Date   

Re: 2467B focus/astigmatism anomaly...

Chuck Harris
 

I tested the cap's leakage at 1KV, and it was 0.3uA.

1uA is 1V on 1M. And here we have impedances around 10M.

It is concerning, especially since the cap has 1.4kV
across it.

-Chuck Harris

satbeginner wrote:

Maybe the cap IS leaking, and heated some of the resistors on the right hand side of the schematic up?

After disconnecting the cap, the resistors cooled back down and found their normal DC working area, hence the focus stayed ok?

Still interested,

Leo




Re: TDS754A

Stephen Hanselman
 

I would suggest you open it up remove the proc board and PS cover. Then blow out the dust. We have found any “new” unit to our facility was fairly dirty. The split wall between the PS and HVPS is perforated but with small holes which clog easily.

Regards,

Stephen Hanselman
Datagate Systems, LLC
3107 North Deer Run Road #24
Carson City, Nevada, 89701
(775) 882-5117 office
(775) 720-6020 mobile
s.hanselman@datagatesystems.com
www.datagatesystems.com
a Service Disabled, Veteran Owned Small Business
DISCLAIMER:
This e-mail and any attachments are intended only for use by the addressee(s) named herein and may contain legally privileged and/or proprietary information. If you are not the intended recipient, any dissemination, distribution or copying of this e-mail and any attachments is strictly prohibited. If you have received this e-mail in error, please immediately notify me and permanently delete the original and all copies and printouts of this e-mail and any attachments.

On Aug 20, 2019, at 07:37, Siggi <siggi@undo.com> wrote:

Hey Dana,

IIRC the standby power supply that allows soft-power on is also responsible
for powering the main switcher. Maybe the standby supply needs recapping.

The TDS5/6/7As are also well documented to suffer from capacitor plaque.
There are SMD electrolytic capacitors all over the acquisition, CPU and
front panel boards. If yours hasn't been re-capped, then that's also a
possible explanation for what you're seeing.

Siggi

On Tue, Aug 20, 2019 at 10:25 AM danadak <danaaknight@gmail.com> wrote:

This scope has been excellent to date. Now when turned on it
power cycles. It will start up, most of the time complete the POST,
then power itself off after a minute or two.

Before I spend the next century trying to find the problem anyone
have a similar experience ?


Regards, Dana.





Re: Need Help Troubleshooting Tektronix PS280

Steve Lindberg
 

These puppies were OEMed by Tek. The one I got had banana plugs broken loose from PCB.

Steve Lindberg


Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10


Re: TDS460A Will not turn on?

Chuck Harris
 

I am duly chastened.

You all have argued, to the internet's satisfaction, no doubt,
that every opto coupler in every circuit should be replaced on
sight... ;-)

...And yet, in the hundreds of switchers I have repaired over the
years, I have never needed to replace even one optocoupler.

How can that be??? The internet clearly knows them to be highly
unreliable, and recommends that they be shot on sight.

I suppose it is possible that some supplies that I didn't fix had
bad optocouplers, but I would think they would have shown open loop
regulation failures, since most of the optocouplers (in switchers)
are used to isolate the PWM voltage regulator's feedback loop.

Which, I am pretty sure isn't happening here with supplies that won't
turn on.

The overwhelming majority of the failures I have seen have been
capacitor related. The overwhelming majority of the completely
dead switchers I have seen have had bootstrap problems.

I guess we will never know if I have been not fixing optocoupler
failures in switching supplies all this time....

Still, I stand by my less than 1% statement.

[If I were an IEEE member, I might check out the papers referenced...
But, like most of my colleagues, I gave up my IEEE membership many
years ago as it just had no tangible value to practicing USA EE's.

Where IEEE could have earned our membership dollars is if they did
anything at all to help prevent USA engineering jobs from being
exported to the third world over the internet. Or, did anything to
prevent H1B Visa holders from taking our jobs, and depressing our
wages. But IEEE, being an international organization, considered
those to be highly desirable things.]

I didn't, but, if I did check out the papers, I bet I would find that
the authors are panicking over a failure rate that is 4 or 5 sigma,
rather than the 6 sigma usually considered human perfection by the
semiconductor industry.

(Note:
1 sigma= 31% good,
2 sigma= 69% good,
3 sigma= 99.3% good,
4 sigma= 99.4% good,
5 sigma= 99.97% good,
6 sigma= 99.999997% good
)

At 4 or 5 sigma, with two optocouplers per switching supply, I would
have to fix a lot more than a few hundred switchers to see any
significant failure problem in optocouplers.

