-Focus".
The Kenwood had a problem that was exactly as what you described and it was occurring due to leakage on the components of the Aut-Focus DC restorer.
*IF* your 2465B also have an "Auto-Focus" circuitry (I`m not sure, I don't have a 2465B schematic at hand nearby), the problem may be there.
Look for an auto-focus circuitry on your scope and, if it's present, it will surely be consisting of a low voltage amplifier (quite similar o identical to the one to the Intensity control) and a DC restorer (likewise, identical to the one on the intensity control).
The DC restorer circuits, of both the Intensity control and the focus control, are quite sensitive to leakage.
=> Look for leakage on the DC restorers' diodes and capacitors.
=> Make sure the area is clean and as free as possible of H.V. soot. Soot can absorb moisture and the DC restorer will leak until the scope is heated, when the soot will dry and DC restorer performance is recovered... until it cools down again.
=> Check the output waveform coming from the auto-focus amplifier during the problem, and after, to see if the problem may be coming from the amplifier itself.
Rgrds,
Fabio

Re: Wanted: Tek 503

Harvey White
 

On Tue, 6 Mar 2018 20:09:11 +0000 (UTC), you wrote:

Would an RM504 do?  I've got one I've been saving to send to a good home.
My understanding is that some of the very first *digital* computers also had scopes on them.  I cannot now find the reference but in one early tube-based computer, the CRT displayed an analog rendition of the address on the vertical axis and an analog rendition of the program counter on the horizontal axis.   IF there program got stuck in an infinite loop, it would end up literally drawing a loop on the CRT.
The HP 1600/1601 logic analyzer would do much the same. Not sure
about the Tek 308. (much later vintage).

Most of the early hardware was considered unreliable enough that there
was considerable diagnostic software/equipment built into the project.
It was at a level where the basic processor functionality could be
checked.

Harvey



Dan

On Friday, March 2, 2018, 12:25:12 AM EST, Ronald Carlson <ronald.carlson.54@...> wrote:

Anyone have a Tek 503 that's looking for a new home?

The 503's specs fit nicely as an output display for an analog computer project I'm working on.  Or, perhaps there's a better, newer model the group could recommend?  The identical low frequency response horiz and vert amplifiers with a square display make it initially an interesting option.

TIA, Ron




Re: Wanted: Tek 503

Daniel Koller
 

Would an RM504 do?  I've got one I've been saving to send to a good home.
My understanding is that some of the very first *digital* computers also had scopes on them.  I cannot now find the reference but in one early tube-based computer, the CRT displayed an analog rendition of the address on the vertical axis and an analog rendition of the program counter on the horizontal axis.   IF there program got stuck in an infinite loop, it would end up literally drawing a loop on the CRT.
Dan

On Friday, March 2, 2018, 12:25:12 AM EST, Ronald Carlson <ronald.carlson.54@...> wrote:

Anyone have a Tek 503 that's looking for a new home?

The 503's specs fit nicely as an output display for an analog computer project I'm working on.  Or, perhaps there's a better, newer model the group could recommend?  The identical low frequency response horiz and vert amplifiers with a square display make it initially an interesting option.

TIA, Ron

Re: Tekmate floppy setup problem.

 

Hi John,

To achieve greater density on a floppy manufacturers had to make the tracks much narrower. To make the tracks narrower required more precise read/write heads, more precise and more repeatable positioning mechanisms in the floppy drives, and much higher magnetic fields when writing on the floppy.

Age can affect the ability of a floppy drive to accurately position its head to the correct location to be in the middle of a given track. But a bigger problem occurred when using floppies which were designed for lower density recording on these high density floppy drives. The magnetic film was not formulated to handle the much greater magnetic fields used by those read/write heads.

Many end users were oblivious to the importance of using media matched to their floppy drive and in some cases intentionally used less expensive low density floppies in high density floppy drives. In the latter case the operating system would often successfully write onto the floppy but only by trying up to 10 times before quitting. If it was able to write under these circumstances the user was given the impression that he/she "got away with it" only to discover some time later, and much too late, that the floppy couldn't be read reliably.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of John Ferguson via Groups.Io
Sent: Tuesday, March 06, 2018 5:37 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tekmate floppy setup problem.

Maybe someone has already suggested this, but i can clearly remember that back in the late '80s when these things showed up that some 1.44 drives were very fussy about which disks they would write to. i assume you've found the little write-protection slide on your disks and it is in the 'write' position and you've tried 720 disks 'just in case'

I'm running a 1992 Sun SPARCstation 10 which has a 1.44 drive. I think I'll check to see if it can still read the disks I have.

john


On 03/05/2018 09:33 AM, Szabolcs Szigeti wrote:
Hi,

Thanks, but I doubt it. I have tried a number of disks, even one from
an original packaging. I'm able to use them in a notebook. The
imteresting thing is that if I try to format them in in the Tekmate,
then format stops with unusable track 0, but it formats that track. or
at least does something with that, because then I have to reformat the
disk to use it again. This is why i suspect that there is some
discrepancy in what bios/dos thinks about the drives and what they are
really. But, I do not see anything else other than the bios setup to change the floppy type.
I can still not beleive that I have 3 equally faulty floppy drives,
but I'll try and get hol of a fourth one or try them in a PC. I'll
also try cleaning them, to make sure that that is not the problem.

