Date   

Re: 3T77 tunnel diodes (again)

Albert Otten
 

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.
It's not weird but perfectly normal. What you see is a Dot response about 75% (upper trace) and slightly less than one (lower trace). Soaome asymmetry in dot response between jumps up and jumps down is also normal and hardly present here. What can be the reason that the real-time mode works fine now when all you dit was 3T77A repair?


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).
Yes the cabling is not nice. There will be serious reflections when you use a T-connector as splitter.

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.
Because of those reflections you must have seen amplitude variations while going though the frequency range of the GR unit.

Photo legend say:
The delay between the two traces is due to the system components, not the cable connecting the tw
(it only accounts for about 4 ns of the visible 10 ns).
The "B Delay" control is hidden behind your cabling...

TD pulser (1 MHz TTL oscillator, trimpot, TD, coupling cap and 47 ohm resistor to a GR cable).
In general coupling caps are not used here and can make things worse.
Why do you think that the falling edge is shown in DSCF0217.JPG?
The level before and after the 1 ns slope look more or less the same to me.
Is it due to a coupling cap with very low capacitance?

Albert


Re: How to troubleshoot a faulty 7B50 timebase

Harvey White
 

Does the beam finder bring anything on screen?

It sounds to me as if the sweep is deflected off screen.  One suggestion would be to follow the ramp through the plugin. Another is to check the horizontal positioning control to see if it provides a voltage.  If the 7B50 has an XY mode, do you get the same problem there?

Harvey

On 3/6/2021 4:44 AM, Thierry Delaitre via groups.io wrote:
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: 3T77 tunnel diodes (again)

 

Yes, it has the Pull for Sync switch (this is a 3T77A with the improved trigger circuit). The original 3T77 is only spec'ed to trigger up to 300 MHz, vs. 1 GHz for the -A).

The back diode did fire multiple times when the knob is pulled, as the manual says, during adjustment. But it doesn't make any difference at the very high frequencies, even on the falling edge which is supposed to give better triggering.

Anyway, maybe it needs more adjustment...


Re: TG501 1NS Schottky

Joel B Walker
 

Remember that the TG501 must be terminated with 50 ohms. If not there may be NO output or distorted and low output. You can use a bnc "T" fitting and put a 50 ohm terminator on one side, and the scope on the other.


Re: 3T77 tunnel diodes (again)

Ed Breya
 

Charles, does the 3T77 have an "HF SYNC" mode in the trigger selection? Samplers are best at showing fast edges but at relatively low rep rates. They sometimes have the HF sync feature to provide stable triggering on RF. It's usually yet another TD circuit that acts as a trigger countdown.

If you have the feature, give it a try, and you should be able to get very nice RF displays up to the rated BW and beyond.

Ed


Re: 3T77 tunnel diodes (again)

 

I'm sure I could make one of some sort (Googling "homemade tunnel diode" comes up with a LOT of results) but one that will have an Ip near 20 ma, trigger up to 1 GHz per the manual, and fit in the clip is a tall order ;)


Re: 3T77 tunnel diodes (again)

 

given that those things weren't even made in clean rooms, and there
are literal tutorials on semiconductor manufacturing at home on
youtube, i'm surprised no one has tried manufacturing tunnel diodes on
their own yet. so many smart people here, you'd think one of us has
some acid and all that other smelly stuff that's necessary :-)

On Sat, Mar 6, 2021 at 8:03 PM Charles <charlesmorris800@centurytel.net> wrote:

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.





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

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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.

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