So might you... How many supplies are we fixing again?

-Chuck Harris

Glenn Little wrote:

Where I used to work, we used optocouplers to Isolate TELCO ring from our circuit and
detect ring.
We found that as the opto aged the ability of the photo device to see the emitter
decreased.
We replaced a lot of these because of this.
It got to the point that when a board came in for repair and was shown to be faulty
in the test set, the first thing replaced was the opto.
This fixed about 90% of the field returns.
It may be that we used optos close to their low limits?

Glenn


Re: TDS754A

Siggi
 

Hey Dana,

IIRC the standby power supply that allows soft-power on is also responsible
for powering the main switcher. Maybe the standby supply needs recapping.

The TDS5/6/7As are also well documented to suffer from capacitor plaque.
There are SMD electrolytic capacitors all over the acquisition, CPU and
front panel boards. If yours hasn't been re-capped, then that's also a
possible explanation for what you're seeing.

Siggi

On Tue, Aug 20, 2019 at 10:25 AM danadak <danaaknight@gmail.com> wrote:

This scope has been excellent to date. Now when turned on it
power cycles. It will start up, most of the time complete the POST,
then power itself off after a minute or two.

Before I spend the next century trying to find the problem anyone
have a similar experience ?


Regards, Dana.




TDS754A

danadak
 

This scope has been excellent to date. Now when turned on it
power cycles. It will start up, most of the time complete the POST,
then power itself off after a minute or two.

Before I spend the next century trying to find the problem anyone
have a similar experience ?


Regards, Dana.


Re: TDS460A Will not turn on?

Bruce Griffiths
 

The HP optoelectronics handbook contained data on designing for aging of LEDs in optocouplers so they saw this as a real phenomenon.

Bruce

On 21 August 2019 at 01:35 Adrian <Adrian@nicol1.org.uk> wrote:


I would echo Chuck's thoughts about opto-couplers, they are pretty reliable but I would also remind you that a meaningful test (especially on old devices) must include checking the CTR (Current Transfer Ratio) of the device. I recently fixed a 1970s HP 8" drive and one problem was caused by an opto-coupler.
The LED side measured like a LED, the photodiode side measured like a diode but with the correct LED drive current the diode was not sinking sufficient current for the next stage to turn fully on. As you will have noticed I'm sure, some panel LEDs from the 70s & 80s have 'aged' and are very dim today and I would speculate that the same thing can happen to the LED in opto-couplers and there is just a lack of photons internally?

Adrian



Re: TDS460A Will not turn on?

Adrian
 

I would echo Chuck's thoughts about opto-couplers, they are pretty reliable but I would also remind you that a meaningful test (especially on old devices) must include checking the CTR (Current Transfer Ratio) of the device. I recently fixed a 1970s HP 8" drive and one problem was caused by an opto-coupler.
The LED side measured like a LED, the photodiode side measured like a diode but with the correct LED drive current the diode was not sinking sufficient current for the next stage to turn fully on. As you will have noticed I'm sure, some panel LEDs from the 70s & 80s have 'aged' and are very dim today and I would speculate that the same thing can happen to the LED in opto-couplers and there is just a lack of photons internally?

Adrian


Re: TDS460A Will not turn on?

Mlynch001
 

Glen,

Excellent advice. A couple of others who have repaired these same power supplies mentioned these same parts as troublesome. These optocouplers cost next to nothing. I can replace and eliminate a potential problem spot.

THANK YOU!

--
Michael Lynch
Dardanelle, AR


Re: Need Help Troubleshooting Tektronix PS280

Lawrance A. Schneider
 

Hello,

On Aug 16, 2019, at 9:27 PM, John Crighton <john.crighton@optusnet.com.au> wrote:

One of the previous posters suggested that you print out the schematics. I am going to adopt a Judge Judy attitude here.
Have you printed out enlarged copies of the circuit diagrams? That is a YES or a NO

Another poster suggested that you start at the transformer and work your way forward.
Have you tested the transformer? That is a YES or a NO

Have you checked the bridge rectifiers as the other poster suggested? YES or NO

The previous helper asked you to make notes on your printed out circuit diagram and component layout drawings?
Have you done as he suggested?

We know your power supply is slightly different from the diagrams. This is the beginning of the "Fun Part." for us hobbyists.
Find a big piece of paper and start drawing the main parts of the circuit as you find it.
Turn this repair job into a learning excercise. Make it fun.
I’ve ben doing this for three days. on my E3630A HP power supply. Still no luck. I don’ have the schematic for the daughter board meter section of the supply. Further, there are NO TEST POINTS! But, I’ll continue working.

larry


Re: 7000 series carrying handles - how strong are they?

