Date   

Re: 549 transformer question

Chuck Harris <cfharris@...>
 

Hi Roger,

Some further research, prompted by another member, had me looking
at some papers on microstepping practices.

When you turn the shaft on most stepper motors, you will feel some
cogging, as the poles on the rotor line up with the poles on the
stator. These cogs line up with the full step positions of the
motor in normal full step operation.

Microstepping is when your motor driver oscillates between two
adjacent full step positions at a rate that is faster than the
motor can quickly move, which causes the rotor's mass to average
out its angular position to somewhere between the two adjacent
full step positions.

By changing the ratio of time in position 1 to time in position 2,
you can, in theory, select any angular position between those two
steps.

The problem is, the rotor is magnetically inclined to be in one
full step position or the other. This inclination causes the
angular positions of the microsteps to be rotated towards the
nearest full step position, leaving a dead zone half way between
the two adjacent full steps.

When your motor driver tries to step over top of this dead zone,
it jumps, creating irregular spacing, noise, vibration, and an
unwanted burst of acceleration.

In my case, I think this unwanted burst of acceleration is causing
the wire to crimp, as the spacing between the crimps doesn't seem
to get finer, when the driver is set to finer microsteps.

On the advice of another member, I have purchased some more
sophisticated motor drivers (TMC2219), that are supposed to
sense when the motor passes through these unstable microstepping
positions, and adjust the drive to eliminate the instability.

I will report back after I have figured out how to use them, and
have done a few trial winds...

-Chuck Harris

Roger M wrote:

Hi Chuck,
I've followed your discussions regarding the use of steppers for universal windings and have at least
a superficial understanding of the torque "jerk" that's troublesome. It has occurred to me that using a
(modulated) eddy current brake might be useful for smoothing the piecewise motion of the offending
stepper(s).

I also have a hunch that a little time hunting through the USPTO might turn up something.

Just my $0.02 of speculation ... I'm not a motion control guy, nor do I play one on TV..
-Roger






Re: TDS784C Signal Path Compensation Error

Siggi
 

On Sun, Feb 28, 2021 at 5:34 PM Steve Hendrix <SteveHx@hxengineering.com>
wrote:

Can anyone guide me as to what type relays,
and how many, I need to be looking at?

Here's an EEVBlog thread with the info:
https://www.eevblog.com/forum/testgear/tektronix-tds784d-successful-attenuator-repair/.
You may want to verify that this information is correct before you order
the relays.
IIRC there are three per attenuator.


Also, is
this a typical contact oxidation problem, that I might be able to
clear by repeatedly cycling those relays?
I took one of the bad relays from an attenuator and cycled it for thousands
of cycles out of the scope, but it didn't seem to help. I even drilled a
hole in the relay to inject some DeOxit then cycled it some more, which
still didn't seem to help.
Maybe if you could run a low current through the contacts as they're
cycled, that'd work, I don't know.


Re: Tek. 454 no triggering on A or B

John Crighton
 

Hello Mark,

Maybe I can help you a little bit.

I have a 454 oscilloscope.

You can use my oscilloscope as a working reference unit.

Set up your 454 displaying the 1 V PP calibration signal
into channel 1 via a coax cable and I will do the same.

Tell me which test points that you would like me to check
on my oscilloscope. I will report back to you what I see.

Regards,
John Crighton
Sydney

----- Original Message -----
From: "Mark Vincent" <orangeglowaudio@gmail.com>
To: <TekScopes@groups.io>
Sent: Monday, March 01, 2021 12:09 PM
Subject: [TekScopes] Tek. 454 no triggering on A or B


