Date   
Re: TEK: 475 Long stabilization times normal: or Failure dooming.

Roger Evans
 

The vertical amplifier and Z axis amplifier are DC coupled throughout and a slightly poor connection on any of the cable interconnects or variable controls can move the beam or change the intensity. The 475 vertical output stage passes current through the distributed vertical deflection plates so poor contacts onto the CRT pins can also move the beam vertically (this was the cause of vertical flicker on a 7934, took ages to find it).

Regards,

Roger

Re: Wanted: knurled nut for earth terminal on 7K scope

Vintage Test
 

Hi David,

One good turn deserves another - you sent me a Fischer connector for my newly acquired Solartron 7081 and I have a few 7904’s that won’t ever work again, so I can send you one. PM me and we’ll arrange it.

Cheers,
Mel
--
you can never have enough oscilloscopes, DMMs, valve testers or soldering irons . . .

Now I know I'm loosing my mind!!

David Slipper
 

I admit that I'm now in my 70s but this has me foxed ...

I have a sig gen churning out 50Hz at 5Vp-p - my trusty 744A agrees with
this and measures it correctly and the trace is a nice sinusoid
symmetrical about 0V.

But when I put a DVM between 0V and the centre of the BNC it reads back
1.81V AC

The scopes p-p measurement is OK.

I have tried 3 different DVMs but they are all the same.

What fundamental law of physics have I forgotten or has senility finally
caught up with me?? ;-)

Dave

Re: Now I know I'm loosing my mind!!

nonIonizing EMF
 

On Fri, Feb 8, 2019 at 08:17 AM, David Slipper wrote:


What fundamental law of physics have I forgotten
Impedance matching?

Re: Now I know I'm loosing my mind!!

george edmonds
 

Hi
Divide p to p by 2.828 to get the RMS that the DVM reads
Regards
George

On Friday, February 8, 2019 4:20 PM, nonIonizing EMF <nonionizingemf@...> wrote:


On Fri, Feb  8, 2019 at 08:17 AM, David Slipper wrote:


What fundamental law of physics have I forgotten
Impedance matching?

Re: Now I know I'm loosing my mind!!

ppppenguin
 

You are measuring peak to peak on your scope, RMS on your DVM.

For a sine wave, the peak voltage is RMS * SQRT(2). Peak to peak is double that.

1.81V RMS is about 5.12Vp-p. So your scope measurement is within about 2% of your DVM.

Re: Now I know I'm loosing my mind!!

Szabolcs Szigeti
 

That seems rigth. 5V pp is an amplitude of 2.5 V. In case of sine wave the
rms value of it is about 1.8.

So your measurement is good.

Szabolcs

2019. febr. 8., Pén 17:17 dátummal David Slipper <softfoot@...> ezt
írta:


I admit that I'm now in my 70s but this has me foxed ...

I have a sig gen churning out 50Hz at 5Vp-p - my trusty 744A agrees with
this and measures it correctly and the trace is a nice sinusoid
symmetrical about 0V.

But when I put a DVM between 0V and the centre of the BNC it reads back
1.81V AC

The scopes p-p measurement is OK.

I have tried 3 different DVMs but they are all the same.

What fundamental law of physics have I forgotten or has senility finally
caught up with me?? ;-)

Dave





Re: Now I know I'm loosing my mind!!

ArtekManuals
 

I believe The DVM is returning the RMS value
Vrms= Vp-p/(2*Sqrt(2))

= 5 /(2*1.141) = 5/2.82 = 1.77

Likely your P-P measurement is a bit off (5.12 Vp-p would give you 1.81 Vrms)

Dave
manuals@...

On 2/8/2019 11:17 AM, David Slipper wrote:
I admit that I'm now in my 70s but this has me foxed ...

I have a sig gen churning out 50Hz at 5Vp-p - my trusty 744A agrees with
this and measures it correctly and the trace is a nice sinusoid
symmetrical about 0V.

But when I put a DVM between 0V and the centre of the BNC it reads back
1.81V AC

The scopes p-p measurement is OK.

I have tried 3 different DVMs but they are all the same.