Craig Sawyers <c.sawyers@...>
 

Even with the 500 series scopes, which weighed much more, and had handles that were covered in
leather
Dennis Tillman W7PF
It was not leather, but leatherette - a plastic faux leather. Which is why it degrades over the
decades (probably because the plasticiser leaches out), cracks and falls to pieces. As does the piece
of fibreboard underneath it without the leatherette to protect it - and that leaves only the metal
strap inside, often rusty.

Craig


Re: 2440 cal errors

Szabolcs Szigeti
 

Hi,

Yes, definitely. The FPP error is 99% because of the nvram battery failed
an lost the calibration. All other fails are likely a result of it. You can
verify it by going into the extended diagnostics and check the detailed
result of the FPP fail.
Then you'll need to replace the battery (older models) or the nvram on
newer models (or hack them for external battery).
But first you shoul try self cal and ext cal, without powering down the
scope and see if the errors go away. They should. If not, you should still
try the full calibration as desvribed in the adjustments section of the
service man.

Mandatory warning: don't run the scope without cover without external
cooling, you risk damaging the CCDmodules.

Szabolcs

Robert Simpson via Groups.Io <go_boating_fast=yahoo.com@groups.io> ezt írta
(időpont: 2019. aug. 19., Hét 19:46):

Well I guess you get what you pay for. At $50 for a 2440 should have been
a clue. So far the first 2440 I turned on has cal errors
4000 FPP fail
7000 CCD fail
8000 PA fail
all others passed

Maybe I should go through an external calibrate first?
Bob




Re: Thoughts on TDS744A

Siggi
 

Hey Mark,

The early TDS5/6/7 suffered terribly from capacitor plague. I have a
TDS684A in parts that will probably never be anything but a parts donor.
All the electrolytics on the acquisition board had leaked and caused damage
to the PCB.
It is possible that the scope in question has been serviced already, but in
your shoes, I’d want to know for sure. If the seller doesn’t know, you’d
have to open it up and inspect the acquisition, processor and front panel
boards.
You’ll want the scope to pass all self tests as well as signal path
compensation (SPC).

Another thing to watch for is the state of the CRT. The color version of
these scopes use an LCD color filter over the CRT, and triple scan the
raster - once for each color. Because of the color filter, the CRT is
driven hard, and they tend to fade early.

I have a TDS784D, which is a powerful scope. Not my favorite or first go
to, though, as it’s loud and slow, and has a fairly unintuitive UI. I view
it as my “truck”, reserved for heavy lifting.
The TDS5/6/7Ds were largely immune to capacitor plague, as Tek had switched
to SMD tantalum caps for decoupling by then.

Good luck,
Siggi

On Tue, Aug 20, 2019 at 03:33 Mark Schoonover <mark@ka6wke.net> wrote:

Hello,

I'm interested in purchasing my first scope and looking for opinions on the
TDS744A. I'm not interested in purchasing a Rigol/Siglent, etc - not that
they are bad scopes, I've used Teks before at different employers. It's
just that I'm not familiar with this particular model. It'll be used for
working on amateur radio related radios, experimentation and general
messing around :) I know it can be modified to a 1GHz scope and might do
that in the future.

Thanks for reading.

73! Mark KA6WKE

Website: https://www.ka6wke.net
Author: 4NEC2 The Definitive Guide EMail List:: 4nec2defguide@groups.io




Re: Fan direction on TEK485

Siggi
 

The 485 has the wonderful temp controlled Siemens motor and impeller design
fan. It draws the air in through the enclosure and expels it at the back of
the scope.

On Mon, Aug 19, 2019 at 20:28 Kevin Oconnor <kjo@cryden.com> wrote:

Did the TEK factory have the fan suck air in or blow it out the back?
kevin




Re: Thoughts on TDS744A

David Slipper
 

Hi, I have had one for a couple of years and I'm very pleased with it.

The fan is a bit loud for a home environment and my wife complains if my
project takes over the dining room, but I can tolerate that :-)

It's a bit heavy so a truly portable it is not IMHO.

Dave

On 16/08/2019 03:31, Mark Schoonover wrote:
Hello,

I'm interested in purchasing my first scope and looking for opinions on the
TDS744A. I'm not interested in purchasing a Rigol/Siglent, etc - not that
they are bad scopes, I've used Teks before at different employers. It's
just that I'm not familiar with this particular model. It'll be used for
working on amateur radio related radios, experimentation and general
messing around :) I know it can be modified to a 1GHz scope and might do
that in the future.

