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Re: 465M

Jim Ford
 

Ah, the lag; that's why I am not interested in a 2465. I had one several decades ago at work, and it drove me nuts. No, you're not ridiculously picky, unless we both are!

7000 series for me, thank you. And someday, an 11800 series.

Jim Ford

------ Original Message ------
From: "Jeff Dutky" <jeff.dutky@...>
To: TekScopes@groups.io
Sent: 9/9/2021 1:36:26 AM
Subject: Re: [TekScopes] 465M

Michael Lynch wrote:

> If I were going to add a 465-variant to my collection I would prefer a 475B

I am guessing that you meant a 465B?
Yes, that is what I meant. I wish that Tek had made a version of the 475 with ALT horizontal mode, but the 465B is almost close enough. The fact that you can see three simultaneous traces on a 465B also makes it interesting to me. I had kind of hoped that the 465M was more like the 465B. I had not realized that it was even more cut down for the sake of cost savings.

I guess that you can view something like the 2465 as the "B" version of the 475 or 485, both because of the 2465's other similarities to the 485 (e.g. higher bandwidth and 50 ohm inputs with overload protection), and because you get the external trigger channels that can be viewed on the display along with Ch 1 and 2. You even get other goodies that the 465B doesn't have, like readout, cursors, and (optionally) a counter/timer.

I have a 2465, which I use all the time, and really like, but I don't like that the price of all those extra goodies was that the controls became much less "direct" and more "fly-by-wire." I especially don't like the position controls that are both laggy, and have a tendency to get out of sync with the on-screen position (they could have remedied that by using knobs that didn't have an indicator, and pots that didn't have a stop, as they did with the cursor controls).

I am ridiculously picky about these things.

-- Jeff Dutky





Re: Help needed bringing a 555 back to life

Selinica Harbinger
 

C640 has 272V across it in mine. The 5651 has -172V across it. The R646/647 pair reads as 498.8Ohm measuring from node to node. I didn't desolder them to check as maybe I'm just blind but they were hard to locate. The plate voltage for V634 was 0V and the grid was -153.5
I can get the -150V adjustment wiper to -148V at best.
Tube were given a check over initially and the weak ones swapped. The indicator cable was checked for continuity and to make sure there were no shorts between lines that should not be there.

I did note a small scorch mark under L790 where the resistor is and the diodes D642, 702, 732, and 672 all seem to have been replaced by a prior owner. They do not match the look of the D762 set nor the manual images or the pictures of other power supply units.
That's just a visual inspection though, all parts tested fine with diode tests and the resistor checked out.


Re: Repair of a 7S14

Ed Breya
 

Yes, the PV MOSFET drivers should work great as current sources, with plenty of voltage - you would just have to shunt regulate them with LEDs. Only a single PV would be needed for each channel. Don't bother with regular transistor optocouplers. You'd need about five per channel to get enough total voltage, making the total parasitic capacitance too large - I've tried it. The transistor optocouplers do however, have significant output current in the tens of uA, but only one Si junction voltage, so you need a bunch to make decent voltage. You take the output from the B-C junction, and run the LED as high as possible. This means you have to use the big six pin type to access the base. The four pin ones only connect the C and E. These generators can be quite useful in certain situations.

My most recent use of this kind of deal was in the Keithley 417 electrometer upgrade project, where I made an adjustable, bipolar voltage source that floats on the output signal, in series with the very large feedback resistors, in order to null out the input bias current. The optocoupler circuit was by far the simplest method.

Ed


Re: 7T11 diode tunnel destroyed connecting a 15pF 1:10 probe?

guy_ellis_1964
 

ESD?


