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Re: Scope grounding and generators

Harrison
 

I've been following this thread from the beginning. Unfortunately I am a bit confused. I am familiar with transfer switches and not back feeding into a panel with out pulling mains, etc. But is the issue the ability/desire to monitor the sine wave with a scope or is the prevailing wisdom that using a portable or stand by generator is detrimental to modern electronic devices, be they a TV, Refer, or whatever. Sorry if the answer is there and just going over my head. Thanks and stay safe. Harrison N1FAM


Re: Tektronix 834 communications tester... what for?

 

One of my 834s has a T-Cabe in the back, with a label "206771-1 8233" on the plugs. And it has the "834R05 extended instruction set ROM pack".

I have one or two things with serial connection still working... but I think I won't make much use of this tool either.
I will give them for free to anybode who is willing to pick them up in Stuttgart...

cheers
Martin


Re: Scope grounding and generators

Jean-Paul
 

Robert if you live on West Coast USA expect longer and more frequent blackouts in future years.

The UPS, and other power conditioners may not clean up a high thd generation effectively

Easier to buy a low THD generator rather than clean up a poor quality waveform.

Electronics with SMPS will not care about the line waveform.

Chuck Harris note re use of a filament transformer to sample and isolate the 120V is the simplest way to see the waveform safely

Just the ramblings of an old retired EE

Jon


Re: Scope grounding and generators

Robert Simpson
 

Yes, it is for rare temporary use. We have had several 12 hour or so blackouts since I have lived here. The reason for the scope test, I want to understand what the generator is producing. As for electronics ( a secondary use) I was looking into power conditioners. I saw a 600 watt Trip-Lite that might work. Again, rare occasional use.
Bob


Re: Scope grounding and generators

Roy Thistle
 

Yes...I see the OP is using a Briggs & Stratton Powermate 5000, and running a fridge, fans, lights (incandescent?)
Anyway... B&S make the engine...maybe the generator is a Generac?
The AVR seems like a standard one... so nothing great. (Unless someone knows better?)
I'd say okay for dumb appliances... maybe short term use, for fancier digital ones... but, long term may fry expensive digital controls.
Put a UPS on one end of it, and use that to power more power quality sensitive devices.


Re: Scope grounding and generators

Roy Thistle
 

On Sun, Oct 25, 2020 at 07:42 AM, - wrote:


Since then I've picked up a largish 440 or 220
to 220 or 110 volt transformer
They will act to diminish the harmonics; but, maybe not in the way you might like.
Every day... somewhere... in some building... distorted sine wave power kills and expensive transformer. Usually, its heat damage... but, sometimes there are fires too.


Re: Scope grounding and generators

Roy Thistle
 

On Sun, Oct 25, 2020 at 11:07 AM, @0culus wrote:


The point I was making was that the OP really should get the right tool
What's the OP trying to do?
If he's only got a cheap/er generator... Iike a harber fright... there is going to be high THD, and poor regulation under heavy load, and surges. So the right tool would be an inverter generator, or to stick to running incandescents, from a cheap one.


Re: Scope grounding and generators

Roy Thistle
 

On Sat, Oct 24, 2020 at 07:33 PM, Mike Dinolfo wrote:


don't under any circumstances interconnect the neutral and/or "hot" wires
between the house and the generator.
That's called a backfeed... unless you have a transfer switch, or have cut the power at the distribution panel... if not...and it's a blackout... and if there is a lineman working on the wrong end of a line transformer... there might be lethal high voltage present, due to your backfeed... the linemen are not expecting that (it's a blackout). Anyway, most power companies will seriously terminate your account, if they find you have potential for a backfeed.


Re: Scope grounding and generators

Roy Thistle
 

On Sat, Oct 24, 2020 at 06:39 PM, Robert Simpson wrote:


I want to see the shape of the power, the frequency and peak voltage.
I dunno. What you want to know (or what I would want to know)... is what the THD is. That might be tough to interpret with a 456M.
Anyway the frequency and the peak voltage change in the power provided by all power companies.
What's the generator you plan to use?