Thanks for reading.

73! Mark KA6WKE

Website: https://www.ka6wke.net
Author: 4NEC2 The Definitive Guide EMail List:: 4nec2defguide@groups.io



.


Re: TOPIC CHANGE: Pro's and Con's of the 576 and 577 Curve Tracers. WAS: 5xx 'Scopes

 

Hi Dennis,

On Tue, Aug 20, 2019 at 09:41 AM, Dennis Tillman W7PF wrote:


Hi Dave,
What does a 7704A with a P7001 have to do with curve tracers???
The reason I changed the topic was to separate the discussion about 500 series
scopes from the discussion going on about transistor curve tracers with the
same subject.
Dennis Tillman W7PF
You're right, we strayed.

This is how we got here:
While discussing the modular construction of the 577 curve tracer and the possibility of changing a 577D2 into a 577D1, this happened:

Hi Dave,
Tek sometimes uses this modularity in very interesting ways. I think the 7704 was the first scope they designed to be modular from the start.
The top section is completely removable and held to the bottom section with only a few screws. This was done so Tek could insert the interface
section of the DPO (Digital Processing Oscilloscope) in between the top and bottom of the 7704. The DPO used a DEC PDP-8 minicomputer
to capture data from the 7704 lower section plugins and display the results on the 7704 upper display section.
Tek listed the DPO in its catalogs from 1974 to 1981. In 1981 Tek introduced the 7854 which does all of this in a normal size 4-wide mainframe
using a microcomputer instead of the PDP-8 minicomputer.

Dennis Tillman W7PF
Very relevant historically, interesting and significant but you're right, not ideal for posterity unless searching for content, not topic.

Raymond


Re: TDS460A Will not turn on?

Dave Seiter
 

In the late 70's I was in a Junior Achievement program sponsored by a couple of guys from HP optical (Page Mill); they took us on tours, told us lots of stories (some rather racy), and gave some of us who were interested lots of "samples" that were mostly seconds (wrong tints, poorly filled molds, loose specs, etc) from single LEDs to laser modules, but never any optocouplers.  When I asked for some, I was eventually given "real" samples because the "failure rate was so low".  At least on the types I was interested in.
-Dave

On Monday, August 19, 2019, 02:33:24 PM PDT, Chuck Harris <cfharris@erols.com> wrote:

Steve,

As a life long EE, I would not have put up with that for
a minute.  Either the circuit would get redesigned, or the
vendor of defective parts get banned.

But, I have always been a bit of a hard-ass about stuff like
that.

-Chuck Harris

Stephen Hanselman wrote:
Chuck,

He would change them 3 or 4 at a time. Now we see two or three over 5 or 6 units.  The 6130C uses 22 (or so) and the OEM HP ones were unstable.  HP got better, but at the time (1979) they broke at the drop of a hat.

Other folks, Monsanto, LiteOn, etc, all seemed more stable and reliable.

steve


Re: 7000 series carrying handles - how strong are they?

Dave Seiter
 

I've had 2 500 series handles break on me- one should have been obvious, it was rusted badly and only the metal was left, but the other one still had remnants of it's covering on it but was also rusted badly, maybe even worse than the first one.  The inside of the second scope also showed a lot of corrosion on the aluminum and steel parts.  My guess was that it spent a lot of time near the ocean in Santa Cruz (where I picked it up). Both didn't fall far, but were pretty used up anyway- only the good parts remain...somewhere.
-Dave

On Tuesday, August 20, 2019, 01:42:43 AM PDT, Dennis Tillman W7PF <dennis@ridesoft.com> wrote:

Ni Nenad,
Not silly. I have been carrying 7000 series scopes around for almost 50 years and I have never given the handle a second thought because I have removed so many of them from instruments I have scrapped. Every one of them is as solid as the day it was made. This applies to the outer plastic cover, the inner spring steel, the way they are attached to the instrument, and the way the rigid aluminum chassis handles all that weight. It is beautiful integration of all those parts into a very sophisticated mechanical design.

Even with the 500 series scopes, which weighed much more, and had handles that were covered in leather, I never saw a handle break.  The leather might dry out and crumble in some climates but the steel hidden inside was still more than strong enough to continue doing its job of making it possible to safely lift a scope (provided you had a couple of helpers with strong backs to provide assistance).