Re: "mottled effect" on anodized front panel

Roy Thistle
 

On Sat, Sep 11, 2021 at 02:38 AM, Sparky99 wrote:


on closer inspection the scope has a slightly mottled effect on the anodized
front panel.
I'm sure I've seen it too. A kind of mild staining? ... in some areas.
It could be, as suggested, and exposure to uv... but, that usually happens when the anodized part is colored. I don't think there is any coloring in these front panels.
The usual thing to do when anodizing aluminium is to seal the anodized part.
It could be that the particular batch that these panels came from did not get sealed properly. Then they would naturally get contaminated, in some areas, over time.
Perhaps these came from the factory with the defect(s) you observed?
It's also possible the scope had 'grime' on the front panel for a long time... that and perhaps a humid environment... that might have engendered an electro-chemically induced etch in some areas.
If you've tried a mild and neutral detergent (you say "soapy water") and it hasn't cleaned up... then anything harsher isn't recommended.
Anodizing... when done correctly, is supposed to to last for a long time. But, these panels have been around a long time already.
Perhaps one will have to live with it? ... or risk doing more damage.

--
Roy Thistle


Re: TEKTRONINX P6139A shorted, metalic, Grow Metal Crystals? any definitive solution?

 

Miguel,

According to the TekWiki entry on the P6139 the cables have "a whisker- or dendrite-growth problem," the fix for which is to replace the cable. There is a temporary fix that involves running current through the BNC connector to burn away the whiskers, but it is only a temporary fix. I have avoided buying cheap P6139s on eBay for exactly this reason.

The literature on tin whiskers is fascinating and bizarre.

-- Jeff Dutky


Re: Repair of a 7S14

 

Roger,

Well, first, the original discussions (blog posts?) by Ed did talk about using an opto-isolator to generate the bias voltage. If I recall the post correctly, the only reason he went with LEDs was because he was pulling things from his junk box. Second, the PVI5080 would require voltage regulators to bring the 5V output down to the 1.35V range matching the output of the mercury cells. Maybe other opto-isolators would have output voltages closer to the target voltage? Third, I was captivated by the fact that you could turn an LED into a voltage source (not exactly DIY self-satisfaction, but satisfying curiosity and entertainment), and am enjoying the experimentation. Finally, while I was not unaware of the existence of opto-isolators, I was not familiar with all of their properties (despite reading Ed's account).

I actually have a couple tubes of old opto-isolators that may be suitable ("old" as in "maybe older than the 7S14 I'm trying to fix"). I should see what their specs are.

-- Jeff Dutky


Re: Suggestion for our group Administrator

Joe
 

I would like to second that, for my two reasons:

- Never change a running system for trifles
- Errors, typos and such are no big deal, science has ever been able to overcome

For me fake news (not in this group but in general) are much worse a problem nowadays

Regards, Joe


Re: Repair of a 7S14

Roger M
 

Jeff,
Sorry I'm more than a little late to this party but I have to ask: since you need an isolated bias supply, one which needs to deliver
little current, and for an application reasonably tolerant of terminal voltage, why the struggle to come up with
a mechanical arrangement for an emitter/detector pair when devices such as the Infineon PVI5080 (a single channel
photovoltaic isolator) are available?

If DIY self-satisfaction is a large part of the answer then I completely understand.
-Roger


Re: TEKTRONINX P6139A shorted, metalic, Grow Metal Crystals? any definitive solution?

Roy Thistle
 

On Sat, Sep 11, 2021 at 07:08 AM, Miguel Work wrote:


there are some king of growing metalic short
Well... I watched the video... and I see you cleaned out the "socket" (on the end of the probe's coax), where the probe tip screws in.... you used alcohol.
Initially... you got a resistance of 0.14229 ohms? (That resistance measurement could be telling.)
We can't really see inside the "socket" to see what's in there... and to observe the phenomenon.
Metal whiskers can grow. It's a known problem; but poorly understood. (Often it is tin whiskers... but, other metals can also have this too.)
Dendrites can also grow: that is an electro-chemical phenomenon.

--
Roy Thistle


Re: Suggestion for our group Administrator

 

I vote NO on editing posts. While I would personally like to be able to fix my typos and mistakes, I value the record of the iterative process.

