Re: HV Probe and DMM Input Impedance

On Mon, Oct 28, 2019 at 11:06 AM, David M wrote:

On Mon, Oct 28, 2019 at 08:36 AM, n4buq wrote:

This last weekend, I found an EICO HV probe in very nice condition at an
estate sale. Opening it up, it contiains a 1.09G ohm resistor in series
with
the tip and cable. I connected it to the input of my Fluke 27 DMM and
measured a low voltage source (all I had handy at that moment). From what I
could tell, the probe gives me a 100x scale factor (e.g 10VDC measured
0.1VDC). While I may need to measure some higher voltages to confirm
whether
this is really accurate, it appears to be at least somewhat accurate.

I have a question, though, regarding the theory of the way this works. The
Fluke has a 10M ohm input resistance which, if I'm thinking about this
correctly, makes the measuring circuit 1100M ohms of which 10M ohm is the
meter and the remaining resistance in the voltage divider network is the
probe's resistor; however, I'm having trouble with the math.

Intuitively, (for me, at least), to obtain a 1/100 divider, I would think
that
ideally the probe resistance should be 0.990M ohms with the meter providing
the remainin 10M ohms. But I find it odd that the resistor has that odd
value
which makes it seem like it was almost intended to work with a 10M device.

If I'm not mistaken, those probes were intended to be used with a particular
device (meter) that provided the proper readings but not sure about that
either (not finding a lot of info on this probe).

Am I off base here? I know that some of the HV probes designed to work with
the Fluke are designed to connect differently and I think the meter is used
in
mA mode with them but not sure about that.

Is it a false expectation that the meter give me a 1/100 reading when used
with the probe in that manner? Is it also possible that the 1090M ohm is
giving me a "close enough" with that low voltage test and the difference
would
become more measurable with higher voltages?

Sorry - this should be simple but, for some reason, I can't make it make
sense
to me at the moment.

Thanks,
Barry - N4BUQ
Barry, the Eico (and other manufacturers as well) made those probes so that
the resistor could be changed to accommodate the particular VTVM or multimeter
you needed to use them with. In the case of the 1090 Meg resistor, it was to
be used with a meter having 11 Meg input resistance. That would calculate to
a 1000:1 divider.
So, to use your HV probe with a meter having a 10 Meg input, you would need to
add an additional 1 Meg resistor into the probe (or wherever you could make it
fit) so that the probe works into 11 Meg.

Cheers,
Dave M
OOps... I fat-fingered the "0" key, & didn't proofread my post. I should have said,,, that would calculate to a 100:1 divider.

Cheers,
Dave M

Re: 11801 bug fixes

On Mon, Oct 28, 2019 at 02:48 PM, Reginald Beardsley wrote:

Executive processor: 10.09
Display: 9.0
Time base controller: 10.11
Acquisition #1: 9.02
Acquisition #2: 9.02
The latest / last F/W kit I've found says 10.09 / 10.12 so if that is true there may be
one minor Time Base version later than yours.

/Håkan

Re: Printing Tek knobs, some details

KeepIt SimpleStupid

I found this
https://www.sculpteo.com/en/materials/

Company that can print a lot of materials including metal.

What's unique and interesting for the group is it's global presence:

"Sculpteo is a global leader in digital manufacturing based in Paris and San Francisco."

On Sunday, October 27, 2019, 8:20:53 PM EDT, EJP <esmond.pitt@...> wrote:

Have a look around thingiverse.com. There is quite a bit of Tek stuff there. I seem to remember some knobs but don't quote me.

EJP

Re: 11801 bug fixes

Chuck Harris

Oh well! I guess there are advantages in
ponying up extra for the "C" model.

-Chuck Harris

junk@... wrote:

My 11801B doesn't have it either. Must have been added in the later versions.

Replacing TDS540B CRT with LCD?

I believe that this is possible given a suitable "open-frame" 6.5" monitor
panel (I assume 640*480).

So far I've failed to locate anything on eBay or AliExpress (even at silly
prices).

If anyone has a pointer to a suitable panel (ideally cheap-ish) I'd be
grateful!