What fundamental law of physics have I forgotten or has senility finally
caught up with me?? ;-)

Dave



--
Dave
Manuals@...
www.ArtekManuals.com

Re: Now I know I'm loosing my mind!!

satbeginner
 

https://www.electronics-tutorials.ws/accircuits/rms-voltage.html

5V pp is a half sinus of 2.5V between 0V and 2.5Vp

It's a sine, so the RMS value is :

Vrms = Vp * 1/√2

So

Vrms = Vp * 0.7071

Vrms = 2.5V * 0.7071 = 1.77 Vrms

As soon as there is a slight distortion in the sine the RMS value will change a bit, hence the 1.81V.

Re: Now I know I'm loosing my mind!!

nonIonizing EMF
 

On Fri, Feb 8, 2019 at 08:17 AM, David Slipper wrote:


has senility finally
caught up with me?? ;-)
Glad I'm a reborn student in electronics and RF engineering doing self study pretty much and new to the electrical characteristics measurement world and haven't hands on enough yet.

I had to read into this.

Here is a good article that details why the RMS measurements on the DMM's now days:
https://www.fluke.com/en-us/learn/best-practices/measurement-basics/electricity/what-is-true-rms

The other AC measurements: https://www.electronics-tutorials.ws/accircuits/ac-waveform.html

Thanks for the details everyone who responded (and questioned)... I needed this re-enforced again since I haven't used the scopes in a while and really not much ever in my life.

400-series feet/cord-wrap

Colin Herbert
 

I have been looking at replacing some of the broken rear feet/cord-wraps on some of my 400-series scopes. I was intrigued to notice that there are differences between these scopes in that not all have this type of rear feet. Typically, the 465, 465B, 468 475 and 475A all use the cord-wrap feet. The 464 and 466 do not (I should probably add that I don't have all of these, but I do have the manuals). This doesn't have any bearing on whether the power-cord is captive or an IEC connector is present. In fact, the only example that I have with an IEC connector is my 468, which was manufactured in Heerenveen (my 7623A also has an IEC connector and was made in Guernsey, so probably this IEC connector is only present on Europe-made scopes - this would make sense to me). To add a little more confusion, there are manuals for the 464 and 466 which show removal of the case where these feet/cord-wraps are present in the "Maintenance" section. I can possibly understand that this was a simple error that came about by an incorrect assumption.

What puzzles me is:

1) why did these differences come about?
2) were some 464 and 466 scopes sold with the cord-wrap feet?

Does anyone have any ideas? I know it is idle curiosity on my part, but it does make me wonder....

Colin.

Re: Now I know I'm loosing my mind!!

Fred Schumacher
 

Hi David,
5Vpp gives you 2.5V top value with respect to 0. Your DVM is calibrated in Vrms. So you have your 2.5V to be devided by 1.41. This gives you almost 1.8V. So your DVM is indicating the correct value.
I am sure you did fotget this and had nothing to do with senility.
Fred

On 8 feb. 2019, at 17:17, David Slipper <softfoot@...> wrote:


I admit that I'm now in my 70s but this has me foxed ...

I have a sig gen churning out 50Hz at 5Vp-p - my trusty 744A agrees with
this and measures it correctly and the trace is a nice sinusoid
symmetrical about 0V.

But when I put a DVM between 0V and the centre of the BNC it reads back
1.81V AC

The scopes p-p measurement is OK.

I have tried 3 different DVMs but they are all the same.

What fundamental law of physics have I forgotten or has senility finally
caught up with me?? ;-)

Dave




Re: Now I know I'm loosing my mind!!

David Slipper
 

DUH - of course !

Thanks all

Dave

On 08/02/2019 16:54, Fred Schumacher via Groups.Io wrote:
Hi David,
5Vpp gives you 2.5V top value with respect to 0. Your DVM is calibrated in Vrms. So you have your 2.5V to be devided by 1.41. This gives you almost 1.8V. So your DVM is indicating the correct value.
I am sure you did fotget this and had nothing to do with senility.
Fred
On 8 feb. 2019, at 17:17, David Slipper <softfoot@...> wrote:


I admit that I'm now in my 70s but this has me foxed ...

I have a sig gen churning out 50Hz at 5Vp-p - my trusty 744A agrees with
this and measures it correctly and the trace is a nice sinusoid
symmetrical about 0V.

But when I put a DVM between 0V and the centre of the BNC it reads back
1.81V AC

The scopes p-p measurement is OK.

I have tried 3 different DVMs but they are all the same.

What fundamental law of physics have I forgotten or has senility finally
caught up with me?? ;-)

Dave






.

