Date   

Re: Odd 453A on ebay UK

Dave Seiter
 

I tried also...   Apparently, I'm an "anorak".  Confused; I politely asked why he was calling me a parka.  It went downhill from there.  He's an angry individual.
-Dave

On Tuesday, March 30, 2021, 02:53:34 PM PDT, Mlynch001 <mlynch002@gmail.com> wrote:

The sad thing is, the seller seems unwilling to even consider that he could be wrong.  I have run into such people on E-Bay, (and elsewhere).  I just move on or sometimes watch the show from the sidelines.

--
Michael Lynch
Dardanelle, AR


Re: 2nd life for a 575 after resting for 30+ years in the attic #photo-notice

Chuck Harris <cfharris@...>
 

On, I think all, of the tektronix curve tracers,
the forward trace, and the backward trace are equivalent
as there is no z-axis control, save for the intensity control.

So, unless you are planning to add a whole bunch of twidgety
circuitry that senses when the sine wave hump that traces the
horizontal trace reaches its peak, and blanks as it returns to
its minimum, I would suggest that you live with it.

The degree of looping that you are seeing can be increased by
stray capacitance, and by thermal effects in the transistor that
cause it to warm on the forward trace, and being warm, retrace
a different path on the retrace. The knowledge it presents is
also useful. You should be able to calculate all sorts of thermal
effects from the width of the loop.

Enjoy! It is a good curve tracer.

-Chuck Harris


On Tue, 30 Mar 2021 13:41:57 -0700 "Joe"
<The-Lohrbach-Family@t-online.de> wrote:
Hello,

Today I let the unit running for an hour at regular mains voltage and
did comparison tests on a pair of BC 238 C transistors. What can I
say? I am deeply impressed by the bright, sharp and stable display.
That is great! Nevertheless I registered a minor problem that has to
be solved: The flyback traces of the beam are "visible, too bright".

@ John: Yes I forgot to mention these sticky fan bearings. Well, a
little "Ballistol" oil did the job quickly. @Jeff: Thanks, your
explanation must be right. That tells us the Tek designers did a very
good job. I know a lot of other instruments where several components
are tied to higher voltage levels and not any provision is done to
prevent shorting or so.

BTW: All of my BC 238 C transistors produced very similar curve
families, so they seem to have close tolerances. I think I will try
some older OC 26 now and see what happens. Joe





Re: Odd 453A on ebay UK

Mlynch001
 

The sad thing is, the seller seems unwilling to even consider that he could be wrong. I have run into such people on E-Bay, (and elsewhere). I just move on or sometimes watch the show from the sidelines.

--
Michael Lynch
Dardanelle, AR


Re: 2nd life for a 575 after resting for 30+ years in the attic #photo-notice

Mlynch001
 

If my memory is serving me correctly, the 575, like the 576 curve tracer does not “blank” the fly back retrace, so there is always a slight retrace visible.

--
Michael Lynch
Dardanelle, AR


Re: Odd 453A on ebay UK

 

I wonder if it's possible to report him to ebay (selling items that are not as described)...
On the other hand, they are unlikely to care since all they are interested in is their hefty commission.


fs- Tek Oscilloscope 533 - $20.00 Orange/Los Angeles county, pickup only.

benx618(g)
 

from craigsList 03/30/21.
Tektronix Oscilloscope 533 - $20 Location- Orange County, California. pickup only.
"Vintage Oscilloscope from the 1960s. This was my dad’s when he was an engineer for the defense industry. I believe it works it powered up last time we plugged it in but that was many years ago. What you see is what you get no cords or cables included.
It’s a very heavy duty unit and has a great vintage patina.
Cheap - Come and get it!"
There are 3 pictures - I looks very restorable.

I have no affiliation but contacted Gabe (the seller) at the CL ad; he has no other electronics available, will be moving soon, wants to find it a good home for this vintage lab scope. I am posting the info here with seller's permission. CL ref. number is 7295941086 and a CL link below. Contact Gabe direct through CraigsList or me OFFLIST if you need help.


https://orangecounty.craigslist.org/atq/d/huntington-beach-tektronix-oscilloscope/7295941086.html



All fir now,
Ben


Re: 2nd life for a 575 after resting for 30+ years in the attic #photo-notice

Joe
 

Hello,

Today I let the unit running for an hour at regular mains voltage and did comparison tests on a pair of BC 238 C transistors. What can I say? I am deeply impressed by the bright, sharp and stable display. That is great! Nevertheless I registered a minor problem that has to be solved: The flyback traces of the beam are "visible, too bright".

