Date   

7 photos uploaded #photo-notice

TekScopes@groups.io Notification <noreply@...>
 

The following photos have been uploaded to the Sampling with 3S2 album of the TekScopes@groups.io group.

By: Charles <charlesmorris800@...>


Re: 3T77 tunnel diodes (again)

 

Yes, both those controls work. The real-time mode still looks weird although now there is only one dot showing during the fall... still should not be any. I'm not going to go chasing that any further since I won't be using a sampler in real-time mode anyway - my other scopes can handle that, and without the risk of blowing the head :)

I played with it a bit more today. First I I threw together a quick TD pulser clocked by a 1 MHz crystal oscillator, and calibrated the sweep on the 0.1 us range using the square wave, then examined the edges after the TD. The waveform is ugly after the ~1 ns edge, but I know lead length and placement are at issue). With pulse inputs I can't go faster on the 3T77A than 20 ns/div equivalent (and using the X10 expander mode i.e. 2 ns/div) because it takes too long for the scope to trigger and display. There's no delay line in the 3S2 and I didn't want to rig one up for now.

Also hooked up my GR 220-920 MHz oscillator to both heads (the S-2 and S-4). It displays sine waves nicely up to about 500 MHz. At 620 MHz the trigger is starting to lose function so the traces get noisy, a bit better with the Smooth switch on, but at 800 MHz it's useless.

Photos in the Sampling with 3S2 album.


TDS544A with strange display #photo-notice

durechenew@...
 

Hello gentlemen,

My first post here, but I've been looking for information on this site for a long while.
Some 8 years ago I bought A TDS544A with normal caps issue; that was solved (removed all old caps, cleaned and replaced caps on all boards, repairing some traces). In the end the scope started to work fairly normal but some exceptions apply here.
Whenever there is a white patch on the right side of the screen (after pressing Vertical Menu, for example), there is a row of horizontal... lets call that bands, starting on the left of the screen, diminishing toward the right (see attached pictures).
These are not of constant length (visible from pictures); wild guess is that at the end of white patch (each line) there is a signal that changes (maybe from 1 to 0, or opposite) that triggers something like a sample and hold which allows dots to be displayed for a while during the next line (only on blue). No white patch at the right, no bands of blue at the left.
VGA output at the back of the scope shows normal (no such bands of blue).
Using a 2235 I tried to see some signals, mostly at J5, J62 (and synchro signals at J18), but that scope is not good enough to see specific lines while synchronized on frame signal.
I've seen some posts that tell me there are people around that know much more than necessary to give me some guidance where to look (and what to look for, in fact).
It maybe related, or not: it seems I cannot convince the scope to go to Auto (in Acquisition) after selecting Single Shot; the only way (i may be wrong in that is the only way) to see it running again is by selecting Autoset.
I would expect a lot of questions, don't keep anything back...

TT

P.S. Not sure why there is no menu at the top of the post, where you can click to add a picture, or format text.. I put a new post to tek500 and it was no issue to upload. What did I do wrong here?


Tek 2230 in needs for a new transformer PN 120-1601-01

Pitpat
 

Hi, as the title says my big boy needs a new HV transformer.
I've found a similar one PN 120-1348-02 for a reasonable price but i'm not quite sure it will work for my scope.
I've also heard that there are some equivalents but since the datasheets of those trafo might be gone lost in time i've no idea of what PN should I be looking for.
So if you have one or know someone who does please send me a pm!
Thank a lot
Federico
PS you can also reach me on telegram to @pit_pat


F.S.: Tektronix CONSOLE PORT TDS 5/6/7xx Oscilloscope Debug Card RS-232 for Opt 013

maurit
 

TEK Console Port Card interface to Opt. 013 (plug&play)

For all TEK TDS 5xx 6xx 7xx Series oscilloscope
Homemade interface card for Debugging and add Options.
This interface uses Option 013 card for the RS232 output .
No need to open the oscilloscope, access from the Opt.013.
Easy to use with any terminal client (Hyperterminal, PuTTY, etc.)
This interface is homemade, new and professionally built

12,00 Euros plus shipping costs.
I ship worldwide from Italy.
Price and conditions are described in the eBay.it listing.

Thanks for watching.
maurizio - Italy

Please, for buy, search on eBay.it:
"Tektronix CONSOLE PORT TDS 5/6/7xx Oscilloscope Debug Card RS-232 for Opt 013"


How to troubleshoot a faulty 7B50 timebase

Thierry Delaitre
 

Hello All

I have a 7704A with 2 x timebase: 7B53 and 7B50

The 7B50 has developed a fault suddenly and the screen is now all lighting as green and cannot see the trace anymore when using this timebase

The led for on the 7B50 still appears to sync with the input signal but the screen of the scope is all lighting green when using that timebase

Swapping the timebases also keeps the fault with the 7B50 which shows this is not a problem with the 7704A chassis itself

I am wondering how to start troubleshooting the 7B50 and whether that fault is a known issue?

