Re: 577D1 itching issue - Haven't touched since, currently in storage

Bruce Griffiths

Matched loads aren't usually used at mains frequencies.

Bruce

On 02 January 2020 at 18:34 KB6NAX <gumbear@...> wrote:

Hi Dennis,

I made my donation so you have to read this (just kidding :-).

This raises another observation about the brush. It must be narrow so it
doesn't span two turns at a time else it will be shorting out one turn to
the next turn and that will short them together. They would heat up as
would the brush which is causing the short. In my example this would cause
a short across two turns that differ by exactly 1VAC. But each winding is
capable of providing from 1 to 10 Amps under normal load situations for
the size Variacs we are likely to encounter. With a brush causing a
shorted winding it isn't hard to see that more than10 Amps could flow. To
minimize the likelihood of a short the brush comes to a chisel point. The
point is slightly narrower than one turn of wire and it is as wide as the
removed enamel area of each turn. <
I studied this on variacs and came to a different conclusion. The maximum
power transfer theorem says that the source and load impedances have to be
equal for maximum power to be transferred. A shorted turn is far from a
matching impedance for the "primary" side, the rest of the variac winding.
In order for a large amount of power to be coupled into a shorted turn the
resistance of the wire would have to be much lower than what copper provides
in order for the reflected impedance to be equal to the source impedance.
Think Weller soldering gun. In addition, the brush, overlapping the pair of
contact points is a resistor. Intentionally, so it throws the impedance
mismatch further off. The result is a very lossy mismatched transformer
action, little power is transferred. Also, the brush is large enough to
dissipate its heat, most of which is caused by the output load current. The
losses are so small you don't realize they are there.

Arden

Re: 577D1 itching issue - Haven't touched since, currently in storage

KB6NAX

Hi Dennis,

I made my donation so you have to read this (just kidding :-).

This raises another observation about the brush. It must be narrow so it doesn't span two turns at a time else it will be shorting out one turn to the next turn and that will short them together. They would heat up as would the brush which is causing the short. In my example this would cause a short across two turns that differ by exactly 1VAC. But each winding is capable of providing from 1 to 10 Amps under normal load situations for the size Variacs we are likely to encounter. With a brush causing a shorted winding it isn't hard to see that more than10 Amps could flow. To minimize the likelihood of a short the brush comes to a chisel point. The point is slightly narrower than one turn of wire and it is as wide as the removed enamel area of each turn. <
I studied this on variacs and came to a different conclusion. The maximum power transfer theorem says that the source and load impedances have to be equal for maximum power to be transferred. A shorted turn is far from a matching impedance for the "primary" side, the rest of the variac winding. In order for a large amount of power to be coupled into a shorted turn the resistance of the wire would have to be much lower than what copper provides in order for the reflected impedance to be equal to the source impedance. Think Weller soldering gun. In addition, the brush, overlapping the pair of contact points is a resistor. Intentionally, so it throws the impedance mismatch further off. The result is a very lossy mismatched transformer action, little power is transferred. Also, the brush is large enough to dissipate its heat, most of which is caused by the output load current. The losses are so small you don't realize they are there.

Arden

Re: 577D1 itching issue - Haven't touched since, currently in storage

Hi DW,
I just remembered another detail that may influence the results of what appears when the Variac is turned to "zero". Variac's are a very interesting design for a transformer for two reasons: The enamel insulation is deliberately removed from the same spot on each turn of its primary. This is done intentionally so the rotating wiper brush can make contact with that turn. Depending on where on the winding the enamel is removed the voltage may not be 0 exactly.

For my example assume there are 120 turns on the primary and the input voltage is 120VAC. Where the low side of the mains (0VAC) is connected to the very beginning of the first turn, the voltage will be 0.0VAC. At the end of the last turn where the high side of the mains is connected the voltage will be 120V. But I checked one Variac I have that I can see into and the enamel insulation is removed from each winding at about the half way point in the turn. The brush would already read 0.5VAC at this point. I don't think there is a point where the voltage is exactly 0.0VAC.