Re: Scope grounding and generators

Roy Thistle
 

On Sat, Oct 24, 2020 at 11:49 PM, Jean-Paul wrote:


Most generators have a distorted sine output, depends on rating, and design.
Yes... even the best motor generators with have an imperfect distribution of the magnetic fields, and pole alignment. The newer inverter generators (Generac et. al.) process the alternator output to get a sine wave with low THD (below what the power company can usually supply to the consumer.)... but they are more expensive than the older sets. The OP did not mention what manufacturer/type of generator he was using... or intended to use.
I have a couple of old...but good UPS units... they are good ones. If they don't trip out when connected to the generator I'm testing (under no load, under heavy load, and under a surge draw)... it's a good generator.
You can also use a distortion analyzer... if you really want to know the THD.


Re: Is it possible to start a TDS784D scope with a blank DS1486?

EricJ
 

NVRAM dump has been uploaded to TekScopes. Filename is dump.bin - can be
quickly found by typing that into the search box in the files section.
Scope options are 13, 1F, HD, 2M, 2F and firmware version is v6.3e - I
don't know if other firmwares might or might not be compatible with this
file, so use at your own risk if yours is different.

--Eric

On Sun, Oct 25, 2020, 5:03 PM Rogerio O <rodd414@gmail.com> wrote:

On Fri, Oct 23, 2020 at 07:22 AM, EricJ wrote:

"
I have the backups from my TDS754D (converted to TDS784D).
"
Would you please send me (or post) the file?
Thank you







File /DUMP.BIN uploaded #file-notice

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

The following files have been uploaded to the Files area of the TekScopes@groups.io group.

By: EricJ

Description:
NVRAM dump from Tek TDS754D (converted to TDS784D). Scope has options 13,1F, HD, 2M, 2F. (Firmware Version v6.3e).


Re: Scope grounding and generators

Greg Muir
 

As many have stated on this list a high amount of respect for dealing with AC mains work is paramount. I think Chuck Harris said I best. I double his comments regarding using a standard oscilloscope. If one must there are ways to do so as to protect the scope and the operator. But that also comes with the operator carefully defining and knowing how to go about it. The better approach is to utilize equipment that is designed for the purpose.

I have seen others who have used their best effort only to end up with damage to instruments because of either wrong connections (probe ground lead to the high side of the AC circuit as one example) or simply not taking into account the maximum input rating of the instrument. And this issue has also extended over to those who decided to try ignition system work on their vehicles with a scope unsuspectingly connecting the probe to the secondary side of the coil. Not as dangerous to the operator but can be sudden death to the scope.

I have not had any bad experiences but did do work for a client who had a captive engineer who didn’t watch what he was doing on a high-power klystron transmitter. Not being careful he managed to get across the 440 volt 3-phase circuit in the contactor cabinet. To put it simply, the replacement engineer commented that he had spent some time picking pieces of the previous engineer’s jeans out of the rack that was located behind him.

I had the luck of purchasing an old BWD Instruments 880 PowerScope at an auction many years ago that had been owned by the Bonneville Power Administration (https://www.radiomuseum.org/dsp_multipage_pdf.cfm?pdf=bwd_880_pamplet.pdf). It is a special purpose oscilloscope specifically designed for use on AC power circuits. To allow proper connection to the circuit under test each of the 4 inputs feed high impedance, high voltage differential amplifiers that allow both the high side and common (ground lead) for each channel to work at voltages above AC ground. The test leads are also designed to protect the operator from contacting any voltages under test. It is a relatively old instrument but the only unit that I use when working with any form of AC mains voltage (120-440V, single or 3-phase).

There is plenty of discussion about use of conventional oscilloscopes on AC circuits if one Googles something akin to “ac power line oscilloscope” or similar.

Greg


Re: First transistors at Tektronix?

Tom Lee
 

Early high-volume transistors were made by an alloy process which was easier to implement for PNPs than for NPNs, so you'll see PNPs dominate the early generations of transistor electronics. NPNs finally came into their own once  diffusion and the planar process were mastered.