Thanks
David

Re: LCD screen for CSA803 or 1180x

junk@...

Reg,

I've been able to use the RS 232 interface to fetch traces and screen grabs from the unit. If you'd like the code (python scripts) I can share them with you.

Also, you might try checking/replacing BT150 on the A18 memory board. This might enable you to keep stored waveforms when powered off. My notes show the following for those:
- Lithium Poly-Carbon monoflouride, BR 2/3 A
- Potential part numbers Panasonic BR-2/3AE2P or BR-2/3AE2SP

David

Re: 11801 bug fixes

junk@...

Reg,

I think that the battery backed NVRAM might limited to 0x10000-0x1FFFF. If my memory serves, 0x0000-0xFFFF is volatile SRAM. FWIW, in my 11801B (SRAM intact) there is nothing interesting until you reach address 0x1EF60. From that address to 0x1FFFF seems to have legitimate data.

David

Re: 11801 bug fixes

junk@...

My 11801B doesn't have it either. Must have been added in the later versions.

Re: HV Probe and DMM Input Impedance

On Mon, Oct 28, 2019 at 08:36 AM, n4buq wrote:

This last weekend, I found an EICO HV probe in very nice condition at an
estate sale. Opening it up, it contiains a 1.09G ohm resistor in series with
the tip and cable. I connected it to the input of my Fluke 27 DMM and
measured a low voltage source (all I had handy at that moment). From what I
could tell, the probe gives me a 100x scale factor (e.g 10VDC measured
0.1VDC). While I may need to measure some higher voltages to confirm whether
this is really accurate, it appears to be at least somewhat accurate.

I have a question, though, regarding the theory of the way this works. The
Fluke has a 10M ohm input resistance which, if I'm thinking about this
correctly, makes the measuring circuit 1100M ohms of which 10M ohm is the
meter and the remaining resistance in the voltage divider network is the
probe's resistor; however, I'm having trouble with the math.

Intuitively, (for me, at least), to obtain a 1/100 divider, I would think that
ideally the probe resistance should be 0.990M ohms with the meter providing
the remainin 10M ohms. But I find it odd that the resistor has that odd value
which makes it seem like it was almost intended to work with a 10M device.

If I'm not mistaken, those probes were intended to be used with a particular
device (meter) that provided the proper readings but not sure about that
either (not finding a lot of info on this probe).

Am I off base here? I know that some of the HV probes designed to work with
the Fluke are designed to connect differently and I think the meter is used in
mA mode with them but not sure about that.

Is it a false expectation that the meter give me a 1/100 reading when used
with the probe in that manner? Is it also possible that the 1090M ohm is
giving me a "close enough" with that low voltage test and the difference would
become more measurable with higher voltages?

Sorry - this should be simple but, for some reason, I can't make it make sense
to me at the moment.

Thanks,
Barry - N4BUQ
Barry, the Eico (and other manufacturers as well) made those probes so that the resistor could be changed to accommodate the particular VTVM or multimeter you needed to use them with. In the case of the 1090 Meg resistor, it was to be used with a meter having 11 Meg input resistance. That would calculate to a 1000:1 divider.
So, to use your HV probe with a meter having a 10 Meg input, you would need to add an additional 1 Meg resistor into the probe (or wherever you could make it fit) so that the probe works into 11 Meg.

Cheers,
Dave M

Re: 11801 bug fixes

Reginald Beardsley

It's not included in the 11801 SAMPLING HEAD FNC'S menu.

However, I learned something about the T1331 error. According to p 391 of the diagnostics manual the T1331 error is a test of four confidence words which are written to NVRAM when the system leaves the diagnostics. So it will fail if the unit has never entered normal operating mode.

There is no mention in any of the timebase controller diagnostics about factory calibration constants. The NVRAM test preserves the contents of two areas:

0x00000 - 0x03FEF
0x13FF0 - 0x1FFFF

which amounts to 1/2 the NVRAM.