This raises another observation about the brush. It must be narrow so it doesn't span two turns at a time else it will be shorting out one turn to the next turn and that will short them together. They would heat up as would the brush which is causing the short. In my example this would cause a short across two turns that differ by exactly 1VAC. But each winding is capable of providing from 1 to 10 Amps under normal load situations for the size Variacs we are likely to encounter. With a brush causing a shorted winding it isn't hard to see that more than10 Amps could flow. To minimize the likelihood of a short the brush comes to a chisel point. The point is slightly narrower than one turn of wire and it is as wide as the removed enamel area of each turn.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of DW
Sent: Wednesday, January 01, 2020 6:36 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 577D1 itching issue - Haven't touched since, currently in storage

Dennis, good response

Where I live, the mains are 120 and 240 volts. I been shocked by 120 before, it hurts. I also been shocked once by 240 which I found REALLY hurts! I have gained respect for mains voltages though it might not seem like that appears to be the case here. The idea I proposed about checking the variac with jumper leads while energized is obviously asking for trouble, I am actually glad I asked this and got the answer I need.

Thanks for your feedback with 577 collector performance data for comparison. I can see you used the magnification on the horizontal scale but regardless from my observation excellent results from your 577. My results according to my notes indicate at 25V 50mV/division a line appears 7 divisions long, with your response we see a nice comparison happening here.

I should probably explain why I am really posting about this again. My idea was to take everything from the previous post and consolidate the information so it can be easily viewed and someone might have a interesting idea or solution as they can easily and quickly look it over. I got good useful responses as a result but I fear it is at the expense of repeating myself and not letting it be.

Dennis, you make a good point of using the instrument instead of nitpicking of the details. Changing my state of mind I realize the instrument is mostly functional and I should be happy about that. I seem to have put myself in a corner worrying about details instead of enjoying the possibilities and the usefulness I could be enjoying. I will take up on that offer. If I come across something I will be sure to report back here.

--
Dennis Tillman W7PF
TekScopes Moderator

Re: 577D1 itching issue - Haven't touched since, currently in storage

DW

Dennis, good response

Where I live, the mains are 120 and 240 volts. I been shocked by 120 before, it hurts. I also been shocked once by 240 which I found REALLY hurts! I have gained respect for mains voltages though it might not seem like that appears to be the case here. The idea I proposed about checking the variac with jumper leads while energized is obviously asking for trouble, I am actually glad I asked this and got the answer I need.

Thanks for your feedback with 577 collector performance data for comparison. I can see you used the magnification on the horizontal scale but regardless from my observation excellent results from your 577. My results according to my notes indicate at 25V 50mV/division a line appears 7 divisions long, with your response we see a nice comparison happening here.

I should probably explain why I am really posting about this again. My idea was to take everything from the previous post and consolidate the information so it can be easily viewed and someone might have a interesting idea or solution as they can easily and quickly look it over. I got good useful responses as a result but I fear it is at the expense of repeating myself and not letting it be.

Dennis, you make a good point of using the instrument instead of nitpicking of the details. Changing my state of mind I realize the instrument is mostly functional and I should be happy about that. I seem to have put myself in a corner worrying about details instead of enjoying the possibilities and the usefulness I could be enjoying. I will take up on that offer. If I come across something I will be sure to report back here.

Re: Push-push switch repair (need some theory of operation)

Mlynch001

Ke-Fong Lin

Those BJT/FET switches are the same type in almost all TEKTRONIX equipment of the era. They are very prone to get dirty or gum up inside. What I do with mine is give it a shot of contact cleaner, work the switch several times let it dry and then follow with a shot of DEOXIT Spray, and finally work it several times. After about 10 -15 cycles they will free up and begin to latch. You can repeat as needed until the switch works. A very common problem as I just fixed a 465 that had a beam finder that was stuck half way between the "normal" and "find" positions. The 576 curve tracer has many of these switches, the problem with them is they are very difficult to access on the 576. But this technique works on 99% of this type of switch. I am not familiar with the +1000 switch, but is may respond to the same treatment.

Good Luck!