I have a 454 that will not trigger on A or B timebase. I bought knowing of
the triggering problem. I have scoped the signal and it will not go through
T670. Overhauling the unit did not help. The power supply voltages are
right on and the small 1mfd decoupling condensers are now film types. The
voltages at points BE, TP646 and CB are what the manual says by the
adjustments. The 8393s tested very good to new. I pulled out known working
tunnel diodes from another unit that works. That did not work. Swapping the
transistors from the known working one to this one did not work. Slight
adjustments of the pots to the three above points did not work. I tested
the diodes for leakage. They are fine. This looks like something common to
both like the power supply or trigger preamp. Those are working as they
should. The power supply outputs are within mV of the rated voltages. Using
the EXT. trigger input did not work. I checked the connectors on the boards
for corrosion and found none. I did tighten the female ends before
reseating them back on the pins. The unit is clean so dirt should not be a
problem. I know the A SWEEP TRIG'D light is good. I ohmed it out. I cleaned
the transistor sockets and moved the transistors up and down a few times to
make sure they were making contact. I resoldered connections in case one or
more were bad. Nothing I have done will make it trigger. I have worked on
this for a few days and cannot find the problem(s). Does anyone here know
of something I missed or what? I waited to ask here until I did what I
could. At this point, I need help. Thanks.

Mark




---
This email has been checked for viruses by AVG.
https://www.avg.com


Re: Looking for P6042 current probe transformer/hall-sensor replacement instructions

 

Actually it was the fixed resistor in the early ones and a potentiometer (wired as such) in the later ones...

David

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of cmjones01
Sent: 01 March 2021 12:00
To: TekScopes@groups.io
Subject: Re: [TekScopes] Looking for P6042 current probe transformer/hall-sensor replacement instructions

Is this anything like the procedure for the A6302 current probe? I've
got a couple of those here and seem to remember that there is an
adjustment for the offset voltage of the hall effect sensor. In early
models it was a variable resistor, but later it was changed to be a
fixed resistor whose value was specified for the individual hall
effect/current transformer assembly.So if that assembly was replaced,
the resistor would probably need changing too.

Some hall sensors needed a positive offset, some negative, so
sometimes the resistor was connected with one end to the positive
supply rail and sometimes to the negative. In either case, the
existing variable resistor would need to be turned all the way to one
end because it's no longer in use, and presumably the fixed resistor's
value is determined based on the variable resistor being set this way.

Chris

On Mon, Mar 1, 2021 at 11:19 AM benj3867 via groups.io
<benj3867=yahoo.com@groups.io> wrote:

@zenith5106 Thanks a lot!

Unfortunately, I do not see the information on how to calibrate R12 :-(
It looks like every manual promises the information will be in another manual. It is highly frustrating.

The P6042 service manual says "...adjustment procedure for R12 supplied with T1. Order Tektronix Part No. 050-0439-00"

The 050-0439-01 instructions you so kindly provided say: "If R11 was installed...adjust R12... to the CLOCKWISE extreme" and "If R13 was installed...adjust R12... to the COUNTERCLOCKWISE extreme", followed by "Refer to Manual Insert for recalibration"

And the manual insert (that you also kindly provided) totally ignores the issue :-( :-(

I can hardly believe that fully clockwise or fully counterclockwise is the final position of the adjustment. If that was the case why use a variable resistor?





Re: TDS784C Signal Path Compensation Error

Steve Hendrix
 

Please contact me offline at SteveHx@HxEngineering.com. Thank you in advance for any info you can provide.

Steve Hendrix

At 2021-03-01 07:32 AM, you wrote:
Steve,

Some time ago I got hold of a 520 digital scope. To my surprise it passed all self tests and looked clean and pristine inside, so I decided to sell it as working OK, with a lot of pics including of the selftest.

The buyer got the item, said its OK but didn't pass selftest and asked for a partial refund. I knew the unit was very well packed, so I became suspicious. I refused and the seller did not really argue about.

As I did not offer to take back in first place, and didn't use paypal or anything similar, Ebay could not interfere. They're trying to change things in Germany these days, so they will be always in the loop. If this suceeds I might not offer anything else than local pickup in future.

cheers
Martin




Re: TDS784C Signal Path Compensation Error

 

Steve,

Some time ago I got hold of a 520 digital scope. To my surprise it passed all self tests and looked clean and pristine inside, so I decided to sell it as working OK, with a lot of pics including of the selftest.

The buyer got the item, said its OK but didn't pass selftest and asked for a partial refund. I knew the unit was very well packed, so I became suspicious. I refused and the seller did not really argue about.