The confidence values are in 0x1FFF0 - 0x1FFF6

Reg

Re: HV Probe and DMM Input Impedance

Dale H. Cook

On 10/28/2019 10:08 AM, Jerry Ingordo wrote:

These HV probes we designed so that you can replace the series resistor to match the input resistance of the meter you intend to use with it.
If you are replacing a very high resistance probe resistor, especially in a high voltage prove, you need to do so with scrupulous cleanliness. Skin oil or other contaminants can adversely affect the probe by introducing a leakage path across the resistor, especially under a high voltage.
--
Dale H. Cook, Member, NEHGS, AGS, MA Soc. of Mayflower Descendants;
Plymouth Co. MA Coordinator for the USGenWeb Project

Re: HV Probe and DMM Input Impedance

Michael A. Terrell

The resistor should be smooth and clean. A goo builds up on those , from
contaminants in damp air. More expensive versions encased the resistor in a
seald, glass tube to keep it clean. Back in my early days in electronics
(>50 years ago) failed 66Meg resistors in the focus circuit of color TVs
failed from humidity, nicotine and HV across their bodies. The HV attracted
the particles from smoking, and the moisture turned it into goo. Spring and
fall were busy times, replacing HV parts in tube color TVs from homes where
people smoked. We rendered to those times as 'It's Flyback Season!' in a
Daffy Duck imitation. ;-)

On Mon, Oct 28, 2019 at 10:59 AM n4buq <n4buq@...> wrote:

I do have older VTVMs (HP 410B, 410C, etc.) so I could use it with those
as well. I have an older HP probe (459A) designed to be used with those
(has a different resistor) but it's missing the spring-loaded end-cap as
well as has a different resistor value. I took a look at that one
yesterday and noticed the resistor has a rather sticky film on it. I
wonder if that was originally there to reduce the effect of arcing?

If the resistor in my "new" probe didn't have fingerprints on it before,
it does now. I'll be sure to wipe down. Thanks for the tip!

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Michael A. Terrell" <@michaelaterrell>
To: TekScopes@groups.io
Sent: Monday, October 28, 2019 9:42:01 AM
Subject: Re: [TekScopes] HV Probe and DMM Input Impedance

That probe was made for a common, TV shop grade VTVM, with a 10M input
impedance, for AC measurements. In DC mode, a 1M resistor at the probe
tip
gave a total of 11M impedance. This was done to reduce the input
capacitance which would detune RF stages, or quench an oscillator. This
was
critical while servicing the high impedances encountered on tube based
electonics.

Add 1090M to 10M, and you get 1,100M wich is 100 times the impedance with
the HV probe. Be sure there are no fingerprints on the body of that
resistor, or it may arc over under HV use.

On Mon, Oct 28, 2019 at 9:36 AM n4buq <n4buq@...> wrote:

This last weekend, I found an EICO HV probe in very nice condition at
an
estate sale. Opening it up, it contiains a 1.09G ohm resistor in
series
with the tip and cable. I connected it to the input of my Fluke 27
DMM and
measured a low voltage source (all I had handy at that moment). From
what
I could tell, the probe gives me a 100x scale factor (e.g 10VDC
measured
0.1VDC). While I may need to measure some higher voltages to confirm
whether this is really accurate, it appears to be at least somewhat
accurate.

I have a question, though, regarding the theory of the way this works.
The Fluke has a 10M ohm input resistance which, if I'm thinking about
this
correctly, makes the measuring circuit 1100M ohms of which 10M ohm is
the
meter and the remaining resistance in the voltage divider network is
the
probe's resistor; however, I'm having trouble with the math.

Intuitively, (for me, at least), to obtain a 1/100 divider, I would
think
that ideally the probe resistance should be 0.990M ohms with the meter
providing the remainin 10M ohms. But I find it odd that the resistor
has
that odd value which makes it seem like it was almost intended to work
with
a 10M device.

If I'm not mistaken, those probes were intended to be used with a
particular device (meter) that provided the proper readings but not
sure
about that either (not finding a lot of info on this probe).

Am I off base here? I know that some of the HV probes designed to work
with the Fluke are designed to connect differently and I think the
meter is
used in mA mode with them but not sure about that.