Many thanks

Thierry


Re: To Beeswax or not to Beeswax: that is the question.

TomC
 

Thank you for mentioning Faraday's “Experimental Researches in Electricity”. I hadn't known about it and have now ordered a copy.

I visited the Faraday museum in London in 2001 and look forward to reading about "the rest of the story".

Tom

On 3/5/2021 9:43 PM, Tom Lee wrote:
Candles of the Regency era were of variable composition, depending on what you were willing to spend. Faraday used whatever was handy to get the job done. He didn’t need to immerse his coils completely in sealants. His goals were modest: Just keep the thing together long enough to finish his experiments. His “Experimental Researches in Electricity” is a fun read, with lots of bits that we might find quaint and charming, but given that there was no electrical parts industry, he naturally improvised with what was at hand. That included gutta-percha, which he discovered was a fantastic insulator — and a thermoplastic one at that — allowing the first undersea telegraph cables to be made (including the first to bridge the Atlantic). It also revolutionized dentistry (where it is still used) and gave us the first non-feather core golf balls.
He was inspired to use silk-covered wire when he learned from his wife that bonnets were stiffened by iron wires around which silk thread was wound (to reduce staining from the iron).
—Tom


Re: To Beeswax or not to Beeswax: that is the question.

John Atwood
 

Microcrystalline wax, derived from petroleum, is similar in consistency to beeswax: sticky and non-brittle. Its melting point is below that of boiling water, so can be safely melted using a double-boiler. It is available in slabs from companies that cater to candle-makers. I’ve used it to pot transformers, although not under vacuum.

See https://en.wikipedia.org/wiki/Microcrystalline_wax for more information.

- John Atwood


Re: Somewhat OT, but maybe helpful info?

stevenhorii
 

Thanks for the info! This reinforces what I recall, but it has been many
years since I purchased or replaced discrete transistors.

Jeff - you guessed right - these are for Sulzer standards. I have a couple
(more than that, but a couple that need work) with one output of the three
bad and that is usually the amplifier for that output. These tend to be
very reliable. The ones that have bad outputs I had used for 20 years with
no problems (well, other than the 327 lamps in the power supply module and
a couple of power supplies that failed - that’s a saga in itself) but have
now been in storage and when I powered them up, they had no output on the
100KHz stage.

Thanks again!

Steve Horii

On Sat, Mar 6, 2021 at 09:53 SCMenasian <scm@menasians.com> wrote:

You can use 'A' versions of transistors just about all the time. 'A'
versions of semiconductor devices
are almost always selected devices with tighter specifications than the
'non-A' version. 'A's are not a 'newer' versions with different nominal
specifications. If in doubt, consult the datasheet. "A" versions of op
amps, for example, often have much better offset and drift max limits than
their 'non-A' brothers and sisters. Transistor gain, breakdown voltage,
leakage, noise limits are often tighter.

A few oddball cases may exist. For example, the manufacturer needed a
device with specs at the extreme high or low end for a particular parameter
and selected outliers. In this case, the parts list should say "selected".
I haven't encountered a case like this in the flesh; however,such a case
might exist. For example, an abnormally low breakdown voltage might be
desired in an avalanche pulser application.






What to do when the 2335/6/7 Front Cover latches break....

 

These two plastic slide latches hold the front cover closed to the main scope for storage and shipping. they are pretty fragile, and the cover can be heavy on the 2336/7 versions due to the circuitry inside, so the latches fail pretty often. needless to say, spares are non-existent. 3D printing might be an option, but it's a two part assembly with a molded in metal nut, so probably not.

Looking at a very nice 2336 I had ready to go, except for the dreaded latch problem, I took Susan's suggestion to try some velcro.
Wow, what a great fix that was. I took some half inch velcro with adhesive backing, and cut it in half (so only 1/4" wide). Then, a short 2 inch strip of adhesive velcro at the middle of the main scope, right at the front edge mates perfectly with an equal length hook strip inside the cover top edge. Too much velcro makes it hard to open, and can rip off the mating part, just a bit is enough.