If having a single, authoritative message on a topic is really important then it should be important enough for somebody to add a summary message to high-value threads. My experience doing research on the group, however, is that most threads don’t get long enough to make reading the entire thread difficult, and the threads that do get long also have so much topic drift that a summary would impossible.

— Jeff Dutky


Re: "mottled effect" on anodized front panel

stevenhorii
 

I’ve seen anodized aluminum exposed to the sun do this.

On Sat, Sep 11, 2021 at 14:24 Sparky99 <jnolan@...> wrote:

Thanks, but I'm sure these marks are not from use as they are distant from
any of the controls - I checked and both plugs ins also have the same
effect, so perhaps due to storage conditions but as I mentioned there are
no signs of any corrosion elsewhere on the plugin.






Re: "mottled effect" on anodized front panel

 

Maybe they are etching from skin contact? Maybe the locations are BECAUSE there are no controls nearby, so that was the convenient place to push when installing the plug-ins, or to rest a hand while using the scope?

It’s too bad you can’t get a good picture of the effect.

— Jeff Dutky


Re: Suggestion for our group Administrator

Tom Gardner
 

On 11/09/21 18:21, pdxareaid via groups.io wrote:
this is my last post on this. i was not leaning at first but am now.
i think we all know we are using yesterday's technology. sure there is much better and i would prefer we use it.
however, this is a legacy forum and the folks with the most knowledge likely would prefer
not to have editing since they are using the email interface.
The content supplied by those with knowledge is why I am here. The email format works well enough for that content.

Web forums have different advantages (and disadvantages). I strongly recommend you look at EEVBlog Forum; it has a lot of Tek and HPAK stuff there.


Re: "mottled effect" on anodized front panel

Sparky99
 

Thanks, but I'm sure these marks are not from use as they are distant from any of the controls - I checked and both plugs ins also have the same effect, so perhaps due to storage conditions but as I mentioned there are no signs of any corrosion elsewhere on the plugin.


Re: Suggestion for our group Administrator

Tom Gardner
 

On 11/09/21 18:09, saipan59 (Pete) wrote:
My 'vote' is also to turn on editing, and to suggest (for those that care) to use digest e-mails so that you don't get many individuals per day.
I don't expect that post-editing will happen 'frequently' anyway. And it feels better than creating *another* post to correct a mistake.
Look at web forums where editing can happen, e.g. the (very good) EEVBlog forum.

A very significant number of posts are edited, some of them several times.

The best thing is to re-read what you wrote before sending it. That reduces the number of times you unnecessarily waste /other/ people's time.

Besides, editing a post is sometimes misused to re-write history. "Students of Soviet history know how difficult it is to foretell the past".

Use emails to their full advantage. Use web forums to their full advantage. Don't accept a race to the bottom of the lowest common denominator of features.


Re: Suggestion for our group Administrator

Tommy
 

My vote: Do not enable editing, do not fix what is working reasonably well...


Re: Suggestion for our group Administrator

 

On Sat, Sep 11, 2021 at 7:16 PM Dave Voorhis <voorhis@...> wrote:

On 11 Sep 2021, at 18:09, saipan59 (Pete) <saipan1959@...> wrote:

My 'vote' is also to turn on editing, and to suggest (for those that care) to use digest e-mails so that you don't get many individuals per day.
I don't expect that post-editing will happen 'frequently' anyway. And it feels better than creating *another* post to correct a mistake.
Unless it’s a different Groups.io <http://groups.io/> forum I’m thinking of, wasn’t editing turned on in the early days of using Groups.io <http://groups.io/>, and didn’t that result in a barrage of emails from a few folks who quite reasonably made frequent edits to their forum posts, but weren't aware it was pumping out emails?
Yes, that's precisely why it's off.

Though maybe that facility has been improved since to only send one email per post per day, or some such.
It's the same as it's been. No changes.