@ John: Yes I forgot to mention these sticky fan bearings. Well, a little "Ballistol" oil did the job quickly.
@Jeff: Thanks, your explanation must be right. That tells us the Tek designers did a very good job. I know a lot of other instruments where several components are tied to higher voltage levels and not any provision is done to prevent shorting or so.

BTW: All of my BC 238 C transistors produced very similar curve families, so they seem to have close tolerances. I think I will try some older OC 26 now and see what happens.
Joe


Re: Tek 2430 Works Fine for 15mins Then Freezes

 

Welcome John!

You should begin at the beginning: open her up and do a visual inspection, you'd be surprised what will jump out at you, even if you're a novice (I assume that you are not actually a novice to electronics, based on the call sign, but even a novice to scopes can still spot some signs of trouble). Next, clean the insides as needed using a static safe brush or compressed air. Finally power it up and have a look at the power rails (as Siggi suggested).

Take pictures. Take notes. People here will be more than willing to assist you with further diagnosis and repair.

You might want to have a look at this document: https://www.sphere.bc.ca/test/tek-parts/troubleshooting-scopes.pdf

Also, download this service manual from TekWiki: https://w140.com/tekwiki/wiki/2430

The TekWiki is a source for a great deal of information, both general and specific, about Tek scopes and other instruments. Here is the "reference material" page: https://w140.com/tekwiki/wiki/Reference_material
and here is the main page: https://w140.com/tekwiki/wiki/

Finally, some of the 2400-series scopes can be damaged if they are run for more than a few minutes with the case off. Some of the hybrids really need the forced air cooling, so if you are running it with the case off (to check the power supply rails, for instance) you should direct a fan to be blowing air over the main board with all the heat sinks. I'm not sure that the 2430 is one of the ones that can be damaged that way, but better safe than sorry.

-- Jeff Dutky


Re: Persuading a 7S12 to play nice with a 7934.

Richard Steedman
 

I've added a photo of the left interface board of my 7S12 so you can compare.


Re: Odd 453A on ebay UK

Michael W. Lynch
 

From the sound of the previous attempts to inform the seller, I doubt that anyone will be successful with any "correction". This is the "Thing that won't go away".

--
Michael Lynch
Dardanelle, AR


Re: Odd 453A on ebay UK

John
 

Well, it's now listed for (minimum) third time.
Desciption states it's a "dual beam" scope, so I do hope someone can politely correct him on this: don't want it sold and then rejected as "not as described" , do we?
john


Re: 2nd life for a 575 after resting for 30+ years in the attic #photo-notice

John
 

Joe:
congratulations, and I hope you enjoy using this wonderful piece of test equipment. I had a very simlar experience with a 575 which I bought "blind" on an auction site a couple of years ago (not Ebay). I've managed to retain the HV electrolytics, but changed all the black jobbies. On my unit, there were quite a few tired valves/tubes: in particular the triodes used as HT regulators. Oh, and the fan bearings were sticky with old green oil, so the fan would not run until things got hot. It took some effort to completely clean the oilite bearings.
John


Re: Tek 2430 Works Fine for 15mins Then Freezes

Siggi
 

On Tue, Mar 30, 2021 at 10:02 AM John Morris <k7rld@comcast.net> wrote:

Scopes are not my expertise so if anyone has an idea where to start
looking, I'd sure appreciate some guidance.
You'd generally start by looking at the power supplies which may simply
need recapping by now.


Re: FS: Tektronix Scope-Mobile 200C

Dave Seiter
 

Grin!  The 7704A probably isn't recommended, but I've had one on that cart for years.  Just last week I was thinking that my 465 would make more sense on it (and be safer!)