Is it a false expectation that the meter give me a 1/100 reading when
used
with the probe in that manner? Is it also possible that the 1090M ohm
is
giving me a "close enough" with that low voltage test and the
difference
would become more measurable with higher voltages?

Sorry - this should be simple but, for some reason, I can't make it
make
sense to me at the moment.

Thanks,
Barry - N4BUQ

Re: HV Probe and DMM Input Impedance

Chuck Harris

The 410C has a 200Mohm DC input impedance. Any HV probe
not designed for the 410C will work poorly, if at all.

That said, to use a probe designed for 11M on a higher
impedance meter, you can add a parallel resistance to
bring the meter's impedance to the probe's design value.

Be careful when using any HV probe with an autorange DVM.

Most higher quality DVM's have super high input impedances
on their native input range... typically the lowest voltage
range. If the autorange starts on that range, the meter will
be likely burn out due to the HV surge.

-Chuck Harris

n4buq wrote:

I do have older VTVMs (HP 410B, 410C, etc.) so I could use it with those as well. I have an older HP probe (459A) designed to be used with those (has a different resistor) but it's missing the spring-loaded end-cap as well as has a different resistor value. I took a look at that one yesterday and noticed the resistor has a rather sticky film on it. I wonder if that was originally there to reduce the effect of arcing?

If the resistor in my "new" probe didn't have fingerprints on it before, it does now. I'll be sure to wipe down. Thanks for the tip!

Thanks,
Barry - N4BUQ

Re: 11801 bug fixes

Chuck Harris

I presume that you have some of the path I mentioned...

If your "unlettered" scope is truly missing this function,
it is a strong indication that tektronix knew about the
LED's affecting the timing, and added it in as a non-electrical
fix.

-Chuck Harris

Leo Bodnar wrote:

My CSA803 does not have this function.
Leo

On Mon, Oct 28, 2019 at 02:16 PM, Chuck Harris wrote:
Assuming that this isn't exclusively a "C" function:
WAVEFORM
-> SAMPLING HEAD FNC'S
-> SELECTED CHANNEL IDENTIFICATION
-> QUIET

Re: HV Probe and DMM Input Impedance

n4buq

I do have older VTVMs (HP 410B, 410C, etc.) so I could use it with those as well. I have an older HP probe (459A) designed to be used with those (has a different resistor) but it's missing the spring-loaded end-cap as well as has a different resistor value. I took a look at that one yesterday and noticed the resistor has a rather sticky film on it. I wonder if that was originally there to reduce the effect of arcing?

If the resistor in my "new" probe didn't have fingerprints on it before, it does now. I'll be sure to wipe down. Thanks for the tip!

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Michael A. Terrell" <@michaelaterrell>
To: TekScopes@groups.io
Sent: Monday, October 28, 2019 9:42:01 AM
Subject: Re: [TekScopes] HV Probe and DMM Input Impedance

That probe was made for a common, TV shop grade VTVM, with a 10M input
impedance, for AC measurements. In DC mode, a 1M resistor at the probe tip
gave a total of 11M impedance. This was done to reduce the input
capacitance which would detune RF stages, or quench an oscillator. This was
critical while servicing the high impedances encountered on tube based
electonics.

Add 1090M to 10M, and you get 1,100M wich is 100 times the impedance with
the HV probe. Be sure there are no fingerprints on the body of that
resistor, or it may arc over under HV use.

On Mon, Oct 28, 2019 at 9:36 AM n4buq <n4buq@...> wrote:

This last weekend, I found an EICO HV probe in very nice condition at an
estate sale. Opening it up, it contiains a 1.09G ohm resistor in series
with the tip and cable. I connected it to the input of my Fluke 27 DMM and
measured a low voltage source (all I had handy at that moment). From what
I could tell, the probe gives me a 100x scale factor (e.g 10VDC measured
0.1VDC). While I may need to measure some higher voltages to confirm
whether this is really accurate, it appears to be at least somewhat
accurate.

I have a question, though, regarding the theory of the way this works.
The Fluke has a 10M ohm input resistance which, if I'm thinking about this
correctly, makes the measuring circuit 1100M ohms of which 10M ohm is the
meter and the remaining resistance in the voltage divider network is the
probe's resistor; however, I'm having trouble with the math.