Re: Now I know I'm loosing my mind!! OT

Michael
 

David, I am 76, and sometimes when I am troubleshooting a stereo (my side business) I make simple mistakes that I would never have made when I was 25. Sorry to say it is aging. I can still write code (C++) but now I can only hold the value of 3 variables in my mind. I used to handle a dozen. It makes coding slower. I keep plugging along. You need to accept the limitations that aging brings and still make a happy life for yourself. I know, off topic. I am just saying that trouble shooting electronics can still be done in old age albeit more slowly. I still love what I do. My wife still loves me. As good as it gets.

Re: Now I know I'm loosing my mind!!

ArtekManuals
 

Dave

My mother was an Alzheimer victim , and all her life she had a very sharp and  dry sense of humor.
Her favorite saying in the early stages of the disease was.....
"Of all the things I have lost ...I miss my mind the most"

Dave
manuals@...

On 2/8/2019 12:02 PM, David Slipper wrote:
DUH - of course !

Thanks all

Dave


On 08/02/2019 16:54, Fred Schumacher via Groups.Io wrote:
Hi David,
5Vpp gives you 2.5V top value with respect to 0. Your DVM is calibrated in Vrms. So you have your 2.5V to be devided by 1.41. This gives you almost 1.8V. So your DVM is indicating the correct value.
I am sure you did fotget this and had nothing to do with senility.
Fred
On 8 feb. 2019, at 17:17, David Slipper <softfoot@...> wrote:


I admit that I'm now in my 70s but this has me foxed ...

I have a sig gen churning out 50Hz at 5Vp-p - my trusty 744A agrees with
this and measures it correctly and the trace is a nice sinusoid
symmetrical about 0V.

But when I put a DVM between 0V and the centre of the BNC it reads back
1.81V AC

The scopes p-p measurement is OK.

I have tried 3 different DVMs but they are all the same.

What fundamental law of physics have I forgotten or has senility finally
caught up with me?? ;-)

Dave





.
--
Dave
Manuals@...
www.ArtekManuals.com

Re: Now I know I'm loosing my mind!! OT

David Slipper
 

Yes - My father used to refer to "The indignities of age" like memory
loss, senior moments, a bladder the size of a gnat's, and hair growing
from the nostrils and ears.  Oh well.

Dave

On 08/02/2019 17:30, ironcoder@... wrote:
David, I am 76, and sometimes when I am troubleshooting a stereo (my side business) I make simple mistakes that I would never have made when I was 25. Sorry to say it is aging. I can still write code (C++) but now I can only hold the value of 3 variables in my mind. I used to handle a dozen. It makes coding slower. I keep plugging along. You need to accept the limitations that aging brings and still make a happy life for yourself. I know, off topic. I am just saying that trouble shooting electronics can still be done in old age albeit more slowly. I still love what I do. My wife still loves me. As good as it gets.



.

Re: Now I know I'm loosing my mind!!

nonIonizing EMF
 

Then there are the head injury victims. I've witnessed and experienced both what was termed as Alzheimers and accidental hidden variable types.

My background is spectroscopy... and there are more molecules that can be "undocked" from where they are not required to be, if that is the causation for the memory impairment... which I believe is more common than most realize.

This wouldn't be known without the electronics test equipment to construct the spectrometers thanks to Tektronix I'm sure. A case example documentary would be a great sales instrument.

Excellent reason to remind others of the valid diagnostics methods to identify the unknown variables that might be hidden since an educated guess without proof is the norm to some.

Re: Now I know I'm loosing my mind!!

Glydeck
 

The meters are measuring RMS volts

(1.81)*2*SQROOT(2)=5

On Feb 8, 2019, at 8:19 AM, nonIonizing EMF <nonionizingemf@...> wrote:

On Fri, Feb 8, 2019 at 08:17 AM, David Slipper wrote:


What fundamental law of physics have I forgotten
Impedance matching?


Re: Now I know I'm loosing my mind!!

Dan Cordova
 

How do you LOOSING your mind? Is that somewhere between LOSING your mind, or loosening your mind chemically?

English 101 was the reason I studied engineering. Yesterday I couldn't spell "engineer," today I are one. I'm not an EE, but I know how to spell it.

Re: Beaten by 7834 LV Regulator

Fred S.
 

I'm really struggling to see where the fault is that's sending those
supplies low.

Hi David,

could you check if you have any voltage acr0ss R1591, it generates the reference ground for the differential amps on the +50V, +15V, -15V, and +5V regulator circuits.

--
Best regards,

Fred S.