--
Michael Lynch
Dardanelle, AR

Re: Push-push switch repair (need some theory of operation)

Kurt Rosenfeld

Re: TDS694C nvram DS1486

George Langston

Happy New Year All!
I got my console port running and aside from the 50 ohm overload issue, things seems to point to nvram problems (?) Here are the errors from the debug log:

"Executing Diagnostics

-> ERRORID: 358 nv storage too small more bytes requested than available
[...]
nvLibrariansDiag ............... ***FAIL***
..error details:
ERRORID: 163 diagnostic test failure nvLibrariansDiag
Libs with crcc failures:
ExtConst
[...]
twoGHz50OhmOvldConf ............ ***FAIL***
..error details:
ERRORID: 163 diagnostic test failure twoGHz50OhmOvldConf
50 ohm Overload stuck; status = 0x0
[...]
optDiagFloppyControllerIO ......0x5fffe80 (tRootTask): libError 358, lib EXTCAL, id=358, msg=more bytes requested than available
[...]
0x5fffe80 (tRootTask): libError 358, lib EXTCAL, id=358, msg=more bytes requested than available
[...]

Smalltalk/V Sun Version 1.12

Copyright (C) 1990 Object Technology International Inc.

ERRORID: 163 diagnostic test failure extended cal librarian reset
100ps > TI value(0) > 3100ps

ERROR ... step of 33792 is smaller than 50 dls

ERROR (0x2c): digPhaseCal failed

ERRORID: 110 Calibration failed measure skew got 0 avgs, expect 16
"

Although my DS1486 is still keeping time might it's 2nd battery be low and causing nvram failures?
It looks like the floppy controller is trying to write to nvram and failing?

Re: MEMBERS PLEASE READ: Our annual Group.io payment is due in 2 weeks.

J. L. Trantham

Dennis,

Just catching up on this. Hope I'm not too late to contribute. Let me know if you do not receive it.

Thanks to you and all the Group Members and their great contributions.

Happy New Year to All!

Joe

Push-push switch repair (need some theory of operation)

Ke-Fong Lin

Hi everyone,

I'm fixing a 5CT1N curve tracer plug-in.
One of the push-push switch (BJT/FET selector) is malfunctioning. It doesn't latch to FET.
The x1000 pull switch doesn't work either.
The BJT/FET switch is a 6PDT (6 poles dual throw), part number is 260-1536-00.

Do you guys have any pointer to a website or better a youtube video explaining the mechanical theory of operation?
I don't think it's a big deal, I'll just have to disassemble the switch and put it back.
But I would prefer some explanation before.

Thank you.

Best regards,

Re: My email address was changed by Groups.io my request for contributions

Sergey Kubushyn

On Wed, 1 Jan 2020, Dennis Tillman W7PF wrote:

I hope you've got my \$20 too...

Hi Bob,
Yes, Transaction ID: 976182746J963223U, December 31, 2019
Thanks, Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Robert Simpson via Groups.Io
Sent: Wednesday, January 01, 2020 12:53 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] My email address was changed by Groups.io my request for contributions

so Dennis, did you get mine, I used the address after changing the spaces and changed the at to @.
Bob
---
******************************************************************
* KSI@home KOI8 Net < > The impossible we do immediately. *
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************

Re: My email address was changed by Groups.io my request for contributions

Hi Bob,
Yes, Transaction ID: 976182746J963223U, December 31, 2019
Thanks, Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Robert Simpson via Groups.Io
Sent: Wednesday, January 01, 2020 12:53 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] My email address was changed by Groups.io my request for contributions

so Dennis, did you get mine, I used the address after changing the spaces and changed the at to @.
Bob

--
Dennis Tillman W7PF
TekScopes Moderator

Re: 577D1 itching issue - Haven't touched since, currently in storage

Hi DW,
I get very nervous whenever I start wondering if I can connect a ground to something that I know is directly connected to the AC line. And I am in one of those 115V countries where I was able to get used to being shocked. I'm so scared every time I have to work on 220V wiring that I will do anything to avoid it. I don't know what your mains voltage is but you are risking a very valuable instrument in search of the answer to something that is only a problem to you.

For instance I have used at least five 577s and the flicker and non-zero offset has never bothered me. I did notice it from time to time on various 577s but since it never affected the operation of the 577 it was simply not important. None of this behavior is unusual for a 577. Because you have mentioned this before, and because I have used so many 577s I thought I could convince you from my personal experience that this is not a problem.

With all the 577s I have owned or used I have seen the flicker many times. Because you mentioned it I finally took a close look at it on the 577 I currently have on my bench. I have been using this particular 577D1 (Storage) for two or three years by now so I know it well. The flicker is there on my current 577 as it has been on all the 577s I think I have used. This is no surprise to me. But this time I measured it so you can compare your results to mine.