Intuitively, (for me, at least), to obtain a 1/100 divider, I would think
that ideally the probe resistance should be 0.990M ohms with the meter
providing the remainin 10M ohms. But I find it odd that the resistor has
that odd value which makes it seem like it was almost intended to work with
a 10M device.

If I'm not mistaken, those probes were intended to be used with a
particular device (meter) that provided the proper readings but not sure
about that either (not finding a lot of info on this probe).

Am I off base here? I know that some of the HV probes designed to work
with the Fluke are designed to connect differently and I think the meter is
used in mA mode with them but not sure about that.

Is it a false expectation that the meter give me a 1/100 reading when used
with the probe in that manner? Is it also possible that the 1090M ohm is
giving me a "close enough" with that low voltage test and the difference
would become more measurable with higher voltages?

Sorry - this should be simple but, for some reason, I can't make it make
sense to me at the moment.

Thanks,
Barry - N4BUQ

Re: Tektronix 475 Oscilloscope - Help With Repair

Mlynch001

I have visually checked the “glow” of the heater filament on 465B, 468 and 475A over the past few weeks. They are all just barely discernible through that white area in the very center of the rear of the CRT. None of my functional scopes has a “bright” glow. My experience with this series of scopes is that These things just do not glow that bright. Probably to save wear and tear on the filament?

--
Michael Lynch
Dardanelle, AR

Re: 11801 bug fixes

Leo Bodnar

My CSA803 does not have this function.
Leo

On Mon, Oct 28, 2019 at 02:16 PM, Chuck Harris wrote:
Assuming that this isn't exclusively a "C" function:
WAVEFORM
-> SAMPLING HEAD FNC'S
-> SELECTED CHANNEL IDENTIFICATION
-> QUIET

Re: HV Probe and DMM Input Impedance

Michael A. Terrell

That probe was made for a common, TV shop grade VTVM, with a 10M input
impedance, for AC measurements. In DC mode, a 1M resistor at the probe tip
gave a total of 11M impedance. This was done to reduce the input
capacitance which would detune RF stages, or quench an oscillator. This was
critical while servicing the high impedances encountered on tube based
electonics.

Add 1090M to 10M, and you get 1,100M wich is 100 times the impedance with
the HV probe. Be sure there are no fingerprints on the body of that
resistor, or it may arc over under HV use.

On Mon, Oct 28, 2019 at 9:36 AM n4buq <n4buq@...> wrote:

This last weekend, I found an EICO HV probe in very nice condition at an
estate sale. Opening it up, it contiains a 1.09G ohm resistor in series
with the tip and cable. I connected it to the input of my Fluke 27 DMM and
measured a low voltage source (all I had handy at that moment). From what
I could tell, the probe gives me a 100x scale factor (e.g 10VDC measured
0.1VDC). While I may need to measure some higher voltages to confirm
whether this is really accurate, it appears to be at least somewhat
accurate.

I have a question, though, regarding the theory of the way this works.
The Fluke has a 10M ohm input resistance which, if I'm thinking about this
correctly, makes the measuring circuit 1100M ohms of which 10M ohm is the
meter and the remaining resistance in the voltage divider network is the
probe's resistor; however, I'm having trouble with the math.

Intuitively, (for me, at least), to obtain a 1/100 divider, I would think
that ideally the probe resistance should be 0.990M ohms with the meter
providing the remainin 10M ohms. But I find it odd that the resistor has
that odd value which makes it seem like it was almost intended to work with
a 10M device.

If I'm not mistaken, those probes were intended to be used with a
particular device (meter) that provided the proper readings but not sure
about that either (not finding a lot of info on this probe).

Am I off base here? I know that some of the HV probes designed to work
with the Fluke are designed to connect differently and I think the meter is
used in mA mode with them but not sure about that.

Is it a false expectation that the meter give me a 1/100 reading when used
with the probe in that manner? Is it also possible that the 1090M ohm is
giving me a "close enough" with that low voltage test and the difference
would become more measurable with higher voltages?