As I did not offer to take back in first place, and didn't use paypal or anything similar, Ebay could not interfere. They're trying to change things in Germany these days, so they will be always in the loop. If this suceeds I might not offer anything else than local pickup in future.

cheers
Martin


Re: TDS784C Signal Path Compensation Error

BRYAN SWAN
 

There is a unit on the usual site if you want to see the relays   item262497920634


Re: 3T77 tunnel diodes (again)

Albert Otten
 

Hi Charles,

I can easily imitate the "staircase" effect, see the picture Real-time.jpg which I added to your album https://groups.io/g/TekScopes/album?id=261250 .
Very likely your loop gain is far below unity, I estimate it will be about 0.1 . You can vary the loop gain with the front panel DOT RESPONSE knob, but probably not far enough to correct it all the way. It's probably due to a very low sampling efficiency of the S-1 with the new "diodes".
In real time mode the 3S2 samples at 10 us intervals. That's very fine compared with your sweep rate and the pulse top and bottom lengths. Hence you see the successive sampling results in sequence from left to right in the display. Because of the low dot response several samples are needed in order to "jump" from pulse top to pulse bottom and vice versa.

Albert

On Sun, Feb 28, 2021 at 04:34 AM, Charles wrote:

---
Put it all together and stuck it in the 3S2. Of course the triggering is still
screwed up in the 3T77A so I will eventually get back to work on that. In the
meantime, the manual does say that a non-sampling timebase can be used at .1
ms/div or slower, so I flipped the internal slide switch on the 3S2 and stuck
a 3B3 in the right-hand slot.

The S-1 head will indeed display the output of my 114 pulse gen (approx 17 ns
risetime) through a 20 db pad. I stuck a tee at the input and ran a cable to
my bench scope to verify the signal and it's correct. But the 561A/3S2/S-1 is
showing a VERY slow rise and fall time, with about 8 or 9 dots at the edges,
which is an indicated time of close to 100 us, not 17 ns! Something ain't
right but I am not sure what it is. The manual says I should be able to use
the 3S2 with full bandwidth of the sampling head, even though I can't display
anything really fast.


Re: Looking for P6042 current probe transformer/hall-sensor replacement instructions

cmjones01
 

Is this anything like the procedure for the A6302 current probe? I've
got a couple of those here and seem to remember that there is an
adjustment for the offset voltage of the hall effect sensor. In early
models it was a variable resistor, but later it was changed to be a
fixed resistor whose value was specified for the individual hall
effect/current transformer assembly.So if that assembly was replaced,
the resistor would probably need changing too.

Some hall sensors needed a positive offset, some negative, so
sometimes the resistor was connected with one end to the positive
supply rail and sometimes to the negative. In either case, the
existing variable resistor would need to be turned all the way to one
end because it's no longer in use, and presumably the fixed resistor's
value is determined based on the variable resistor being set this way.

Chris

On Mon, Mar 1, 2021 at 11:19 AM benj3867 via groups.io
<benj3867=yahoo.com@groups.io> wrote:

@zenith5106 Thanks a lot!

Unfortunately, I do not see the information on how to calibrate R12 :-(
It looks like every manual promises the information will be in another manual. It is highly frustrating.

The P6042 service manual says "...adjustment procedure for R12 supplied with T1. Order Tektronix Part No. 050-0439-00"

The 050-0439-01 instructions you so kindly provided say: "If R11 was installed...adjust R12... to the CLOCKWISE extreme" and "If R13 was installed...adjust R12... to the COUNTERCLOCKWISE extreme", followed by "Refer to Manual Insert for recalibration"

And the manual insert (that you also kindly provided) totally ignores the issue :-( :-(

I can hardly believe that fully clockwise or fully counterclockwise is the final position of the adjustment. If that was the case why use a variable resistor?





Photo 20210226_145404.jpg uploaded #photo-notice

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

The following photos have been uploaded to the Sampling with 7S14 album of the TekScopes@groups.io group.

By: Jouko Koskinen <jouko.koskinen@...>


Re: TDS784C Signal Path Compensation Error

Steve Hendrix
 

At 2021-03-01 12:16 AM, Martin via groups.io wrote:
be aware of buyers that take out or swap parts they need for a defect unit of their own.
A friend once showed me a Tek scope that came back with the processor chip removed from its socket...
Thank you for the heads-up. Is there any way to guard against that?