I thought setting the horizontal deflection to 0.05V/Div. would give me the best chance to see any flicker or non-zero voltages. I then turned the collector voltage to the 1600V range. With the Variac turned down to zero the trace goes 9 divisions across the screen and it flickers faintly in many spots along the trace. That would be the equivalent of a zero voltage of 0.45V.
With each collector voltage setting this is what I get:
1600V: A line 9 divisions across the screen that flickers faintly in many places along the trace.
400V: A line 1 division long at the 4th graticule. Where that ends there is a flickering faint line 3/4 division long.
100V: A line 1 division long at the 4th graticule. Where that ends there is a flickering faint line 1/2 division long.
25V: A spot at the 4th division, a flickering faint line beginning at the spot and extending half a division to the right.
6V: A spot at the 4th division, a flickering faint line beginning at the spot and extending half a division to the right.

The fact that on four collector voltage settings the line or spot is at the 4th graticule tells me I need to tweak an offset or balance trim pot somewhere inside the 577 to move that spot over to the origin.

I recommend that you explore the many different things you can measure with this fascinating tool instead of worrying about the flickering line at 0V. It took me years to do that. Each time I learned how to measure another transistor or semiconductor parameter with my 577 I became a better circuit designer. The versatility of this instrument is so great that I am probably only familiar a third of half of the things it can do. I'm looking forward to all the things I can still be taught by the 577.

You are very lucky indeed to own such a valuable instrument. I can't wait to find out what you design with it.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of KB6NAX
Sent: Wednesday, January 01, 2020 11:52 AM
Subject: Re: [TekScopes] 577D1 itching issue - Haven't touched since, currently in storage

Happy New Year, DW,

Could jumping a clip lead from Neutral to the wiper with the brush
insulated from the windings be useful to diagnose why the ollector
will not go to 0V or near it? My theory is if this causes the
collector to go to 0V or near it then perhaps I have enough resistance
occurring from the neutral terminal to the first windings of the
variac causing the collector issue I am experiencing, would you agree?
That's a bit risky if you forgetfully turn the variac CW. Better to measure resistance between the first turn of the winding and the neutral terminal.
Deteriorated connections are accompanied by increase in constriction resistance. Like to know what you find.

Arden

--
Dennis Tillman W7PF
TekScopes Moderator

Re: My email address was changed by Groups.io my request for contributions

Robert Simpson

so Dennis, did you get mine, I used the address after changing the spaces and changed the at to @.
Bob

Re: 577D1 itching issue - Haven't touched since, currently in storage

DW

I agree with your response Arden, a resistance measurement is less risky and preferable, good call!

When I can pull the 577 out of storage I will perform these checks

I will check the resistance from the neutral to the first winding, then I will check the resistance from the hot to the last winding and see what the differences are. Then repeat the tests with the probe on the wiper instead of the winding.

Re: 577D1 itching issue - Haven't touched since, currently in storage

KB6NAX

Happy New Year, DW,

Could jumping a clip lead from Neutral to the wiper with the brush insulated from the windings be useful to diagnose why the ollector will not go to 0V or near it? My theory is if this causes the collector to go to 0V or near it then perhaps I have enough resistance occurring from the neutral terminal to the first windings of the variac causing the collector issue I am experiencing, would you agree?
That's a bit risky if you forgetfully turn the variac CW. Better to measure resistance between the first turn of the winding and the neutral terminal. Deteriorated connections are accompanied by increase in constriction resistance. Like to know what you find.

Arden

We have multiple Owners. WAS: Do we need multiple owners?

Hi David,
This reminds me of something Mark Twain once said: "Reports of my death have
been greatly exaggerated" :)

Michael Dunn, who created TekScopes 20 years ago, is still very much
involved in TekScopes. He acts as my back stop any time I am on the road or
too busy to respond quickly. We are in regular communication. Any messages
sent to the Moderator go to both of us. We both have full moderator
authority to do whatever is needed. It was Michael who saw the need a few
years ago to insure a 2nd person could take over in the event something
happened to him.