On Tuesday, March 30, 2021, 10:29:37 AM PDT, ppppenguin <tekscopes@borinsky.co.uk> wrote:

Hi Dave, I didn't realise that. But then I've never worked with 7000 series kit. I don't think it would take my 547:)


Re: FS: Tektronix Scope-Mobile 200C

ppppenguin
 

Hi Dave, I didn't realise that. But then I've never worked with 7000 series kit. I don't think it would take my 547:)


Re: FS: Tektronix Scope-Mobile 200C

Dave Seiter
 

Also works for 7704As, well strapped down, of course!

On Tuesday, March 30, 2021, 02:40:16 AM PDT, ppppenguin <tekscopes@borinsky.co.uk> wrote:

For sale: Tektronix Scope-Mobile 200C . Suits many 400 series and 2xxx series instruments.

Good condition.

https://w140.com/tekwiki/images/e/ea/062-1533-04.pdf

Best collected but might be possible to dismantle and ship at cost. Location is London N12, UK.

Donation to BECG (registered charity) please: https://becg.org.uk/


5000 Series Scope Deflection Plate Driver Transistors

Jim Adney
 

Many years ago, in a former life and former employer, I was using a 5112 Dual Beam Scope that was perfect for my project. The 2 MHz bandwidth was plenty for what we were doing and, while the dual beam wasn't really necessary, it gave us confidence that what we were shown on the screen was actually coincident in time. This scope, however, had a problem. It would occasionally stop showing one half of one of the traces. The EEs with me on this project would "fix" this by removing the affected plugin and SLAMMING it back into place. The shock often cured the problem, but this "solution" annoyed me.

I managed to get the scope manual and noticed that there were 6 identical output transistors which drove the 6 deflection plates, 4 vertical and 2 horizontal. This scope had dual beams, but only one time base. Reading thru the circuit description I could see that each transistor drove its beam over half the screen. So I figured out which transistor seemed like it might be the problem and swapped it to a different location. This was easy because they were in sockets. Sure enough, the next time the problem occurred, it was in that new location, and I found that I could make the problem come and go by tapping that transistor.

The manual gave a Tek part number for that transistor and also a suitable replacement from some Japanese manufacturer. I ordered 2 or 3 of the Jap replacements, so I would have spares. I replaced the bad transistor and taped the spares inside the scope case, in a zip lock bag. A couple months/years later, another of the OE transistors failed and then another. I ordered more spares, and eventually used all of them. As far as I know, the replacements never failed.

So the question is, was this a well known problem with these transistors and were these common to all the 5000 series 2 MHz scopes? The scope was probably 10-15 years old by the time I started replacing transistors, but I'd never run into streaks of failing parts like this before. Sorry, but I don't remember the Tek part number or the Japanese replacement; this was circa 1985-1990.

Other than those problem transistors, I really liked that scope.


Re: Tek 2430 Works Fine for 15mins Then Freezes

 

Is the fan running? Is there a lot of dust on the heat sink fins?

On 3/20/2021 5:40 PM, John Morris wrote:
I've got a TEK 2430 that seems to work just fine for about 15 mins. Sometimes more. All tests PASS.
I've input a function generator and all different inputs look fine on both channels. Then after 15 mins and sometimes more, I'll look over at it and the screen is still showing a nice looking sine wave, for instance that I've input, but when I go to make a change, the scope is frozen with that image and no other controls seem to make a change.
Relays click when I make some control changes but the screen remains frozen with that sine wave image.
When I turn the scope off and wait 20-30 secs and then turn it back on, it will show the standard horizontal line but will not detect an input.
I can turn the scope completely off and after a few hours it will again come up and work just fine but eventually the same thing happens.
Scopes are not my expertise so if anyone has an idea where to start looking, I'd sure appreciate some guidance.
Thank you. John / K7RLD



--
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https://www.avast.com/antivirus


Re: FS: Tek 206-0104-00 Straight Tips for 6-32 Probes

Jim Adney
 

5 of these have now been sold. I'd like to keep 5 for myself, so that leaves 10 still available.


Re: Repair of Set Screw Attachment for Tek-made VAR Pots

Jim Adney
 

On Fri, Mar 26, 2021 at 09:39 PM, Dave Wise wrote:

You ought to upload the article to TekWiki at w140.com .
Okay, done. Took me awhile to figure out where and how to do this, but I think I (pretty much) managed.

https://w140.com/tekwiki/wiki/Potentiometers/Repairs

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