Steve Hendrix


Re: 2465A CT Lessons and Leroy's Breadcrumbs

VK1GVC
 

Brian, that latest link works for me ... but do you have the data in a more user-friendly form for possible use by others, eg plain text, Excel or CSV?  The PDF is entirely legible but would need a lot of massaging to get it into a form digestible by EPROM programmers and PDF is not an ideal starting point - whereas data text or Excel is much easier to massage.  While I hope I never need it, could you possibly post again in one or more of those other formats?

Secondly, in your first post in this thread you said in Lesson 3 " ....there is a simple way to back up the configuration data ... " but you didn't actually say which method you used.  Is this the method where you step thru' the calibration data on the 'scope screen and take pictures or a video, or is there a better/simpler way?  I have a plain vanilla 2465, no GPIB.

Thanks in anticipation (from Down Under)

Graham

On 1/03/2021 3:28 pm, Brian Nordlund wrote:
I'll try the file one more time: https://groups.io/g/TekScopes/files/Tek2465A_CT_RAM_022521.pdf

Hopefully this works...




Re: Looking for P6042 current probe transformer/hall-sensor replacement instructions

benj3867
 

@zenith5106 Thanks a lot!

Unfortunately, I do not see the information on how to calibrate R12 :-(
It looks like every manual promises the information will be in another manual. It is highly frustrating.

The P6042 service manual says "...adjustment procedure for R12 supplied with T1. Order Tektronix Part No. 050-0439-00"

The 050-0439-01 instructions you so kindly provided say: "If R11 was installed...adjust R12... to the CLOCKWISE extreme" and "If R13 was installed...adjust R12... to the COUNTERCLOCKWISE extreme", followed by "Refer to Manual Insert for recalibration"

And the manual insert (that you also kindly provided) totally ignores the issue :-( :-(

I can hardly believe that fully clockwise or fully counterclockwise is the final position of the adjustment. If that was the case why use a variable resistor?


Re: Sampling with 7S14

Roger Evans
 

The noise level displayed on sampling systems is sensitive to the setting of the loop gain for the DC balance amplifier (R231 and R232 on the 7S14). If you change the sampling diode bias voltage then you should set the loop gain accordingly, but this is all part of the calibration anyway and is well described in the manual. Basically you look at a fast edge at a relatively low sweep speed and adjust for no undershoot or overshoot, the noise increases rapidly once you get into the overshoot region.

Roger


Re: 3T77 tunnel diodes (again)

Albert Otten
 

Hi Charles,

This is probably because the purpose usually is to display/measure rise time. A real-time time base needs a pre-trigger for this. If you have a stable repetitive signal then a sampling time base unit can display details of the rising edge of the next pulse after the trigger event.
For varying or jittery pulse periods you would in both cases be forced to view the edge of the trigger event itself, again requiring a pre-trigger. In for instance the 3S76 this is accomplished by delaying the signal after the trigger pick-off circuit.

Albert

On Sun, Feb 28, 2021 at 06:04 AM, Charles wrote:


I also found (in the 3S2 manual) one line that says, "The TRIG OUT signal is
not useful for externally triggering a real-time time-base unit". Hmm. But it
does not explain *why*. It certainly seems to be doing exactly that... and the
3S2 does not appear to be capable of internal triggering a sampling time-base
like the 3T77A so the external line is definitely needed there.


Re: O.T. Digital scopes versus Tek analogue.

Sean Turner
 

Ed,

The newest high end ones (I'd say within the last 10 years) definitely are very nice. I'd love to have one for my lab, but I'm going to have to wait till used units start showing up. I can't justify the expense for my personal lab since it isn't a business venture.

I actually quite enjoy using the aforementioned megazoom scopes at work. The distinct lack of latency in control responses is a real treat for someone who likes their boat anchors. People like to hammer on them for a focus on waveform update rate and lower memory depth than the competition, but excellent triggers and excellent UX make up for that IMO.