For the past 2 or 3 years we have shared the load on the important items and
I have looked after the day to day stuff. For instance Michael, more than I,
was instrumental in choosing Groups.io more than 2 years ago. We both
handled the logistics of the move. I am the main contact point between
TekScopes and Groups.io.

Both of us will be responsible for the contributions jointly so they will be
safe if something happens to either one of us. We are also in different
geological areas and in different countries (I'm on the northwest coast of
the United States and Michael is much further east in Ontario, Canada).

Dennis Tillman W7PF,

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of David C.
Partridge
Sent: Wednesday, January 01, 2020 8:44 AM
Subject: [TekScopes] Do we need multiple owners?

more of our current moderators or members as co-owners?

That way we avoid the problem of "silent key" owner resulting in an orphaned
group.

David

--
Dennis Tillman W7PF
TekScopes Moderator

Re: My email address was changed by Groups.io my request for contributions

Marvin,
My apologies but groups.io is partially to blame. I had no idea that groups.io was going to change my email address. Since this happened I found out they do this to protect us from SPAMBots who could easily harvest all our email addresses.
The only way that they would not have interfered with is if I spelled out my address word for word like this
Dennis at ridesoft dot com.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Marvin Moss
Sent: Wednesday, January 01, 2020 7:44 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] My email address was changed by Groups.io my request for contributions

I sent you money via Paypal but it went to wrong place. So I have to get my money back before I can forward to you. A real mess-up for me. Wish we had better info to get money to you. It is a shame that it is that hard to send you money :-)

--
Dennis Tillman W7PF
TekScopes Moderator

Re: My email address was changed by Groups.io my request for contributions

HI Albert,
Groups.io changed my real email address without my knowing it so non-members could not search our posts and harvest our email addresses. I didn't know this is what groups.io did. The only wat I can tell you what the correct email address is if I spell it out like this:
dennis at ridesoft dot com.
You can figure out from this what my email address really is.
Dennis

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Albert Otten
Sent: Wednesday, January 01, 2020 3:29 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] My email address was changed by Groups.io my request for contributions

There is one more issue Dennis. I use the website. There @Dennis... is a link which points to https://groups.io/profile/Dennis_Tillman_W7PF . This is not your profile at Tekscopes since /g/Tekscopes is missing from the path. I can read your Tekscopes profile, but I get a "404 not found" error on that link.

Albert

--
Dennis Tillman W7PF
TekScopes Moderator

Re: TDS694C nvram and tektool

Ragnar S

Hi Gudjon,

(I tried to reply using the Web interface some hours ago, but for some reason that didn’t work. If it later does, I am sorry for the double replies.)

Do I need to flip the nvram protection switch to read the content?
At least I have to boot them with the nvram protection switch flipped on 694C:s with FW v6.3e and v6.4e.
Note that they then get address 29.
Also note that the scope appears more or less dead in this mode, but it responds to GPIB.
I have found versions of tektool that have the address 1 coded in, so maybe on some models or firmware versions they work with the scope booted normally.

I actually just recently modified tekfwtool (and tektool and getcaldata) to work on Linux (and ARM), and published it this morning.
It should be quite possible to make it work on MacOS too, perhaps using macosx_gpib_lib, but I haven’t tried.

You can find it here:
https://github.com/ragges/tektools

Let me know if you need any assistance, or debug output, or something. I have the setup rigged up in front of me, and can test things if you want to.

In my testing, it was quite sensitive to extra commands. For example, a “*IDN?” in NVRAM unprotected mode screwed up the communication.

Best regards,

Ragnar

Re: TDS694C nvram and tektool

Ragnar S

Hi Gudjon,

This is really funny - I have too played around with tektool (and tekfwtool, getcaldata and tdsNvramFloppyTool) on Linux just the last days, working on TDS 694C:s.

So reading the NVRAM and firmware actually works for you when the scope is booted normally (without having flipped the NVRAM protection rocker switch), on GPIB address 1?
Does writing work too?

I have so far only gotten it to work in unprotected mode (which also sets the GPIB address to 29).

Also, if I leave the "*IDN?" request in the tektool program, it will not work in unprotected mode, so I have commented that out.
I have firmware version v6.3e and v6.4e.

Here is a link to my versions of the programs:
https://github.com/ragges/tektools

Best regards,
Ragnar