On Sat, Sep 11, 2021 at 6:59 PM Keith <coolblueglow@...> wrote:

The data and ideas we post here are quite long-lived. I routinely search out old threads, hoping for correct and trustworthy answers. I then quite often trust, and apply the claims and advice present therein. But, in doing those searches, I do sometimes find howlers in there, my own and others! In the current model, the person who is quite wrong (like me, sometimes) but also quite convinced when they hit "post", simply has no way to make good on his or her mistaken idea. That is, except to post another tiresome explanation of the thing, admitting, warning others "not to read post #xyz123" etc. It is not efficient.
Editing is enabled on HPAK. No one *ever* does anything like what you
describe. The *only* edit notification emails happen when someone
clueless about the notification emails corrects single-letter typos
one at a time with 5 subsequent notification emails. Infinitely honing
forum posts in here to perfection is a nice pipe dream, but in
practice, no one does this. I can't say it's due to one thing
specifically. I think it's because our memory and recall are finite,
so once you figure out something new, you don't think about the fact
that you made a post about this two years ago, one of 10 000 posts you
made. I think you're looking for a wiki, not for a mailing list.

NB the Tek/HPAK Discord allows editing messages. It can be joined
here: https://discord.gg/g5C2jaAX

I'm not against editing messages, I'm just against editing messages
here, because it's absolutely terrible on what essentially is a mail
reflector with file hosting.

And, when those old posts cannot be corrected, except by re-posting and/or deleting, it just doesn't seem to be building a clear and trustworthy library for future readers. So, just my opinion here, but the long life of mistaken or less-than-best-thinking postings tends to spread mistaken ideas... and it is hard figure out which ones are right and which are wrong. That is, unless one wishes to follow the entire (sometimes extensive) thread and "find" that the misstatement was corrected twenty five messages later. This can be very frustrating and time-consuming.
That's what most people will do anyways. So you're not spared the
search. When reading a post, you won't know if the poster is of the
editing type, or of the follow-up type, and I bet that most will be of
the follow-up type. In fact, most will be of the no edit, no follow-up
type. So you're saving nothing, and you're really killing the email
interface with absolute garbage.


Re: PG506 in need of parts T130

Zentronics42@...
 

Hmm ok something is odd. Transformers should show almost a dead short at DC when you are looking at the windings end to end. However on the different set of windings there should be no connection at DC. Which is what the meter is using. Next thing to look for is a pin out of the transformer or the schematic of the power supply that should tell you what pins are connected and what pins are not connected. In circuit measurements can be influenced by the active components in the circuit. A meter can have enough voltage to forward a transistor or diode and part way turn them on. This will throw off measurements and cause readings to be at best weird. At worst fry a sensitive component. For instance a DMM can kill a tunnel diode. Also check the board. I had an issue in the power supply of one of my TM5006 units. The through hole on the circuit board went bad. Had voltage on the top of the board but not the bottom. Very odd fault and definitely not common. Probing around the transformer with the unit powered up should be done with care there is high frequency high voltage AC at that location. And the PG506 specifically has some elevated voltages in it.

Zen

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Timothy via groups.io
Sent: Saturday, September 11, 2021 1:41 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] PG506 in need of parts T130

I measured 5M ohm resistance between the windings and I understand you cant trust that with the part in circuit so I did unsolder the leads however I left it in place when I retested. After reading your reply I decided to double check my work and I should have pulled the part free from the board. I have seen people test parts in place after desoldering on youtube, but my hand must be too heavy and I complete the circuit. I pulled it free and its a dead short now, I think it is ok. However on the board there is now 1M ohm resistance between say the pin locations 1 and 10.


Re: PG506 in need of parts T130

Timothy
 

I measured 5M ohm resistance between the windings and I understand you cant trust that with the part in circuit so I did unsolder the leads however I left it in place when I retested. After reading your reply I decided to double check my work and I should have pulled the part free from the board. I have seen people test parts in place after desoldering on youtube, but my hand must be too heavy and I complete the circuit. I pulled it free and its a dead short now, I think it is ok. However on the board there is now 1M ohm resistance between say the pin locations 1 and 10.

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