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Nenad Filipovic
Sent: Sunday, August 18, 2019 2:41 AM

Well I suppose this sounds silly, but I just can't get over it. This thin metal sheet inside the handle is surely tough, high tensile strength steel, but somehow subjectively it doesn't nearly impress as the rugged 465 handle, for example. In my head thin metal sheets tear and crack. Every
7000 handle end I inspected showed some minor bending around the hole where it pulls against the main screw.

So my question is, has anyone ever had that handle crack or snap? 7000s are no longer costly lab instruments handled with utmost care, today we use them in our homes, shops... They get transported probably a lot more frequently than they were intended to, possibly against some rules which were in power back then, now forgotten or never even known. Should the instrument be supported by your other hand from below?

I don't use my 7104 often, but when I do I need to carry and lift it on the table. And every time I get shivers in my feet. Some reassurance would help.

Best Regards,
Nenad F.




--
Dennis Tillman W7PF
TekScopes Moderator


Re: Improving the odds with the 7S11/7T11 Sampling Plugins

 

Hi Nenad,
The diode bridge in the front end of the sampling head is extremely delicate. It doesn't take much to blow one out at which point there is nothing you can do except find another sampling head to replace it. 7S11s seem fairly rugged by comparison.

An untested 7S11 and S-6 for $200 does not sound like a good deal to me. It is too risky. If the seller said it works and was reputable then it would be a good price.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Nenad Filipovic
Sent: Sunday, August 18, 2019 12:37 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Improving the odds with the 7S11/7T11 Sampling Plugins


I would like to hear from others what they do to make the 7S11/7T11
sampling plugins easier and more reliable to use.
Strange that nobody responded, summer vacations? I was really hoping to hear about this, I currently don't have the 7S11/7T11 but I'm considering getting them. What I do have is a 7S12 with S-4 and S-53, so I plan to move the S-4 to (future) 7S11 and find S-6 and S-52 for the 7S12.

Everything depends on getting the 7T11 to trigger.
Can it free run like the S-53? I suppose not, otherwise you'd hardly say it's difficult to set. With S-53 in 7S12 I set it to free run (Stability CW, Level CW, Slope +). The noise I get as a signal on the scope screen is enough for a good estimate of offset and amplitude. If both of these make sense I fiddle with the S-53 to trigger, and most of the time get it stable. My overall experience with 7000 series sampling plugins is limited, obviously 7S12 is not intended for general purpose sampling - requires a clumsy signal fork to sampling and trigger recognizer heads.

Just a few days ago on eBay there was a 7S11 with S-6 untested for $200, and it was gone pretty quick. I have no idea how realistic this price was, seeing it gone now surely does not make it easier...

Best Regards,
Nenad F.





--
Dennis Tillman W7PF
TekScopes Moderator


Re: 7000 series carrying handles - how strong are they?

 

Ni Nenad,
Not silly. I have been carrying 7000 series scopes around for almost 50 years and I have never given the handle a second thought because I have removed so many of them from instruments I have scrapped. Every one of them is as solid as the day it was made. This applies to the outer plastic cover, the inner spring steel, the way they are attached to the instrument, and the way the rigid aluminum chassis handles all that weight. It is beautiful integration of all those parts into a very sophisticated mechanical design.

Even with the 500 series scopes, which weighed much more, and had handles that were covered in leather, I never saw a handle break. The leather might dry out and crumble in some climates but the steel hidden inside was still more than strong enough to continue doing its job of making it possible to safely lift a scope (provided you had a couple of helpers with strong backs to provide assistance).

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Nenad Filipovic
Sent: Sunday, August 18, 2019 2:41 AM

Well I suppose this sounds silly, but I just can't get over it. This thin metal sheet inside the handle is surely tough, high tensile strength steel, but somehow subjectively it doesn't nearly impress as the rugged 465 handle, for example. In my head thin metal sheets tear and crack. Every
7000 handle end I inspected showed some minor bending around the hole where it pulls against the main screw.

So my question is, has anyone ever had that handle crack or snap? 7000s are no longer costly lab instruments handled with utmost care, today we use them in our homes, shops... They get transported probably a lot more frequently than they were intended to, possibly against some rules which were in power back then, now forgotten or never even known. Should the instrument be supported by your other hand from below?

I don't use my 7104 often, but when I do I need to carry and lift it on the table. And every time I get shivers in my feet. Some reassurance would help.

Best Regards,
Nenad F.




--
Dennis Tillman W7PF
TekScopes Moderator

20221 - 20240 of 179312