The 2336 on the stuff season page was fixed that way, the picture clearly shows the velcro placement if you can't quite envision it. It fixed a really annoying problem for me, and looks and works great. Might be a useful fix for your unit too.

see it here: https://www.sphere.bc.ca/test/2021-4-equipment/tek-2336a2-open.jpg

all the best,
walter (walter2 -at- sphere.bc.ca)
sphere research corp.


Re: TG501 1NS Schottky

 

Hi Rick,

What are you using to look at this signal?

Regards

On 3/6/2021 11:11 AM, Rick wrote:
So a new CR515 diode did not bring the 1ns signal back to life. Seems like the only thing left is the signal getting hosed up under the Ft Knox shielding on the other side of the board. I'm still thinking the problem has to be at the entrance to the 1ns circuit because the 2ns signal is there, albeit a little lower than it should be.

Does anyone have any tricks or experience removing the completely soldered on shield to get to the traces? It's heavily soldered on all four sides. I'd surely have to overheat it to get all the solder off. I thought about cutting an access hole in it but the filings from a Dremel would be impossible to get out. I'd have to snip the hole.

Rick

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


Re: TG501 1NS Schottky

Rick
 

So a new CR515 diode did not bring the 1ns signal back to life. Seems like the only thing left is the signal getting hosed up under the Ft Knox shielding on the other side of the board. I'm still thinking the problem has to be at the entrance to the 1ns circuit because the 2ns signal is there, albeit a little lower than it should be.

Does anyone have any tricks or experience removing the completely soldered on shield to get to the traces? It's heavily soldered on all four sides. I'd surely have to overheat it to get all the solder off. I thought about cutting an access hole in it but the filings from a Dremel would be impossible to get out. I'd have to snip the hole.

Rick


Re: Replacing Variable Vertical Attenuator Shaft

Dick
 

After looking more at the situation, I believe the only answer is
to remove the Vertical Input assembly. That's not going to happen.

So, I repaired as much as I could and re-assembled the scope. The
only missing function is the Variable input on Channel A. I can live
with that.

Thanks for all the responses and offer of parts.

73, Dick, W1KSZ
________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of SCMenasian <scm@menasians.com>
Sent: Friday, March 5, 2021 10:56 AM
To: TekScopes@groups.io <TekScopes@groups.io>
Subject: Re: [TekScopes] Replacing Variable Vertical Attenuator Shaft

Several years ago, I had some fiberglass rod in my junk collection. I think it was a part of a fishing rod. I used it for just this sort of thing and I think the diameter was close to 1/8". Also, if Amazon has delrin, I would prefer it to nylon.


Re: Somewhat OT, but maybe helpful info? Tarnsistors :plain vs "A" etc.

Jeff Kruth
 

Hi Steve!

Way back in the early days of semiconductors, repeatability was a crap shoot. Thats why there were SO MANY early part numbers, a run would be made and they would see what they got, if not up to spec for a 2NXXXX it became a 2NXXXY, slightly different specs.So, as they got better making the :cookie dough" for the transistor recipes, the uniformity, and things like operation over extended temperature range, breakdown voltage, leakage current, etc. became better.A JANTXV 2N2221A would be the ne-plus-ultra replacement for the plain jane 2N2221.Mainly because, I assume "H"type biasing in the circuitry, so small variations in Beta, etc. are swamped out. The JANTXV device has a better "bathtub" curve and guaranteed specs.Heck, a wide variety of devices would probably work in the same slot. Early designers had to work within the wide spec variation of the devices and so made their circuits fairly tolerant. Esp. since they did not want to spend excessive time "tweaking" on the production line. Also a lot of companies had in-coming test depts, to screen the critical parts needed out from the wider variance devices. Usually marked in the manual for "selected". SO relax, you are probably in good shape with "A" devices (tighter specs), unless something is weird, which it probably isnt in a Sulzer. Man, I had SO MANY of these I got from NASA in my early surplus days. Passed them all along. Probably owned 20-25 of them.Regards,Jeff Kruth In a message dated 3/6/2021 9:35:08 AM Eastern Standard Time, sonodocsch@gmail.com writes: Though I follow the group postings regularly, I do not do as much “repair on the bare metal” as many of you do. However, I have some vintage equipment (frequency standards) that use discrete transistors. I have repaired these in the past - usually a transistor in a buffer amplifier or divider stage fails. Fortunately, these are mostly readily available: 2N2221. My question has to do with substitution. Not substituting a different transistor with similar characteristics, but “A” versions of them. This is partly due to availability. 2N2221A transistors seem much more common on the eBay market than the 2N2221. I vaguely recall that you can substitute the “A” versions of transistors for the older (?) ones with no problems. However, before I stock up on replacement transistors, I am interested in the opinions of this group’s members on this. I know this is pretty basic, but surprisingly, my various online searches on this topic always result in sites that either tell me the characteristics of the devices or offer to sell me various replacements (but not simply the “A” versions) - sometimes with very large minimum quantity orders. I have not found (yet) anything that just says, “sure - go ahead and use the “A” version of a transistor or the JAN version in place of the original”. I have used JAN transistors as replacements as they generally have similar electrical characteristics but have a much larger operating temperature range spec. Any advice will be appreciated. Steve Horii


Re: Somewhat OT, but maybe helpful info?