--Cheers,
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 10/25/2020 14:45, Christian via groups.io wrote:
Some good suggestions to dig into, thanks! According to the wiki, the Type R, released in 1958, was the first plug-in with transistors. It had 10 - nine PNP and one NPN, which is interesting. In the service manual for it you can see Tek upgrading parts presumably as they became available, it's kind of amusing to read between the lines there. Now I want to find the Common Design Parts from 1960 or so and see how things went.




Re: Tek 455, bad crt ?

Mlynch001
 

I would second what Tom is saying. This is not typical of a “bad” CRT. I would look closely at U550, which is the HV multiplier, DC restorer and other circuitry, all built into one module. This is a known failure component. Good Luck!

--
Michael Lynch
Dardanelle, AR


Re: Scope grounding and generators

Carsten Bormann
 

On 2020-10-25, at 19:07, sdturne@q.com wrote:

Sure, if you have one of those it is probably suitable as long as it's in good condition.

The point I was making was that the OP really should get the right tool, be it a scopemeter, a 222/222PS, etc. A laboratory oscilloscope is not the right tool for scoping high energy circuits. Just because you can doesn't mean you should!
Surprised that nobody has given the obvious answer yet:

Get a high-voltage differential probe.

These can be expensive, but if it does not have a to be a Tek, the original question would scream for a Micsig DP10013 or DP20003 (depending on your budget and the voltages you need to look at).

These come from Shenzhen, but are not bottom-drawer garbage.

The main limitation of these is the noise: ≤ 40 mV rms in 50x, ≤ 230 mV rms in 500x (DP10013 specs).
So you can’t measure a dynamic microphone that is stuck at 300 V from earth ground :-)
(These are 100 MHz probes, so setting a bandwidth limit on the scope is going to help some.)

https://images-na.ssl-images-amazon.com/images/I/91h8jF1eMFL.pdf
https://www.amazon.com/dp/B074K4XPW3 (a bit expensive)

Grüße, Carsten


Re: First transistors at Tektronix?

Harvey White
 

IIRC, it was far easier to make germanium PNP transistors at the time rather than NPN.  (see CK721 and CK722).

Once the silicon transistor made its debut, NPNs became more prevalent.  May have been a process thing, but mixing tubes and transistors was easier with the same polarity power supply needed.

Harvey

On 10/25/2020 5:45 PM, Christian via groups.io wrote:
Some good suggestions to dig into, thanks! According to the wiki, the Type R, released in 1958, was the first plug-in with transistors. It had 10 - nine PNP and one NPN, which is interesting. In the service manual for it you can see Tek upgrading parts presumably as they became available, it's kind of amusing to read between the lines there. Now I want to find the Common Design Parts from 1960 or so and see how things went.





Re: Scope grounding and generators

Robert Simpson
 

First , thanks everyone for the feedback. I do want to be safe.
So, I haven't, don't and won't be floating the scope. Never have and don't see why I would. In the house if I need that type of measurement, I would use my 7A22.
For my generator test, the scope will be plugged in normally which means the scope frame will be at earth ground. By only temporarily connecting the generator frame to house earth ground, I don't see danger.
Again, my only use of the generator will be with extension cords. No plans on connecting the generator to house power.
The generator is a Briggs & Stratton Powermate 5000. Which is 5000 watts max continuous and 6250 surge. My use is planned at less than 4000 watts. (small freezer, refrigerator, one light and two small muffin fans in my heating wood stove.) as a side note for my motivation, you may have seen news articles about power shutdowns in California.
Bob


Re: Is it possible to start a TDS784D scope with a blank DS1486?

Rogerio O
 

On Fri, Oct 23, 2020 at 07:22 AM, EricJ wrote:

"
I have the backups from my TDS754D (converted to TDS784D).
"
Would you please send me (or post) the file?
Thank you


Re: First transistors at Tektronix?

Christian
 

Some good suggestions to dig into, thanks! According to the wiki, the Type R, released in 1958, was the first plug-in with transistors. It had 10 - nine PNP and one NPN, which is interesting. In the service manual for it you can see Tek upgrading parts presumably as they became available, it's kind of amusing to read between the lines there. Now I want to find the Common Design Parts from 1960 or so and see how things went.

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