The highest end modern machines (like the Teledyne LeCroy "Labmaster" series, and the Keysight UXR) are simply mind blowing in capability (mind blowing price too!) The highest end UXR is a 110 GHz _real time_ oscilloscope that has some serious mmwave ASIC black magic on the frontends (see: https://www.youtube.com/watch?v=DXYje2B04xE).

Ultimately, today's fundamentally not a whole lot different than the environment that the Tek we know and love was born into. Howard Vollum and company made an oscilloscope that blew the recurrent-sweep oscillographs of their competition (particularly Dumont) out of the water. Tek couldn't make them fast enough once word got out! Designers used them to build faster circuits and those demands beget a furious development cycle of faster and faster oscilloscopes to satisfy the requirements of faster and faster electronics. Nowadays we've got 5G and mmWave electronics dominating the space and now becoming commodity goods (phones+5G infrastructure, integrated radars in automotive, and probably more). What's next? Who knows? But hopefully some of today's gear will both tumble in price and still be serviceable for the hobbyist.

I won't hold my breath though. I'd bet my Tek scopes will still be working though. :o)

Sean

On Sun, Feb 28, 2021 at 08:38 PM, Ed Breya wrote:


One thing to remember, is that right from the beginning, the main goal of DSO
design has been to emulate an analog scope, and take advantage of digital
capability.

DSOs offer all kinds of nice capability not available in analog, yet lack that
feel and confidence in basic, simple (and most common) measurements. I'm not
familiar with the latest kinds of DSOs, which should be much better - my
newest ones are at least twenty years old. I'd think the latest ones are
closer to that ideal. The choice of one or the other depends as always, on
what you're doing with it, and what you have.

My rule of thumb is quite simple. If you CAN use analog, then do that. If you
MUST use digital, then do that. If you have only one or the other, then make
the best of it.

Ed


Re: 549 transformer question

Roger M
 

Hi Chuck,
I've followed your discussions regarding the use of steppers for universal windings and have at least
a superficial understanding of the torque "jerk" that's troublesome. It has occurred to me that using a
(modulated) eddy current brake might be useful for smoothing the piecewise motion of the offending
stepper(s).

I also have a hunch that a little time hunting through the USPTO might turn up something.

Just my $0.02 of speculation ... I'm not a motion control guy, nor do I play one on TV..
-Roger


Re: TDS784C Signal Path Compensation Error

 

Hi Steve,

be aware of buyers that take out or swap parts they need for a defect unit of their own.
A friend once showed me a Tek scope that came back with the processor chip removed from its socket...

cheers
Martin

On 28. Feb 2021, at 23:33, Steve Hendrix <SteveHx@HxEngineering.com <mailto:SteveHx@HxEngineering.com>> wrote:

Well, the buyer has turned uncooperative, said something about just needing a scope to make some measurements on a current project, and has formally requested a return thru eBay. So it looks like I'm out about $120 worth of shipping, and will have a go at fixing the relays when it gets back here. Can anyone guide me as to what type relays, and how many, I need to be looking at? I have the service manual, but they don't seem to drill down to that level of detail. Also, is this a typical contact oxidation problem, that I might be able to clear by repeatedly cycling those relays? What's the best way to tackle this one?

Steve Hendrix


Re: O.T. Digital scopes versus Tek analogue.

Ed Breya
 

One thing to remember, is that right from the beginning, the main goal of DSO design has been to emulate an analog scope, and take advantage of digital capability.

DSOs offer all kinds of nice capability not available in analog, yet lack that feel and confidence in basic, simple (and most common) measurements. I'm not familiar with the latest kinds of DSOs, which should be much better - my newest ones are at least twenty years old. I'd think the latest ones are closer to that ideal. The choice of one or the other depends as always, on what you're doing with it, and what you have.

My rule of thumb is quite simple. If you CAN use analog, then do that. If you MUST use digital, then do that. If you have only one or the other, then make the best of it.

Ed


Re: 2465A CT Lessons and Leroy's Breadcrumbs

Brian Nordlund
 

I'll try the file one more time: https://groups.io/g/TekScopes/files/Tek2465A_CT_RAM_022521.pdf

Hopefully this works...

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