Szabolcs

2018-03-05 4:04 GMT+01:00 battyhugh <@Hugh>:

It might surprise you, but your floppys are corrupt. I would suggest
getting a tube of disk cleaner (10%alcohol and a drop of detergent) -
and using a nice clean tissue - I recommend toilet paper - open the
shutter and clean the disk carefully on both sides. I have to do this
to recover old disks with files.

Good luck

Hugh @Hugh









--
Dennis Tillman W7PF
TekScopes Moderator

Re: Capacitors Question?

Chuck Harris
 

The problem will never really be completely solved, as
long as manufacture involves putting a plastic/rubber
sealed, liquid filled, component into an oven heated to
soldering temperatures as a means soldering its leads
to the board. You are heating up a lot of things that
don't want to be heated up, just to solder a couple of
tiny little tabs to the board. Heat them a little too
hot, or a little too long (same thing), and the seal will
be damaged, and won't keep the electrolyte inside of the
capacitor.

However, you can be pretty confident that if the capacitor
didn't start leaking electrolyte soon after it left
the factory, it probably won't. The damage to the
capacitors, if it is going to happen, starts right in
the factory, not on your bench.

If your solder is shiny, and I do mean shiny, it is good.

-Chuck Harris

Mlynch001 wrote:

We all know the horror stories about the leaky capacitors in TEK Scopes. This may have been answered, however, I cannot find this in a search. I am thinking that the first Surface mounted caps were used in the late 80's and early 90's and these were the ones that had serious electrolyte leakage issues. My question is, about WHEN was this issue solved so that these types of caps were no longer a serious problem? I have a TDS460A that has an inspection date on the CRT of mid 1998 and the caps on the main board look beautiful. Solder joints are clean and bright, there is no apparent leakage or corrosion present. The scope works fine, so I do not want to mess with it unless it begins to exhibit problems.

Michael Lynch

Re: What calibration items to buy.

Chuck Harris
 

I am not certain of your question, but I think you are
asking how good does a cal lab need to be to calibrate
a scope.

Generally, tek scopes run out of accuracy somewhere
worse than +/-1%.

A good rule of thumb is that your calibration gear must
be 10x as accurate as the item you are calibrating. It's
a rule of thumb, not a law. You can shrink that divide
through tricky means, which is how marvelous things like
HP3458A's can be calibrated/checked.

So, for a 2465, I must use calibration equipment that I
know, or strongly believe to be better than 0.01% accurate,
to be confident that my result will be better than Tektronix's
specifications for the 2465..

I can do that easily with time/frequency. GPS disciplined
quartz, or rubidium, standards are readily available, and
offer NIST traceability fairly easily.

Volts are a bit harder. There are plenty of good DVM's that
get into that range, and much much better... An HP3456A,
is one currently very cheap example. There are plenty of
good AC and DC calibrators, which you can use essentially
as a stable voltage source, checked with your "golden" meter.

But still somewhere down the line, you have to connect your
"golden" meter to NIST's volt.

Possibly a more useful metric is how long can I expect
a kit with an SG503/4, PG506, and TG501 to stay accurate
enough to meaningfully calibrate a 2465. To that I would
say 6 months, a year on the outside.

Did I get close to answering what you wanted to know?

-Chuck Harris

Kevin Oconnor wrote:

Chuck,
At what point would you say that the intermediate cal was good enough for the work at task?

Sent from kjo iPhone

Re: What calibration items to buy.

Chuck Harris
 

I know, I got your gently pointed hint.

I often tag onto someone else's reply post to further
elucidate (hopefully not obfuscate?) their useful response.

Anyone that gets at all serious with calibration very
quickly discovers that they are stuck in a never ending
cycle of verification. The cycle must, by definition,
extend to some other entity that holds the national
standards.

The issue that anyone considering buying a set of
calibration items needs to consider is why they believe
said items are better calibrated than what they want to
calibrate. It pretty much always sends you down the
rabbit hole, as I described... probably always.

-Chuck Harris

Merchison Burke via Groups.Io wrote:

Thanks Chuck. I asked the question for the benefit of the original poster who wishes
to calibrate his own scope.

I have worked in a few calibration labs and regardless of how state-of-the-art or
cutting edge the equipment is, if one is serious about the integrity of ones
equipment, one will end up having to send ones equipment to a certified calibration lab.

Keeping equipment properly, calibrated can be an expensive proposition and as you
indicate one must be in a position to make it pay off (like you do) or have deep
pockets like antique collectors.


On 2018-Mar-06 8:35 AM, Chuck Harris wrote:
A thorny question.

Calibration is a rabbit hole that I fell into a third
of a century ago, when I started my small electronics
business.

You buy a scope to use, and pretty soon it reaches its
end of calibration date, so you check out the local cal
labs, and find that it costs about 1/6th to 1/3rd the
price of a new scope to get it calibrated.