Sorry - this should be simple but, for some reason, I can't make it make
sense to me at the moment.

Thanks,
Barry - N4BUQ

Re: HV Probe and DMM Input Impedance

EB4APL

Hi,

I have a couple of HV probes, one is a Metrix HT-212 with a 990 MOhm resistor that is intended for 10 MOhm meters, and your math is ok.

The other is an old RCA WG-206, with a 1090 MOhm resistor, just as yours.  These old HV probes were designed to be used with the (then) common VTVM's.

These meters usually have a 10 MOhm input resistance which was complemented with one 1 MOhm resistor inside the normal DC probe, so the VTVM - probe combination have 11 MOhm input resistance. The meter scale was made in such a way to account for this 1 - 10 MOhm resistor divider (10/11 ratio).

If instead a 1MOhm input resistor a HV probe with a 1090 MOhm resiswtor is used, the new input voltage divider is now 1100 - 10 MOhm (10/1100 ratio, 100 times bigger), so the multiplication factor is 100.

I got the RCA probe first, and I had planned so use an adaptation circuit between the probe and the DVM, which had to reduce the ratio to 1000/1, still useful with the sensitivity of normal DVM. In part due to the probe connector was an old microphone connector almost impossible to obtain today at a reasonable price, and the acquisition of the Metrix HV probe, I left the RCA one as is, to mate my Kyoritsu K-142 VTVM.

Best regards,

Ignacio EB4APL

El 28/10/2019 a las 14:47, n4buq escribió:
BTW, this is what the probe looks like:

https://www.etsy.com/hk-en/listing/491393770/eico-high-voltage-uni-probe

Not sure, but it appears the one pictured has a scale factor of 106 (as stated on the home-made label when used with a 10M ohm meter) so maybe that's more the case (e.g. not exactly a 100:1 divider when used that way)?

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "n4buq" <n4buq@...>
To: TekScopes@groups.io
Sent: Monday, October 28, 2019 8:36:37 AM
Subject: [TekScopes] HV Probe and DMM Input Impedance

This last weekend, I found an EICO HV probe in very nice condition at an
estate sale. Opening it up, it contiains a 1.09G ohm resistor in series
with the tip and cable. I connected it to the input of my Fluke 27 DMM and
measured a low voltage source (all I had handy at that moment). From what I
could tell, the probe gives me a 100x scale factor (e.g 10VDC measured
0.1VDC). While I may need to measure some higher voltages to confirm
whether this is really accurate, it appears to be at least somewhat
accurate.

I have a question, though, regarding the theory of the way this works. The
Fluke has a 10M ohm input resistance which, if I'm thinking about this
correctly, makes the measuring circuit 1100M ohms of which 10M ohm is the
meter and the remaining resistance in the voltage divider network is the
probe's resistor; however, I'm having trouble with the math.

Intuitively, (for me, at least), to obtain a 1/100 divider, I would think
that ideally the probe resistance should be 0.990M ohms with the meter
providing the remainin 10M ohms. But I find it odd that the resistor has
that odd value which makes it seem like it was almost intended to work with
a 10M device.

If I'm not mistaken, those probes were intended to be used with a particular
device (meter) that provided the proper readings but not sure about that
either (not finding a lot of info on this probe).

Am I off base here? I know that some of the HV probes designed to work with
the Fluke are designed to connect differently and I think the meter is used
in mA mode with them but not sure about that.

Is it a false expectation that the meter give me a 1/100 reading when used
with the probe in that manner? Is it also possible that the 1090M ohm is
giving me a "close enough" with that low voltage test and the difference
would become more measurable with higher voltages?

Sorry - this should be simple but, for some reason, I can't make it make
sense to me at the moment.

Thanks,
Barry - N4BUQ

--
El software de antivirus Avast ha analizado este correo electrónico en busca de virus.
https://www.avast.com/antivirus

Re: TDS3044B repair

Oz-in-DFW

I'd still remove and reseat both ends.

Where are you in the world? I have a VGA/serial/GPIB card in my 3014 that we might be able to mate with your scope briefly.