SCMenasian
 

You can use 'A' versions of transistors just about all the time. 'A' versions of semiconductor devices
are almost always selected devices with tighter specifications than the 'non-A' version. 'A's are not a 'newer' versions with different nominal specifications. If in doubt, consult the datasheet. "A" versions of op amps, for example, often have much better offset and drift max limits than their 'non-A' brothers and sisters. Transistor gain, breakdown voltage, leakage, noise limits are often tighter.

A few oddball cases may exist. For example, the manufacturer needed a device with specs at the extreme high or low end for a particular parameter and selected outliers. In this case, the parts list should say "selected". I haven't encountered a case like this in the flesh; however,such a case might exist. For example, an abnormally low breakdown voltage might be desired in an avalanche pulser application.


Somewhat OT, but maybe helpful info?

stevenhorii
 

Though I follow the group postings regularly, I do not do as much “repair on the bare metal” as many of you do. However, I have some vintage equipment (frequency standards) that use discrete transistors. I have repaired these in the past - usually a transistor in a buffer amplifier or divider stage fails. Fortunately, these are mostly readily available: 2N2221.

My question has to do with substitution. Not substituting a different transistor with similar characteristics, but “A” versions of them. This is partly due to availability. 2N2221A transistors seem much more common on the eBay market than the 2N2221.

I vaguely recall that you can substitute the “A” versions of transistors for the older (?) ones with no problems. However, before I stock up on replacement transistors, I am interested in the opinions of this group’s members on this. I know this is pretty basic, but surprisingly, my various online searches on this topic always result in sites that either tell me the characteristics of the devices or offer to sell me various replacements (but not simply the “A” versions) - sometimes with very large minimum quantity orders. I have not found (yet) anything that just says, “sure - go ahead and use the “A” version of a transistor or the JAN version in place of the original”. I have used JAN transistors as replacements as they generally have similar electrical characteristics but have a much larger operating temperature range spec.

Any advice will be appreciated.

Steve Horii


Re: 3T77 tunnel diodes (again)

Albert Otten
 

These are nice results Charles!
Although less important now I wonder about the previous strange result in real-time mode. Is that still the same?
In equivalent-time ranges of the 3T77A, do the DOT response and SMOOTH do their job? That will only be visible at slower time/div such that only very few dots are shown in the rising and falling edge.

Albert


Re: [Tek 485] No intensity control

marcosjl31@...
 

Ozan,

Remove C1537. It measures ,27uF with an ESR of 9.1 ohms. Scope does not power up if the cap is removed.

Checked R1536. It was above specs : 2.8Mohms (ref is 2.2 10%). Replaced it.

But still no trace in X-Y mode or 50ms and slower time div.

Jose


front protective cover for 2455b with dmm

Scott Adams
 

I have a tek 2455b with option 01 dmm and was wondering if there is a front protective cover for this scope.


Re: To Beeswax or not to Beeswax: that is the question.

Tom Lee
 

Beeswax is quite versatile. Old tech, perhaps, but versatile nonetheless. Bees sure seem to be fond of it!

Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 3/5/2021 23:09, Merchison Burke via groups.io wrote:
Back in the 1960s, beeswax was used in RF and IF transformers (which used powdered iron cores for tuning) to secure the cores after tuning.



On 2021-03-06 12:27 a.m., Jeff Dutky wrote:
Tom,

Sealing wax, according to wikipedia, can contain beeswax. I'm a little surprised that candle wax would be used to try to hold a transformer together, my impression of it is that it is both brittle and slippery, especially compared to either beeswax or sealing wax (the latter being known for its tackiness). I would think that you would want something that was a little sticky to keep the windings in place.

Other obvious candidates would seem to be things like shellac, pine sap, animal glues, and natural rubbers (e.g. latex). Again, my rudimentary research on Wikipedia yields very few details about the electrical properties of most of these substances, with the exception of shellac, which is mentioned as having been used "for fixing inductor, motor, generator and transformer windings."

-- Jeff Dutky




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